idle problem
 

Recently bike has become hard to start and idles poorly. Runs OK when at operating RPM
(going down the road). When I adjust idle to good level, it will maintain this RPM for
10-15 seconds then idle down and die. Also, when engine is rev'd and throttle is
retarded back, the engine RPM slows down, slower than normal... It idles back
slowly, then after a few moments, idles down further and dies.
I've removed and cleaned carb (B12), fresh gas, new plug.
Problem remains. I can't seem to get it to idle.
I suspect some sort of air leak or misadjustment in an idle jet/setting. I'm unsure what
to look for. Is there a carb kit available? But, I don't think this is necessary. I'm
more inclined to think something has a slight clog, or there is an air leak...
Looking for the simple fix...

what year is the bike, how many miles ....

have you checked ALL your lines to the carb? i had one small air line to the carb come off once and cause this problem. havent had a GZ in almost a year, but i remember it was on the left side (if u were sitting on the bike) of the carb. it popped off and caused the same problem you are having. i may be wrong, but i think later on it failed (thin wall and it was collapsing) and i had to replace the line.

i would go over the bike with a fine tooth comb .. checking ALL air lines to the carb/tank, wherever. check the airbox ... air filter etc. really sounds like an air leak.

i'll try
 

this is a 2004, w/about 8,000 miles

the only lines on the left side are the main fuel line, and a vacume line that runs to the fuel petcock. This vacume line hold open the the petcock (when in the on or res posit). If the engine quits the fuel line is shut off (keeps from spilling fuel in a crash).

I'll look at that line closely. I don't recall seeing any damage, but there might be a leak at the petcock.

still no joy
 

i tinkered w/the vacume line. when i disconnected it ran just fine, but now is drawing unfiltered air into the air/fuel manifold.

i thought that might have been the problem, but now i'm begining to think i have an idle mixture problem. the bike was bought and riden in Colorado (>6,500'MSL). it's now in Kansas (<1,500'MSL).

w/the line disconnected i've leaned out the mixture. i'm thinking i might need to change the idle jet. what do you think?

Re: still no joy
 

If you disconnect the vacume line that goes to the fuel petcock it should only run until the gas in the carburator is used up.

Re: still no joy
 

Well, yes, but I think he was saying that the vacume leak he created made it idle better......up to the point that it died. Probably would idle for a fairly long time just on the fuel in the bowl.

So.........it does indeed sound like he is rich at idle. Could be a clogged air filter. Could be a plugged exhaust (not likely). Could be that the idle mixture screw just needs adjusting (fairly easy if the cover/plug has already been removed).

Just another thought on the bad idle. The hose might be porous and allowing some air through. Remove the hose and hold your finger over the fitting if possible to stop all vacumn at that point. Rule out the simple stuff first.

Uuuu........but it runs BETTER when it IS leaking! :??:

Easy Rider, you are absolutely correct. But it may be that it is now getting a more correct and constant air flow. My guess after that being ruled out would be the diaphram in the fuel petcock having a slight vacumn leak. Also checking the boot between the cylinder and carb for proper fit and tightness might be worthwhile. Vacumn leaks can be a real pain and bitc* to track down. Okay, I am done speculating so back to bed for me. It is 3:30 and far to early to be awake for the day.

What am I missing here.............
One does NOT suspect a vacume leak when the introduction of an additional vacume leak makes it run BETTER.
Right ??? :roll: