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Chevelle70SS

Time on Top End ?

18 posts in this topic

Hello everyone,

I've got a friend that runs the pro class in the OMA and local Harescrambles. He is a 2strk guy and this year in july he purchased a 08 450F to race locals and the OMA Moose Run. He has got 40 hrs on the hour meter now and was asking me if it was time for a top end. I didn't really know what to tell him since the kinda of abuse his bike goes thru in one 2hr race I don't think my bike would see in a lifetime. Any Ideas ? He's really good about oil changes and air filter maintainence. I've checked his valves 3x's and every thing is fine with those.

Thanks,

Chevelle

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I have heard of guys on here that have put over 200 hours on a single piston in their yamis, But to tell you the truth, If he races and has the money, why not. This way, when the bike is apart you can see what the piston looks like after his style of riding for 40 hours. This will give you a good indication of how long he could safely run one. if the piston that comes out still looks good, then he could run the new one for longer. Lets say 80 hrs. etc.

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if he can do the work himself that's something to consider. i change my top end at about the 50 hour mark, as well as my cam chain. i'm not sure what the manual recommends, but i'd rather be on teh safe side. if something happens and other parts get involved, valves, head, etc. it can get expensive.

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40 Hours! It just got broke in:lol:

Check the valves and let that be his guide.

I have an 06 with well over 100 hours and I just did my first valve adjustment.

I race Expert and beat up mine pretty good and still pulls hard:excuseme:

I suppose a PRO level racer would change the top end sooner.

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Thanks for the reply's. We do the work ourselves on his bkes. Like I said he's been a 2strk guy all his life and he can tell when it's time for a top end on those. The 4strk just has great power and runs fine yet and he was just curious as to how many hours he should expect out of a top end. We have 2 top end kits and timing chains on our spare parts shelf so parts aren't a problem. We just didn't want to dig into it if it was to early to worry about those parts.

Thanks,

Chevelle

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I'd at least put a cam chain in it and some rings. I do it to mine every year and I'm far from a pro level rider. And if he's one of the guys who are constantly on the rev-limiter, I would replace the valve springs too.

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250F every 20hours

450F every 40hours

Thats my advice of top end

WOW! That seams a bit overkill.... Have someone do a leak down test on the motor and you will get your answer there. My guess is that he will be well within the spec and not need to pull his motor apart.

Original top ends last longer than any others. It seams that the factory plating is better than most of the aftermarket shops, at least in my experience.

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Original top ends last longer than any others. It seams that the factory plating is better than most of the aftermarket shops, at least in my experience.

It is, and the fit is better, unless the fit is adjusted on a custom basis. Add to that the fact that the match between the various materials used is usually better than almost anything available. I doubt that I would replate a cylinder instead of replacing it if I were to use the stock bore size in a rebuild.

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Id say my 03 has roughly 300 hours. Still pulls the front wheel up in every gear and the valves are still in check.

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In Belgium tracks are different from USA, it's always deep sand or muddy.

That changes a lot.

You've never ridden Glen Helen, Millville, etc., have you?

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so if i put a new oem piston in it, it wont last just as new factory motor ? or the factory guys have some magic tricks?

for how long do i need to break it in after i put new piston ?

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At 50 hours I put new rings and cam chain. At 100 I put in a new piston and cam chain. I've used this schedule since the '98 400F and never had an issue racing nasty Wasington Hare Scrambles and Enduros plus training rides at least once a week.

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I put a piston, rings and timing chain in at 75 hrs..... I could feel a difference next time I rode.

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It's no offence that I am saying tracks are more sandy in Belgium and the netherlands

I'll grant you that because of the geography, sand tracks are more the norm in Belgium, but it's a mistake to say they're uncommon here in the U.S.

Just to name 3:

Millville:

1138-dungey_npg_web.jpg

Glen Helen:

rob-moto%27s-glen-helen-photo%27s-498.jpg

Cahuilla Creek:

cahuillacreek101506007.jpg

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Ok, I understand you, but thats what I tried to say.

In belgium there are more sand tracs than hard-packed. I did't say there was no sand in the usa.

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