Dies when throttle is let off

[bughiker21]

Hi Guys
I have a 2001 GZ250. I had trouble starting the bike, so I cleaned the carb and flushed the gas tank. That did the trick. The bike starts right up. Now the problem. When the bike is running and I let off the throttle the bike will die. This is when the bike is cold or hot. As long as I feather the throttle the bike will stay running. When it dies it will start right back up. Yes I use the choke for cold starts. I am using 87octane gas with no additives. Let me know what is going on?

[alantf]

Have you checked the idle speed? When the engine is HOT, you need to screw the big white knob so that the idle speed is between 1200 and 1400 RPM. Sounds like it's set too low, so the engine dies.

[raul10141964]

if you move the pilot screw set it to two turns an then adjust the white knob

[blaine]

if you move the pilot screw set it to two turns an then adjust the white knob

Two turns out is just a good starting point.The pilot screw (idle mixture adjustment) needs to be adjusted with the engine idling & warmed up.Adjust slowly to obtain the highest & smoothest idle.Than you can adjust your idle.
:) :cool:

[bughiker21]

Thanks everyone. I adjusted the idle speed when the bike was HOT and now the bike stays running. On my GZ the pilot screw is covered with a plug. I did not want to mess with that again, right after I replaced the plug when I cleaned the carb. Thanks

[bughiker21]

OK, my bike is giving me fits again. Two things have happened. First my bike was running fine with no idling problems. I took a long trip about 40mile then bike started to back fire and then started dieing at every stop again. I adjusted idle speed and the bike ran fine the rest of the trip. Then this morning was a cool morning, bike ran fine to work, but on the way home when I apply throttle it revs high and stays high when I let go of the throttle. When it does come back down to idle the bike dies. My work is only 5miles away. What have I done?

[jonathan180iq]

When you rev the throttle and it stays high, that indicates that there is a lean condition in your mixture somewhere. You have some sort of air leak in your intake and you need to track that down and correct it. It could be a loose vacuum hose. It could be a loose carb boot.

I would pull the gas tank and give everything a once over. That's just good maintenance practice anyway. :)
For a poor-man's air leak test, take your can of WD-40 and, with the engine running, spray it at different connection points on your intake. If the idle changes at all when you do this, then you know where there is a leak.

[rotrekljohn]

I am having this very exact same problem. Can anyone help us? Got the diagrams, the ability to comprehend,and the tools. Point me in the right direction guys! Also, my "module" under the storage gives me a clicking noise now when i go to test fire it. My battery has died several times during all this which I think is making that module click, am I right? Recharged it about 6 times since new about 4 mo. ago, but mostly due to this problem. When it ran good, it would occassionally backfire at shutoff only? Any ideas? On the starting problem, I know it's not the external idle adjustment.

[mrlmd1]

rotrekljohn - I am having a hard time trying to understand what you are saying, but as far as your battery goes - and here it is again - if you bought a new AGM battery and never bothered to charge it up fully yourself before you first used it, despite what the guy in the store says, it will never hold a full charge and will keep dying until you can't rejuvenate it anymore.
That clicking is a relay and is making that noise because of the low battery voltage.

[rotrekljohn]

Ok. Well my carb has been cleaned and it started fine and was in cold start choke. Started fine, but idled high, evntually idleing down and dying. Won't ever start on second try but only starts after each carb rebuild only to die. Any other suggestions?

[jonathan180iq]

If your bike was popping on shut off and was exhibiting other symptoms of being lean, then I would wager that you have an air leak somewhere in your intake system (or a clogged jet) and it's not letting the bike do what it needs to do to run properly.

I would inspect all vacuum hoses, the condition of the carb inlet and exit boots, and ensure that the mounting flanges that connect your exhaust to the bike are all secure. Once that is done, move on to the carb issue.

If you spray starter fluid into the chamber directly, can you get it to fire? If you can, then you know you have a fuel problem.

[rotrekljohn]

No. on start up the bike runs at a good rpm, but kinda high. runs for about 4 minutes before I put in reg choke and can put on reg choke but runs for about a minute there, before it starts to peter-out, unless I rev it, in which case it'll rev high for about 20 sec. then peter-out, unless revved, then cycle repeats.

[rotrekljohn]

As one guy said here, got fire, gas, and air.