KX500 AF Running like a 200

[RKPerformance]

So i just picked up a new to me 2000 KX500AF scoot.  Took it out for the initial run and it is a major dog compared to my CR500.  This thing will barely, i mean barely pull the front wheel in first.  So I start looking into things including the jetting.  It has a FMF Fatty pipe with fmf silencer...rest is stock.  162main, 52pilot.  Seems reasonable to me, but it runs so crappy i think maybe it is lean.  Put a 168 main in it and it wouldnt get out of its own way at all, now runs like a pw80.  Check the compression it is 150 after a few kicks with shoes on cold.  So then i decide to check the needle and i find a n4we needle in it.  Never heard of that needle before and from what i can find it belongs in a kx250?  Does anyone know why that needle would be in there and if that probably has something to do with why it runs like a pile of crap.  Is 150lbs acceptable comp?  Any help would be appreciated!!

[kxpegger]

Pull the KIPS actuator/rod cover off on the right side of the cylinder (rectangular silver plastic piece). Start the bike up and see if the KIPS rod is pulling in and out smoothly when you give it some gas. Sounds like your exhaust valves may not be working correctlty.

[RKPerformance]

I will check the powervale operation, but im thinking this needle that is in here has the bike all jacked up???

[don46]

I don't think it is the needle, not sure which you have but I run the 250 carb bored to a 40.5 and use the 250 needle and have no issues.

[Goat]

I too have run the 250 carb and needle before with no issues. Running a 38mm Pwk with #7 slide and 250 needle in my 87 for the past 3 years.

Hows the spark plug look? Pull the pipe and look at the piston skirt. Could be a crank seal which is the same issue I'm going through with my 87. If the plug is dark it's too rich and could be caused by a leaking right crank seal. If it's white it could be the stator side crank seal.

[alward25]

Might be the air filter, there was another guy on here that went to replace his air filter and eventually got to the bottom of his problem.  He started a whole thread about it.  The other ideas are good too.  plug,reeds,crankcase seal, KIPS.  i had a mouse build a nest in my pipe once.  It was strangely quiet and ran like butt. 

let us know what you find out!

[RKPerformance]

Well I took the rod cover off and the pipe off to check operation of the valves.  Rotating the arm all 3 valves appear to move and close as they are supposed to.  I noticed a little coolant in that rubber elbow that houses the rod lever.  No idea why there would be a little coolant in there??  Piston looked really good as did cylinder.  One thing troubling to me was the pipe.  It is a FMF Fatty pipe and whoever did this conversion really rammed this pipe in there.  The neck bend coming off the cylinder is pinched very very tight. I dont know hoe it can breathe. Also near the end of the main expansion chamber the pipe is smashed waay in for clearance issues.  Im starting to think this pipe is a major restricting point on the bike.  The frame is a 2000 kx250AF.  DOnt know who did the conversion either so i dont know what kind of pipe i can use to try and see if another pipe is better>>>?

[USMC 500]

Might be the air filter, there was another guy on here that went to replace his air filter and eventually got to the bottom of his problem.  He started a whole thread about it.  The other ideas are good too.  plug,reeds,crankcase seal, KIPS.  i had a mouse build a nest in my pipe once.  It was strangely quiet and ran like butt. 

let us know what you find out!

Gee Alex, who could that guy be that you are speaking of......

[RKPerformance]

Here is a pic of the neck

[RKPerformance]

Here is the pipe near the end.  I know it is hard to tell how far in the dent goes but it is huge and goes for a long ways, same with the neck bend it is amazing air can flow thru it!

[Goat]

Those dents seem to be a bit overkill. It should still run better than described though. I'm not sure if you can get just the pipe or not but Service Honda was building pipes for the aluminum frames at one time.

[RKPerformance]

Frame is a 2000 KX250
Pipe is a FMF Fatty
No idea who did the conversion, but the welds and overall conversion look minty

[Charlie500]

Well I took the rod cover off and the pipe off to check operation of the valves.  Rotating the arm all 3 valves appear to move and close as they are supposed to.  I noticed a little coolant in that rubber elbow that houses the rod lever.  No idea why there would be a little coolant in there??  Piston looked really good as did cylinder.  One thing troubling to me was the pipe.  It is a FMF Fatty pipe and whoever did this conversion really rammed this pipe in there.  The neck bend coming off the cylinder is pinched very very tight. I dont know hoe it can breathe. Also near the end of the main expansion chamber the pipe is smashed waay in for clearance issues.  Im starting to think this pipe is a major restricting point on the bike.  The frame is a 2000 kx250AF.  DOnt know who did the conversion either so i dont know what kind of pipe i can use to try and see if another pipe is better>>>?

I'm pretty sure they didn't make aluminum frames in 2000... Did you buy this bike from the ktm dealer in medford oregon?

[motopunk]

first kx-f aluminium frames were build in 2007 .
 i think only your engine is a 2000 . 
 i also think you should buy the stock needle for the kx500E-models and take the dents out of this pipe,as much as possible. check the crank seals, base gasket and reed insert for air leaks.
 
thats the only way to solve that problem... 

[alward25]

2006, close enough