2005 GZ 250 idling problem
 

I have adjusted the throttle cables, and set the idle adjustment. It idles ok for a while, then speeds up. If I let out the clutch a little it slows down, then when I engage it, it speeds up again. It does this when I ride and stop. I noticed what looks like a crack in the intake tube so I ordered a new one. Does anyone know if I can replace it without removing the gas tank?

Are we talking about the tube between the carb and the engine?

You CAN remove it without taking off the tank. But, honestly, it's going to be much easier to just pull the tank and do your work without having to cram your fingers in tight little spaces.

Removing the tank takes all of 2 minutes. It's just 2 bolts, the gas line, and 2 vacuum hoses.

Absolutely remove the tank as Jonathan suggests. Why fight for a little finger room when you can create lots more and also improve the ease of the repair. Just the added visibility is a bonus.

I would like to thank you Jonathan, and Water Warrior for your reply. That's what I wanted to know. I will remove the tank. Plan to do it tomorrow or Thursday. I'm hoping that's the problem, the tube between the carb and engine. I'll check a few other things as long as I have the tank off.

They either age and crack around the intake neck, so a vacuum leak here isn't unheard of. I've not seen a crack on one, but it's withing the realm of possibility.

While you're in there, check out the condition of your vacuum hoses. If they are brittle, go ahead and replace them to avoid having to search out another vacuum leak in the future.

Vacuum hose should be available at any auto parts store. Take in the old hose to get the right diameter.

Well I changed the tube and O ring. What I thought was a crack was just a deep scratch possibly from some tool used before I bought the bike. I checked the hoses and they seem fine. I took it for a ride and it was still messed up. When I'm moving it's fine but when I stop it either speeds up or slows down so much it stalls. Not too happy.

Don't fret yet. This is going to be an easy fix once we nail it down. There is only so much that could be causing the vacuum leak, which is causing the hunting idle.

Check to see that the drain tube out the bottom of the air box is plugged. It is supposed to be plugged to keep unfiltered air out and to keep oil blow-by and other crap contained until the rider can properly drain it.

Take come WD40, while the bike is running and spray different parts of the intake system. Feel free to be liberal with the application. If you spray the WD40 over any area that is sucking in air and it shouldn't be, the idle will change. This can help you zone in on where the leak it, at best. And, at worst, you have a clean and shiny carb and hoses ;)

Have you had the carb removed or worked on lately. There is a thin rubber diaphragm in the top of the card that often gets squeezed or pinched when people are messing with their carbs. (How me how I know. And ask me how 3 hours and some epoxy took care of it.

Start there - it'll tell you a lot. Let us know.

Well I tried the WD-40, checked the hoses again. The plug is on the end of the drain hose.While it was running okay I turned on the choke to see what would happen. It raced and when I turned the choke off it still raced until I turned off the ignition and restarted. Then it was fine again. I AM PUZZLED.

Just to clarify the wording. When you let out the clutch you are engaging the clutch. Pulling the lever in will disengage the clutch. Proper terminology will keep us and you on the right path.
Have a question. Did you have the irratic idle before adjusting the throttle cables??

OK, when I SLOWLY let out the clutch lever the idle slows down and when I pull the lever in it speeds up.I do this when I am stopped and my brake is on, just so it doesn't race for too long especially at a traffic light. I did have the irratic idle before I adjusted the cables which is why I readjusted the cables. I don't really think that had anything to do with my problem but I tried anyway. I could be wrong.I'm no expert that's for sure.

Okay. Just wanted to eliminate that as a possible cause.

Today I rode until almost out of gas on purpose so I could fill the tank with premium octane gas. I thought it would be worth a try. I'll ride tomorrow to see if I have the same issues.Maybe the carb needs to be cleaned and new jets. I'm lost. Maybe it's something else. I've been reading other posts and it seems like there are a lot of these bikes with the same or similar trouble. I thank you guys for helping me out. At least I can eliminate some possibilities. Maybe the floats are sticing. Lots of maybes. All I can do is try the different things you're telling me.

