QuestionHi Mark,
I'm back with my cursed GZ 250 (2001). A quick refresh, I had the heads replaced in the bike, then it started to give me problems such as idling high, cutting out and backfiring, stalling and not restarting for ages. I got a new diaphragm installed and the problem didn't really go away, but certainly improved.
I dropped it in again, and explained the following: The bike can drive beautifully for 2 - 10 miles, then I will have poor response from the throttle, usually as I come from a high speed (for my bike that is :-)) to a lower speed and try to maintain about 30/40Kph - I will notice the bike starts to jump and hunt. As I close the throttle, it may not respond for a second or two, I get the same effect on opening it again - nothing then a surge and off you go - you end up trying to second guess the effect opening/closing the throttle will actually have. After this problem starts, it always reults in a stall eventually. At a junction, I will try to move off but the initial degrees of throttle opening kill the engine. If I stop the bike, kill it and start it again - it turns over nicely - but if you touch the throttle it dies a death. I've noticed that if you open it enough that the bike will get some power but the first quarter of the throttle opening will certainly kill the engine. Given a few minutes it will return to normal and then the cycle starts again. I've also noticed that whenever I start the bike, and try to pull off that there is some sort of 'weak' spot. It moves off then dies for a second and dependent on her mood either keeps going or leaves me rolling with no power. When the bike is not giving trouble (e.g. long stretches at full throttle, or when I am driving very easy) it drives like it is brand new, a beautiful smooth comfortable ride. After I dropped it in the last time, they said they cleaned the fuel system - it ran fine for about a week around the city, but it raised it's ugly head out of the blue.
I am a very AMATEUR enthusiast as you might say, but from what I've read I am wondering if there is something wrong with my pilot jet in the carb. This seems to be the one that has 100% control at low throttle openings and a relatively lesser effect as it is opened. Could it be jamming?
Anyhow, you are the expert - so I'll leave the diagnosis to you. Once again, thanks for your timely, prompt, polite and accurate help. You inspired me to get my hands dirty with this thing!
Regards, Alan
AnswerHi Alan,
The carbs will need tweaked to correct the air-fuel mixtures. You spot-on about the pilot circuit.
Send me an email and I'll return plenty of carburetor tuning "tech" files for you to review. Review the files and I think you'll find the source of the problem.
Describe the appearance of the spark plugs in your email. Have you measured cylinder compression? If not, why not? I'm just kidding! : ) Check ccompression if possible.
Knowing the term "hunting" I suspect your skills are above elementary. : )
Send to my email: mshively1@woh.rr.com
Respectfully,
Mark Shively
