I have a 2000 Honda 400ex. I just got done putting a new cylider, piston, rings, and valves on it. It's stock. It starts fine when on choke, but once it warms up, it won't idle when I take shut off the choke. I've taken the carb apart twice to clean it and the second time I put a new carb kit in it. I'm out of options.....any suggestions? It runs strong and seems to have smooth acceleration.

Thanks,

Brad

 

Did you put in the new pilot jet?How many turns out is the mixture screw?

 

I put in the new #38 pilot jet. The mixture screw is set at 2 1/4 turns.

 

Is this with the air filter and air box lid on? It sure sounds like its too lean on the idle circuit. Is the idle speed screw turned up far enough?

 

Yes the air box and air filter is connected. I'll clean the air filter to make sure it is getting enough air. Also, I noticed that some people in the forum switched the pilot jet to a #40, is this somthing that I should consider? Can the mixture screw make a big difference? Thanks!

 

Think of the pilot jet as the coarse adjustment, and the mixture screw is the trim to that jet. They work together.
Ive gone to the #40, and it helps the cold starting, by allowing richer mixtures.
If you have a new 38 in there, and it dies off choke, I dont think a #40 is gonna fix the problem.
Is th ecarb tight to the manifold..no air leaks?
How did the assembly go....valves adjusted right, valve timing correct? decompressor working right? Have you done a compression check?

 

Thanks for all your help. After taking the carb apart twice and making sure it was clear and clear, it still wouldn't idle. Therefore, I bought a compression tester and found out I only had 90 pounds of compression. I found that one of the exhaust valves were too tight. Once I re-set everything, I got about 150 pounds of compression and the bike ran great!

Thanks again!!