48 hours should i do a piston or just rings and a wristpin.


10 replies to this topic
  • ThumperKid250F

Posted October 29, 2009 - 05:16 PM

#1

well long story short. my bike broke a wrist pin 2 years ago on the ice and i got it fixed by last years ice season.. since then i put 48 hours on my bike. 10 hours on the ice and the rest was in the woods.. so im just wondering should i just do a new piston and rings or should i just do a new wrist pin and rings?

btw im useing CP pistons

what does everybody change theres at?

  • grayracer513

Posted October 29, 2009 - 07:28 PM

#2

Help me remember what went on when your bike broke before. Were both circlips in the piston, or was one missing? Stock or aftermarket pins?

  • ThumperKid250F

Posted October 29, 2009 - 08:03 PM

#3

Help me remember what went on when your bike broke before. Were both circlips in the piston, or was one missing? Stock or aftermarket pins?



both circlips were still in the piston and the wrist pin snaped in half. it was a weisco hi comp piston

only reason im asking is because i just dont want the same thing to happen again..

i no the piston is prob still good so new rings would make it like new and to be safe a new wrist pin..

can i put a new wrist pin in a old piston or does it come as a set?

  • grayracer513

Posted October 29, 2009 - 08:25 PM

#4

That changes the story a little, and I remember it now. You said you were using CP pistons, and I hadn't heard of one of their pins breaking before.

Wiseco did have a problem with marginal wrist pins at the time you broke yours, though. To be fair, I haven't heard of it for a while, so it may be they've addressed it.

Anyway. Wrist pins are made to a standard diameter for each engine since the pins have to fit the OEM connecting rods. The only possible difference that would affect fit is the pin's length, but that will matter only if the aftermarket piston has a significantly wider or narrower pin boss.

Yamaha sells the pins separately from their pistons, and a lot of people avoided trouble with Wiseco pistons by using an OEM pin in them. Most aftermarket pistons come with a new pin, but not all.

I would replace the pin with any piston, but at least in the case of a Yamaha pin, I wouldn't replace the pin where the piston was OK, unless it showed some damage. If you do a lot of ice racing, at least inspecting the piston would probably be a good idea at this point.

  • ThumperKid250F

Posted October 30, 2009 - 05:36 AM

#5

That changes the story a little, and I remember it now. You said you were using CP pistons, and I hadn't heard of one of their pins breaking before.

Wiseco did have a problem with marginal wrist pins at the time you broke yours, though. To be fair, I haven't heard of it for a while, so it may be they've addressed it.

Anyway. Wrist pins are made to a standard diameter for each engine since the pins have to fit the OEM connecting rods. The only possible difference that would affect fit is the pin's length, but that will matter only if the aftermarket piston has a significantly wider or narrower pin boss.

Yamaha sells the pins separately from their pistons, and a lot of people avoided trouble with Wiseco pistons by using an OEM pin in them. Most aftermarket pistons come with a new pin, but not all.

I would replace the pin with any piston, but at least in the case of a Yamaha pin, I wouldn't replace the pin where the piston was OK, unless it showed some damage. If you do a lot of ice racing, at least inspecting the piston would probably be a good idea at this point.


thanks grey.. so would you say it would be ok to just re ring my CP piston and change out the wrist pin with another CP wrist pin ( just for a peace of mind) and it would be good to go, as long as the piston is in good shape?

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  • grayracer513

Posted October 30, 2009 - 06:21 AM

#6

IF the piston is in good shape, yes, but that will be your call. Be certain to check the ring grooves for wear (excessive ring side clearance and "belling"), and the fit of the pin in the pin bore.

  • ThumperKid250F

Posted October 30, 2009 - 08:02 AM

#7

thanks gray. your a big help:thumbsup:

  • DrThumper

Posted October 30, 2009 - 11:39 AM

#8

If I'm taking it apart that far I'm replacing the piston too.

  • moto_x2005

Posted October 30, 2009 - 11:42 AM

#9

i look at 40 hrs max on a mx 4t.. btw there is a wiseco guy here on TT that may be able to address the pin problem

  • ForsheeMS

Posted October 30, 2009 - 11:46 AM

#10

You may already know this but order a new set of wire locks when you order the rings and wrist pin. Never reuse wire locks.

For what it's worth I would replace the piston.

  • ThumperKid250F

Posted October 30, 2009 - 04:25 PM

#11

You may already know this but order a new set of wire locks when you order the rings and wrist pin. Never reuse wire locks.

For what it's worth I would replace the piston.



yes i no im prob going to replace the piston too. just asking a question thats all





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