New - lower crank bearing - connecting rod - piston - rings - clutch plates - new spark plug

Got back from the shop and now it bogs before transitioning into the powerband.

At the shop and the mechanic is stumped.

He checked out the power valve for proper assembly and smooth working order
He played with a jetting every which way.

?????

Starts fine - idles fine - revs up fine with no load.  Once it is ridden, it takes off, hesitates and slowly starts the transition before reving out again???

Swapped the electronics off a 2012 model - no difference. - not electronics

I know you said that the mechanic checked the powervalve for operation, but I would check its position and adjust that.  I know on my 150 when adjusting it to find the position that I liked most if I went too far one way or another it would bog under load.

The mechanic said he did play with that, how touchy is it?   1/4 turn? 1/2 turn?

When we open the cap on the left side (opposite the power valve), we do see the power valve operating as the throttle is twisted.

Yea, I'm for sure leaning towards powervalve, especially since he split the cases.

I haven't ever had a problem re-aligning the powervalve actuator after re-assembly, but if your careful you can put it back together again without needing to adjust it.

The powervalve actuator could be misaligned... its more complex then some people think.

Edited by tye1138, 13 June 2012 - 04:10 PM.

PV setting does affect how the bike runs, or comes into it's power, but a bog under load is a lean condition.  I don't trust many mechanics when fine tuning an engine.  I know I know as much or more than many local guys.  What jetting changes did they make?  That, IMHO is where your issue is.  I am not as familiar with the 150, but it sounds like you have a lean clip position or needle diameter.  

I adjust in 1/4 turn increments till I am close, then fine tune from there.

I have re-thought this problem and I just built my motor last night and noticed something that could be a problem for you. Obviously before you even think about this, I'd set the carb back to factory settings. Messing with too many things at once, causes lots of problems. So once you've verified everything is OEM, the float hight, jetting and reeds are all good, no leaks on the exhaust either then you can think about what I'm about to say.

The right side crank seal.

If that seal wasn't working right, during the compression stroke, it would leak out of the hole and outgas into the crankcases. It should run fine at lower RPM's, but once you whack the throttle open, it would start to do strange things because it would all of a sudden not have the normal mixture necessary for it to run.

The seal is a two part system. The case has an "outter" seal on it which touches a little race that sits on the crank. Then there is an inner seal and this is where it becomes tricky. The race which slips onto the crank output shaft, pushes against the inside of the bearing and there is an o ring there which seals it. All of that needs to be in good working order, seals need to be good and the main gear needs to be put in the right way to hold everything in place. Its not plainly obvious how to install it properly, it takes a little bit of a thought process to figure it out and my guess is, your mechanic probably dropped the little tiny black o ring which sits on the inside of the race. Its not sealing very well and likewise, is leaking very slightly, just enough leaking to cause an issue.

You can check to see if this is a problem because you'd have fuel mixed in with the transmission fluid and it would literally fill up the cases. So I'd dump the transmission fluid and see how much comes out. If you get out a perfect 700cc then its probably not an issue. If you get a lot more or a lot less, then I'd start looking there.

http://www.ktmpartsh...2007&fveh=23404

Look at part 14, 80, 71

Edited by tye1138, 15 June 2012 - 11:21 AM.

Like others said try putting jetting back to stock first.  Try moving the powervalve mark upwards till the "bog" is not felt.

gmoss357, on 13 June 2012 - 04:42 PM, said:

I'm with you, sounds like jetting to me. Easy to find out, throw a larger main in and see if it gets better or worse. Might even find good results by moving the needle up so take the clip down one. Again see if it gets better or worse. If you notice any change better or worse your on the right track to fix it. If adjusting the power valve helps anyone with a problem like this I would think your jetting is off to begin with.

OP pull that carb apart and post up your jetting.
main
pilot
needle and clip pos
slide

Also, that is a 38mm carb right?
Joe........

tye, I hear you on the seal but this bike is pretty new to be having seal issues. Also, you know you have a seal issue when you get fuel in the tranny oil or oil seeping into the stator cavity so that is easy to check out.
Joe.......

JoeMcLaughlin, on 16 June 2012 - 11:49 AM, said:

I was thinking right seal, the one that goes into the crank case.

Its actually a common problem to blow that one up and unless your super meticulous with the motor build, its VERY easy to leave the sealing o ring out by accident.

I honestly don't see how it could be a carb issue, if the mechanic didn't touch the carb until AFTER the bike didn't work. Ya gotta take the stator off to get in there, so perhaps an un timed stator... etc.

Thanks so much for all the suggestions

I managed to borrow a friends bike.  I have have switched carbs - no change, I have switch coil, stator and computer, one at a time and all together, no change.

My oil looks normal, no tell tale signs of leakage under the stator.

As a last resort, I am going to change out the whole wiring harness as well just to rule that out.

Will let you know

Well it's hard to mess up a top end but it happens. I would pull off that cylinder and double check everything.
Joe.........

Excuse the brief hijacking.
I'm doing a top end in my 09 150sx and have just got the barrell back from re-plating after a ring caught the exhaust port.
The powervalve seems quite tight. When moved to the ends of its travel its hard to get it to move back the opposite way again just with your fingers.
Is that normal/ok?

Also plug colour looks ok. (dark tan) its got stock jetting, (182 main) and runs perfectly, however this is the second time its stopped in 5-7 hours.
Whats the biggest main anyone is running in a 150?

RobinWatson, on 26 June 2012 - 02:34 AM, said:

You have to wash that new cylinder for quite a while with soap and water. Then you need to dry it very carefully with a high pressure air line. I usually clean the two little valves that go on either side of the flapper with a scotch bright pad, get them super clean. Then I lubricate them with gearbox oil and make sure they twist in place very cleanly. I like to replace the flapper during re-builds, its cheap and you'll be surprised at how much carbon build up is on the one you have now. Its hard to get it all off and make the flapper clean without damaging it, so you might as well just throw in a new one.

After that, throw on the little rollers and the actuating assembly. It should move butter smooth from one complete location to the other. If it doesn't you need to find the binding point and fix it. Sometimes those pins that hold the actuating assembly get bent slightly and its easy to find out which one it is, just pop the upper roller off each one until it unbinds and then you know what it is.

Hope that helps!

Fluffy450, on 18 June 2012 - 08:02 AM, said:

Thats right, nobody is suggesting for a moment that the stator side is an issue.

Unless you added a specific amount of oil to the crank case, then re-measured it on pulling it out, you wouldn't be able to tell.

I'm still guessing its the right hand crank seal.

Have you checked the reeds and reed cage?  1 bad reed petal can destroy low end response on a small bore 2 stroke.

Edited by kan3, 26 June 2012 - 07:49 AM.