97 600 twin, ring caught exhaust port...

The problem with the Wiescos is they are forged pistons, and they are softer than stock pieces, a forged pistons has more clearance because they grow more, they are softer and the skirts collapse. While some people will tell you they use forged pistons and let their motor heat up good before using may be true, however, if you're talking about a 97 and newer twin, how long does it really take to heat soak the motor before you stomp it? It has no thermostat so you would have to run it for what 5 to 10 min. on a cold day before you engage the clutch? Nobody does that. And while you're warming it up for that period of time the pistons are just rocking around in there scrubbing the skirts off.

Last time we were up, my buddy has a 800 Viper, he has a digital water temp gauge on it. When we started the motor it read -18, it took 7 1/2 min for it to get to 80 deg. because he has no thermostat in it, just some food for thought.

Because of the inherent problems with the 600 twin the only correct piston to use is the Yamaha service piston, the 8CR, with the AO at the end of the part number, while other parts may be cheaper, they're not gonna last as long.
 
800 said:
The problem with the Wiescos is they are forged pistons, and they are softer than stock pieces, a forged pistons has more clearance because they grow more, they are softer and the skirts collapse. While some people will tell you they use forged pistons and let their motor heat up good before using may be true, however, if you're talking about a 97 and newer twin, how long does it really take to heat soak the motor before you stomp it? It has no thermostat so you would have to run it for what 5 to 10 min. on a cold day before you engage the clutch? Nobody does that. And while you're warming it up for that period of time the pistons are just rocking around in there scrubbing the skirts off.

Last time we were up, my buddy has a 800 Viper, he has a digital water temp gauge on it. When we started the motor it read -18, it took 7 1/2 min for it to get to 80 deg. because he has no thermostat in it, just some food for thought.

Because of the inherent problems with the 600 twin the only correct piston to use is the Yamaha service piston, the 8CR, with the AO at the end of the part number, while other parts may be cheaper, they're not gonna last as long.
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I agree for the most part, but Yamaha designed the first set of pistons so terribly I figured I would try my luck with another design, being wiseco.
 
motoxjb said:
I agree for the most part, but Yamaha designed the first set of pistons so terribly I figured I would try my luck with another design, being wiseco.
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ALWAYS oem in a Yammie!!!!!!!!!
 
daman said:
Whats with the trip going down all the time???
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I don't know. 1st time it went at 9000 km rebuilt with OEM parts, the jug was reconditioned and the other jugs were like new, measured them and they were all well wihin spec. Deglased the cyl's and put it together with all new gaskets. Went down again at 14,000 km same jug PTO end. Piston clearance on the other 2 jugs was well within spec. This time I am trying Wisceo pistons, checked the crank, it was .0035" out on the PTO end, limit is .0012", had it straightened. Waiting for my pistons to get here. so that I can do it over again. Why its doing that I don't know.
 
are you lean or something? Get us some pictures of your piston and cylinder, easier to diagnose.
 
I'l get some pics next week as I just finished nights this morning and then I'm going up to give a buddy a hand with his house for the week end.
 
Pics of piston jug cyl head and plugs for the 700. see the next post for the 500
 

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Pics of the 500
 

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But the crank on the 500 was right on .ooo" I watched the guy check it. The crank seal on the 700 was warn but no where near to the point of failure, but maybe it could be passing. :?: :o|
 
01 SXR 700;Your piston failures. My 97 XT600 twin has failed twice on me; Mag side. Your pics resemble mine for the most part. Pto side has never been an issue. Perhaps it is a timing issue or that cylinder is more prone to fuel issues. I know we have a lot of ethanol fuel up here and even gas line antifreeze could cause issues. I bought my sled when it was 3 years old with almost 4000km on it. I assume the pistons had never been touched. When it let go the first time it would have been around 8000km. I put wicso pistons in it. It worked maybe a bit better; especially when cold out. But now my Mag side piston has failed again in slightly fewer KM than stock failure. So what does that say? I spoke to wisco and they admitted that something went wrong but would not take full blame. They would have gave me a deal on a new piston but they had no stock; strange? This starts to get expensive after a while. I have an 800 4cyl with original pistons; 13000km; why is it fine?
 
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