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KTM EXC 125 2009 - power valve does not open fully

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Morning!

I have little problem with my KTM EXC 125 2009. Basically bike already had general repair - top and bottom of engine, frame paintwork, new parts as seat, handlebar etc.

After repair I went to some light ride, used all tank, after it, I change gearbox oil and go to first hard ride but bike is very weak at high RPM's. In low and medium RPM's everything is fine, but in high RPM's there's no power. There's no interruption or other issues - just lack of power. 

First thing I have checked was spark plug and stator but this parts are ok. So I checked the power valve - power valve works but open only to half-open position and don't want open fully. In this point I would like to say, the PV is assembled correctly and it's clean:

QK33W2A.png

In high RPM mark No. "1" should be visible in window No. "4" - but mark No. "1" move only to half of that way. 

Power valve as I wrote, is assembled correctly.

 

 

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59 minutes ago, lucky_looser_ said:

Morning!

I have little problem with my KTM EXC 125 2009. Basically bike already had general repair - top and bottom of engine, frame paintwork, new parts as seat, handlebar etc.

After repair I went to some light ride, used all tank, after it, I change gearbox oil and go to first hard ride but bike is very weak at high RPM's. In low and medium RPM's everything is fine, but in high RPM's there's no power. There's no interruption or other issues - just lack of power. 

First thing I have checked was spark plug and stator but this parts are ok. So I checked the power valve - power valve works but open only to half-open position and don't want open fully. In this point I would like to say, the PV is assembled correctly and it's clean:

QK33W2A.png

In high RPM mark No. "1" should be visible in window No. "4" - but mark No. "1" move only to half of that way. 

Power valve as I wrote, is assembled correctly.

 

 

Start with the basics:

Did you ensure the fork was aligned with the tab coming from the governor?

Did you ensure that the PV flap was moving freely? Wasn't gummed or carbon-ed up?

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Quote

Did you ensure the fork was aligned with the tab coming from the governor?

Yes, it's assembled properly.

 

Quote

Did you ensure that the PV flap was moving freely? Wasn't gummed or carbon-ed up?

Today I will check flap for freely moving. In evening I will post how it works.

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If everything was working fine before refresh and power valve was fully opening, and you haven't stripped the cylinder parts for any reason or adjusted the pv opening times, then your problem is elsewhere. You say all is good in the cylinder and it is connected to lever F - the part that sticks out of the clutch cover, then it is probable that your balls in the centrifugal timer have jumped ramps, stopping lever F sliding all the way up the shaft. It is an easy fix, but make sure your completely satisfied with all the parts in the cylinder first. Hope this helps, Bob.

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13 hours ago, 7Tktm said:

If everything was working fine before refresh and power valve was fully opening, and you haven't stripped the cylinder parts for any reason or adjusted the pv opening times, then your problem is elsewhere. You say all is good in the cylinder and it is connected to lever F - the part that sticks out of the clutch cover, then it is probable that your balls in the centrifugal timer have jumped ramps, stopping lever F sliding all the way up the shaft. It is an easy fix, but make sure your completely satisfied with all the parts in the cylinder first. Hope this helps, Bob.

I'd almost bet avatars it's the lever.

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Hello my fellows :) 

Maybe I should start from basic informations, to clearance situation with my bike.

Basically I bought it last year in medium condition:

EtPYId8.jpg

 

After I've bought it, I rided it maybe for 3-4 hours and I dont even check PV and other stuff for proper working, as I remember - when winter came, I just start repair. So I can't say much more about situation before I dissasembled bike. For sure there was some lack in cylinder pressure, nicasil was in poor condition (I've send cylinder to Langcourt GB) and some other parts was used, I don't really know whether PV works properly - I just checked position of it. Now bike looks like that:

6gGxeFV.jpg

 

But according my power valve situation:

Yesterday, I get issue from friend to check dimension of bolts No. 21 which provides smooth move of power valve clap No. 20 - bolts were in good position, but friend suggest me I should try to unscrew it for extra 1/8 of full turn. 

