97 ktm 300 Wont Idle Down

[ronlikestobike]

I have a 97 ktm 300, Its in Immaculate shape. The top end, and Bottom end rebuilt with all new beaings seals, etc. 1.5 years ago.
After a long Run, its not ideling down, Almost like a lean condition. To just sit there and rev it in neutral, it idles down fine, however thats quick blips of the throttle. After a 3rd or 4th gear run however it doesnt like to idle down. However Im running a 45 pilot in the Kehin carb. However My silencer packing is completely gone, so its almost like a free flowing exhaust, maybe that could be it, causing an excessively lean conditon? IM running in about 45 degree temps, and it is a bit boggy on the bottom end. I have checked carb boots, etc, no air leaks?
Any Advice appreciated!
Thank you!

 

[Matt90GT]

1.5 years is wore out on a top end. ANd if it has sat without use that long, your seals are dried up.

You have an air leak. Plain and simple. use some carb cleaner around the carb, carb boot, left side crank seal behind the stator, base gasket and reed gaskets. you will find it.

 

[ronlikestobike]

Its had about 500 miles on it in that time, it has WONDEFUl compression, and excellent pull in the mid to top. Im thinking POSSIBLY a left side crank seal. Am I correct that those can be replaced without splitting the case?
Thanks again!

 

[whenfoxforks-ruled]

You can have great compression, and the rings are past service. Sounds like a lean condition though, old age. That black rubber they make seals out of does not last for ever. Vintage Bob

 

[ronlikestobike]

Can I replace the crank seals without splitting the cases in the ktm?

 

[uts]

1.5 years is wore out on a top end. ANd if it has sat without use that long, your seals are dried up.

You have an air leak. Plain and simple. use some carb cleaner around the carb, carb boot, left side crank seal behind the stator, base gasket and reed gaskets. you will find it.

Assuming his top end is worn is not helping anyone. I really don't understand why a worn top end is automatically assumed around here. After 1.5 years my top end is not even close to worn out, but ooh I better change it anyway, because some dude on DRN forum says so. 2 stroke top ends do not usually require changing anywhere near as often as most think, and telling people, better change ya top end because it's worn, without any evidence of this is wasting their time and money.

Your advice about the air leak seems like good advice though, because it matches the symptom.

 

[ronlikestobike]

Yes, I know the hours on the current top end, and baring some horrible jetting or other issues, it should be in good shape. I got 3 years out of my first 300 and still 178 lbs of compression. I usually spend more time in the low and midrange, but I appreciate the help!
So, I sprayed fluid around the base gaskets, the carb boots, and any other place That could possible leak air, the idle didnt raise, so by process of elimination, Im really leaning towards the left crank seal. I believe I just pull the flywheel and stator, and dont need to split the cases, correct?
Thanks again for the help!

 

[ronlikestobike]

O.k, I had a SMALL, VERY small smidgeon of oil on the flywheel side, However I have sprayed the bike with carb cleaner all around the carb boots, bottom end, behind flywheel and stator while running, and I cannot get it to idle up?????
It ONLY does it after running through the gears, .and after its warm (after about 10 minutes). I can sit there and blip the throttle a million times and it idles back down fine, I was really expecting it to take off after spraying behind the flywheel??
Anywhere else to check? The small smidgeon of oil suggests the left seal, however its only enough to wet a paper towel?
What am I missing? Could the silencer and lack of back pressure be contributing?

 

[uts]

Crank seals on most bikes come out without splitting cases.

Sounds like a tough one, is it possible your throttle slide is sticking on occasion? Sounds kinda like an air leak that is only there when the bike is at full operating temp. Small amount of oil like that around left seal is ok, I have seen this before on a perfectly operating 2 stroke. Have you cleaned the carb, could be a slightly blocked pilot circuit

 

[whenfoxforks-ruled]

If the left main bearing is going out, it may only leak under load? Did the old piston have blow by?

 

[ronlikestobike]

IM pretty sure its the Left seal, It does it even barely pulling into the midrange, really not underload. There is no play that I can tell. IF anything Im running rich in the bottom end with a 45 pilot only 1 turn out as I was trying to figure if it was a lean pilot circuit, fair amount of splooge, when Im ruunning in the low ened, but the plug looks excellent. I think, since its relatively easy, I should just replace the seal to eliminate it if nothing else?
I know I said it wont Idle down, but it does, it just takes a few seconds. On my other 300, when the left seal started leaking it was VERY obvious, after a 5th gear pull it would rev towards the moon for a second or so?

 

[whenfoxforks-ruled]

The fine art of catching it before it blows?