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Old 10-16-2012, 08:36 PM
UrbanMadness UrbanMadness is offline
Motorized Bicycle Newbie
Join Date: Oct 2012
Location: Sacramento, Ca
Posts: 4
Default basket case, Mountain bike

I've got a Gary Fisher that's been a basket case. It's got a nasty Engine mounting stud habit. So far I've had to replace the studs on the back of the engine twice, but I did figure out part of the problem.

One, the original builder broke one of the studs off pretty deep in the case and then just put a new one in over the old one, so that it was kept in place with only about 1/2 the treads before it would bottom out on the original stud. We broke an easy out trying to get it out, soooo we ended up building a mount, drilling a new 8mm hole and tapping it, welding studs to the bracket using the old holes for locating pins. I think it will hold, short of that, it will be time for a new motor which at this point won't hurt my feelings much.

I think they other part of the problem is the builder didn't use a chain tensioner so the chain would slap around a bit and bind in the chain housing on the motor, transmitting that torque thru the motor, thus breaking the studs. Does this sound about right?

Other problems include bike just not performing all that well. I only get about 15mph out of it and it in general runs like crap. We have cleaned the carb, cleaned and set the plug gap. It's like it pulls hard, then acts like it runs out of gas. We have also tried setting the float level in the carb. I thinking maybe I'm pulling a vacuum in the tank?

I need to get a new chain, and tensioner. I haven't had a chance yet, to test my tank venting theory, on this tear down, we actually did drill a hole in the gas cap, so when I get it running I'll test that. This bike actually really used to run strong (about a month ago). Maybe the petcock is plugged? I am running an inline filter and it has been changed and yes the direction of flow is correct.

I'm ready to entertain other idea's tho.

between my buddies, we have four of these bikes and this one has been the problem child.
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