Piston lifetime for a XR600

After talking to a friend who was doing his yearly piston replacement on a CRF bike, I started wondering about the XR600. When is it time to replace the piston? I've been into my engine a couple of times and the piston has always measured as new even though it has a lot of hours on it. I've been riding it 60 or more times a year and it still has the same piston as when I got it in 2000. It's not the stock one that it had in 93, so it is at least seven years old and maybe more.

Do theses pistons ever break off a skirt? Is it time for a new one before metal fatigue causes the skirt to break? How many hours is too many?

After talking to a friend who was doing his yearly piston replacement on a CRF bike, I started wondering about the XR600. When is it time to replace the piston? I've been into my engine a couple of times and the piston has always measured as new even though it has a lot of hours on it. I've been riding it 60 or more times a year and it still has the same piston as when I got it in 2000. It's not the stock one that it had in 93, so it is at least seven years old and maybe more.

Do theses pistons ever break off a skirt? Is it time for a new one before metal fatigue causes the skirt to break? How many hours is too many?

it all matters on how you maintain the engine. I would look into it when one of the following happens (in no particular order):

  1. Piston slap
  2. Smoke
  3. Loss of power
  4. High oil consumption
  5. High fuel consumption
  6. Your weiner falls off

It's an XR. I'd go with number 6!

In all seriousness, as long as the piston AND the cylinder are in spec, you will have nothing to ever worry about. The skirts will only break if there is excessive piston slap, and that is not a common problem. I've seen old XR500s that are used, abused, and still using the stock piston.

The only reason to put in a new piston is when you overbore the cylinder and put in a bigger piston to make it a 630.

A CRF and a XR are completely incomparable in terms of engine longevity and parts replacement schedules.

i also am in agreeance with #6. also piston slap is the main 1 to look out for. as long as its within serviceable limits, all good!

i also am in agreeance with #6. also piston slap is the main 1 to look out for. as long as its within serviceable limits, all good!

What is piston slap?

What is piston slap?

piston slap is an upper end piston "knock". it happens when the piston skirt to cylinder wall clearance becomes excesive. the noise comes from the piston rocking side to side(in small amounts, not talking about much here) and causes a sort of hollow, upper end knock.

I guess that I'm good then. Last year I was blowing oil out the breather. When I opened her up the rings were completely shot. The end gap was about .150". The piston measured new. After honing I still had .001 to go on the piston to bore clearance before it was too big so I just popped in new rings. She has been a one kick starter ever since.

I remember the first time I saw/heard a CFR450. The thing was slapping like crazy. I even said to the guy "that thing makes a lot of piston slap how many hours do you have on this bike?" He said "this is my second ride."

I guess that I'm good then. Last year I was blowing oil out the breather. When I opened her up the rings were completely shot. The end gap was about .150". The piston measured new. After honing I still had .001 to go on the piston to bore clearance before it was too big so I just popped in new rings. She has been a one kick starter ever since.

I remember the first time I saw/heard a CFR450. The thing was slapping like crazy. I even said to the guy "that thing makes a lot of piston slap how many hours do you have on this bike?" He said "this is my second ride."

no wonder they are O/H constantly!

I had an 1986 XR600 that developed a knock and the wristpin had developed play between it and the piston after about a million miles. Cylinder was still in spec. a wristpin and piston and it was back on the trail as a loaner/guest bike. That was after 7 years of abuse.

I remember the first time I saw/heard a CFR450. The thing was slapping like crazy. I even said to the guy "that thing makes a lot of piston slap how many hours do you have on this bike?" He said "this is my second ride."

The other thing to remember with a CRF is that the piston really has no skirt to even start with. It is nearly a flat chunk of aluminum with a spot for the piston pin and rings. This is to minimize piston reciprocating mass to allow the motor to rev much faster at the expense of service life (obviously).

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