2017 150sx power valve

Hello, I just picked up a '17 150sx about a month ago. The bike has 91hrs on it but I haven't ridden it. The po said it needed a top end and I could tell by the feel of the kick starter. Anyway, I started the tear down on Friday and yesterday was assembling the power valve and it seems very binding. The center valve moves very easily, but when the end ones are connected it takes alot of force to make the valve move from fully closed to fully open. I don't see how this is going to work after the engine is assembled. I have read a couple articles on the control arms for the two end valves. This seems to be where my problem is. The control arm has a very sharp turn on it. Has anyone tried modifying the the cut out in the control arm? I saw an article about some custom arms, has anyone tried them? Or any other solution to this problem?

Hi this is not the problem you think it is. I bought a 150 Powerparts kit for our 125 - it had the same problem, just couldn't turn the round side valves more than a quarter. My dealer contacted KTM Austria about this twice and they said it was quite normal and NOT to do anything to them adjustment wise (like lapping them in or anything). First time we started it, I left the left hand inspection cover off and the valve was fully opening and closing as far as the adjuster. The pin in the valve runs round the 'corner' no problem. Just put it together - mind and get your flap height spot on. Hope this helps. Bob.

Edited by 7Tktm

Thanks for the reply. Hopefully it is supposed to be this way. It just seems tighter than what I am used to dealing with. I gotcha on the flap setting. I made a guide/tool to get this correct. Also will be checking x, as I am not sure what the po has done.

Well KTM say it is and it certainly was ok with us. Ours ran very smoothly once connected - mechanics stronger than my fingers lol. Could it be to do with the aluminium cylinder expanding faster than the steel valve? Don't know. I cut down one of the 'noses' on a set of sliding digi callipers so it would fit inside the cylinder for dimension z.

I have a 16 TC 150 that has issues. It got bad enough to bind up totally.  The PV will stick half open. 

 

 Ive bought new barrels and acuation arms for the transfer ports but havent installed them yet. 

 Horrible system in my opinion. 

  Someone here posted the aftermarket arms didnt help. After shipping to the US  i think they were around 100$. I tried tweaking mine a little but had no sucess. 

Yes, not sure why KTM changed from a system that worked fine. Seems bizarre that yours would stick so badly, while they are tight on the 150, the valves do push back in no bother, just a bit tight to then turn by hand. I followed KTMs advice and didn't have any issues. Having said that both our 125 move by hand no bother. Bob.

Plus side is the exhaust flapper.  SUPER simple and smooth . 

Thought I had this same problem on my 17 150xcw, some said this contributed to the low end throttle bog...I tried the aftermarket PV arms from Australia, they were machined poorly and very tight fitting, didn't bother installing them, waste of $100 if you ask me. I then removed the roller drums...it's very easy. Cleaned the drums/o-rings up and applied Ultra Slick engine assembly lube, much better movement. Someone on here mentioned they can take 10 to 20 hours to break in also for newer bikes.

I pulled the left side cover and watched the arms move when throttling up/down....they moved fine.

Trying to move them by hand, sometimes they felt as if they were sticking....wasn't the case with bike running.

Edited by hopsterj

I bet they get clearance once the engine is warm

2 hours ago, mog said:

I bet they get clearance once the engine is warm

:thumbsup: that's the key, letting the engine warm up a little longer. usually let mine idle for a good 5 to 10 min before riding.

 

Edited by hopsterj

 I tried mine with a warm engine. Valves were stuck half way and never budged. Open OR shut. Even aftet i polished and lubed them they would grab. 

 

 Illl try to remember to post a pic of the barrels. They have visable wear from the transfer ports. 

45 minutes ago, seer said:

 I tried mine with a warm engine. Valves were stuck half way and never budged. Open OR shut. Even aftet i polished and lubed them they would grab. 

 

 Illl try to remember to post a pic of the barrels. They have visable wear from the transfer ports. 

interesting...wonder if it's a mfg casting flaw. the slots where the drums go could be a microhair out of round?

Edited by hopsterj

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