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Thread: 81 250R Rebuild/no start

  1. #1
    Join Date
    Jan 2019
    Location
    Montana
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    3

    81 250R Rebuild/no start

    Well, might introduce myself. I was given 5 tricycles about 6 years ago. Non of them ran, I had a 81 250R, 82 200s, two 185's, and a 110. I have since gotten rid of the 185's, and the 110. I had the 200 going, but gotta fix a spark issue.
    Now to my story/question.
    The 250R I had running after I got it. Some airhead (that is me...) didn't bother replacing the air filter (that was disintegrated) so the motor lost compression. totally not cool... on both accounts. I sent the jug out, got it machined, put a wiseco piston in, put a air filter on, put boysen two stage power reeds on. after all this, it wouldn't start. It sat like that for the next 5 years (yeah, I know. Why would anyone allow that to happen?). I decided to get down and get the thing going again. here's what I got.
    Good spark
    Fuel
    Compression (lots of it)
    Spark plug properly gapped (new). Was damp when I pulled it
    I cleaned and blew the carb out, and set the float level
    After stomping on the kickstarter for a long time, I tried tow starting it to. No joy.

    I pulled the reed cage out, and inspected it. the reeds have a paper thin gap to the cage, and are pretty stiff. With the cage off I kicked the bike, and it fired and ran for about 1-2 seconds... So are my reeds keeping it from starting by being to stiff? From what I understand, they are supposed to help the engine have compression, so I am stymied. I tried searching this forum and the internet, but couldn't find anything. So, here I am!

  2. #2
    Join Date
    Apr 2014
    Location
    Edmond, KS
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    1,561
    I'm no two stroke expert, but I don't believe that you are supposed to have any gap at the reed valves. If you are getting a good compression reading, then you are able to pull the air/fuel mixture through them. Maybe you could try flipping the reeds over. That could eliminate the gap and help it start. Another clue that you're getting fuel through the reeds is that your spark plug is wet. Another thing could be that your spark timing is off. I'm not sure about that one. I know that Yeagerb and others know way more about these than I do. Another thing that you can check. You didn't mention your air filter set up. If you have the stock air box, a rodent could have built a nest in there during the 5 years that it sat. This could cause an air blockage.

  3. #3
    fabiodriven's Avatar
    fabiodriven is offline Aspiring romance novel cover model, and the Official 3WW slayer of thieves and swindlers. Catch me if you can
    Join Date
    Jun 2008
    Location
    East Bridgewater, MA
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    I highly doubt your reeds have anything to do with the bike not running.
    85 Tri-Zinger 60
    85 ATC250SX
    86 ATC250SX
    87 ATC250SX
    02 XR650L conversion
    84 ATC 480R

  4. #4
    Join Date
    Jan 2019
    Location
    Montana
    --
    3
    Thanks for the suggestions. Will pop that aircleaner box apart. It does still have the oem box. Looking down into it I don't see anything. But will do a little disassembly and see what's going on. Will find some lubed starting fluid when I go to town tomorrow, see what that stuff also does for me. Will keep yall posted.

  5. #5
    Join Date
    Mar 2010
    Location
    Slidell, LA
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    4,510
    Don’t use ether to start your bike, especially on fresh rings. All things being equal it will fire if you have spark, fuel and air. You say you have them but you don’t or you would fire. When you say good spark, are you using a tester or your eye? I have seen “good spark” still not start a bike because it was weak and the piston actually blows out the spark. If you are only using your eye, look for a blue spark but I would still get a spark gap tester and see if you can actually jump a gap larger than OEM. I would also be looking at the woodruff key on the flywheel side of the crank. If that’s shot and your fly wheel is out of time you can have spark all day long and not be firing correctly. Lastly, bikes will still fire with clapped out reeds. If yours have a gap why keep them in there? Get a new set of boyesen power reeds. They are stupid cheap and are an upgrade over stock.
    Last edited by yaegerb; 01-06-2019 at 08:48 PM.
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  6. #6
    Join Date
    Apr 2014
    Location
    Edmond, KS
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    1,561
    He did say that the reeds are new Boysen two stage power reeds. Another thing to check while you're looking at the air intake. If it's built like a utility style trike and has a hose that attaches to the backbone of the frame, that's another place for a blockage to occur. I have no idea if a 250R is set up like this or not.

  7. #7
    fabiodriven's Avatar
    fabiodriven is offline Aspiring romance novel cover model, and the Official 3WW slayer of thieves and swindlers. Catch me if you can
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    Jun 2008
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    East Bridgewater, MA
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    Yes I just wanted to agree with Yaeger about the ether. Unless you're starting a diesel in cold weather, put the ether away. Any gas engine working properly will never need ether.
    85 Tri-Zinger 60
    85 ATC250SX
    86 ATC250SX
    87 ATC250SX
    02 XR650L conversion
    84 ATC 480R

  8. #8
    Join Date
    Mar 2010
    Location
    Slidell, LA
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    4,510
    Quote Originally Posted by 350for350 View Post
    He did say that the reeds are new Boysen two stage power reeds. Another thing to check while you're looking at the air intake. If it's built like a utility style trike and has a hose that attaches to the backbone of the frame, that's another place for a blockage to occur. I have no idea if a 250R is set up like this or not.
    The reeds were new 5 years ago and now he has a gap between the reed and the block. Either they were installed incorrectly or they are already warped from sitting. If there is a gap then they aren’t doing there job. Like I said earlier reeds are cheap and easy to replace. I would remove that question mark off the table.
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  9. #9
    fabiodriven's Avatar
    fabiodriven is offline Aspiring romance novel cover model, and the Official 3WW slayer of thieves and swindlers. Catch me if you can
    Join Date
    Jun 2008
    Location
    East Bridgewater, MA
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    81 250R Rebuild/no start

    I never saw where he said there was a gap in the reeds worth considering. In the first post it says there was a "paper thin gap between the reeds and the cage and the reeds are stiff". That sounds pretty much correct to me.
    85 Tri-Zinger 60
    85 ATC250SX
    86 ATC250SX
    87 ATC250SX
    02 XR650L conversion
    84 ATC 480R

  10. #10
    Join Date
    Jan 2019
    Location
    Montana
    --
    3
    Popped open that airbox. The new air cleaner is still good. Still has lotsa oil in it to. Nothing extraordinary in the airbox. I took the fuel line off and dribbled iit straight into the carb. The motor went "pop, pop". So I think I got a fuel delivery issue. All damp and what in the carb tho. Will disassemble the carb again, and blow it out again. Make sure the little rubber bullet thing ain't sticking or something. Carbs are fairly simple, but I never seem to have much luck with them. Well, tenth times the charm.
    Ordered a gasket set to replace the reed cage mounting gasket I destroyed.

  11. #11
    Join Date
    Sep 2005
    Location
    MICHIGAN
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    2,015
    A fresh rebuild and fresh oily air filter will result in rich jetting. The reeds may not be helping. You can buy bulk sheets of gasket and make your own for things like reed cages, ect...

    Since its winter the rich jetting may be a blessing....

    Is the plug new and gapped correctly?
    Is the plug wet after failing to start?

    I used to drip a bit of mixed fuel (often with the fuel line) right into the spark plug hole to get a stubborn engine to fire or to test....if you do that and it runs until the fuel in cylinder burns up and then stalls/doesnt rev, you know it is a fuel/air delivery problem.
    86 T3
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