Buying a bike for MPG/Vetter Challenge, what would be your favorite?

[HHOTDI]

Very good info Sendler, thanks. I live in a rural area that does not require any emissions testing still and I am wondering if that is why I didn't need any of that when I titled/reg my last vehicles from there..? I will make a trip down to our DMV and see what they are saying to confirm. I don't want to raise any eye brows that are not needed you know. :{)

[sendler]

I asked this a while back but didn't get any answer. In choosing a donor bike for a full streamliner conversion, what is the overall efficiency of a V-Matic scooter transmission versus gears. How long do the belts and drives last? I have read on the scooter forums that these CVT transmissions can wear out the belt and groove/ put sticky spots in both pulley assemblies every 5,000 miles. The Honda SH150i would make a good starting point if they weren't so expensive as they have a fuel injected 15hp single, 53 inch wheelbase and 16 inch wheels. And a nice combined ABS system.
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2010 SH150i Specifications - Honda Powersports
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[Frank Lee]

My experience is with snowmobile and atv cvts, and their efficiencies are quite a bit lower than gears.

[sendler]

Originally Posted by Frank Lee

My experience is with snowmobile and atv cvts, and their efficiencies are quite a bit lower than gears.

Loss in the belt or from ineffective rpm tuning?

[Frank Lee]

The belt needs to be squeezed very hard and transfers power solely via friction.

[TedV]

Generally speaking, CVT trans eats more power than a geared trans. In the ballpark of the best CVT is maybe as good as the worst manual as far as efficiency. True, there is a black art to tuning a CVT. The advantage of a CVT is; tuned correctly it allows the motor to run at the best motor efficiency. YMMV with application of the 2 types of trans.

[Ken Fry]

Originally Posted by sendler

I asked this a while back but didn't get any answer. In choosing a donor bike for a full streamliner conversion, what is the overall efficiency of a V-Matic scooter transmission versus gears. How long do the belts and drives last? I have read on the scooter forums that these CVT transmissions can wear out the belt and groove/ put sticky spots in both pulley assemblies every 5,000 miles. .
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These vbelt cvt's (the v-belt stage) can be 96% efficient, with some manufacturers claiming even a little higher. The same is true of any v-belt drive, if properly tensioned. (Gates, I think uses 97%, maybe.) The CVTs are self-tensioning, so the effective ratio changes (minutely) with a stretched belt, but the tension does not. Different systems have different numbers of gear meshes before and/or after the CVT. 98% for each mesh is a reasonable estimate.

At very low speeds, when the drive is not fully engaged (which happens in different ways with different scooters (some have independent centrifugal clutches, some use the v-belt drive unit) efficiency is awful.

If your streamliner is for you own use, and not for a competition, then the packaging ease and compactness of the scooter motor transmission unit is appealing, and may outweigh efficiency concerns . If you want, you can be seated over the front of the motor, while still having a low seat height.

Disadvantages include the difficulty in changing final drive ratios, and maybe 5% overall lower efficiency -- but that's assuming identical engine efficiency: the 150 is apt to be more efficient at 10 hp than a 250 cc bike at 10 hp. Honda has been publishing fuel economy numbers, which I think are reliable for comparing Honda models against one another. The 91 mpg quoted is pretty impressive as compared to the CBR 250's 77 -- which is a very efficient 250.

Some of the larger scooters have very high priced belts in the name of efficiency (they bend more like a chain). One I checked was about $250 or so.. or maybe $350... a lot in any case.

[sendler]

96% efficiency is actually a pretty reasonably small amount of loss which could even be made up by fine tuning the pulley weights to keep the engine right in the sweet part of the power band. A case full of constant meshed gears slinging lube might not be much better.

[Frank Lee]

96 is about 8 better than any figure I've ever seen for CVTs. Must be a scooter unit with a much more pliable belt and lower pinch pressures.

[sendler]

It's hard to find much on scooter CVT efficiency. I found an article on the Honda S-Matic variable transmission which shows a chart for belt slip. Does this give an almost complete view of the losses?
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Honda Worldwide | Technology Close-up
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