HF 79cc in frame friction drive build

daRog

daRog

New Member
After a couple months of information researching and parts searching, I'm about ready to start building a 4 stroke HF 79cc bike.

I have a few unanswered questions about the engine itself I'd like to resolve. First, can someone please identify the function of the carb screws shown in this picture?

ZwBKl.jpg


Next, I'd like to know if the number on the side of the block is a serial number unique to each engine or if it's just some generic code number.

Yky1B.jpg
 
Hey daRog, glad to see that you're interested in using in frame FD. You won't be dissapointed in it's performance with that engine.

#1 is the idle mixture adjustment. The 99cc Predators carby doesn't have this adjustment screw.

#2 is the main jet tube, not an adjustment.

#3 is a drain valve.

Good luck with your build. Don't hesitate to ask for opinons or advise :~)

That number is unique to that engine
 
Thanks, wayne z! My decision to use a 79cc was based on several factors, one being simply that it will fit in the small frame mountain bike I have:

ymrfN.jpg
 
It will work,for f/d...Just look at Wayne Zs fine build....I have a Schwinn Legacy w/ 99cc predator f/d. I used the same set-up as Waynes, but will be using a minibike clutch/chain drive to the roller.....Tigmaster....
 
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Yes I did follow the builds of cannonball2 and then waynez. Waynec is also building the version in one speed like cannonball2 did his.

They all look great.

Ron
 
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Well, as cool as that in-frame mount would look, I've decided to put it off for a while and just do a rear mount for now. I figure I'll have time to work out all the in-frame details this winter.
 
Are you gonna use a jackshaft? If so, there's no reason why you couldn't leave the roller on the rack mount and move the motor in-frame later.
The roller on a rack would probably be more sturdy than the seatstay mount that I used.
 
for the main jet tube you pointed out... would that be the thingy i will have to drill out if ever it need be?..... please respond anyone who has drilled a main jet on a HF 2.5hp:D
Thanks in advance
Eric
 
The only down side to a rear rack mount with and HF engine is the bike is tail heavy with the engine centered. Has perfect balance other wise. You never notice the tail heaviness while riding, it just in handling the bike while off. This is the easiest to ride bike I have, its the only one my wife will use. An inframe like Waynes would be better, but the rear rack makes a really nice bike with the engine behind you, and can be easily swapped to another bike. If used with an oak or good metal roller would be just about maintence free and the ratios can be quickly changed with a pulley swap. The variable pitch pulley also works well.
 
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