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I have a 2005 cr125 new to me. I had millennium tech replate cylinder and supply new piston. I replaced crank bearings and now it won't hit power ban. It feels like a 4 stroke bouncing off rev limiter. It is also putting a lot of black spooge out of exhaust i mean a lot. The plug is black. I cleaned carb and adjusted floats. I also repacked silencer. I noticed the carb leaking gas out overflow the other day. I suspect it is running really rich. I have a brand new pwk from Jd jetting I'm going to try out. I also did a leakdown test and it held. I also am not 100% sure the power valve is set up right. The manual doesn't go into great detail about this. But it seems like there is only one way to put it back together. I have the engine out I'm going to do another leakdown test and double check my power valve and put it back together with this pwk. Any other thoughts out there?

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Damaged reeds ?  (making the engine act super rich)

 

Float level may be to specs by if gas is leaking from the carburetor that would 

indicate the inlet needle and it's seat are either worn or dirty. (not sealing)

Edited by mlatour

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Reeds look new. I suspect there is something wrong with the carb. I'm hoping using a known good carb will help sort it out. 

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The overflow problem is a carb issue. Float not being set correctly, and/or valve seat worn. The bike not being able to hit the rev limiter seems like in conjunction with the carb issue, a reed not being able to seal (chipped or broken) and for sure look into proper power valve operation. But most likely the proper carb setup should clear it up.

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Thanks for the help I really appreciate it. I'm going to replace the reeds. And try this new carb.

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The reeds and carb are something to check, but possibly open up the side cover where the powervalve linkage arm is located and make sure the arm is secured to the linkage. If so check to make sure it isn't suck open (suck open you'd have some low end power but no high end or powerband).

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One thing to check on the powervalve is the two cables behind the "RC" cover. those cables should not be excessivley loose. usually you can check for tension on them by lightly prying on the cables with a screwdriver. They should not be tight, but at the same time not be loose. those cables are responsible for opening and closing the valve. Had the same issue in my '02 CR250 not revving out nicely. tightened the cable on the right side and had zero issues. 

As for the carb leak it could be anything from an improperly set float or bad seals. I believe the '05 still has the TMX like my '00 used to. If that is the case I would definitley look at replacing it with the PWK anyways. Way easier to jet IMO.

Really those are the only two things I can think of. 125's are pretty simple and cheap to build. 

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On 2/4/2018 at 1:27 AM, Enduromadness said:

One thing to check on the powervalve is the two cables behind the "RC" cover. those cables should not be excessivley loose. usually you can check for tension on them by lightly prying on the cables with a screwdriver. They should not be tight, but at the same time not be loose. those cables are responsible for opening and closing the valve. Had the same issue in my '02 CR250 not revving out nicely. tightened the cable on the right side and had zero issues. 

As for the carb leak it could be anything from an improperly set float or bad seals. I believe the '05 still has the TMX like my '00 used to. If that is the case I would definitley look at replacing it with the PWK anyways. Way easier to jet IMO.

Really those are the only two things I can think of. 125's are pretty simple and cheap to build. 

No RC cables on the 125. Only 02-07 CR250s

IMG_7706.JPG

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No RC cables on the 125. Only 02-07 CR250s
IMG_7706.JPG.a46d96fa30f1d89671684a194bae0529.JPG


Unless you have a mighty 04 125! It was the only year of the cable operated power valve on a 125.

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 did did they put the right piston in? Some of those if they don't have enough Dome and they don't match the squish band correctly it can cause that black fouling. I e a dome is required and they put a flat piston instead.  also, using the wrong base gasket or head gasket can change the chamber volume and mess up your Port timing.

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Thanks for the replies. I sent the cylinder/piston back to milenium. They looked it over and said it looks good. I am going to look the bottom end over and make sure power valve linkage is assembled correct and put it back together with new carb and see what happens. I thing there is something wrong with the floats on the carb making it run super rich. 

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