1974 800cc V twin in BMW R80 Frame.

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1974 800cc V twin in BMW R80 Frame.

Postby Mouse » Mon Feb 01, 2010 11:27 pm

I've done enough to know the project is a goer. I've had so many no-starters that I dont normally like to post up progress until I've actually got somewhere. :)

The project is based on a Motorenwerk Cunewalde 2VD 8/8 - 2SVL engine, which is German and made in 1974. It is 800cc V twin air cooled and rated at 15PS on the engine plate. Its engine plate also states it weigh 125kg but I kind of suspect it is a bit more than that.

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This is a Multicar M22 a typical use of the engine I have, there are many examples of the M22 multicar if you go looking :wink:

I firstly attacked the weight issue by removing all the auxiliary bits and lightened the flywheel. Stripping all the bits off also allowed me to clean it properly as the build is going to take place in the spare room of my house as I don't have a garage any more.

The flywheel was turned down on a friends lathe. It was initially 35kg and I was aiming to reduce it by 50% but only managed to loose about a third of the weight which is a starting point. I will re address lightening it some more after it is on the road and working. I went into a bit of a You Tube frenzy so the flywheel conversion is documented in video...

http://www.youtube.com/watch?v=zrZJmNuRPfo
Weighing the flywheel and assessing the modification needed to get it to take the BMW clutch

http://www.youtube.com/watch?v=3_A6l3WPTEA
Turning the beasty down. This took a whacking 9 hours in a friends lathe. I am so glad I'm not paying a workshop for this sort of thing.

http://www.youtube.com/watch?v=tn6rqwNumrw
Weighing it after modification.

http://www.youtube.com/watch?v=MgNZF0EzUNg
This is how I removed parts of the flywheel after using the lathe.

[EDIT] I estimate the engine will weigh just less than 100kg after these mods.

After getting the clutch fitted to the fly wheel I cut the BMW frame on a key weld on the spine and also cut a section out of the bottom tubes so I could get it around the engine. This was easier than I imagined and after much faffing about It looks like I'll only have to extend the frame length by about three inches.

the next series of photos is a complete mockup of a few bits to make it look bike shaped and nothing is welded or aligned properly yet.

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The mockup. Frame balanced around engine, chop tank in place, car battery on gearbox and Jaguar 18" space saver wheel up front. I cant remember buying the tank, it was at a show I know that much and I was with people I haven't hung about with for at least 10 years.. ....

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Side View: You can see its starting to look like a bike.

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Back View

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The top tube of the frame needs to be extended by about this much which is a hell of a lot less than I was expecting.

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Gearbox needs to be supported within the bell housing. This is a technical problem as the shafts need to be aligned with 0.5mm (hopefully much tighter than that) as there is no provision for eccentricity in the clutch unit.

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Front engine mount. Nice and sturdy as the engine is a stressed member. It bolts to the original engine support mounts.

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Frontal view. The engine is sitting on the floor which is about 6" or so lower than it should be which makes the front wheel look badly out of place. The wheel is a 18" jaguar space saver wheel which should take a 18" bike tyre.

You can see Suzuki GSX / GSF1200 alternator on the floor that will most probably be used as its a bit smaller than a car one which will make fitting it into the available space a lot easier.

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Aerial front view, things look almost in proportion.

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Front side view.

There is some 25mm bright bar in the headstock ready for when I start building the front end. It will be a single sided cantilever type setup, like a one sided Earls Forks. I've seen a load of the big trikes done like this and kind of like the setup.
Last edited by Mouse on Wed Mar 31, 2010 10:50 pm, edited 2 times in total.
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby roguetek » Tue Feb 02, 2010 3:28 am

ok so you're using a mid 80s BMW tranny and a desiel plant. cool. watch the gear ratios, and be careful how much HP you apply.

those BMW trannys are... touchy.
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby Stuart » Tue Feb 02, 2010 10:14 pm

Best of luck with your project Mouse :D Looking good mate.

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Re: 1974 800cc V twin in BMW R80 Frame.

