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4 Stroke Bicycle Engines & Kits 4 stroke engine kits are great if you want reliability or do not want to mix your oil and gas. Learn from each other how to get the most out of your 4 stroke bicycle engine

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Old 12-12-2016, 03:06 PM
Sam Bousak Sam Bousak is offline
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Default 5/8 straight shaft vs 78mm tapered shaft for 4G Engine kit

Hello all,

I am looking into purchasing a 4 stroke engine kit from

http://www.bicycle-engines.com/

and see that they offer a 5/8'' straight shaft and a 78mm tapered shaft for the engine. What are the differences/pros/cons between the two? Thanks.
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Old 02-07-2017, 07:07 PM
quik225 quik225 is offline
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Default Re: 5/8 straight shaft vs 78mm tapered shaft for 4G Engine kit

Bump to the top.

I have the same question.

If you have the choice between the 5/8" or 78mm shaft, which one would you buy?

Bicycle-Engines are out of the of the 5/8" shaft 4g's.
Their web page now states the kits now come with a 1/2" (not 78mm) tapered shaft F142.
http://www.bicycle-engines.com/49cc-...ngine-Kit.html
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Old 02-07-2017, 07:33 PM
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Agreen Agreen is offline
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Default Re: 5/8 straight shaft vs 78mm tapered shaft for 4G Engine kit

5/8" straight shaft. Try finding a tapered shaft clutch. It may be possible to find one, but it will be harder to find and more expensive.

A 78mm shaft is something like 3 inches. A common metric shaft size is 17mm, maybe that's it?
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Old 02-07-2017, 10:04 PM
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scratchbuilder scratchbuilder is offline
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Default Re: 5/8 straight shaft vs 78mm tapered shaft for 4G Engine kit

Hey, if you go to 'gasbike' under 4stroke parts, they have a tapered shaft clutch that goes with the 'primary' KC vale could give you good info. Even bicyclengines prolly has the same deal. The 5/8 shaft is for your own clutch, while the 78 is referring to the diameter of the centrifugal clutch the goes with there 4g belt drive primary

Last edited by scratchbuilder; 02-07-2017 at 10:14 PM. Reason: thought
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Old 02-08-2017, 08:10 AM
quik225 quik225 is offline
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Default Re: 5/8 straight shaft vs 78mm tapered shaft for 4G Engine kit

Bicycle-Engines web site shows 78mm tapered clutches in stock.

Does the 78mm bell shaft ride on a bushing or bearings?
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Old 02-08-2017, 06:30 PM
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scratchbuilder scratchbuilder is offline
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Default Re: 5/8 straight shaft vs 78mm tapered shaft for 4G Engine kit

That I'm not sure of,It's my understanding, the clutch has to be used with the 4g. I bought the straight shaft engine only. And it is a bushing.
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Old 03-06-2017, 10:28 AM
KCvale KCvale is offline
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Default Re: 5/8 straight shaft vs 78mm tapered shaft for 4G Engine kit

Quote:
Originally Posted by Sam Bousak View Post
Hello all,

I am looking into purchasing a 4 stroke engine kit from

http://www.bicycle-engines.com/

and see that they offer a 5/8'' straight shaft
and a 78mm tapered shaft for the engine.
What are the differences/pros/cons between the two? Thanks.
On the 5/8" long shaft engine you have to mount your own clutch AND it's bell to the actual engine shaft and then a transfer case around it.

The clutch bell rides on a bushing, not any bearings, and needs a lot of service.

The clutch attached short shaft engine (142F-1G) is all set to bolt a 4G full bearing supported clutch bell and output shaft belt drive transfer case right to it.
It's the best combo I've found for trouble free operation good performance and you can get creative with it...

For example, if you can't fit a 4-stroke 4-G in the bike frame with a SBP shift kit, just add a second set of mounting holes in the 4G and rotate it.



I do the same thing but the other way for my long shaft 10G's.
It has to go down so the long shaft clears the oil filler.

I had some longer output shafts for a 20T/100TFW 4G made, and 'press replace' the new longer shaft to the transfer case to put the left hand drive to the right hand side.



Granted, these are not things Joe Casual Builder can do well even if they had the right tools, but that's not my point Sam, I am just showing off hehe ;-}

I recommend going with the HS 142F (or 144F if you can find one) -1G clutch attached short shaft engine and 4G transfer case.

There are several versions of the 4G, I use a special version for my 10G's, but just go with what B-E has, it all the right parts for most people and one of the few places you can get the real thing.
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Last edited by KCvale; 03-06-2017 at 11:18 AM.
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