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Thread: 85 250sx kick and motor stuck

  1. #1
    Join Date
    Jan 2019
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    85 250sx kick and motor stuck

    Hey,
    Started working on my 250sx thats been sitting for abour a year or so... was running last time parked. Thought the motor was stuck as the kick would not move, but then took off the left side (shift lever side) cover and can turn the flywheel bolt and motor 1/2 turn each way... but only half turn then it stops abruptly. Where's the hangup... something in the clutch or kick mechanism?

  2. #2
    Join Date
    Apr 2012
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    Hmm turning the engine by the flywheel is only turning the engine, the gears the kick starter uses would be turning the transmission gears and such. Sounds like you have an issue on the engine side of things, stuck valve, spark plug too long, etc. I'd say to pull the spark plug first and see if it moves any further. If you have a bore scope, check if the bore is rusted. Also pop the caps on the valve cover off and see if any valves are stuck open. I'd guess the cylinder started to rust, depending how bad it is, you might be able to work it out and things will be fine, but if it's bad (pitting etc), it's best to get the cylinder bored and new piston/rings, or get another cylinder in good shape that matches your piston size.

    FYI, the engine shouldn't be turning the transmission gears when rotating it the correct way. When going backwards, I think it would be turning the transmission gears. Based on the description, it really sounds like it's something directly related to the crank though (it takes several turns of the engine to make 1 turn of the clutch gear).

    Kind of hate to be the bringer of bad news, hopefully it's something simple like somehow some junk got in the engine and popping the head off and removing it fixes the problem, or there's a liquid causing it to hydro-lock on compression stroke.

    Good luck and keep us informed on what you can find.

  3. #3
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    Thanks. I will check the valves first. The plug is already out and i can feel compression and suction depending on which way im turning the flywheel with a wrench. Not too familiar with the clutch and gearbox on it as i never had to go into it before. I did notice that the kick wont move no matter what position i turned the motor to by hand... (except when it doesnt catch and slips by... but thats been an ankle buster for years!) i guess i need to find a schematic to help figure out the linkage in my head....

  4. #4
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    Lol I was guessing the one way bearing was bad too. It's item #25 in the diagram. If I recall correctly there's cheaper new ones on ebay, not sure where they are made for sure though.

    https://www.partzilla.com/catalog/ho...250sx-a/clutch

    I don't directly see where that would have any effect on the issue though. Basically the bearing is there for kick starting, and engine braking. #14 and #1 are the two main gears under the right side cover and they are not directly tied to the crank, that one way bearing is what engages it one direction, or if the engine is spinning fast enough, the clutches lock the two together.

    If the kick starter isn't working even if the engine is rolled to a center spot, then clearly something is messed up with the kick starter, and most likely unrelated to the engine turning 1/2 over and stopping. Sounds like pulling the right side cover is needed to see if anything is clear on what's going on.Wouldn't hurt to grab one of those bearings so you can fix the kick start problem too. FYI, the electric start has the same one way bearing setup, but it's only used during electric start from my understanding.

    I've had a somewhat similar issue, bought a Yamaha Moto4 350 quad with a "seized up" engine. When I pulled the right cover off, the clutch pins were all bent and the clutch pads were hitting the case and locked up against it. Replacement primary clutch got it going again to only find out it's a smoker so needs rings bare min and also the timing chain is shot. The Yamaha doesn't have a metal ring to support the pins like the Honda does though. Before I went under the right cover, I pulled the left cover off so I could turn the engine by hand, and it could move it about a 1/4 each direction and it was a hard lockup, not like just getting hard to turn (like rust feels like).

    Anyway, I'm interested in what's going on since I tend to buy 250es and sx machines in horrible shape for spare parts and such. Just never know when one will have the same issue.

  5. #5
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    Great info. I will try to take off the right side and look around over the next few days... will let you know what i find... and likely ask more questions. Thanks!

  6. #6
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    Don't forget to grab a side cover gasket, they are like $10. RTV isn't really ideal, and the old gasket will likely rip. The right side has to seal to keep the oil from leaking out.

    with the cover off, you'll be able to spin the bell of the clutch in one direction to check for any binding on the gears and such and also be turning the transmission input shaft. If you shift it into gear, the machine would move. Turning it in reverse will try to turn the engine if the one way bearing isn't slipping.

  7. #7
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    Just an update, finally got back to working on it. It was heavy corrosion in the top third of the cylinder. Looks as if water got in and sat for a while either from loose plug and sitting at the edge of a shelter. Anyway, piston wedged up and stuck. Broke it loose turning the flywheel but would only travel back up to the stuck position. Pulled the top of the head off and cleaned it up to where it travels freely, but its so pitted i think a bore is in order. Went ahead and pulled head. Rings are pretty gunked up too.

    So.... bore recommendations? Looks like several oversize kits available now... including a 350cc kit.

  8. #8
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    85 250sx kick and motor stuck

    That's up to you! My recommendation would be the least amount of material off the cylinder as they can get away with while still cleaning it up. If you want to do a big bore that's your choice, but get ready for modifications because it's not going to stop there!
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  9. #9
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    Yea I agree, depending how deep the pitting is, bore it just to the point where the pitting is gone. Probably best to talk to a machine shop so they can give advice since normally a cylinder is bored to a piston size so it has the correct clearance etc.

    Big bores are a whole new can of worms, a lot can be involved with resleeving a cylinder, boring out the center cases etc. If you go that far, cam, intake, porting, exhaust etc should probably be done too which adds up $$$ fast.

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