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wiseco pistons?

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hey guys, im thinking of putting a wiseco piston in my yz250f, the bike is stock excwept for a k&N filter and fmf slip on exhaust, im looking for a little more bottom, wiseco offers 2 high comp std bore pistons, one they are both 13:5:1 but one has a moly skirt coating and says its for race use only, uses 2 rings and nikasil bore and costs 220, and the other uses armourglide coating and its shot pined, racers choice for 272$, so my question is which piston is better? can they both run pump gas? i dont race often i mostly drive in pits and ditch banging and a little trail, so any imput would be great, my biggest concern is can i run supreme pump gas(canada) on one of these pistons? thanks!

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i bought one and got 30 min out of it before it broke and destroyed my topend and then about a month later my buddies broke and destroyed his motor so i will never touch one again!

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i bought one and got 30 min out of it before it broke and destroyed my topend and then about a month later my buddies broke and destroyed his motor so i will never touch one again!

lol did you do the ring end gap? no? I didn't think so.

In fact, did you bother to measure anything at all? Or did you just throw it together and expect it to run?

Edited by moose_338

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1. Think twice before installing a high compression piston into a worn motor, if this is indeed the case with your 250f. They put more stress on the crankshaft and connecting rod.

2. I'd contact Wiseco directly with your question- they will know best what octane is needed with their pistons.

3. I'll always use Wiseco, never had a failure having installed many of them in the 25 years I have been wrenching on bikes. Forged pistons are the way to go and Wiseco makes a great one.

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The YZF250 is a Standard 13.5 to 1 Compression in the 08,09 and 10s.

If you want a really good piston buy a CP (From Moose Racing) or even better a Cosworth.

If we do not want to spend the money on the above we will get the JPC Powersports Piston which works well for us.

We used the Weseco in our two strokes and they were OK but we rang the hell out of those things.

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lol did you do the ring end gap? no? I didn't think so.

In fact, did you bother to measure anything at all? Or did you just throw it together and expect it to run?

You don't even know me so you automatically go to thinking I'm a bad mechanic and i don't measure stuff and do it right.For one your right i don't touch the motor. Thats why I didn't put it in. My friend put it in who used to be a test bike mechanic for factory Yamaha. and went to mmi. i also know of another wiesco piston that this happend too. the left lobe breaks off. i know off 3 pistons this happened to. Oh i forgot it was a new cylinder and rod to.

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lol did you do the ring end gap? no? I didn't think so.

In fact, did you bother to measure anything at all? Or did you just throw it together and expect it to run?

And in jwalk's defence if ring end gap was too tight it would cease. If it was too loose it wouldnt run. That would not cause the piston to break. But regardless alot of wiseco pistons do come out of spec. Oem is the best bet. The stock piston is a really good strong piston.

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I've been using wiseco pistons with great success for a while now. To the op, the first thing that you need to do is toss that k&n filter in the trash and buy a foam filter and keep it clean (k&n have "better air flow", but they also have better dirt flow, too). To the person that had the piston grenade in his bike in 30 minutes, you should have contacted wiseco about it. There had to be something that was incorrect about the installation. I'm not trying to pick on you, so don't take it as that. About the comment of the "left lobe" breaking off on a piston? If you are referring to the piston skirt, than that generally means that the bore is either worn out or out of round. The best thing is to take all the measurements from the factory service manual. If you have someone doing the work, they should be able to tell you all the specifications and if the part was in spec.

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No experience iwth the high comp pistons, but I put a wiseco in my 525 and it's performed well since. No issues.

I don't recommend them for snowmobiles though, they've got a nasty habit of cold-seizing when you're warming up a motor. Cylinder, piston, and water jacket warms up, then when the thermostat opens and the rush of cold coolanat floods the water jacket the cylinder shrinks up and the piston seizes. OEM and SPI pistons don't seem to have that issue. :smirk:

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I have used nothing but Wiseco and have never had a problem with them. The best advice i can give with any piston or bike is to MAKE SURE YOU WARM IT UP PROPERLY! Especially with a forged piston because they must expand more and you can cold sieze the motor. Another good thing about forged is if the piston breaks, its large pieces rather than the thousands of pieces that would come off of a cast piston.

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lol did you do the ring end gap? no? I didn't think so.

In fact, did you bother to measure anything at all? Or did you just throw it together and expect it to run?

Where in the F*&^ do you get off talking to people like that. He was asked for an opinion and gave it. Who do you think you are?????????????? Jerk.

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1. Think twice before installing a high compression piston into a worn motor, if this is indeed the case with your 250f. They put more stress on the crankshaft and connecting rod.

2. I'd contact Wiseco directly with your question- they will know best what octane is needed with their pistons.

3. I'll always use Wiseco, never had a failure having installed many of them in the 25 years I have been wrenching on bikes. Forged pistons are the way to go and Wiseco makes a great one.

the motor in my bike is seized right know(rod bearing seaized) so it will be a complete rebuilt crank/bearings piston rings timing chain and also new valves/seats and springs. so it should be fine

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The YZF250 is a Standard 13.5 to 1 Compression in the 08,09 and 10s.

If you want a really good piston buy a CP (From Moose Racing) or even better a Cosworth.

If we do not want to spend the money on the above we will get the JPC Powersports Piston which works well for us.

We used the Weseco in our two strokes and they were OK but we rang the hell out of those things.

my bike is a 2006 which is a 12.5.1, i had put a 2008 piston that has the compression you said, i noticed some more punch and some bottom end, am i better off doing this again or going with the real thing?

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thanks for all the great answers everyone but id also like to know if i can run supreme gas on a high comp pistion?

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The forged vs. OEM discussion is a great way to get into an arguement, similar to "which oil is best" or "which religion is best". I've been around a while and I've seen it go both ways - good and bad. And I HAVE broken a Wiseco, they're not indestructable. Lately, I've only been rebuilding with OEM. But that doesn't mean many (thousands!) of guys have had good experiences with Wiseco. I think the best plan is to give the Wiseco piston that you bought to your engine guy and he can spec. the new bore accordingly. As someone said, warm-up is super-important too. I think thats a pain too when they tell you "2 MINUTES" to the green flag. I always had guys looking at me strange at the starting line wondering WHY I was idling and revving my bike. I was the ONLY one running. I was trying to warm up the dang thing. And BTW, that's the one that broke the Wiseco, so the careful warm-up didn't seem to help me.

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