Postby johnfireball » Tue Feb 02, 2010 11:41 pm

Hi Mouse,
It's gonna be great. To allign gearbox take the flywheel and clutch to your friend with the lathe and ask him to center the friction plate for you, once under spring pressure it wont move and will allow you to mate gearbox perfectly.
John.
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby toyotaracer9 » Sun Feb 07, 2010 8:39 pm

Wow , thats gonna look great . Call it the viscous V !!!!
If it isn't broken , break it .
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby Mouse » Wed Mar 31, 2010 10:46 pm

The next and final instalment of my bike build.
I wrote this for another forum and don't really have the time to redo any of it so please excuse my potty mouth if I've left any foul language in it. :oops:


First was the exhaust. After a brief discussion over at the Diesel Bike forum I found out that Diesels don't need as much silencing as a comparable petrol engine. So armed with this gem of knowledge I set about resuscitating The Sorties that got me pulled by the cops on their last outing. I think bought for a tenner about 18 years ago when I was on an XS250.

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first was the flanges, using an old gasket as a template and a hole saw bought for about 50p from a carboot sale.

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Then it was a rummage right to the bottom of the shed to find The Sorties. They are in a bit of a state but.....

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Some soapy water and a scrubbing pad soon brings a glint back to them.

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A ninety degree bend was cut in two to give two forty five degree bends that were then brazed together. I'm running real low on Mig gas and want to avoid buying more until after the bike is finished.

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Cut short ready to fit the flange bits.

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The finished exhaust and a handful of real exhaust fiberglass wadding I bought many moons ago for the GSX550 rat exhaust.

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Pokeing it in with a Pokey Dokie!

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The finished thing all ready to install on the bike.

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:D

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You get rather a lot of wadding for your it for your money This has packed the GSX550 exhaust the Diesel ones and there is this much left over!



ALTERNATOR
I've been hoarding a spare Bandit 1200 alternator (Actually the same as a whole bunch of the larger GSX based engines) the alternator has a tapered shaft which holds a cush drive and gear for driving it. Rather than spending a whole lot of time on a lathe turning a tapered boss up I simply dismantled the cush drive and the pulley wheel from a car alternator slipped over the shoulder on it with minimal filing. The two were brazed together after which it can be easily bolted to the alternator shaft.

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The tapered part fo the cush drive and the car alternator pulley.

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The pulley filed out and placed in position on the cush drive bit.


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Brazed together and cooling before I pick it up. :wink:

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Bolted onto the tapered shaft of the alternator.

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The position it will be fitted in. Opposite the starter motor in a futile attempt to balance the bike.

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Mounted and adjustable. This is fully one way...

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and this is fully the other way!
Now all I need is a belt to fit, This will wait until I can ride it to the Bearing & Pully shop so they can measure it themselves. I've had trouble specifying belts with them in the past.


http://www.youtube.com/watch?v=zeLQwl3zJ-s
Video of the smooooth adjustable action.

FRONT END
After abandoning the idea of building my own front suspension for the moment as the work and effort is worthy of a project of its own. So instead I will fit a Bandit 1200 front end as I have one on a dead bike. I've fitted new bearings to the BMW headstock and the Suzuki spindle is just as wrong as it could be so I heated up the ally bottom yolk and beat out the spindle so I could for a new one. I turned down some 25mm bright bar I already had and will hold it and the yolks together with a nut at each end. I'd prefer to use metric fine and also not use chunky nuts. After a lot of hunting about for cheap dies and nuts I chose to use M20 metric fine (1.5 pitch) because it...
A] Is the same thread as a VW car front hub nut and therefore cheap light weight nuts are available.
B] It is the same thread as electrical conduit trunking and therefore cheap dies are available.

Don't underestimate the cost of dies. If I went to a machine shop and bought a good quality M20 metric fine die it would be about £90 but a conduit die, Screwfix sell them for about a tenner but suspect the quality.

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This is the blank spindle turned down from a piece of 25mm bright bar.

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One end is shoulderd to take the top yolk and a nut.

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The other end is turned to take a nut.

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After going to the shed to cut the thread I realised I didn't have a die holder thingy so I made one with a bit of tube and some bar.

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This took about 45 mins to make and worked very well.

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After struggling to start the thread straight I simply popped my spirit bubble on the die and all went well after that.

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The El Cheapo die was s**t, it cut the thread but only just and it lost cutting teeth as about 5 - 6 of them chipped off. I didn't enjoy using it at all as it felt like it was going to lock up and smash the whole time I was using it, but at least it did the job for £10 :D

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One thread cut.

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Other thread cut.


GEARBOX FLANGE ALIGNMENT.
I've been putting this off for a bit because I have to completely dismantle the bike to get to the flywheel.
For this to work properly I need to get the engine shaft and the gearbox shaft aligned as best I can, preferably perfectly.

