sx 700 motor diagnostics?

enticer300longtrack

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Joined
Dec 17, 2013
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Location
Frazee, MN
hi, well today i bought a 97 sx, got there, guy said it ran, and it was all dirty, but is long traveled in the front, and has a brand new camoplast predator 1" track. Problem is, when i got there, it didn't run worth a $#^%... we did a compression test and on on cylinder and it read 0lbs lol. The other two we didn't check but will easily blow your finger off, so we found it had the airbox loose and completely off the pto side cylinder (the bad one), so i am thinking it was leaned out and melted a piston, due to my garage being used for the next month i can't open it up... any thoughts? i know this is very limited info but see what you guys come up with. Also i am building this sled into a ditchbanging monster! So i ordered some power inc. pipes tonight, so my elevation is about 1500ft, any clutching and jetting start points? thanks
 

If it grenaded a piston you will want to tear the case halves apart to inspect the bearings and make sure everything is cleaned out. If you want to, send the crank out to get checked and have new crank seals put on while it's apart.
 
yep, exactly what i'm gonna do with it. I tore it down to find that the other two pitons and cylinders are 100% ok with 145lbs on each, but the bad one busted a chunk of piston out due to it breaking a ring, a very small piece got to the skirt and made a score mark on the cylinder, so that is now junk. Head is kinda messed up but there is a performance guy near me... he loves yamaha triples and has a 170hp viper.... so he does his own head work and really knows how to make power in the yamahas, so he is gonna machine my head to his specs and take the squish to 30 thou, bump compression up to about 165.. so i'll be ordering 3 pistons and rings, gaskets, a cylinder, splitting the cases and sending and changing the crank seals. Should be a good motor when it all done!
 
It's always nice to have a knowledgable yami guy close to pick his brain every now-and-then. I am graced with two. One owns probably the oldest yamaha dealership in the country and the other raced yami and sno-jets.
 
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i have a performance guy... he loves building yammi triples! he really knows how to make power out of em. I have fett brother performance 4 miles down the road so i have them help with clutching!
 


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