97 xtc 600 melt down???

[yamahamark]

Hi guys, I just bought a really clean almost complete 97 xtc 600 twin. The guy I bought it from said he rebuilt it 3x's in a month top to bottom new everything. He originally wanted $1200 but it didn't sell so he decided to part it out and only sold a few things off it before I bought the sled for $200.
My question is what might be the cause of 3 melt down's in a row? It's all stock except for the silencer mod.
I'll try to get some pics up tomorrow or something.
Thanks for any help

 

[super1c]

Who knows. What went down each time? Same cylinder? Didn't take engine down all the way and blew out crank? More info

 

[Throttle Junkie35]

I will guess the mag side cylinder kept going down?? Show me the piston.

 

[shaggyzr2]

crank seals

 

[yamahamark]

I was thinking seals as well but he said he replaced them. 1st melt down was mag side 2nd was both and this time it was clutch side.

 

[yamahamark]

Sled was to nice to pass up for that price.

 

[Vincent]

That was a score! Lots of usable parts!

 

[shaggyzr2]

Maybe he forgot to bleed the oil pump. I have a really nice low mileage bottom end if you're looking for one.

 

[Throttle Junkie35]

What does the sides of the piston look like?? I never 100% believe any seller that says they replaced the crank seals. Its worth pulling the motor and throwing in some new ones for piece of mind. My guess would be bad crank seals, dirty carb, wrong main jets, bad gas, or some other air leak.
Judging from the piston wash, it looks like it might be rich or atleast acceptable in most operating rpms yet obviously shows signs of a lean condition. I would see what main jets are in it and check the needle position in the carb.
Also, verfy that the head gasket is a stock, full thickness gasket. THIS IS IMPORTANT on a 600 twin.
Maybe check to see if it has the correct CDI box on it. From what I understand, running a 500 CDI on a 600 makes for a very unhappy motor.
-PS, was the previous owner running the air box?

 

[yamahamark]

It was a great steal I figured for that price it would save me a ton of money when something breaks on my sx.
I don't know what the sides of the pistons look like I'm waiting till I get moved and the garage setup before I pull it apart. I don't know if he was running the airbox. But it did come with the airbox.
Things I know are missing are what he sold. Carbs, head gasket, complete chain case, cdi box, track, rear shocks, and 1 trailing arm.
When I get moved and start tearing into it I'll post more pics of what I find.
Thanks for the responses it gives me a starting point when I start.

 

[yamahamark]

Quick question
Looking at the numbers on The pistons I found it is a wesico .50 over pistons. Does anybody know if spi makes a .50 over piston? I have searched and can't find anything from spi for .50 over just wesico.
Thanks for any inf guys.