1996 440 backfires under certain conditions - Snowmobile World : Your #1 Snowmobile Forum
 
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post #1 of 4 (permalink) Old 01-03-2009, 04:31 PM Thread Starter
 
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Question 1996 440 backfires under certain conditions

I have a pair of Arctic Cat 440s (ditch pickles, as someone recently pointed out to me) one '96 and one '97. I just got them last year from a relative, and they needed quite a bit of cleaning up to get them running after they sat (with gas - yikes) for 3 years. I completely disassembled the carbs and gave them a thorough cleaning, new gas lines, filters, plugs, etc etc. They both run great now with the following exception:

When warm, with back pressure (medium-hard deceleration, braking, etc) the '96 will cut to a very low idle and sometimes backfire. When I say "cut" I mean that it's very immediate - almost seems like the kill switch was hit, but it doesn't quite stall, just drops to a lower idle than normal (600rpm?) and backfires. This only happens when it's several miles warm. Slight pressure on the throttle while slowing or braking will prevent this, or recover from it if it starts happening. It's performing fine otherwise - plenty of pep.

This was happening last year too. Tanks and bowls were drained last summer, and they started easily this season with new gas and plugs. The Mikuni web site or carb manual didn't help with this particular problem, but it's a little bit of an oddball as far as I can tell. Any help would be appreciated.
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post #2 of 4 (permalink) Old 01-03-2009, 11:56 PM
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Sounds like a choke is not seating on one of the cylinders causing it to get flooded out when it gets warm. Remove, clean chokes and adjust down if necessary. If this isn't the problem, it could be a clogged pilot jet in your carbs, then you'll have to remove your float bowls again and remove and clean the pilot jets. Make sure your carbs are synched also.
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post #3 of 4 (permalink) Old 01-16-2009, 12:12 AM Thread Starter
 
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Thanks Thundercat! I spent a lot of time cleaning jets last year, so I'll start with the choke.
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post #4 of 4 (permalink) Old 01-16-2009, 09:49 AM
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Sounds like a TSS problem to me. If you unplug the 3 wire connector coming from the throttle (unplug at the steering column) and the problem goes away, it's a TSS issue. Most common problem is that your throttle cable is too loose or the 2 plastic bushings (look like washers) on the throttle pivot pin are worn out.

The way the TSS system works is it senses the position of the Throttle by a switch in the throttle which trips when the throttle is at Idle and also senses that the carb slides are all the way shut with magnetic switches on the carbs that close when they sense a little steel insert built into the slides. If the system detects that the throttle is at idle but the slides are not, it will kill the ignition. By putting slight pressure on the throttle, you disable the throttle switch. Unplugging the 3 wire connector mentioned above disables the whole system but also disables your kill switch.
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