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I've borrowed a friends magnetic surface gauge to help me. The magnet is stuck to the cast cylinder fins and the business end is on the inside of the flywheel centre bush I made.

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Now in order to turn the engine with minimal force I took the rockers off and removed the push rods so I'm not having to compress the valve springs. I also inserted the bit of wood so the valves are kept open a bit and there is no compression.

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The error is 0.006" or 0.15mm. I'm not happy but continue.

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Inserting a length of 9mm ground bar the error is now 0.005" 0.13mm.

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The gearbox slides over the 9mm bar and the flange is held down but not tightened so as the engine is rotated the surface gauge will indicate the error in alignment. It is unsurprisingly 0.005" out :(

Not happy with 0,005" I tok it all apart and back together about three times and after a bit of tapping with the rubber mallet I managed to get it so the surface gauge didn't flinch at all as the engine was rotated :D

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You'll have t take my word on it that this is where the needle stayed!!
After this was achieved the bolts holding the flange plate to the bell housing were carefully nipped up tight.

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After that the gearbox was removed to that locating holes and pins could be fitted.

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These are the engineering pins and the hole they go in. They are tapered ones so I had to ream the 6mm hole out with the correct matching tapered reamer.

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In it goes....

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And tapped home with my smaller hammer = Everything in alignment again :D

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I then had to reassemble the gearbox because I was suffering a severe case of lazy*****tus when I decided to mend it so I'd have a working spare on the shelf. This was about 5 years ago. The original fault that made me take it apart was a broken Shift Pawl Return Hair Pin Spring!!

GEARBITS
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The foot lever is connected with two ball joint thingys like this one.

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However I'm missing the 'ball' bit of the second one so a fix is needed.
After a bit of a rummage in the bits box I found a couple of grease nipples and the body of the nipple is almost exactly what I need.

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The foot lever was then tapped out to M7 (Yep you read that right!)

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In action and working!!
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I also had to adjust and fit the break lever arm bits.

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Making little fiddly bits like this adjustable cable end holder bit takes about an hour!

SIDE STAND
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Next was a side stand. the wheels are on the bike and I need to move it about without having to chock it up on bricks every time. This is a spare stand from the sidecar project of yesteryear. (It can stand up by its self :wink: )

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LOOK! The bolt holding the stand on is a tad smaller then the hole in the mounting bracket cut from the bike frame so I could fit the diesel engine.

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After another rummage in the gas fittings bits box I found this bit that looks like it may be brassy and useful.

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It was then up into the attic to my epically s**t mini lathe for some rotating butchery.

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More uber s**t lathe action. I am not cutting with a trowel I am using it as a shim :wink:

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From another angle - Note the lay-shaft assembly.

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The business end!

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There we have it a sh**ty turned brass bit.

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Does the job simply perfectly.

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The bracket bit welded in place and the side stand assembled in place!



HEADLAMP
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I was relying on the leftover Bandit 1200 headlamp and shell but when I went to mount it I saw that the reflector was shagged, The photo hides a lot but you see the orange tint which is the rust inside it

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After a hard think I remembered I had a VW reflector left over from something else and probably only set me back a fiver or so.

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It is the same diameter (almost) to the damaged one except for the mounting brackets.

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The other mounting bracket.


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Half a cup of tea later I decided to swap the brackets over. SO using some cunning and a pair of mole grips I removed the bracketry bits.

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Then I marked out the mounting points and cleaned the paint back to the bare metal ready for fitting..

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Using the welder on its lowest setting I welded the buggers on!

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The brackets line up with the rest of the bits.

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:D Finished. a completely refurbished headlamp.

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Head lamp shell fitted and the main wires poked through ready to connect up.

FINISHED!!!!!!
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The finished Bike ready for MOT.

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VIDEO.
http://www.youtube.com/watch?v=7MdpgARjh8M


It Failed the MOT on a few things but the main ones were,
A] Knackered rear disc, I didnt spot some rust pitting that almost caused the needle on the brakeometer in the test station to snap off.
B] Knackered pissing oil and 'riding low' rear shocks.
C] Cant turn the engine off without letting go of the bars ie Kill Switch inoperative, he dug his heals in over this one

So not serious just a pain and having to spend money on a rear disc :(
Kubota Z482 which is plodding on with unnerving reliability. Three years so far.
1900 Diesel Bike being rebuilt with better clutch control.
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby coachgeo » Thu Apr 01, 2010 2:43 am

Like the report, ingenuity, and resourcefulness!!
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby andrewaust » Thu Apr 01, 2010 4:20 am

Excellent run down of the build Mouse, awesome 8)

So just a case of putting a good disc on, replacing the shocks and putting a fuel cut off in the form of a solenoid or similar and your done.

