4 stroke friction drive engine kit from 80ccmotorboys.com

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deniswhite

New Member
hello everyone, i am new to this but have spent 2 days researching about dif kits, and 2 stroke vs 4 stroke. my bike is a Magna Air Tension with step-through frame, so that limits my choises. i also want a 4 stroke because of the less noise.

does any one have a 4 stroke friction drive engine kit from 80ccmotorboys.com or had any experience with this kit? i cant seem to find any details on this engine or the kit, and does any one have any finished pics?

Thank you
 
Just went to the site and it looks the kit is using the HS 31cc 4stroke engine. Thats about all I could find out. I have a FD with the same engine and it works well. Not a great big hill climber, but gets around pretty well.
 
cannonball2 said:
Just went to the site and it looks the kit is using the HS 31cc 4stroke engine. Thats about all I could find out. I have a FD with the same engine and it works well. Not a great big hill climber, but gets around pretty well.
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I am looking for top speed
how would you say it stuck up against the 66cc 2 stroke chain drive?
 
You are talking low 20s depending on roller size. The China girls are much faster. If you want speed with a 4 stroke a 50cc chain drive is about it, unless you DIY.
 
cannonball2 said:
You are talking low 20s depending on roller size. The China girls are much faster. If you want speed with a 4 stroke a 50cc chain drive is about it, unless you DIY.
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i have a step through bike, but i have a feeling that i can make the 66c China girl fit, and i would think of something for the gas tank.

do i understand it correctly that the 2 stoke has about 3 times more power (3-5 hp) compared to the HS 31cc (1.5 hp?)? but reliability wise the HS will run laps around it?
 
Its apples and oranges. The china girl makes more power, they vary Im guessing 2.5hp on the average stock, some more maybe. Its gonna be faster. I have had 3 of them, Im a slow learner. All my bikes now are 4stroke except for my Solex type bikes. The prep for using the 4strokes in to put in oil and gas. A good prep for a china girl is to totally dismantle it, clean it and repair whats wrong with it. With some care you will probably have a good engine. Not really knocking them, this is a reality. Many people love em and its a cheap ticket to speed, but you are asking for trouble with out a tear down. Probably get a bunch of replies about how mine ran great right out of the box-if so Im real glad for ya. There are probably just as many that didnt. Still they are kinda fun if you like to tinker, and I am considering another to build a shift bike.
 
cannonball2 said:
Its apples and oranges. The china girl makes more power, they vary Im guessing 2.5hp on the average stock, some more maybe. Its gonna be faster. I have had 3 of them, Im a slow learner. All my bikes now are 4stroke except for my Solex type bikes. The prep for using the 4strokes in to put in oil and gas. A good prep for a china girl is to totally dismantle it, clean it and repair whats wrong with it. With some care you will probably have a good engine. Not really knocking them, this is a reality. Many people love em and its a cheap ticket to speed, but you are asking for trouble with out a tear down. Probably get a bunch of replies about how mine ran great right out of the box-if so Im real glad for ya. There are probably just as many that didnt. Still they are kinda fun if you like to tinker, and I am considering another to build a shift bike.
Click to expand...

thanks you, sounds like 2 stoke is more hands on, and needs more adjustments. my priority is reliability so i guess i will go with the 4 stroke friction.

what is the formula for calculating top speed?
i have 26" wheels, and now trying to figure out what size roller to get
 
Go to page two of the "66cc BMX with vertcial engine" thread in DIY, there is a calculator I posted a link to, you can download it-REAL HANDY. Roller size is determined by a bunch of factors, not just speed. Weight, hills, engine size and engine rpm. The 31cc HS turns fairly high rpms, manual says 10,000 no load so 8,000 is probably realistic, at those rpms top speed is 23mph. A 1/4" makes a bunch of difference. If you have hills a 1" is about as big as I would go with that engine.
 
Are you going with friction drive to save money over a chain drive? The chain drive would give you way more usable power from the limited cc's.

Take a look at both here: http://www.staton-inc.com/default.asp

Because Doug makes his product right here in the USA he might be a little higher than Chinese imports. Lifetime warranty on his drives. Forever.
 
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