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Discussion Starter · #1 ·
My 1997 Ski Doo Summit 670 died on me the other day while riding. It sort of just puttered out while I was riding in some pow, which had never happened. I had not been running it for that long and nothing was too hot when I inspected it after it died. I could not get it to start for a while then after some tinkering got it to start but would barely idle and when I applied any throttle it would choked it out and die. When I put fresh spark plugs in, it started up easier and idled nicely but as soon as I applied some throttled it would kill the engine before moving. I have cleaned the carbs out and found no problems with the jets and there was fuel in the bowls. I am suspecting some type of fuel pump issue or ignition problem. Trying to get my hands on a compression gauge as well to check that. I am a fairly novice sledder and mechanic so looking for any suggestions for possible solutions. Anything would be appreciated, thanks!
 

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Discussion Starter · #5 ·
Checked the compression and had about 110 psi for both. I don't have an air box so can rule that out. I tightened the idle screws a lot so that it would idle very high and got the clutch to engage when given throttle without dying but seemed to be bogging a little bit. When I loosened the idle screws some so that it had a normal idle it I encountered the same problem as before where it was difficult to start and when it did the engine would die when throttled. Wondering if my carbs may be out of sync? anyone encountered this before??
 

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Checked the compression and had about 110 psi for both. I don't have an air box so can rule that out. I tightened the idle screws a lot so that it would idle very high and got the clutch to engage when given throttle without dying but seemed to be bogging a little bit. When I loosened the idle screws some so that it had a normal idle it I encountered the same problem as before where it was difficult to start and when it did the engine would die when throttled. Wondering if my carbs may be out of sync? anyone encountered this before??
I believe your Compression should be around 130psi on a Standard 670 which use's 11.5cr, a 670HO should be higher PSI with a 12.5cr, depending on what you have in it. Real 670HO's were only made 1998-99. I would do another Compression check, then if still low, pull the head, and inspect Piston Tops, you probably need new Rings, and Pistons. These motors require 91+ Octane. The low CR, indicates Ring & Piston problems, you could have even more issues, like a plugged fuel filter, bad fuel pump, Fuel Line collapsing, case seals, failed Oil Injection(Siezure), etc. Pull the Exhaust, and look in the Ports, at Piston sidewalls. If it was running ok before this problem, I wouldn't think the Carbs would be out of sink.

How many miles on this?
 

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My 95 Summit 583 had all sorts of HAC problems. I wound up just by passing it all together and rejecting the carbs to a 583 Formula spec.

It would run good, idle good, then suddenly load up, real rich.
 

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Discussion Starter · #8 ·
The sled does not have a working odometer so it is hard to guess how many miles, got it for cheap to get started with sledding and it's all I could afford. Also I don't have a HAC.
 

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When you tested the compression was the motor hot or cold? Might want to check your primer lines as well, might be sucking air threw those?
 
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