Small word of warning, be careful of the wording in the post, one particular word could get us in some serious do-do !! This goes to anyone else who is posting, try and keep it civil, all pages are viewable by everyone on the web.

A ;)
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby Crazymanneil » Thu Apr 01, 2010 7:32 am

Good job and nice info. Wondering if I should have used a dial gauge on my engine but probably too late now ho hum :roll: . Note the exhaust packing won't last with a diesel because it will clog with soot but then again diesel is much quieter to start with like you say so should be fine anywway.

Nice pics.

N
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby Dan J » Thu Apr 01, 2010 8:47 am

Mouse - looks brilliant.

Definitely in agreement with Neil - get that exhaust packing out as it'll quickly clog and you'll be sat in the middle of nowhere trying to explain to the AA why they need to bring the world's largest tweezers out with them.

Are you going to bring it to the UK rally for all to see?
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby Nanko » Thu Apr 01, 2010 1:37 pm

Looking at the pictures there is a perforated sheet tube inside the muffler
the damping material is wrapped around it , exhaust gasses are not passing
through the glass fiber
I am using this construction too , no problems with soot.
Worst case the holes to the damping materal get blocked and it
makes a bit more "sound"
peugeot TUD5 - MOTO GUZZI 16.500 km so far
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby Stuart » Thu Apr 01, 2010 8:00 pm

Nice one Mouse :D It was a good find that engine :D Yes, I'll echo Dan and say it would be good if you could make it to the rally on that bike. We are expecting/hoping to see several new bikes this year 8)
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby Mouse » Thu Apr 01, 2010 8:34 pm

Thanks for the encouragement. The engine is currently sitting on the floor with all the casings off and the only thing that remains on the frame are the footpegs. :?

I have a MOT retest at the weekend if they are open (bank holiday weekend) and have taken the opportunity to replace the shaft seals and redo a couple of joints that were leaking oil.

Yea I cant believe the engine was good for £150 and a 400ish mile trip in the sidecar to get it. As for the rally I'll definitely be there unless I drop dead or something equally as serious. I've always felt a bit silly turning up not on a diesel but haven't had the opportunity to sort out a bike until now.
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1900 Diesel Bike being rebuilt with better clutch control.
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby sbrumby » Fri Apr 02, 2010 12:38 pm

Very good effort Mouse. Any chance you could make Uttoxeter you would certainly have a few people looking at it ?
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby Mouse » Mon Apr 05, 2010 9:40 am

The madness continues with the MOT retest bodgery. I wrote this last night so if you have a short attention span and want to know the fail then scroll to the bottom.

The flywheel was far to heavy even after removing 11kg from the original mammoth 34kg so it was back into the lathe and another kg was removed bringing it down to about 12kg giving a total loss of about 22kg. When I say to heavy the bike would speed up or slow down to match the engine speed if you got the rpm wrong on a gear change. It also pulled the bike over by about an inch to an inch and a half when you revved the engine which was a bit disconcerting when riding it. If I shut the throttle or opened it with the bike banked over the torque reaction against the flywheel would both push the bike sideways and forwards / back the reaction was to do the opposite on the throttle which made things worse.

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First cut

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Second final cut - Much lighter.

One benefit is that I was able to totally remove the evidence of the superior German casting perfection!
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then it was a ghtening of the flyweights to increase the max RPM a tad. I dont want much and can always set the mechanical stop t where I want it.
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The governer.

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Flyweights removed.

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Weight before.

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Weight after.

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Back in place.

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Holding pin.

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Inserting onto place and ....

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Knocking home! :D

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Tapped it into place with a special tool I bought years ago. this is the second time I've used it.

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Then the centre punch to stop it coming free.

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YAY fixed into place.

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Timed up.

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These timing gears are bigger than a large car transmission.

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The shockers are shocking. Pissing all their oil out everywhere and

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SO the start of a god bodge is to take apart what you have.

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Left over from the trike project that was abandoned a month before the SVA was active. A pair of Fiat 126 and a pair of Mini Shocks. Laid ut next to the dismantled BMW shock one is surprisingly similar. A reminder to us all to horde more crap.

