96 Summit 670 jetting and chain case

[Tmann]

I have 2 questions

1. Changing oil in the chain case. What can I use or do I need to buy the Skidoo chain case oil?

2. This sled has the H.A.C (high altitude compensation) Will this adjust for mods to the intake or exhaust? What are some disadvantages/advantages of the H.A.C?

 

[JedInUtah]

I have a 670 and my answer to #1 is ATF. Works just great and a bottle will cost you $2-3.

Not sure on question #2.

 

[2zeros]

Be careful on intake mods.........

My father has a 98 summit X. He removed the baffles in the airbox, added 1 or 2 jet sizes. Burned it down, ever so slight. The airbox is restrictive, but is also key in the HAC system. I would make sure you are a good plug reader, or have an EGT gauge. Digatron makes some good stuff, a good gauge is an awesome tool for guys who like to tinker with their stuff. It's been awile since I rode my 670 sled, after getting a 900 cat. We also use a light motor oil in the chaincase. Don't want somthing too thick. Good Luck -00's

 

[Zachmandu]

#1 - I use synthetic lower-unit lube from my Merc dealer if I cannot find/get actual synthetic chain-case lube. In a pinch, I have used auto tranny fluid, std gear lube, straight 30wt, and yes (can't believe I am admitting this....but it was on the mountain and was all we had!) 2-cycle oil (!!)... whatever I have laying around the shop to get the bucket of bolts goin' goes in the 'case, especially if it is an older or low-powered fan-cooled sled. For my new and/or higher-horsepower sleds, I'm a little more paranoid, and run a synthetic lube. Everybody has thier own special "lube" that they feels works better than the next guy. I feel that anything is better than nothing.

#2 - I have had six 670's over the years. I have NEVER had the HAC system work correctly, or for very long. After 10+ years, I would expect the HAC diaphragm to be suspect to failure. First thing I do on an HAC equipped 670 is to pull the HAC system off, and go to MXz 670 jetting on the mains and pilots, usually dropping the mains one size smaller than factory spec. My altitude riding range only varies about 3000', so I do not see any disadvantage to eliminating an altitude compensator. If you feel that you are personally keeping NGK in business, get rid of it! About the HAC working with mods, if the sled is jetted correctly for said mods, the HAC will not know the difference.