1fsdwB5.jpg

I've done what my friend says and now situation is much better - first I check power valve position in idle run when full throthle. Powervalve now opens almost to full open position. Please look at photo:

JiR2ZdM.jpg

So as you can see, powevalve work but still not open to full open position. Part 67 is connected with part 66:

LNB6NC9.jpg

 

 

But there is one more wierd issue. Before I started repair I have power valve in standard position - as now. Basically my PV is in position showed on image above. But... before repair screw for valve regulation (no. 51) was in that position:

UAyVA5a.jpg

but now, after repair it's screwed much more inside clutch cover (but as I said, pover valve position is the same):

ulXIOWq.png

During repair I change elements No. 57,66 and 67 for new ones - it can be reason of this situation?

Regards and best wishes from Poland ;)

 

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Ah, so you never said that you had stripped the power valve!! My reading was this problem had just occurred. I presume you assembled the power valve components yourself. Presuming you have timed it correctly, and centred the flap in the exhaust port - 0.20mm clearance at each side, why on earth did you tighten the flap bolts. You put a little grease on the smooth part that goes into the flap, hand tighten the bolt just until you feel resistance, then turn each back out 1/8 of a turn. Take it part 57 was worn at the end that runs against the timer shaft and was the reason you changed it? You cannot mount any of these parts you have changed incorrectly apart from 67, the strokes on which have to line up with the dots on the valves and flap lifter. Does your lock bolt at 4 o'clock position on clutch cover lock up the 2 sided adjuster? Lots of times the o ring string which it drives into the threads of the adjuster stops doing its job and allows the adjuster to turn in as you tighten the large alloy cover cap. You should have renewed it when you had the clutch cover off as it is simpler then. Did you check the bearing in the clutch cover which the end of the timer runs in - it is bad for wearing and becomes really sloppy. You turn the adjuster in or out to change when the flap opens - we generally ran our 125s (mx racing) at 6mm out and never went past 9 mm out when measured from the top of the adjuster to the mating face of the clutch cover. Tip - if you are asking again, best to say what you have done to the engine - makes diagnosis/help/guesses easier.  Bob.

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Dear Bob - thank you for your time and clues. As I wrote, my bike had general repair of engine. All components of top and end engine were dissasembled and checked for wear. Engine was disassembled to single bolt. I changed standard parts such as clutch discs, piston, rod, all bearings with seals etc. Parts No. 57,66,67 were replaced during this repair because were worn. Power valve is assemled corectly, according to signs on parts No. 18,61,62 and 67. 

Basically all works and maintenances I've done were made according to KTM Repair Manual and/or User Manual - tightening torques, lubrication etc. all of this according to manual. I never work like partisan ;) - I have video from assembling engine so I can watch what I did anytime.

Gaps between clap (part No. 20) and exhaust port were correctly, made with feeler and set to 0,20 for each side - but I turn out bolts No. 21 more, for about 2/8 out of full turn. And now powervalve works better, but still not good enough (always bolts are locked by parts No. 11 and 79 with oring 10)

When I adjusting powervalve by screw/unscrew part No. 51, I always release bolt No. 17 (about two full turns).

2P2dQ9h.jpg

 

 

Now I have situation:

8kEY5mV.jpg

ynhArle.jpg

and power valve setings according to this:

mKzVAXM.jpg

I can't screw more element No. 51 to thread in clutch cover. It's maximum position of element No. 51

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Dear All - thank You for support. 

I fixed problem with my povervalve - there was missing distance washer pos.26, also ball bearing was totally used - pos.23
2P2dQ9h.jpg

I bought and mount all parts and now povervalve is open to full position. But still I have problem, I think it's somthing with ignition - please look at topic:

It's other kind of problem, so I decided to make new topic - I hope it's right way.

Regards and best wishes for all.

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