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View Full Version : 01 ex won't rev past half throttle after warm


sanders86
10-22-2011, 11:11 PM
I was wondering if any of you had ever had a problem like this. My 400 starts and runs great when its cold. It will run for 2-3 minutes with no problems through all rpm ranges. After it gets warm it will not rev past half throttle it doesn't just miss but completely cuts out. Once it dies back past half throttle it picks right back up until the point it dies again. Nothing has been touched on the carb, and I've ran it with the same jets and settings for the past 3 years. The air filter is clean has a brand new plug in it also. It also starts smoking some when it does it but I figured it was just the raw gas that wasn't being burnt. It was dark and I couldn't tell if it was black smoke. I tried a search and couldn't find this specific problem either so sorry if I overlooked a common issue. I thought maybe my coil was getting to hot, but I'm not sure? :confused:
CJM
10-22-2011, 11:46 PM
Sounds either to rich or your rings are worn out. Is it burning oil?
sanders86
10-22-2011, 11:53 PM
Very little and only on startup.
CJM
10-22-2011, 11:58 PM
Then thats your valve seals, not a huge worry but they do need to be replaced one day.

Start with the basics, fresh gas, adjust the valves, clean the carb, etc.
sanders86
10-23-2011, 02:41 AM
OK, thanks man I'll find my set of feeler gauges and adjust them tomorrow. See what that does for me. I haven't adjusted them since I got the thing 3 years ago anyway... :eek2:
Pipeless416
10-23-2011, 09:40 AM
before digging into it, just quickly make sure your choke is not on. those are almost the exact symptoms.
sanders86
10-23-2011, 05:20 PM
No I wish it was as simple as the choke. Now that you mention it though yes it is acting exactly like it would if the choke was on. I did adjust the valves today and it hasn't acted up since and seems to be much more responsive. It sure did make the valves a lot louder though...:huh
B.C.#11TRX400EX
10-23-2011, 05:56 PM
I had that problem before and it was my needle arm, it came unbolted from the cylinder in the carb and it would only go half throttle then just rev up, but just open the carb up and check it out before u open the engine up