No need for higher grade gas. GZ designed for 87. Perhaps Seafoam with that fresh gas would help. Never hurts to use Seafoam. It keeps the GZ happy. As Jonathan and Water Warrior 2 suggest, clean the carb. check air cleaner and spark plug. That plug fouls easy.(At least mine has in the past) Goodluck and happy riding.

Thanks for the reply. Probably no need for the high octane gas but I try the easy things first. I do use B-12 Chemtool every other tankful. I've heard it's better than Seafoam from other riders. I did change the air cleaner but haven't checked the sparkplug. I will do that this evening. I'm leaving the carb removal as last.

Definitely no need for high octane, unless you are a money launderer out of options!!.

Well I think I've run out of options. Do you think I should just rebuild the carburetor? If so, where's the best site to order one and what would be the correct one to order.

Wait for one of our more senior members to respond before buying a new carb. Jonathan and Alantf are pretty good with carbs. and idle adjustments. Idle adjustment can be a pain. If you do not have an ear for RPM's, you need a tach.

With the idle - some people set it too low. With the engine HOT, it should be between 1200 and 1400 RPM. If it's set too low, the bike will try to shut off when you release the throttle. Is this what you mean, or is it entirely different? When you're stationary, out of gear, there should be no difference with the clutch lever in or out.

When I'm just sitting on the bike it speeds up and slows down. I bought a K&L carb repair kit and did it this evening. I'll have to wait until Thursday to go for a ride due to bad weather tomorrow. I took it for a quick ride when I finished and it seemed better. I'll let you all know.

Well the carb rebuild kit didn't do the trick. I'll wait to hear from Jonathan or Alantf. My buddy keeps telling me to just buy a new carb but they're not cheap.

When I set the idle it sounds perfect. After a few minutes it just speeds up to about triple the correct idle speed without me touching anything.Then I turn off the ignition and restart and it's ok again.

I don't know much about carbs (my knowledge is mainly electrical), but, do you think the throttle slide may be sticking open, after you've accelerated away?

try to set the pilot screw be twin 2.5 and 3 turns from the close position

Where is that screw?

Is that the screw with the white knob?

That's a possibility but how would I know that? When I removed the carb to do the repair kit I sprayed the inside of the carb with carb cleaner. Would that free it?

pilot screw (pilot jet)

Thanks Raul. I never knew there was a screw there. I'll check that out in the morning. I hope I can adjust it without removing the carb, maybe using a mirror if I have to. I wish I knew about this before when I had the carb out to do the repair kit.

thees 2 pdf are a good reading

adjusting the carburetor
https://onedrive.live.com/view.aspx?...LXqjwWYP15aWi8

mikuni carb theory
https://onedrive.live.com/view.aspx?...EfGAdFO4PPypws

WOW....that is very confusing for me. I'll mail you the carb haha

I checked it out with a mirror. I'll try to tilt the carb after loosening the clamps and removing the necessary hoses and then do as you said, remove the plug and adjust the screw. I hope it works. I hate to remove the carb again but if that's the cause I'll be happy.

page #9 of mikuni carb theory explain haw to remove the plug

I recommend to read the book explain on very simple way haw the carb work and haw to tun it

Someone told me it could have a blown head gasket. What do you think? How would I check for that if it is a possibility?

A compression test would reveal a blown head gasket if everything else is in proper order.

What should the reading be? I guess it's time for a mechanic.

Not sure what the actual compression should be. Some one with more knowledge will be along shortly though.

You may be able to borrow a compression tester from a local auto parts store in your area. Some one who has done the test will walk you through the procedure. Actually quite easy.

Thanks, I think I'll see if Autozone will do it if I pull the plug. If not I'll see if one of my friends has one....stupid me, I looked in the manual and the reading should be standard=142-149psi and the limit should be 114psi. I'm keeping my fingers crossed that it's ok and no blown head gasket

low compression can be valves to tight check them before you pull the head

Thanks for the reply. I went to Autozone and they charge $40.00 to rent a compression tester. Won't be doing that. Went to a motorcycle service shop and it's $225.00 for a tune up...plus parts. Don't know if I'll be doing that either. I think I'll probably just keep riding it the way it is until the Fall season and wait until next Spring to do something. Maybe I'll go to the casino.