Sunday, June 22, 2008

Carburetor Tuning

I'm starting to have carburetor nightmares that wake me up at night.

Since my last post I determined the bike is running pretty good with 180 main jets at 3/4 to full throttle but everything else sucks. Won't idle, can't start it without manually priming it, backfires constantly at low-to-mid throttle, just not right. Adjusting the pilot screw doesn't seem to affect the way it runs at any setting. I began to wonder if the 180 was really too lean. Tried 190's and well... everything sucked again.

Put the 180's back in, tried my best to make certain the pilot jets were absolutely clean, adjusted and synchronized the chokes and synchronized both throttle slides. I then dropped the needles to the middle position. Bike ran well at 1/4 to 3/4 and 3/4 to full throttle. It refuses to idle at all and I still have to prime it to start it. I had to adjust the pilot screws all the way in (full rich) and still effectively ran out of adjustment. Tried dropping the needle to the bottom slot (richest setting). It doesn't run quite as well at mid throttle but the throttle opening and pilot screws actually now do something when you adjust them. It will now idle at about 3000 RPM but it dies if you drop the idle below that.

Something about the pilot circuit just seems screwed. I'm at a bit of a loss for what to do next. Dad may help me check the timing later in the week, it really seems like a two person job. I don't feel like I'm making any real progress, just "sweeping the same pile of dirt around the garage floor over & over." I just noticed it seems to be leaking oil from the head gasket after it's been running for several minutes.


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