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Thread: 340 Bearcat Backfiring?

  1. #1
    Member Yukoner's Avatar
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    Default 340 Bearcat Backfiring?

    Picked up a great deal on a 98 Bearcat 340
    2400 miles. Tore it apart, cleaned things up, new recoil. Runs great, but i'm getting some low end bog, intermitantly, with some backfiring.
    I cleaned the carb, but didn't note the main jet size. I'm wondering if the main jet being too fat would load the carb and give me this bog/backfiring?
    It doesn't look like you can adjust the needle on this carb.
    Any ideas?
    Thanks

  2. #2

    Default BackFireing Arctic Cat

    Blown Crank Seal..... 98% sure..... very common on AC motors espically lower cc air cooled motors. I have had this problem 3 different times on 3 different sleds.

    Tom

  3. #3

    Thumbs up

    Quote Originally Posted by Cresent Hills View Post
    Blown Crank Seal..... 98% sure..... very common on AC motors espically lower cc air cooled motors. I have had this problem 3 different times on 3 different sleds.

    Tom
    That is the first thing I would check for as well.
    "96% of all Internet Quotes are suspect and the remaining 4% are fiction."
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    Member Yukoner's Avatar
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    Default

    Thanks gents
    Any other symptoms on the blown seal to further narrow the diagnosis?
    Further to the bog issue, i would be going slow, then give it a bit of gas, then bog, then feather the throttle to get the RPM's back up, then off i would go, no problem, but the backfire would usually occur then.
    It was warm-ish out, so thats why i was thinking too large a main.
    I only paid $750 for it, and its in fantastic shape otherwise, so rebuilding the mill in my shop is no problem.
    Thanks

  5. #5

    Default Backfire

    Are you in the valley ? If so i have a guy that is super reasonable and sharp as a tackand if he can't fix something..... It is junk... But i doubt that is your case. If you are interested pm me me and i will get you in touch with brent. He has a sweep shop at his house.

    Tom

  6. #6

    Default try this

    if it's a bad seal, just spray some starting fluid at the seal while the engine is running. if it's bad, the rpm's will pick up. pto side only, kinda hard to spray the seal under the flywheel

  7. #7

    Default

    Quote Originally Posted by yetnaman37 View Post
    if it's a bad seal, just spray some starting fluid at the seal while the engine is running. if it's bad, the rpm's will pick up. pto side only, kinda hard to spray the seal under the flywheel
    Not really to difficult to do the same thing on the Mag side. I usually take a plastic bag and wrap it around the end of the motor and spray into the plastic bag. It helps hold it there long enough for it to get sucked in, if the seal if bad. There are also generally tell/tale visible signs of leaking, with some grime and oily build up around the clutch area. I have seen some seals actually blown out of the case, due to backfiring and then it is very obvious.
    "96% of all Internet Quotes are suspect and the remaining 4% are fiction."
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  8. #8
    Member Yukoner's Avatar
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    Default

    Appreciate the info!
    Given that a piston kit is about $70, and a seal/gasket kit is about the same, i might as well tear it down.
    Thanks again

  9. #9

    Default

    Quote Originally Posted by Yukoner View Post
    Appreciate the info!
    Given that a piston kit is about $70, and a seal/gasket kit is about the same, i might as well tear it down.
    Thanks again
    I would troubleshoot it first, as you might have other issues. Rebuilding the crankcase will not resolve electrical issues, Carb Mounts cracked, Carb issues etc.
    "96% of all Internet Quotes are suspect and the remaining 4% are fiction."
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  10. #10
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    Default Seal

    How big a job is the crank seal?
    I believe I am experiencing similar bog on a Puma 340, although it only has 1300 miles.
    I cleaned up the carb and got it starting first pull, but still takes a little throttle feathering to get going sometimes.
    Any special tools required, or is this pretty straight forward for the somewhat mechanically inclined? Thanks,
    David

  11. #11

    Smile

    Quote Originally Posted by AKFloats View Post
    How big a job is the crank seal?
    I believe I am experiencing similar bog on a Puma 340, although it only has 1300 miles.
    I cleaned up the carb and got it starting first pull, but still takes a little throttle feathering to get going sometimes.
    Any special tools required, or is this pretty straight forward for the somewhat mechanically inclined? Thanks,
    David
    Pull the motor.
    Remove the Driven Clutch. Need a special tool for this.
    Remove the motor covers and recoil starter.
    Pop the bottom off of the Crankcase (carefully, don't mar the mating surfaces).
    Clean it all up and install new seals, sealing and greasing them.
    You will need a special sealant for the lower end of the crankcase.
    Reassemble and torque the crankcase bolts/nuts and clutch bolt to the correct ft lbs.
    Reinstall the motor.
    Usually takes me three to four hours, but I am slow and methodical.
    Fairly easy job, I would rate it about a number 4 for difficulty, on a scale of 1 to 10.
    "96% of all Internet Quotes are suspect and the remaining 4% are fiction."
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  12. #12