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Next is the springs. the MOT failed because the bike was sagging low at the rear end or some such shite. Another relic fleft over from scrapping a Metro for the abandoned trike project is a bunch of springs that assisted the hydrospastic suspension system. They are thicker and about the same length (two of them) and diameter as the BMW unit.

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All the bits layed out next t each other.

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I think we have a winner!!! :D
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then it was onto the manky springs.

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Some undercoat.

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And some silver spray just because I can. :wink:

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The business end cut to length and tapped to M10. M10 tap cost me a tenner but I'll always have it.

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Then it was to weld the lugs onto the main body. Some studding and some bits welded to it that I used for rebuilding the Dnepr shocks about 5 years ago.

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One lug in place! YAY its going to be easy I thought. The second lug weld blew through to the oil filled inside. the heat vaporised the oil and so pressurised the inside of the thing. I was sprayed with flaming shock oil until it cooled enough for me to blow out. Then I had to fill in the hole which was no simple task. I then drilled a hole in the top (Bottom) of the shock and squirted in some fork oil. I have no idea if I used the correct amount and suspect I used to much. The second shock was equally as difficult I resorted to unrestrained foul language and eventually got the job done.

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There we have it. Two heavy duty motorbike shock absorbers!!! I dont know why I went to the effort of painting them silver the flaming oil soon made a mes of that!

THE MOT and FAILAGE!

Then it was off to the MOT the next morning. I'm not in the mood to go writing any funny whitish-isms about the experience other than having to get them to back the van into the test area so I could jump start the bike. He eventually passed it and as he handed me the precious document said the best thing I could do was photograph it for the memory and then set it onfire.

On the way home I was on the motorway doing about 55ish and there was an almighty row from the engine and it lunged to a stop. The oil filler cap had fallen off and blown all the oil out and it had seized up!

Am seriously effed off!

Insert your favourite scotty quotes at will.

The tare down of the diesel.
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Right side first as this one always smoked a bit and was always the second to fire up. It almost suggests that there was existing damage.

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Exhaust off.

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Cover off.
Rockers off.

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Head + Barrel off.

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The head was stuck fast to the barrel. No amount of levering with a screwdriver would shift it.
So an application of heat was applied and.....


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They simply fell apart :)

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One side of the bore.

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And the other.

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An improvised puller for extracting the gudgeon pin.

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The piston, one side.

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And the other.

Tomorrow it will be the sump off and checking big end bearings.

Not really in the mood to speculate at the chance of recovering the bore and piston.
Kubota Z482 which is plodding on with unnerving reliability. Three years so far.
1900 Diesel Bike being rebuilt with better clutch control.
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby Anorak_ian » Mon Apr 05, 2010 10:26 am

Oh bugger!
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby coachgeo » Mon Apr 05, 2010 5:54 pm

grrrrrrrrr.... let me guess.... if you can make her work.... you'll install an oil pressure gauge or level sensor.
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby Mouse » Mon Apr 05, 2010 8:42 pm

You're a mind reader. :lol:
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1900 Diesel Bike being rebuilt with better clutch control.
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby Anorak_ian » Mon Apr 05, 2010 10:17 pm

Surely no one ever looks at a pressure gauge while on the move, what's needed is a red flashing light on the dash or head light.
I have an oil pressure switch but wasn't going to use it, now I think I'll rig it up to my 12volt flasher and the un-used red light at the back of my head light.


What damn bad luck after all that hard work.
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby Byrdman » Mon Apr 05, 2010 10:43 pm

Great project, I love the fact that you used an old, odd engine.

Sorry to hear that she grenaded on you though. Where did the oil all go? Thankfully not onto the rear tire!
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby Mouse » Mon Apr 05, 2010 11:26 pm

When I was a kid I used to think my dad was silly for fitting a fire alarm bell to the oil pressure switch of his boats engine. From what I remember you had to push a switch to silence it while cranking. :wink:

Surely no one ever looks at a pressure gauge while on the move........

As for not noticing idiot lights, how many times have we all left the indicators on until some car driver starts flashing their lights at you??

Where did the oil all go?

