Ktm no power at high rpm

Gents,

I have a 2012 KTM 300 xcw. i have recently had an issue with the bike bogging at high RPMs.  When you get to the point where the power band should kick in it stutters like bah-bah-bah and loses power.  It happening before about a month ago and I did the following which seemed to fix the issue  

- New piston and rings and gaskets 

- changed oil, spark plug, and coolant

-replace exhaust gaskets and repacked silencer

- verified stator resistance reading were OK  

- checked ignition coil and found primary winding out of spec and replaced

I rode yesterday, power washed bike, and went for short ride to dry and the issue is back!!!  I check ignition cool and primary winding has no resistance. I am measuring the coil with it off the bike. Is this correct? When it is on the the bike the primary winding ohms OK.  I also drained carb and cleaned jets. Since I messed with so many items last time I'm not sure where to start but the issue seems to stem around water from the power wash. Any advice is appreciated.

 

 

Did you check the reeds out?

Is it dependent on throttle position? Mid vs WOT?

if so, Could be gummed up MJ circuit.

Do those have power valves? If so, make sure it opens.

 

 

I know this is pretty simple, but often overlooked.  Did you use a little dielectric grease on the spark plug boot before you put it on the plug?  If getting the bike wet with forced water that may be an issue.  And even if its not the problem its a darn good idea anyway.

I checked the reeds out on the last go around and saw no issue and I also tore apart the exhaust valve assembly cleaned and put back together.  It was running like a top until the wash....  I did not use dielectric grease, will get some though. 

Seems to be wide open throttle issue. Also it will rev fine in neutral.  

Seems to be wide open throttle issue. Also it will rev fine in neutral.  


Do you have any dirt in the bowl? The main jet is the circuit you should check out. May have some dirt in there.
While your in there take a minute and verify float height.

Already cleaned out the jets and verified float bowl height. 

Already cleaned out the jets and verified float bowl height. 

 

Did you spray and blow out all the circuits?

You probably did just had to ask

Yes sir 

I would re-evaluate if it was me
Power valve operational?
Main jet circuit?
Perform a leak test
Good luck

If it is water related then disconnect all your connections, blow them out and put dielectric grease on them all. Are all your connections sealed from the factory like my 500?

Just doesn't seem electrical to me but...

Do have all you vent lines on the carb and facing down?

 

A water sogged air filter and running really rich on the main already. ?

 

 

 

2 minutes ago, seer said:

A water sogged air filter and running really rich on the main already. ?

 

 

 

Rich on the main jet was my guess too. Could relate to your original bog issue too. 

Reeds are a wear item just like a piston and rings,

they may look fine with no apparent damage but they do wear out with usage and loose their tension,

moreso common with high revving small bore bikes (85-125).

 

Weakened reeds will 'flutter' at high rpm, create turbulence and kill top end power.

Edited by mlatour

i put a clean air filter on and went for a short ride with no improvement.  Could the MJ circuit be an intermittent problem?  I pulled it out through the float bowl and blew it out already with no luck. I am going to try doing a leak test on the engine case this week per gitenby suggestion. Also I figured out I was test ignition coil wrong it is OK. 

This sounds a lot like a plugged or too restrictive of a silencer.. I would remove the silencer (quick test) and see how it reacts

 

I live in a neighborhood and do my test runs down the street and back and no one seems to mind. I think a test run without the silencer may ruffle some feathers LOL. I repacked my silencer on the first go around about a month ago but I have been riding in a lot of mud and did plug it with mud after a nice wipe out and cleaned out with a stick while on the trail and just reved it up and blew the rest.  I will take the silencer apart and report back   Thanks 

 

 If you are on the edge of being rich enough to not get on the pipe a 10 degree temperature swing can have it be intermittent. 

Check your inner head o-ring for cracks. Not cracks like you pulled it apart (transverse cracks), long way around cracks (longitudinal cracks).

I have had this condition you are explaining pop up where it seems like the bike would not clear out. A long split was found on the head seal under the grove where it lays in the cylinder. Higher RPMs under load it would pull a tiny bit of coolant in enough to disrupt the combustion.

Did it ever run right with the main you have in it? Summer you need to go leaner on the jetting for top performance.. Just drop in a smaller main and take it for a rip. You will feel the difference if the current main jet is way too rich for your conditions. 

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