Hard to start, low power

[ggreen199]

I just got a 2000 gz250 that won't start when cold. A shot of starting fluid will get it going. Once it is warm, it starts right off. There doesn't seem to be much poser at the high rpm's either. It sees 45mph in 4th gear. It struggles going up hills as well.

I browsed through the forum on related topics which gave me a bunch of stuff to try out. The problem now is that I'm out of ideas. What I've done so far is:

Had the carburetor cleaned. I replaced the diaphragm and the o-rings in the carb at the same time.
Had the carburetor cleaned. I replaced the diaphragm and the o-rings in the carb at the same time.
Put in some sea foam. I've gone about 10 miles with that, haven't noticed any change.
Replaced and gapped the spark plug, the old one was a little black but seemed ok.
Checked the valve adjustment.
Checked the compression. It was 120psi when cold. I put in a little oil and it went up to 130. I saw after that the compression should be done when warm but I haven't done that.
Took apart the fuel valve. There were a couple of flakes of what looked like paint on the screen.
Had the Battery tested, it was EOL, so replaced it.
Looked at everything visually to see if anything looks out of whack. Didn't find anything that looks wrong.


So what else should I check out?

[alantf]

Won't start when cold, but starts when hot? Sounds like a problem with the choke. These bikes need the choke (or fuel enricher to give it it's proper name) to start from cold. Check that the cable is free, and the plunger in the carb is working properly.

[ggreen199]

I've had the choke fitting off, it all seems to work. When running i can pull the choke and it speeds up like its getting more fuel. Still won't start when cold though. This won't affect the low power at high rpm's would it?

[alantf]

I mentioned this because I once forgot to turn the choke off, after I set off, and it gave me the same symptoms as you. The engine struggled and wouldn't accelerate. When I realised what I had done, and turned the choke off. the bike was back to normal, so that meant that the problem was too much fuel, not too little. But when you say that it will only start from cold with starter fluid, but starts ok when hot, it still seems, to me, to be a choke problem.

Something just occurred to me. When you say that you turned the choke off, and the bike speeded up, are you sure that you're using the choke correctly? To use the choke, pull it towards you. To switch it off, push it away from you.

[ggreen199]

Ah, that's good to know that it would act that way.

I had thought it was the choke also. Have had it off at least 5 times checking it out. What i was trying to say with my bad grammar is that when i turn on the choke, the engine speeds up, . And when i turn it off, the engine winds down. So I am pretty sure the choke is at least partially working.

The repair manual has a long list of causes. What is common between hard starting and low power at high speed is valves. So I think I'm going to take the head off and have a look.

[tintinnabulations]

My 2004 doesn't like to stay running when cold and I have to leave the choke on for quite a while before it'll idle. The guys at a local bike shop told me I should re-jet it with the next size larger jet to allow better fuel flow; they said these bikes are notorious for running lean.

[alantf]

They run lean because of the American "nanny laws" regarding emmisions. All new American bikes are fuel injected. My European bike is set up fine, from the factory, and still passes the emmision tests in the two yearly examionation.