This build was originally going to be a 212cc Predator with GTC TC1002P torque converter but when all the parts were here it looked to be way to big so I exchanged the 212 for 79cc.
I went with Quentons special Q-matic for the 79cc Pred from E-Z Motoribikes.
The engine shaft is a bit too long for the thin profile cover (which is good) so I just cut a hole for it but you could cut 1/2" off the end of the shaft.
The bike is a 29" Macargi Fatal Love I put a pair of caliper brakes on to help the coaster brake and of course HD tubes and liners in each wheel.
The engine mount base and wide cranks were left over from a 49cc HS jackshaft shift kit build. By leaving the engines mounting plate off the engine it mounted to the plates front slots but we had to drill rear mount holes.
Note we tack welded the plate joints on the underside of the plate as we didn't any adjustment after it was fit.
The exhaust was removed and we fabed a new pipe using the flange on the stock exhaust welded to a spare section of SBP expansion chamber pipe and then a 2-stroke Cat muffler with spiffy heat shield.
If that pipe proves to be too restrictive I'll pop the end cap, pull out the Cat Plenum and make the end covers hole a little bigger.
We redrilled a 56T Maniac Maniac #41 chain sprocket for a 9 hole rag joint fit.
The gas tank was removed and the linkage from the manual throttle/governor, then we fashioned an adjustable throttle cable end to the engine.
The normal pull for a throttle is ~ 1.5" and 1/3 throttle turn, the throw of the carbs throttle tab would have made the throttle about 1/8 turn from idle to wide open so we extended the throw by adding an 1.5" tab to the carb top.
This worked out great! It gives the full 1/3 throttle twist response and lined it up perfectly with the cable stay.
Then we just used an old NT carb spring for a very nice 'snap back' throttle action.
The gas tank is 1.2 gallon Whizzer tank that was mounted with a combination of 1.5" muffler clamp stays, frame tube brackets, long bolts and spacers.
It has a drive side chain tensioner for future adjustment but with use of a #41 chain 1/2 link it is darn near direct drive.
Last but not least the hard rubber grip was removed from the throttle barrel and BMX foam grips with spiffy end caps installed as well as nice new brake handles from a bike that got a dual pull for the front and rear calipers.
We still have some odds and ends to do today like put the pedal chain guard on then get some test riding to decide about the exhaust but that's easy stuff.
If you are an experienced builder with welding skills and lots of spare parts around this project isn't too bad (~60 man hours).
BUT, if you are an MB rookie or just don't have the tools, skills, and misc parts I highly recommend you just start with a 49cc HS with 4G tranny complete MB kit for ~$360 as just the 79cc Pred and Q-matic were $400 and you still need a mount plate, rear sprocket, wide pedal crank set, gas tank, custom exhaust and throttle to make it go.
I went with Quentons special Q-matic for the 79cc Pred from E-Z Motoribikes.
The engine shaft is a bit too long for the thin profile cover (which is good) so I just cut a hole for it but you could cut 1/2" off the end of the shaft.
The bike is a 29" Macargi Fatal Love I put a pair of caliper brakes on to help the coaster brake and of course HD tubes and liners in each wheel.
The engine mount base and wide cranks were left over from a 49cc HS jackshaft shift kit build. By leaving the engines mounting plate off the engine it mounted to the plates front slots but we had to drill rear mount holes.
Note we tack welded the plate joints on the underside of the plate as we didn't any adjustment after it was fit.
The exhaust was removed and we fabed a new pipe using the flange on the stock exhaust welded to a spare section of SBP expansion chamber pipe and then a 2-stroke Cat muffler with spiffy heat shield.
If that pipe proves to be too restrictive I'll pop the end cap, pull out the Cat Plenum and make the end covers hole a little bigger.
We redrilled a 56T Maniac Maniac #41 chain sprocket for a 9 hole rag joint fit.
The gas tank was removed and the linkage from the manual throttle/governor, then we fashioned an adjustable throttle cable end to the engine.
The normal pull for a throttle is ~ 1.5" and 1/3 throttle turn, the throw of the carbs throttle tab would have made the throttle about 1/8 turn from idle to wide open so we extended the throw by adding an 1.5" tab to the carb top.
This worked out great! It gives the full 1/3 throttle twist response and lined it up perfectly with the cable stay.
Then we just used an old NT carb spring for a very nice 'snap back' throttle action.
The gas tank is 1.2 gallon Whizzer tank that was mounted with a combination of 1.5" muffler clamp stays, frame tube brackets, long bolts and spacers.
It has a drive side chain tensioner for future adjustment but with use of a #41 chain 1/2 link it is darn near direct drive.
Last but not least the hard rubber grip was removed from the throttle barrel and BMX foam grips with spiffy end caps installed as well as nice new brake handles from a bike that got a dual pull for the front and rear calipers.
We still have some odds and ends to do today like put the pedal chain guard on then get some test riding to decide about the exhaust but that's easy stuff.
If you are an experienced builder with welding skills and lots of spare parts around this project isn't too bad (~60 man hours).
BUT, if you are an MB rookie or just don't have the tools, skills, and misc parts I highly recommend you just start with a 49cc HS with 4G tranny complete MB kit for ~$360 as just the 79cc Pred and Q-matic were $400 and you still need a mount plate, rear sprocket, wide pedal crank set, gas tank, custom exhaust and throttle to make it go.
