Hi all

I recently rode my air cooled gas gas for the first time. I bought as a complete bike but have had to do quite a bit so far such as fitting an 18mm kickstart shaft and a pedal and clutch case to match from a JTX model.

I noticed two things in the 30 mins test. 1. It gets very hot, the tail pipe is almost too hot to touch where it exits the middle box so i wonder if the timing is retarded too far. I seem to remember they kicked back a lot but this doesn't.

The second issue is the bike has quite a flat spot at 1/4 to 1/2 throttle, this may also be timing related but the bike has a noticeable induction noise. The filter box is the proper one but the lid has been drilled which ill tape up for now. It sounds like an air cooled yam with the seat off and as the splash guard down the rear of the filter box is home made im wondering if the proper part acts as some kind of baffle for the air intake?

Has anybody got a picture of this model with the seat off ?

Hot and a flat spot sounds like weak mixture or retarded timing, possibly both.

Does the bike lack torque from just over tickover to near half max RPM? as this can be a sign of retarded timing.

Edited December 10, 201411 yr by dadof2

Its not pinking so i think timing is retarded. Being an old bike may not even be the right stator. Still think that there's something wrong with the air intake though

I don't know if these have fixed or electronically variable timing. If it only has a fine wire source coil it is probably fixed, if it has a separate trigger it is probably variable.

I would mark the flywheel at about 3mm and check the timing is about that with a strobe light.

Next I would mark the throttle at 3/8 open and ride it up a long hill several times with it pulling steadily at that throttle opening, then check plug colour to see if mixture is rich or weak.