Snowmobile Fanatics banner

1 - 20 of 47 Posts

·
Registered
Joined
·
957 Posts
Discussion Starter #1
Welll I slapped the compression gauge on my 96 Ultra... I'm getting 94 mag, 91 center, and 94 PTO ...... I might as well do a ring job (granted I haven't cracked open the heads too see what things look like) but other than new rings and top end gaskets is there any thing else I should replace (for preventive maint.) while I have the engine apart????

What special tools am I going to need to do this job other than a torque wrench??


Thanks
 

·
Registered
Joined
·
4,322 Posts
only special tool ide get is an extra set of hands to help get the heads back on. other then that just clean everything up and check everything over. otherwise i cant think of anything else

bobby
 

·
Registered
Joined
·
2,307 Posts
I'm sure you plan on it anyway, but since you didn't exactly mention it.......change the base gasket as well.

How do the crank seals look? Now would be the time to change those. I know it means taking the engine completely out. Guess it depends on how long you intend on keeping the sled.
 

·
Registered
Joined
·
2,770 Posts
You didn't mention this but since your pots will be off, you should have them honed to get a nice seal on the new rings.

I like a guy who fixes before it needs fix'n.
 

·
Registered
Joined
·
3,188 Posts
It's common sence, but check over all the components 100% before re-assembly. Look for cracked piston skirts and check all bearings for smooth operation. You might need a feeler gauge to check proper ring end gap.
If your splitting the crank case open, i'd replace the crank seals no matter what.
 

·
Registered
Joined
·
957 Posts
Discussion Starter #6
What was it about these 680 triples that would go south in a really bad way???? I'm thinking the crank, but I'm also thinking that was on the smaller and lighter XLT's... I'm thinking I might as well go all out since it is only mid juse... and I figure I won't be rideing till early november at best... As for the crank seal on the PTO... Thats one of the only areas on the entire engine that you can't see clean aluminum...so....
 

·
Super Moderator
Joined
·
11,272 Posts
the 680s had strong cranks in them, iv never heard of anyone breaking a stock one, or a modded one for that matter.
 
G

·
Guest
Joined
·
0 Posts
What are the specs. for the compression on that engine. The numbers you posted don't sound that bad. I have always tried to stay clear of unnessasary tear downs. If it is still running and pulling well. Not missing or fouling, why mess with a good thing?

Dennis
 

·
Registered
Joined
·
528 Posts
I agree with D Noel. Your cylinders are within 3lbs of each other, sounds pretty good to me.

I couple of other things to consider. How many miles are on the engine and does it run good? What should the compression be? I'm generally more concerned with the difference between the cylinders than the actual number. If you have a cheap compression gauge it may not be giving your true compression, say for instance it may read 10 or 20lbs low. The other thing to consider is did you have all the plugs pulled when you did the test and did you hold your throttle wide open?

If you do go ahead with the ring job then I'd suggest purchasing a shop manual. Be careful if you plan on honing the cylinders because a conventional hone will screw up the nikasil bore (assuming polaris are nikasil or a similar material). You will also need to check the end gap of the new rings or you may end up with a seized motor or a messed up jug.
 

·
Registered
Joined
·
957 Posts
Discussion Starter #10
If I'm not mitaken (which I could Be) the Polaris triples compression when new is around 120. If someonbe knows the acctual spec on the 680 please let me know! As for gauge accuracy... It's accurate.....
 

·
Registered
Joined
·
2,261 Posts
i got a 96 xcr 600 sp but the first owner put 680 cyls on it. i recently redone the top end and i got a lil over 130psi in each one
 

·
Registered
Joined
·
957 Posts
Discussion Starter #13
That's what I figured... It needs a ring job at the very least....

Thanks for al the replys fellas, I'll probably tear into it in the next week or two.
 

·
Registered
Joined
·
1,966 Posts
HighSierra you should have around 120 lbs of compression on a stock motor. You are going to _hit in your pants when you start pricing the parts. It will cost you about $300.00 just to rering. Riley
 

·
Registered
Joined
·
957 Posts
Discussion Starter #15
Maybe $300 canadian!!! You can get a complete matched/balanced wiseco piston set with rings, clips. and pins along with the top-end gasket set for around $340 US. I've seen the rings for around $12 each so about $72 for rings and another $25 for a top end gasket set.
 

·
Administrator
Joined
·
13,092 Posts
I don't know what exchange rate you are using, but 100 US is not 300 canadian. Your money might be worth more than ours but it sure as heck ain't that big of a difference.
 

·
Registered
Joined
·
4,983 Posts
Exchange rate went to $0.79 yesterday. Highest in years.
 

·
Registered
Joined
·
1,966 Posts
HighSiera you may be able to do a rebuild cheaper using Wiseco pistons and rings but IMO Wiseco is not as good as OEM. I just got done reringing my race motor and with purchasing the parts through one of my sponsors it still cost me just about $300.00 Riley
 

·
Registered
Joined
·
218 Posts
I agree with Riley...pass on Wiseco's and go OEM or at least aftermarket cast piston. If you split the case and change seals (I recommend)make sure you check the PTO end bearing. In '96 Ultra/XCR SP motors, I have seen several PTO bearings that want to fall right off in your hand off the PTO stub. They had soft inner races and wear easily.
 
1 - 20 of 47 Posts
Top