Polaris Sportsman 90 won't rev

BarnyardEngineering · May 23, 2020

I got a "free" Polaris Sportsman 90 non-running to fix up for my nephew. It's a 2-stroke reed valve type engine.

Replaced the carburetor and reed valves. Now it starts and idles. Pulling the choke causes it to flood and die at idle.

Still won't rev up. Acts like it can't get fuel. It will start to rev, then bog down and die. Pulling the choke does not help. Overhauled the original carburetor and it's WORSE than the new one. Won't do a thing with that carb.

Starting to think this thing is cursed. I know my engine troubleshooting. This engine is not reacting normally. It has not reacted normally to any of the troubleshooting I've done.

wore out · May 23, 2020

Clogged exhaust???

SVcummins · May 23, 2020

Bypass the reverse overide switch

marloweg · May 23, 2020

check scv and wore out that is my first thing to do mice love them little holes if it sat for anytime

BarnyardEngineering · May 23, 2020

(quoted from post at 13:32:24 05/23/20) Bypass the reverse overide switch

It doesn't have reverse, and it does start and run. It just bogs and dies like it's short on fuel when you try to rev it.

UncleTom · May 23, 2020

It could be a plugged main jet, and is running on the idle and the needle that raises when you open the throttle but with a pluged main jet it wont go past that. Buuuut, some ignition coils have retard and advance built in to the coil itself. If the advance part of the coil is not working it will act just like a pluged main jet. See if it is loosing spark at mid range and above. It learned me on a moped like that once. I never new the coils were like that.

neverfear · May 23, 2020

It's a long shot but....look for a crank case drain and open it. I've seen 2-strokes get loaded up on fuel and not
run right until the excess is drained off.

Steve@Advance · May 23, 2020

Things that will cause fail to rev:

Too lean. Easy test, get an oil squirt can with gas, give a shot into the carb when it bogs, see if it responds. Did you try rinsing the tank and new gas?

Weak spark. Put a piece of bare wire into the plug boot with a loop so it will stay on the plug. Get it running, slowly pull the wire away from the plug observing the spark quality as you try to rev it. I assume you did replace the plug, they can look good and do strange things.

Clogged exhaust. Common on 2 strokes, especially if it has a spark arrester.

BarnyardEngineering · May 23, 2020

I've tried fresh fuel on multiple occasions. I've cleaned out the tank. I've eliminated the tank by using another test tank, which was brand new out of the wrapper.

Found out that it will rev up if I choke the intake down with my hand, so it's definitely not enough fuel, or too much air. Crankshaft seals maybe?

504 · May 23, 2020

Does the carb have a main jet that screws in with the throttle cable attached it? Some of the Japanese carbs you can put the main jet 180 deg off,they will run either wide open or only idle.

TimV · May 23, 2020

Does it have a carb boot? Air leaks are common and can cause symptoms like you describe. Check for cracks, splits, and badly seated clamps. I assume you've already checked the air filter, airbox and spark arrestor for blockages.

P. Coltrane · May 23, 2020

Aren't those set up so you can govern the
speed on, wonder if it could have
something to do with that.

RusselAZ · May 23, 2020

Likely the exhaust ports in the cylinder are plugged or restricted

Polaris Sportsman 90 won't rev

BarnyardEngineering

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wore out

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SVcummins

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marloweg

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BarnyardEngineering

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UncleTom

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neverfear

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Steve@Advance

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BarnyardEngineering

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504

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TimV

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P. Coltrane

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RusselAZ

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