2 stroke fun for 200 bucks

Discussion in '2 smokers' started by hardwaregrrl, Feb 16, 2011.

  1. stainlesscycle

    stainlesscycle Long timer

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    no doubt about that. blew up a rd400f that i had just rebuilt 1 hour before. timing was too far adavanced. went 3 miles.. it happens.
  2. AC Swank

    AC Swank Banned

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    If you have the right tools, you can measure the clearance. Measure the ID of the bore and the OD of the piston at the ring area. You should be shooting for .0015" - .0018" clearance. I suspect you will find it to be greater than .0025" and if so, another rebore is in order. PM me your email address and I'l send you a PDF article on 2 stroke top end rebuilding which should help you out.
  3. hardwaregrrl

    hardwaregrrl Can't shoot straight Supporter

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    Hmm. I wouldn't think that was something I would have to do since they bored and ordered the piston and rings. Bummer, I really didn't think to have to check their work. The guy that bored it out has a very good reputation. Do you guys think that it was the bore and piston job that caused the seizure, or does it look as though oil was not getting to the jug?
  4. Stagehand

    Stagehand Imperfectionist

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    OIl wouldnt be getting to the jug separately, its included with the fuel, remember :D I dont know from two strokes but its better to have them a bit rich at first, if you ask me, rather than too lean, and I'd think your spark plug was maybe on the lean side of oiled. But you say you ran pre-mix... I dunno.
  5. AC Swank

    AC Swank Banned

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    Rich = more fuel and oil = a larger pilot jet size.

    The picture of the plug did look like the motor was a bit lean. When you get it back together, increase the pilot jet size, make sure the timing is not too far advanced, and use a hot plug. After 500 miles, change the pilot jet back to the orginal size and use a standard plug.
  6. hardwaregrrl

    hardwaregrrl Can't shoot straight Supporter

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    The oil injection system has 2 ports on the jug in which it feeds it the oil. I only used premix on start up so that there would be no question that oil was getting to it. Oh well. Still screwed it up.:D
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  7. hardwaregrrl

    hardwaregrrl Can't shoot straight Supporter

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    I have to time this bike running, as it has the PEI system. I never got that far. No static time on this guy. Also, depending how much I'm going to need to go up in cylinder size, I need to increase jet size anyway.
  8. WVhillbilly

    WVhillbilly Long timer

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    Well, that sucks.

    Not anything you did, I agree that it looks like it could have been a machining problem.
  9. Whitey1

    Whitey1 Long timer

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    Can you plug off the lines going to the carb and just use the pump for the squirters? I always trusted premix more so then pumps myself.

    BTW You are doing a great build and this too sahll pass and it will all be worth it in the end!

    :thumb
  10. hardwaregrrl

    hardwaregrrl Can't shoot straight Supporter

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    I hope so, and thanks for the props. There are no oil lines going or coming from the carb, they are delivered to the bottom end by the pump. The more you roll on the throttle, the cable opens the pump more and more oil flows into the bottom. I have been told for years that the injection system is the way to go. Not really anything to fail, unless you have air in the line.
  11. willierides

    willierides Been here awhile

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    Actually only one of the lines goes to the "bottom end" (ie. the left crank bearing). The line right above that injects oil in the the intake stream right after the carb. So, you're right, it doesn't go to the carb, but it still inject oil into the charge going into the case.

    I know the manual tells you how to set the timing with the bike running, but you can get it pretty close without doing that. I just recently rebuilt a TS250 top to bottom. I don't remember EXACTLY what was where, but there is a line scribed on the backplate (stator) that you line up with an arrow point cast into the case. Pretty sure the marks are at the point where the "top" screw (of the three that are used to mount the stator plate). That's how you set the timing initially and it was dead nuts on when I set mine that way.

    If the bike was run without oil in the mixture, the intake side of the pistone will be scraped and damaged. If the damage is on the exhaust side and looks kind of like it disintegrated (powder in the cases) then it was most likely caused by a lean condition...either a leaking left side crank seal, leak around the intake somewhere or a clogged pilot jet of something in the carb. Did you go through the carb? My failure was due to a lean condition and I chose to split the cases to clean it out. I'm glad I did. I don't think I could have rinsed all the debris (aluminum powder, basically) out successfully. Wonder if this was a contributing factor to your failure after rebuild?

    One more point, sometimes putting more oil in the mixture actually causes a lean condition. It sounds counter-intuitive. But if you are adding oil to the gas/oil mixture without changing the a/f mixture (where a=air, f=fuel, in this case gas and oil), then you are effectively supplying less gasoline in proportion to the air supplied and creating a lean condition.

    Sorry this response seems to be kind of erratic, just trying to hit a few points I thought of reading through all the posts (which took a while...whew!).
  12. hardwaregrrl

    hardwaregrrl Can't shoot straight Supporter

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    Hey, thanks for the info. I looked at the piston and it is more scored on the intake but is also scored on the exhaust, not sure what thats telling me.? I think I'll just take the cylinder to be bored again somewhere different and have them tell me what size piston to get and try to source it for a cheaper price. I've already located a few oversized under 50 bucks.

    There seems to be an awful lot of opinions flying around about proper start up procedure for a new top end. At this point I'm afraid to take anyones advice evern though I know everyone is just trying to help. You've just said the opposite (concerning the premix at start up) of what so many others have said. I'm pretty lost right now, so hoping the ride shop can look at the cylinder and piston and give me some advice.

    Now I'm not sure what to do with the carb as far as going up a main jet size.


  13. Grider Pirate

    Grider Pirate Long timer

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  14. Stagehand

    Stagehand Imperfectionist

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    whoa, there's news. I always assumed it was better to err on the side of too much oil than not enough. I mean, like 55 or 60 to 1 rather than 70 might be better than 85 to1. but how far can you go before its a real problem?
  15. AC Swank

    AC Swank Banned

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    Think of it this way, the gas is for cooling and the oil is for lubrication. Make sense?
  16. hardwaregrrl

    hardwaregrrl Can't shoot straight Supporter

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    Yes! Makes total sense but also takes away from the fact to "cover all your bases". Seems kind of impossible to do, or no? I just don't want to toast another top end and I'm trying to figure out how to keep that from happening.
  17. bgoodsoil

    bgoodsoil Dare to be Stupid

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    I'm sorry. I know you put a lot of work in to it and it must feel bad having it go wrong. Sounds like you're still trucking though. Ya know where I'm at if there's anything I can do to help.
  18. baldwithglasses

    baldwithglasses Godspeed, Robert

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    What bgoodsoil said.

    I've got some dumb stuff to do for the first half of this upcoming week, but I'm happy to lend a hand in the later part of the week.

    Good job, tough break, keep up the good work, etc.
  19. Beater

    Beater The Bavarian Butcher

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    +1 Let us know if we can help :freaky
  20. AC Swank

    AC Swank Banned

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    Use the injection system, it will supply the needed oil (lubrication). Up the pilot jet to increase the gas and increase the cooling. Make sure to use a hotter plug as the increase in the gas will require it unless you want to foul your spark plug. After 500 miles, switch back to the standard pilot jet and spark plug. Also during these first 500 miles, do not run at full throttle for extended periods.