It certainly has been a busy year, but we still managed to design the Q-Matic drive to fit the latest motor from Harbor Freight. We produced a fair number of drives for the 79 CC and finally had time to test the drive on the current 99 CC HF motor. Many parts are interchangeable between the motors, and the drive side bolt pattern is also the same.
Some things are surprising, including the 5/16 fine thread bolt used on the 99 CC in place of the 8 MM on the 79 CC. The 79 CC was rated to use 89 octane, however the 99 CC wants 87 octane. The "foot" bolt pattern is very close on both motors, however the 99 CC uses a staggered system, meaning the boltholes are closer on one side than the other. The bolthole centers are 102 MM on one side and 104 MM on the other. This was first discovered when we noticed the extra mounting [foot] plate holes didn't line up, if we rotated the plate the holes lined up. Next we noticed the crankshaft on the 99 CC is over size, and requires the pulley I.D. size increased to fit.
The 79 CC is 80.7 CC and the 99 CC is 98.5 CC a difference of 17.8 CC. The 79 CC has the same size 15 MM carburetor, but loses the air/fuel mixture screw on the 99 CC motor. The motors produce very similar power, however the 99 CC is slightly slower in stock form. The 79 CC has a higher top end with identical drive ratios, but the 99 CC pulls harder on the way to top end. After a few minor modifications, the 99 CC will pull harder and reach a higher top speed.
Blue or black? My test bike is blue; the 79 CC motor housing is blue. The 99 CC used to have black covers and didn't match my blue bike. The used test 79 CC motor now has black cover & black rope start, whereas my 99 CC test motor now has blue cover & blue rope starter assembly.....this means they are interchangeable.
After the few minor modifications to the 99 CC motor and some break-in time, here are the facts.. Easily hits 6000 RPMs, pulls very hard, can pull a harder ratio [gig her top end, slower start]. With the ratio of 11.55 X 1 the following numbers were the results 3000 RPMs = 20 MPH 3600 RPMs = 24 MPH, 4500 RPMs = 30 MPH, and 6000 RPMs = 40 MPH.
If I can find a little extra time I will try changing the Q-Matic ratios and see what happens at 9.52 X 1..... Should easily pull the numbers and should look like this:
3000 RPMs = 24 MPH
3600 RPMs = 29 MPH
4500 RPMs = 36 MPH
6000 RPMs = 48 MPH
6155 RPMs = 50 MPH
Way too fast for a bicycle, and I am sure no one will want to go that fast. BTW I had the test bike at 6300 RPMs several times during testing using the 11.55 ratio drive.
Have fun,
__________________
Quenton