The oil came out of the side of the engine through the filler so mostly missed the tyre.
Kubota Z482 which is plodding on with unnerving reliability. Three years so far.
1900 Diesel Bike being rebuilt with better clutch control.
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby Crazymanneil » Tue Apr 06, 2010 8:08 am

I admire your tenacity Mouse. I have a DR 350 that did a similar thing only the oil came out an oil line connection over time. Only thing I knew about it is when I slowed down on the motorway and then noticed the engine sounded like a cement mixer full of nails. No oil light on it either. Its still sitting parked up waiting on some attention. Best of luck, Neil
Smart engined 800cc turbo diesel triumph tiger. 100mpg (imp)
Belfast to Kathmandu overland, 2010/2011 - http://www.suckindiesel.com
Bangkok to Sydney ???
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby thundercougarfalconbird » Tue Apr 06, 2010 4:40 pm

mouse, you might have to reconsider your choice of running that engine without the cooling fan, looks like a classic overheat seizure.
I'll do what i feel.
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby coachgeo » Tue Apr 06, 2010 5:12 pm

thundercougarfalconbird wrote:mouse, you might have to reconsider your choice of running that engine without the cooling fan, looks like a classic overheat seizure.
so your thinking the heat pressure popped a weakened oil filler cap, or something like that? Might be some plausibility in that?
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby Anorak_ian » Tue Apr 06, 2010 6:17 pm

Mouse, does your engine have a breather pipe?

If not, I'm guessing that your engine needed a rebore, and the pressure was passing the piston rings and building up and up in the crank space until the cap which is the weakest link flew out.


Oddly enough Harley oil caps fly out if you add too much oil to the tank.

Thinking about it, my old CB360 honda twin chugged the oil out via the breather pipe in to a bottle strapped to the back of the bike, that was caused by 3 broken rings. I'm sure that if it had a push in cap it would have shot out.
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby mark_in_manchester » Wed Apr 07, 2010 11:41 am

Goodness, what a major setback, as they say on TV before 9pm.

At least the pistons are flat(-ish) topped rather than incorporating any fancy swirl chamber, so there's a chance you may be able to find something alternative to fit if original oversize are not available. I've used CX500 pistons in a Ural before - gudgeon pin size and outer diameter is correct (the most important factors) but crown height is too low, which would have meant machining to barrel ends...I gave up as originals became available.

Does anyone know whether diesel pistons are especially hardy compared to ones from petrol engines? It would help to know before trying to find friends in motor trade with big pattern part books...

Did I read on one of your posts that this was a DDR product? I might be able to suggest contacts via MZ world who might be able to assist or suggest where to go looking.

M.
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby albertaphil » Wed Apr 07, 2010 6:44 pm

Diesel pistons (and rods and "wrist pins" as we call them over here) are generally much stronger than their gasoline counterparts because of all the extra compression and the relatively uncontrolled combustion. I really doubt that any piston from a gasoline engine or even another diesel would work satisfactorily.

On the other hand...the pistons look superficially similar to those out of any MkII VW diesel (1.6L) and the displacement works out (400cc/cylinder). Of course, equal displacement doesn't mean equal bore or wrist pin size or placement.
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby Nanko » Sat May 01, 2010 7:13 pm

Found this on a german site
especially the rpm limits ( betriebsdrehzahlbereich)given are interesting/alarming

Motortyp 4 KVD 8 SVL [2 KVD 8 SVL]
Hubraum 1600cm³ [800cm³]
Leistung 30 PS [15 PS]
spez. Kraftstoffverbrauch 215g/PSh [220g/PSh]
Zylinderbohrung 80 mm
Kolbenhub 80 mm
Verdichtung 20:1
Betriebsdrehzahlbereich 1500−3000 U/min
niedrigste Leerlaufdrehzahl 600−800 U/min
Drehrichtung links (auf Schwungradseite gesehen)
Motorgewicht trocken 178 kg
Schmierung Druckumlaufschmierung mit Zahnradölpumpe
Fördermenge der Ölpumpe 17 dm³/min
Öldruck 2,5−4,5 kp/cm²
Ölmengen Motor 5,5 l [3,5 l] Getriebe 1,75 l Hinterachse 1,2 l
Ölverbrauch 75 g/h [40 g/h]
peugeot TUD5 - MOTO GUZZI 16.500 km so far
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby Mouse » Sat May 01, 2010 7:58 pm

Thanks Nanko.

I've also just got hold of a czech manual which is entertaining me at the moment.
Kubota Z482 which is plodding on with unnerving reliability. Three years so far.
1900 Diesel Bike being rebuilt with better clutch control.
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Re: 1974 800cc V twin in BMW R80 Frame.

Postby Anorak_ian » Sat May 01, 2010 8:16 pm

How goes it now mouse?
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