79cc Pred direct drive tranny?

GoldenMotor.com

KCvale

Well-Known Member
Feb 28, 2010
3,966
57
48
Phoenix,AZ
The GTC torque convert I got for this bike won't work, the drive sprocket is just too out of alignment with the wheel sprocket.

The object of the build was to have a torque converter and I am already $260 for the one I bought because I pained the blue black so I am DESPERATELY seeking some tips for a new transfer case on this build torque convert or not.

Thanks guys as I am really taking this one up the poop chute so far.
 
Last edited:

GearNut

Active Member
Aug 19, 2009
5,104
11
38
San Diego, Kaliforgnia
Folks have modded Q-Matics to fit the 79Preddys with excellent results.
If I am not mistaken (happens alot recently :( ), the clutch needs a different spring which Quenton has already worked out. Just let them know which engine you are using so you get the correct clutch.
 

runnermike

Member
Nov 18, 2012
936
0
16
Sanford, FL
I will be watching this thread closely. I am getting ready to start a 79cc Pred build myself.

What rear sprocket are you running? Rag joint or sprocket adapter? Just curious...
 

KCvale

Well-Known Member
Feb 28, 2010
3,966
57
48
Phoenix,AZ
I will be watching this thread closely. I am getting ready to start a 79cc Pred build myself.

What rear sprocket are you running? Rag joint or sprocket adapter? Just curious...
MM 3 prong hub mount with like a 36T small sprocket I drilled as I was assuming a torque converter shifting tranny so I guess we'll see.

I will look up the JS and go from there.
If anyone wants this brand new GTC torque converter for a 212 pred with the blue mount plate already painted black let me know as I have one I paid $270.80 to my door for and can't use it and that really crips my working capitol.
 

culvercityclassic

Well-Known Member
Sep 27, 2009
3,115
177
63
Culver City, Ca
I have to break the bad news again...that 36 tooth will not work with a jackshaft. need at least a 48, 56 would be ideal. Welcome to the world of four strokes and jackshafts...

BTW that CVT would not have worked with a 79cc motor, it does not have enough hp to operate it properly...Back to the drawing board...
 

KCvale

Well-Known Member
Feb 28, 2010
3,966
57
48
Phoenix,AZ
My bad, I was thinking of the 24" chopper I just did, this Macargi Fatal Love has a 9 bolt spoke mount 56T on it.
 

KCvale

Well-Known Member
Feb 28, 2010
3,966
57
48
Phoenix,AZ
I went with Quentons special Q-matic for the 79cc Pred.
The engine shaft is a bit too long for the thin cover so I cut 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 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.

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 motorized bicycle 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 motorized bicycle 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.
 

KCvale

Well-Known Member
Feb 28, 2010
3,966
57
48
Phoenix,AZ
Here is some more on the throttle management using just a spare 2-stroke throttle and spare parts.









All that unused engine mounted throttle stuff and heat shield may come off today as well for a cleaner look but I didn't take the engine apart to disconnect the governor, didn't have to with my own direct to carb throttle system ;-}
 

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,505
24
38
Ridin' inSane Diego, CA.
All that unused engine mounted throttle stuff and heat shield may come off today as well for a cleaner look but I didn't take the engine apart to disconnect the governor, didn't have to with my own direct to carb throttle system ;-}
If you really want a cleaner look....and I really mean "cleaner look", get rid of that gigantic p-nut looking whizz tank and use anything else for fuel reservoir. Anything!

Do you mean to say that these 4-stroke Predator builds are more challenging and take a bit longer than a kit build? Really?

What happens when you want to build your own custom bike frame from scratch, from the ground up? How much does one charge for that kind of build?

Just curious cuz one day I would like to build a motorized bike too ;)
 

KCvale

Well-Known Member
Feb 28, 2010
3,966
57
48
Phoenix,AZ
If you really want a cleaner look....and I really mean "cleaner look", get rid of that gigantic p-nut looking whizz tank and use anything else for fuel reservoir. Anything!
I will pass that on to the customer that ordered this custom build that way if you like but considering how happy he is with it that would seem like a useless 3rd party backhand slap for his taste.
Do you mean to say that these 4-stroke Predator builds are more challenging and take a bit longer than a kit build? Really?
Heck yes it was a new challenge I welcomed and why I took the job!

Besides helping someone choose the best power plant/drive/bicycle combination for their needs, coming up with my own solutions is my favorite parts of this business and I share how I did it with for others here.
Sorry of that offends you.

What happens when you want to build your own custom bike frame from scratch
Funny you should ask that...

I'd jot down my rough designs and specs, have a professional turn it into a CAD machine readable production file, and then find a local shop that can make them...
Thing is, I don't want to get into that business so a moot point, heck I don't want to be any business that requires me to make more than a 30' commute to work from bed and don't have to hehehe ;-}