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When do you rebuild your top end?

4.5K views 12 replies 8 participants last post by  Jake86  
#1 ·
I was just wondering do you guys rebuild your top end after a certain mileage or by compression readings or when it breaks? When it breaks it is a very expensive fix.
 
#2 ·
Reduced compression, or a difference in PSI of more than 5 lbs between the 2 cylinders is when I usually did it. I have also done it when the engine reaches 5000 miles just as a preventative measure. But mileage would depend on how the sled was being used. if it was mostly offtrail or racing, I would consider doing it sooner. To be honest, I have done it many times, and more often, it was after it burnt down, not before :p
 
#3 ·
I agree with wyelde, if it is not noticably low on compression, or has 5000+ miles on it, I will run it til it blows. If you are any good with motors, or have tuned a few snowmobiles, seat time will get you used to how your snowmobile reacts. If something sounds funny, or it is not running like usual, I dont ride any farther than the shop and I fix what is wrong. Not saying that I have always been able to tell, but if the sled has been dialed in, listen to it, and if it responds different and you notice it, dont push your luck.
 
#8 ·
What engine are you talking about? If this is a 600 twin, you should definitely do it. Those engines typically need a new topend in the 5-6,000 mile range.

Since you have this engine out and easily accessible, regardless what size it is, I would do the topend before putting it in the sled. With the motor out, you could do the job in two hours, and you have a solid piece of mind when you ride it. You should be able to get the gaskets and pistons for less than $200-300 depending on the model. It'll cost you more than that when she blows.
 
#5 ·
If it's out, you can get a good look at the pistons. Or you may just want to put pistons and rings in it. Less work now.
 
#9 ·
I come down on the safe side with 3000-3500 on a twin with fresh flanges, 6500 on a triple. By the time you get to 6500 on a triple it's time for the insurance of crank seals and water pump maintenance and intake flanges anyway.