Idea For simple diesel bike...

[IgorVigor]

I had a bit of a thought while fiddling with a 50cc scooter...

The drive system is a CVT gearbox which I have seen a lot of you use for diesel bikes...

So, if you took a working scooter (or one you know the CVT is in good health)

Fit the diesel engine in between your legs in a frame
Modify the scooter engine piece so you could run a chain and sprocket (or belt and pulleys) from the diesel to the crankshaft (or replace/modify the crank so its a straight shaft).

Would be a fairly easy and cheap method of a conversion.

Most 50cc scooters produce 3~6 hp and 125cc scooters produce between 8~14 hp depending on engine.

They all seem to use Kevlar drive belts now which are very strong yet small (less heat, same traction)

The one on the 50cc I was playing with had a V belt 3/4~1 inch wide and about 3/4 inch thick

I wouldn't recommend a large diesel, but a Yannmar (or clone of around 10hp should be fine)

And you could alter the acceleration/top speed by altering the sprockets and chain (belt and pulleys) from the diesel to the moped CVT.

Most 50cc scooters only rev to around 7000rpm so a 3600rpm diesel running a 2:1 drive the gearbox would equate to a similar speed

so the top speed would be around 40~50 mph depending on scooter, but it should get there quickly...

Just an idea I thought I would throw into the ideas pot

Any thoughts or questions?

[Sphere]

The petrol engines in scooters are really compact, even in 250/400cc models. Where would you leave the Yanmar/Hatz/Chinablock

[IgorVigor]

As I said, between your legs...

Even the smallest 50cc scooter has a good amount of leg room...fit the engine between your legs (and maybe a bit under the seat if wanted/required) and fit a pair of footpegs for your feet (if needed)

Jobs a good'un...

its only an idea...

Look around and you can get scooters for £100 running order...

Locally to me there is a Gilera DNA for £80, with spare engine.
Its a non runner because of an immobiliser or something...

Pics of a Gilera DNA if you dont know what they are:
http://www.maxmoto.co.uk/images/39%20Gi ... A%2050.jpg
http://www.tapetky.cz/wall/13611_1280x1024.jpg

Tempted to buy it because they do look quite nice

Believe it or not, they are still a 50cc scooter...it looks like a bike, but has a CVT gearbox...


EDIT:
the other thing is it would give a proven transmission though, so it might be a way of sourcing cheap CVT's for diesel bikes...
most scooters have a single sided swingarm, on which the wheel fits to a splined shaft, so you could mod the wheel shaft for a sprocket to fit, for a chain drive bike...

[Crazymanneil]

Hmm interesting idea. What rev range does the scooter have though? Might be tricky to get the cvt to engage properly with the limited rev range of the diesel but I guess that could be overcome by gearing before coupling to the cvt or modifying weights or whatever voodoo magic cvt works on...

N

[Sphere]

I see. Well I tried looking for dna 180 workshop manuals, since there is no point in trying to dieselize a moped in Holland. I could not locate anything useful except for easyparts. Well, I'm looking forward to see the details of this plan

[pietenpol2002]

Here's an example from Japan I posted some time ago. A rather crude arrangement and interestingly drives from the flywheel side, presumably for coupling to a jackshaft opposite the left mounted CVT. There is little narrative to accompany the photos other that to give it a positive report.

http://blogs.yahoo.co.jp/valkan243/17317150.html

[IgorVigor]

Hmm interesting idea. What rev range does the scooter have though? Might be tricky to get the cvt to engage properly with the limited rev range of the diesel but I guess that could be overcome by gearing before coupling to the cvt or modifying weights or whatever voodoo magic cvt works on...

N

As i said in an earlier post, basically run a 2:1~3:1 increase via a chain and sprocket...
The 50cc scooter I have in the shed revs to 7~7.5k rpm max

So accounting for a diesel that revs to 3600rpm and idles at say 750rpm.

a 2:1 (e.g. 36tooth sprocket on the engine, 18tooth on the jackshaft/crankshaft) would put the gearbox idling at 1500rpm and peak rpm of 7200rpm (ignoring any slight losses)
The scooter will do 45mph as standard so a similar speed should be ascertainable with the diesel engine...
If anyone is concerned about the bike trying to creep, I wouldn't worry...
The scooter doesn't try and move until 2.5~3k rpm, but that can be altered by changing the roller weights...
if you altered the weights so it would try and pull from 2000rpm, the diesel would basically have a usable rev range of 1000~3600rpm

The advantage is the extra torque you would have

if you used a 3:1 system, on the right scooter CVT, you could be up to 60~70mph...

Obviously, it would need to be tuned to your individual requirements...

[IgorVigor]

Here's an example from Japan I posted some time ago. A rather crude arrangement and interestingly drives from the flywheel side, presumably for coupling to a jackshaft opposite the left mounted CVT. There is little narrative to accompany the photos other that to give it a positive report.

http://blogs.yahoo.co.jp/valkan243/17317150.html

Thats basically what I thought of doing...

personally if I had built that bike I would have used a clockwise rotation engine and retained the pull start/crank starter instead.....

But oh well, I'm sure he/she had their reasons...