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yamsuzpolaris, Motorcycle Mechanic
Category: Motorcycle
Satisfied Customers: 156
Experience:  service technician on yamaha suzuki polaris products since early 70's. currently own and manage deal
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I have an 04 sportsman 700 with the same problem described

Customer Question

I have an 04 sportsman 700 with the same problem described on this page...won't idle without the choke on some.
Submitted: 2 years ago.
Category: Motorcycle
Expert:  yamsuzpolaris replied 2 years ago.

it could be any of the following:

leaking intake manifold

valve clearances a little on the tight side not allowing valves to fully close and seal tight when engine is running

carburetor pilot jet restricted

intake manifold is a visual. look at it closely. if rubber is cracking or has a larger crack in it needs replaced. carburetor sometimes restrict pilot or idle circuit if allowed to sit for length of time without running, and with ethanol in gas the gas varnishes faster partially restricts jet size. putting choke on just a little compensates for this. so that's what I usually do first, a carb overhaul and very carefully use cleaner and compressed air to blow thru the passages and jets. sometimes I gotta use a very thin wire to push thru jets but that's only extreme cases when they sit for a long time with bad gas. also smell gas, if it smells rank then dump all of it and use non-ethanol gas with additive to keep gas fresh longer.

the last issue with valves we check last. you will need a hand and someone with a leakdown tester to make sure with piston at top dead center, and you pressurize the combustion chamber that it has no more than 5% loss.

so look at manifold, clean carb or have someone who is familiar with this do it, and if it still needs choke on a bit to run then its a valve issue. usually these engines are pretty tough.