Exhaust Valve - Well I think

[c-152]

I think I am having trouble with my exhaust valve opening and closing properly.  I had to pull of during a hare scramble today (The trail was extremely tight with no chance to open it up) because I couldnt keep it running.  I would come over a short hil and get on it and it would die.  I have run it in tight stuff before and never had this problem.  I noticed when I replaced my clutch that the valve didn't open and close well.  I have a clymer manual but It doesnt tell you how to check it out.  Anyone have any ideas or am I barking up the wrong tree.  The main reason I think it is the exhaust valve is because I pulled the side cover off to replace the clutch and it has been acting this way ever since.  It starts fine and seems to run clean until it gets hot then it just stalls out.  I assume that it is something I screwed up while puting the thing back together but I do not see how.

[hughes]

I could be wrong but I think the engine would still run and make power even if the power valves were stuck. My bikes low speed idle sucks with the hot weather hard to keep it running and stalls from time to time. Give alittle more info about the power problem you had.

[openclass]

Hughes is right, it will run fine. I once got a wild hair. I though that by disconecting the the power valve I could ride a two hour harescramble faster sence it wouldn't hit so hard. It ran fine for the race but it wasn't fast.

It sounds to me like your having jeting problems. If its bogging down after long periods of slow running, you are probilly a little fat on the pilot jet which is dumping to much fuel in when you first crack the trottle, but not reving high enough to clean it out. It may want to foul a plug, on the next cold start. I had to put a new plug in before every ride, Especially if it was a tight race.

[hughes]

We rode some real tight single track this sunday and with my bike I had to clutch it alot to keep it running at those low speeds and the 98 degree heat. Yes I could have made some mixture adjustment with the air screw but I was hot into this trail and didn't stop.

[Hillclimb#42]

 Possibly, fat on the mixture screw or pilot jet. That mixed with tall gearing. Also my k5's clutch adjustment loosens up when it warms up. It slows idle somewhat while in gear, and needs tightened a little. You Global members keep bringing up the jetting chart. I had excellent results with it. Where are you according to that? Is it hard to restart also?

[hughes]

http://www.kxriders.com/forums/index.php?page=11

Here's the chart just in case you didn't know where to find it.

[c-152]

Thanks for the great info guys.  It sounds as if you guy are saying that the exhaust valve wouldnt cause this kind of problem even if it were completly broke.  To give a little more info about the problem - After about 40 minutes into the race on a tight trail with no chance to open it up, I had to constantly clutch and rev or risk bogging and stalling the bike.  It would fire back up okay but then bog again.  I know some of the time it would stall due to operater stupidity but it was getting tothe point that I had to be on the pipe all the time or it would just cut out.  Towards the end before I pulled out, it would cutout as I was getting on the gas.

I will check out the jetting mixture then go from there.  Thanks guys

[hughes]

Mine does that same thing during the summer heat. I try to stick with same jetting for fall,spring,summer and winter. My bike runs strong until the weather gets around the 85 plus degrees and the low speed suffers. Strong off idle and midrange and top but low speed I'm always clutching it to keep it running.