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Discussion Starter · #1 ·
Hello everyone. I have a 1993 polaris 350L 4x4. I took it out this weekend and it was running great, but all of a sudden, it lost power. It wouldn't even make it up a small hill. Then after getting it back to my cabin, it wouldn't even start at all. I would attempt to start it, but it would just crank, then backfire, blowing the exhaust pipes apart at the spring loaded connections. I put the pipes back together, and try again, just causing another backfire. This is a 2-stroke bike. I would normally think a timing problem, But unless I am wrong there really is no timing in a 2-stroke. any thoughts? :dunno:
 

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Polaris...

It kinda sounds like a cylinder I had before. The one I had, had a cylinder sleeve incorrectly installed. The guy bored out the cylinder TOO big(for the sleeve) and when the engine warmed up the WHOLE sleeve would spin and put all the ports sideways. I put the cylinder in the oven to heat it up to remove the sleeve(One hot cylinder ready...lol) and the sleeve just dropped out...lol
 

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It also could have a hole in the piston. Yes, 2-stroke timing can be adjusted w/ a timing light, but most of the time there is a notch/mark in crank case that you align with stator.
 

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Discussion Starter · #4 ·
That sounds interesting, But I have never had any work done to it. granted I have only owned the bike since august, but it is obvious that no major work of any kind has ever been done.
 

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well that cancels that out.
Maybe the ETC = eletronic throttle control is adjusted right at the handle bar in the throttle housing. basicly it has to have about 1/8" slack in the throttle cable before you actually feel the throttle being pushed and this is to prevent the bike from having a frozen throttle and it will go into a override mode and not letting the bike run. Back firing does sometimes mean a lean condition, but the spark plug would be a white color instead of BLUE.. check the intake boot for cracks or other air leaks to explain the lean condition if it has one. It might be something simple but hard to find. Check all wire connectors/connections.
 

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hmmmm...backfiring. Have you checked the spark after it started acting up? Do you have a compression tester? Have you disassembled and cleaned the carb. recently? Carb. jets can clog real easy.....Floats can stick....Does the engine backfire when the choke is on? If it does it is a clogged main needle jet.

Allways=Change spark plug and re-cut spark plug boot.
 

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Discussion Starter · #7 ·
okay, wow lots of stuff to check. Here is what I did tonight. I opened the bike up, (removed all the plastics, rack, etc.) First thing I went for was the reed valves, heard from another site that may be the problem. They are slightly out of tolerance, so I am ordering a new set of reed petals. I pulled the cylinder head to inspect the condition of the piston/cylinder walls. Everything looks good there. I have opened and inspected the carb. it wasn't full of gunk like I have seen on other bikes before. No I haven't rebuilt the carb yet, but it is on my to-do list. I have also heard from other sites that it may be the override malfunctioning, will be checking that next along with the etc module in the throttle. the bike is a 93 and has like 5700 some odd miles on it, so I know it is worn, but before the problems this last weekend, it ran perfect! there's lots of other things it needs like in one of my previous threads about the starter, looks like I need a starter and reduction gear set, looking to also do brakes all around, and a throttle cable. Trikemaster, a question I have for you, is, If I want to bypass the oil injection system, and pre mix my oil/fuel, is there anything I need to do to the existing oil injection system to do this? and what would the ratio be? thanks in advance for all your help
 

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350l...

inspecting the oil pump ever so often insures you wont have a failure Ive had 2 2 strokes and never had a engine burn up but i did have one pump go to crap but stuck open I was wondering why it smoked so bad and i was going through so much oil. now I check it once a year and make sure the spring looks good and its staying clean inside.
Bleed the pump by loosening the phillips screw on the top until oil comes out. Also check tank vent and the little filter in the line from tank to pump.
 

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Polaris 350L....

Not a good idea to bypass the oil injection completely. The oil pump also feeds oil into the crankcase which is to help lubricate the crankshafts main bearings. If you would like, you can remove the oil line from the carb. and block it off. Then pre-mix the gas to 32:1 ratio. But I wouldn't bypass the system completely...

I allways run 32:1 on my ATV's. People think you can get more speed running 50:1 witch is retarded because with less oil you get more piston ring blowbye(less compression).
 

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Discussion Starter · #10 ·
okay, I agree with not bypassing the oil injection. I have the bike apart now. and nothing looks out of order. when I pull the pullstart, the piston pumps proberly. smoothly and the cylinder walls are very clean (not scratched) any possibility it is the reed valves?
 

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okay, I agree with not bypassing the oil injection. I have the bike apart now. and nothing looks out of order. when I pull the pullstart, the piston pumps proberly. smoothly and the cylinder walls are very clean (not scratched) any possibility it is the reed valves?
Reeds could do that....Have you cleaned the carb. recently? I just keep thinking the floats are sticking....
It seems to sound like carb. or timing and timing don't just go out on 2-strokes...
I wouldn't say I'm against bypassing the oil injection because if that pump goes out......Booom...there goes all your work. You just have to plug up the carb oil intake and leave the crank oiler connected.
 

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Discussion Starter · #12 ·
yes. The head has been removed. yes I tried to start it with and without the choke on. Carb is extremely clean, but I am going to rebuilt it anyways, especially as cheap as the kits are.
 

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Discussion Starter · #14 ·
the first thing I did when it atarted acting up is to drain and replace the fuel. I always run 93 octane in my atvs, just to keep 'em clean
 

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Nice....If it had power valves it would be that. We will find the rat that's eating the wires...
 

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well that cancels that out.
Maybe the ETC = eletronic throttle control is adjusted right at the handle bar in the throttle housing. basicly it has to have about 1/8" slack in the throttle cable before you actually feel the throttle being pushed and this is to prevent the bike from having a frozen throttle and it will go into a override mode and not letting the bike run. Back firing does sometimes mean a lean condition, but the spark plug would be a white color instead of BLUE.. check the intake boot for cracks or other air leaks to explain the lean condition if it has one. It might be something simple but hard to find. Check all wire connectors/connections.
Have you checked ETC?
 

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Newby to ATVz

I'm getting a lot of oil in the carb, and the same symptoms wth the backfires. Compression, fuel/oil feed good.
This is my first ATV but I've had numerous dirt bikes.
Would it hurt anything to just mix my fuel like I did for my dirt bikes?
 

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It kinda sounds like a cylinder I had before. The one I had, had a cylinder sleeve incorrectly installed. The guy bored out the cylinder TOO big(for the sleeve) and when the engine warmed up the WHOLE sleeve would spin and put all the ports sideways. I put the cylinder in the oven to heat it up to remove the sleeve(One hot cylinder ready...lol) and the sleeve just dropped out...lol
I second this
 
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