2004 rmz 250 idles but wont rev past idle HELP!

I have been helping a friend of mine put together his 2004 RMZ 250 that was taken apart due to a cracked bottom end. His old bottom end was unusable but the top end was left un damaged. He bought another bottom end off Ebay that was supposedly for the same year and model of bike. Everything appeared to be in working order. I put everything back together with the proper torque specs etc. The valves are in spec, I checked the timing multiple times and it appears to be perfect. Compression is good, the spark plug is good, and the carb has been completely gone through and cleaned. The fuel/air mixture screw is 2 1/2 turns out.


The bike will start up without the choke after 3 or 4 kicks but if you give the bike any throttle at all it dies. Even with the choke on the bike will sputter frantically then die. I thought it was the carb right away, after I took an excessive amount of time cleaning it and making sure the accelerator pump was operating I ruled that out. There seems to be absolutely no air leaks, the gas is brand new and ethanol free, the oil filter is brand new, the oil is new, the coolant is new, and the air filter is freshly oiled.


I just don't know what to do anymore, I have worked on this bike every day after work for the past 2 weeks and can't seem to come up with anything. My final hunch might be something to do with the time, although it appears to be set properly. I am not very knowledgable of ignition timing.

By the way, I am aware there is a CDI issue but the bike ran perfectly before it got the crack in the old bottom end and the bike sat for a few weeks waiting for the new bottom end.


Any help would be greatly appreciated

thanks, Cody

Anybody have any ideas?

Hmmm...i know you said you cleaned carbs but id check the main circuit again. Run a guitar string through all the holes. Check your needle. Also check the float level..

Id also go through all connections relating to ignition. Clean with sand paper and reconnect with dielectric grease.

Also check plug gap.

If cdi was faulty it wouldn't work in my opinion.

Lemme know

Alright, so I went through the carb again and thoroughly cleaned it. Which needle are you referring too when you recommended checking that? I believe that it may be ignition related. The spark plug gap is good and the float level is good. The reason I think it is ignition related is because I have set the timing 3 times in 3 different places. All 3 times the bike ran the same way, idled perfect but died when given gas. Could the ignition timing be off?

Just a guess, but the cdi for an 04 (0038) will only work on an 04 bottom end. If you maybe have an 05 or 06 bottom end, you need the 0041 cdi, me thinks.

What is the difference between the 04 and 05 bottom end? Because I have a bunch of old parts from the bottom end that cracked.

So I am running an 04 top end with an 04 stator and 04 cdi. The rest of the motor is from an 05 rmz. Could that be the culprit?

Me thinks you also need the 04 rotor in there with ALL the other 04 ignition system.

Alright, I figured it out! I simply took the stator and the flywheel off the cracked bottom end that was originally on the bike and replaced it with the stator and flywheel on the 05 bottom end. I fired the bike up and it ran perfectly! Thank you so much for the help everyone! 

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