Home Forums Shifter Karts CR 125 with problems…..

This topic contains 6 replies, has 3 voices, and was last updated by  James O’Brien 4 years, 8 months ago.

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  • #37418

    Robert Lawson


    I have a CR 125 engine here that I’m working on for a friend, its on a CIK RR application.

    It has a badly leaking exhaust plug (ign side) and it will not hold air for pressure check of crankcase. (pissing out at this location)

    Is this a common issue?

    Would like to hear how some of you address this.

    And….yes, it had TONS of RTV in there!!!!!



  • #37424

    Randy McKee

    Do you mean power valve plug or manifold?  I’m  assuming you mean power valve because you mentioned ignition side.  Yes, it’s common for them to leak, but it’s usually not a huge performance problem… just a mess and it’s hard to do a proper leak test.

    If you only put rtv on the exterior, try pulling it from cylinder, swab in rtv and re-install.  Be sure to cleanup any excess rtv inside cylinder.  If it’s an o-ringed type, put a new o-ring on it.


  • #37475

    Robert Lawson

    Sorry for not being specific, yes…..it is a “power valve” plug. I have not removed it so I’m not certain if it has an o-ring or not.

    The leak is excessive, no pressure can be built up at all. Plenty of exhaust “juice” under that cover and evidence of it being blown all around in there too. Best guess is there are no o-rings on it.

    What concerns me is the fact that it will also “draw in” air from that same leak. This can cause a few different possible issues, fuel pump function being one and of course a lean condition as well.

    I could be wrong about this…. but this engine blows up every time it is run, and with very little running time needed to do so.

    There where other issues as well but correcting these are easily done. I like to pressure check the entire set-up before handing an engine back with a clean bill of health.

  • #37484

    Randy McKee

    Ooh!  sounds worse than I thought.  Usually the plugs will have a very slight leak if any.  I’d pull ’em and see what’s up.

    What year is the cylinder?  If it does need new plugs, you can get the o-ringed type from Swedetech (depending on cylinder year).  If the cylinder is modified, you’ll probably need to reshape the new plugs to match.  Hope you don’t have to go down that road though.

  • #37515

    Randy McKee

    Robert, another thing I just considered… if it’s a 2000 to 2002 cylinder (I think?) hold off on removing the plugs.  Those years have difficult plugs and can’t simply be re-installed.  I believe those have to be glued in place.  Anyway, tell us the year of the cylinder and any other details about the ‘blow-ups’ and maybe someone else can chime in with suggestions.

    P.S.  I could be wrong, but I don’t think the power valve is the reason for the blow-ups.  I believe people used to just wire them open and run it that way (before plugs were readily available).

  • #37679

    Robert Lawson

    Hey Randy,

    Not sure what year it is, I was told when he orders parts he orders for a 99′ model.

    The cylinder has been stripped and recoated MANY times so I’m sure the plugs have been removed. I was going to glue them in with Devcon and move on but wanted some input into the chance this was a common issue with a simple repair.

    Timing, CCV and squish were all way off. All or any combination of these can cause the seizures but it always melts the piston just at the area where the leaking plug is at.

    Thanks for the info!


  • #37829

    James O’Brien

    RPM, If that’s a 99 chances are those plugs do have O-rings that just need to be replaced. Very few cylinders are floating around without o-ring plugs.

    Those need to be pressed out, then either buy a new set for 60 bucks or just the O-rings (Swedetech has them listed), if it were me I’d just buy a new plug set.


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