I think that there might be a reason for the idler other than limited availability of different length belts. I have used double sided tooth belts in a new type of telescope drive I designed, much less robust than the ones in these photographs, and a huge range of length is available. Instead, I suspect that by using the design they have the belt covers a larger area of the main shaft and clutch sprockets and thus spreads the load over more teeth.
Misc: Electric Starters Mark Cooper Rapide Electric Starter
- Thread starter Peter Holmes
- Start date
Sorry about the guy On the audio. 
I think the better way to go is build a REAL soft engine,
But I can't bring myself to do it !,
After all , If one of ours can start his with his HAND !.
But I can't bring myself to do it !,
After all , If one of ours can start his with his HAND !.
Yes it cranks over ok........But.......if you open the throttle by so much, the added volumetric efficiencey added will cause a huge amount of extra effort on the starter........Also, On a hot engine this also has an effect as the rings/valves are all sealing much better. The main issue I see is the starter to crank turning ratio is very poor.........I worked it out on a late model Godet 1330 twin, and it was about 5 :1 cranking ratio........Compare this to a car engine which is around 10 :1 obviously using a large diameter starter ring gear would be the best fix, but lack of room buggers that idea. Yes an engine of low tune specs would be fine, but anything that has bigger capacity, big cams, big compression, and you are in for some trouble........I've been planing for this same set up on a new engine/bike i am going to start building soon........Luckily the late model TP heads I bought have the central decompressor passage as a small 3 mm hole between the valve seats.......This then uses a 12 volt solenoid popet type valve that are made for some later Harley engines.......These work well and are not expensive.......I've even used them on 600 singles to aid in turning the engine just over TDC using the kick start lever.
This particular starter system has been running in two or three bikes here in NZ with zero issues. I am sure Mark or Ivan would be happy to talk about the intricacies of the design. Another one is being completed as we speak.
Some starter motors have a reduction gear built into the drive before it get to the large ring gear. These tend to be used on diesel engines. Perhaps it uses something similar to that.
There is a .5" aluminum gasket available from Cometic. You can get it through Paul Holdsworth. I am not certain of the price he charges, but Pat Manning has used them on certain engines.
Pat's Grosset starters seem to work fine on his 1200 TPV engines. He uses a decompressor on both cylinders and both cylinders have two plugs. Each decompressor is an automatic one, set by hand and easily accessible.
I mentioned this setup many years ago on this forum, but Brian Rutherford did the hard work of pulling it all together. The spark plug runs through a ring and what looks like a mini float bowl that holds a decompressor. The plug that is chosen to run through the decompressor is a long-reach plug that appears to be easily available.
I believe a 0.125" milling tool is used to cut the groove and bore the hole. This pathway leads to the decompressor, which operates through the button on top.
The decompressor is expensive at $150 each, but the engine starts easily with both cylinders turning over.
These engines use Terry's stock pistons and a cam that Megacycle makes for me with about 0.5 lift. I think Greg has it right that the starters are unhappy with the amount of compression they are hitting. This is just another approach. Pat's heads are mostly the earlier TPV heads with no decompressor hole.
David
Pat's Grosset starters seem to work fine on his 1200 TPV engines. He uses a decompressor on both cylinders and both cylinders have two plugs. Each decompressor is an automatic one, set by hand and easily accessible.
I mentioned this setup many years ago on this forum, but Brian Rutherford did the hard work of pulling it all together. The spark plug runs through a ring and what looks like a mini float bowl that holds a decompressor. The plug that is chosen to run through the decompressor is a long-reach plug that appears to be easily available.
I believe a 0.125" milling tool is used to cut the groove and bore the hole. This pathway leads to the decompressor, which operates through the button on top.
The decompressor is expensive at $150 each, but the engine starts easily with both cylinders turning over.
These engines use Terry's stock pistons and a cam that Megacycle makes for me with about 0.5 lift. I think Greg has it right that the starters are unhappy with the amount of compression they are hitting. This is just another approach. Pat's heads are mostly the earlier TPV heads with no decompressor hole.
David
So that is why Bigfoot is so hard to find. I can just see one of those heading though the forest and poor Bigfoot having a sudden and spontaneous bowel movent and seconds later being at the top of the highest tree around