Very High Idle - Snowmobile World : Your #1 Snowmobile Forum
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post #1 of 2 (permalink) Old 02-11-2018, 05:10 PM Thread Starter
Join Date: Dec 2002
Location: Rockford, IL
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Very High Idle

Gents, I am at an absolute loss as to the source of my high idle. Sled is a 1995 Mach 1 670 all factory no upgrades. When very first starting the sled it will within a few seconds go to a 5500-6000rpm idle to the point where it engages my clutch. First thing I thought was carbs and I have had them off 3 times and cleaned them and I also bought new needle and seats for them but didn't help. Carbs idle screw and jets are set to factory settings. I thought maybe fuel pump problem but tore that down rebuilt it and still high idle. I also checked the seal at the primary clutch and that seems to be fine. What the heck could be the cause of such a high idle. I checked the impulse line to see if there was any fuel in there that may be feeding into the engine but that was fine too. The only things that will stop the high idle is if I hit the kill switch but then as soon as I pop it back up it goes right back to 6000rpm the other thing that will decrease the rpm's is putting my hands in front of the mouth of the carbs to cut the air off. I did change all the fuel and oil lines as there were 24 years old but I didnt go with original measurements regarding ID/OD but they are very close to original size. I have noticed there are some air bubbles in my fuel lines which wasn't the case with the original lines...I cant imagine that would have anything to do with the high idle as the extra air would vent through the carburetor vent tubes correct? Any thoughts are very welcome I am baffled at this one and we finally have enough snow to ride here in northern IL Thanks much!
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post #2 of 2 (permalink) Old 02-12-2018, 11:38 AM
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Join Date: Mar 2002
Location: Pence WI
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You haven't mentioned it, but with the age of the sled, have you lubricated or replaced the throttle cable?

It could even need to be adjusted.

You mentioned putting your hand over the carbs and it slowing down, assume you don't have a factory air box on?

What does the spark plug burn look like? Does it show lean?

It's cheaper to replace the decals, then build up a little sled. The first time I drove a snowmobile was 7/4/72. It was a 71 488 Polaris Charger.
Previously owned sleds:
1970 433 Polaris.Mstng, 2013 MXZ 600 ACE
1974 530 Cust II, 2012 MXZ XR 1200
1975 SS250, 2014 900 A RENE ADREN
1976 TX 440
1978 TXL 340
1979 TXL 340
1979 Cent 500
1980 TXL Indy
1981 Indy 500
1984 600 LE
1986 Trail Indy SP
1986 600 SE
1988 400 SKS
1989 Indy 650 ( 3)
1990 Original RXL
1992 500 EFI SKS
1993 RXL SKS
1995 RXL
1997 Ultra Touring
1998 Indy 500
1998 500 Classic touring
2001 800 XC/SP (2 )
2002 550 Classic
2002 800 XC/SP
2002 800 Vertical Edge
2005 900 Fusion
2006 600 H.O Fusion
2006 900 Fusion
1974 440 Electra
2008 600 CFI LX
2008 FST LX
2008 D700 RMK 163
09 D600 Swbk
11 Pro R 600
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