    Red face

    Quote Originally Posted by Akres View Post
    Pull the motor.
    Remove the Driven Clutch. Need a special tool for this.
    Remove the motor covers and recoil starter.
    Pop the bottom off of the Crankcase (carefully, don't mar the mating surfaces).
    Clean it all up and install new seals, sealing and greasing them.
    You will need a special sealant for the lower end of the crankcase.
    Reassemble and torque the crankcase bolts/nuts and clutch bolt to the correct ft lbs.
    Reinstall the motor.
    Usually takes me three to four hours, but I am slow and methodical.
    Fairly easy job, I would rate it about a number 4 for difficulty, on a scale of 1 to 10.
    I failed to mention in this post:
    On some motors you have to remove the stator and/or flywheel. This requires the use of a puller and make sure you mark the location of the stator winding plate. E Gap can be be altered if you don't do this.
    "96% of all Internet Quotes are suspect and the remaining 4% are fiction."
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    Default Easy Fix

    Turns out it was no big deal. Took it to Brent. (Thanks Tom) He diagnosed the problem before it was off the trailer, and fixed it the next day. Throttle microswitch. Used to be a $30 part, but now you've got to buy the whole assembly, so it was $140. Anyway, runs great now. My buddy's 550 was doing the same thing, so sent him to Brent, the next day, and he had the same problem. Guess it's not uncommon, for ACs anyway. Maybe I should carry a spare. Anyway, glad I didn't have to pull the motor and do a crank seal. Ready for another weekend. Hope it will be warmer than the last.

  14. #14
    Member Yukoner's Avatar
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    Default

    I am thinking that my problem might be same as yours. I believe you can diagnose this by jumpering the throttle switch?
    The way mine cuts out then backfires, it keeps nagging to me that it might be electrical
    Anyway, i've ordered new seals, gaskets and pistons/rings. Cheap, i'm going to re-build at some point anyway.
    The crank seal thing, while it could be the problem, i looked pretty closely and there was no oil staining by the primary clutch.
    Great info guys

  15. #15
    Member Yukoner's Avatar
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    Default

    Turns out is (was?) the throttle switch. Put a continuity tester on the lead to the kill switch/throttle switchs, and there was enough slop in the throttle retainer pin assembly, that you could get the circuit to open while the throttle was engaged, especially if you had the side of your hand on the top of the throttle instead of your thumb, like you do when your sidehilling etc. Shimmed the circlip out a bit with a 3/16" washer to tighten the pin assembly and no more opening of the throttle switch circuit. Easy fix instead of buying a new assembly.

  16. #16
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    Default

    Most times you can replace the plastic washers to resolve the problem. Be careful snugging that pin that you are not going to bind the flipper.

    Spray the switch with your favorite lube when you have it the shop defrosting, to help keep the moisture out of the switch.

  17. #17
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    Default Polaris too?

    I have had similar problems with an old 440 Sport. It starts easily enough, but won't idle. When it dies it will need to be restarted with full choke. When riding, it is like on or off; high speed is fine; low speed it runs as long as you hold the throttle in. Back off and it will die in a few seconds, and it will then need the choke and some fancy fingering to get it up to speed again.

    I've cleaned the carbs thoroughly to no avail; taken it into two shops here, and they both said it was a water problem. One of them even adjusted and synced the carbs. The seat was torn anyway, so I bought a fairly new seat/tank combo which was bone dry and while I was at it, replaced all fuel line, pump, filter, etc. just to make sure there would be no possible water left. I even added some Sea Foam for good measure... but still the same problem several hundred dollars later.

    Could the throttle switch be the problem?

  18. #18
    Member Yukoner's Avatar
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    Quote Originally Posted by Dupont Spinner View Post
    Most times you can replace the plastic washers to resolve the problem. Be careful snugging that pin that you are not going to bind the flipper.

    Spray the switch with your favorite lube when you have it the shop defrosting, to help keep the moisture out of the switch.
    Should have mentioned that i did also replace the bushings I worried about binding too, but no problem at all.
    Sayak, the throttle switch, if it is the issue, is either on, or off. Yours doesn't sound electrical to me.
    You mentioned cleaning carbs, has the pilot jet been cleaned?
    Y'know, yours almost sounds like crank seal symptoms. If you can, find some to do a crank compression test.

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    Default

    back from the dead, 340 is back firing, have the oil leak by the clutch and bottom of engine. Bogs down all that, you guys are saying crank seal, should I do it myself, ( I think I can do it) or take it to the dealer? Its a 98 bearcat 340. Thanks

  20. #20
    Member Yukoner's Avatar
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    Default

    How many miles you have on it? Are you sure its leaking at the PTO seal? Those engines usually always leak oil past the exhaust manifold gasket and then the oil leaks down.
    Could be lots of things.
    Never wrestle with a pig.
    you both get dirty;
    the Pig likes it.

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