I guess my carb cleaning didnt help my "stalling after 45 minutes" problem. go figure. My valves are chattering though. I also found out that my radiator fan fuse was broken in two. I replaced it and verified the fan and temp sender are working. however after a hard 30 minute ride and a long steady hill, the power dropped off and eventually backfiring started again. i could push the primer on the side of the carb for a brief burst of power, but that was all it would do until I let it idle for a bit, then full throttle, then sputtering. The engine wasnt too hot, I could hold the hose with my bare hand, it was 30 degrees outside also, so I dont think it was overheating at all. My exhaust was pretty hot though, but I couldnt tell if it was glowing.
When I cleaned the carb, it wasnt really dirty, all the lines were good, nothing nasty aside from a drop or two of water came from the float bowl. The tank was removed and flushed, just some bottom floaties from gas cans, and im running all new gas just pumped today. im hoping this eliminates my carb as I would think it would mess up before 30 minutes.
I guess what this novel is asking, is could a valve be causing this brief backfiring and sputtering situation by hanging or floating after warming up? its due an adjustment for sure. thanks.

 

Most certianly check those valves. But also at 30 degrees out jetting does become a factor. Check your plug and see how the engine is burning, depending on that go from there- but first and foremost check those valves.

 

If you can hear your valves it won't cause the problems you are having. You will just loose a bit of power because they aren't opening as much as they should. You should adjust them though.
This statement speaks volumes. For some reason you are running out of gas. Could be many things. Are the carb vent hoses clear? Is the tank vent clear? Put new fuel filters on even though they may look good. Water can plug them up if they are paper. Check all gas lines to the carb and make sure they are clean and clear. Also check the carb needle valve.
For some reason this thing is not getting gas. It's up to you to figure out why. Let us know what you find.

 

If the timing of the sputtering stays the same it sounds like you may have a plugged tank vent and it is vapor locking. When it starts to exhibit the backfiring and such, have you tried to pop the gas cap off?

 

I thought all the same things, so I took the carb apart (on the machine) a few weeks ago, all gas, vent lines were cleared, float bowl cleaned, cleaner sprayed through every concievable place. Everything was looking good. I have ran it without the gas cap and get the same results. I have had it at a dealership 3 times for this and I dread going there or anywhere else again. It would cost me a fortune. I think its time to remove the carb and take it somewhere for a rebuild, or even just replace it. As disapointing as that is for a 2002 machine with 141 hours......

 

I wouldnt pitch the carb just yet. Its gotta be something fixable.
I know you said you cleaned the vent in the carb, but it sure sounds like what is wrong. Did a wire go thru it? If its resricted, or closed up some, it would evenually cause a pressure build up in the carb and not let gas in. Look at my photo page and the picture of the carb float bowl shows the vent sticking up. That brass tube and the rubber hose that extends past the carb, need to be able to vent. Have you tried running without that rubber tube on the bottom of the carb yet? You should be able to easily blow thru the brass tube.
Valves could cause a backfire, but it wouldnt come and go. Lean is whats causing the backfire. If they are making noise, there shouldnt be a drivibility issue...only when they get tighter and quiet, then it can get very hard to start.
When it starts to cough and sputter...quickly pull the choke on( this will richen it up, if theres enough gas in the float bowl), and see if it runs better. If it does, then youll know its a jet or something plugging. If it doesnt improve, then the float bowl may not be full enough. That primer has its own supply for a couple squirts worth, even if the float bowl is dry.
Bottom line..I think the float bowl isnt keeping enough gas in, now and then, and this causes the stalling.
I was hopeing you got it fixed, when we hadnt heard from you in awhile. But dont give up...youll get it fixed.

 

I need to use it over the holidays, so I will just live with it until after the new year, then I can work on it in a heated garage and take the carb all the way off this time. I hate working on carbs, so I might just take it somewhere for a re-fresh.

Thanks for all the help so far, I will eventually figure it out. Hard when you only ride one or two times a month.

 

I wonder if it could be electrical then. A problem with the CDI when it gets hot and intermittently firing. What about the switch that throws it into limp mode? I guess also when it starts to sputter, can you pull the line from the fuel pump to see if it pumping? Also, try replacing the spark plug and eliminate that as a possible problem (eliminate the cheap stuff).

 

I personally think its electric, ive posted a thread or two about this problem. My dealership is convinced that its the carb, and they really dont troubleshoot, it juts sits there for weeks on end. After I eliminate all doubt that its the carb, it goes back in for warranty repair and I raise h$ll. they tell me the carb isnt a warranty repair item.

 

I had two 400 I kind of had the same prodlem not as bad thow. my 97 the dealer puta carb heater on it. and solved 99pct of the problem they told me that the snorkle was so long that the air would get so cold the carb would start to freeze up ride for a half hour it would just die when you came to astop Iwould go walk around the woods or water I was doing for ahalf hour get back on it would run fine the rest of the day started using isoheat to this help me alot the problem was only when it was cold 30 or below