Another 99cc Predator build

[MikeJ]

Hi jbcruisin, Quenton -

That is a very nice design and a good choice of frame and engine combinations. It just "looks right" and you will get a lot of miles out of it before something needs attention. And it probably will not be the drive train.

Just a quick question, I don't recall seeing this: At what engine RPM does the clutch lock in? I may re-spring mine to avoid the "pulsing" I am feeling at low RPM acceleration. (I am not using Quenton's fine product, but one of my own designs that takes advantage of a jackshaft and the rear cassette gears.)

Thanks,
MikeJ

[Quenton Guenther]

Hi MikeJ,

The Q-Matic drive uses custom designed primary ratios and the clutch "ticking" and "lock" speeds are lowered to work smoother. The stock Q-Matic drive used on the 49 CC motors spin the clutch at 723 RPMs at idle [2000 RPMs]. The HF version of the Q-Matic spins the clutch at 533 RPMs at idle [1100 RPMs]. If you have the clutch mounted on the motor crankshaft, it will be difficult to totally remove the "pulses". In order to reduce the "pulsing" you will need to determine the cause....
Is the gap from idle to "ticking" narrow or wide?
If the gap is wide the spring needs to be weaker, if the gap is narrow, then a stronger spring is needed. Most often the spring needs to be stronger, as the shoes tend to kick in and out at lower RPMs if the "ticking" threshold is close to idle.

Have fun,

[MikeJ]

Hi Quenton -

Thanks for writing. You gave me some ideas for a new modification to my drive train. I wonder if I can move my centrifugal clutch to the cassette side of the bike. That may give me a little more flexibility for gear ratios. It's time to experiment some more!

MikeJ

[jbcruisin]

Today I took it out for the first real test ride. I opened it up & it went up to 46 mph easily. It was doing 6000 rpm's according to my "Tiny Tach". Goes great up hills. I'm very happy with it.

[Quenton Guenther]

Hi Jay,

6000 RPMs is about the max on the motors we are testing at the factory level.

Try resetting the primary adjustable pulley [larger] to reduce the RPM level. I have managed to get one of the factory test bikes to exceed 50 MPH with the front pulley set at 3.1". The final ratio is 8.76 X 1 with the front pulley set at 3.1", and hit 50 MPH at 5675 RPMs.


Have fun,

[MikeJ]

30 mph is my upper limit; I'm a conservative type. Tech specs make that engine sound pretty durable. Let us know the conditions of your riding and how that engine and Q-matic drive performs. Maybe more readers will convert to this 4-stroke combination....

[jbcruisin]

Hi Jay,

6000 RPMs is about the max on the motors we are testing at the factory level.

Try resetting the primary adjustable pulley [larger] to reduce the RPM level. I have managed to get one of the factory test bikes to exceed 50 MPH with the front pulley set at 3.1". The final ratio is 8.76 X 1 with the front pulley set at 3.1", and hit 50 MPH at 5675 RPMs.


Have fun,

I'll be playing with that pulley to get the best performance It's tightened about 1/2 way out now.

[jbcruisin]

Here's a picture of the 3/4 inch electrical conduit strap that I used for the top drive mount.

[brizzle9725]

Can someone explain to me how to go about making a mount for the 99cc hf engine? I don't know how to weld either. Thanks in advance!