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1981 Honda CM400E

Discussion in 'Moto Club' started by nsb22, May 9, 2006.

  1. nsb22

    nsb22 TEAM OAF

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    I've got a 1981 Honda CM400E and I can't get it running right!

    What it does: It runs fine at low and high rpms, but in mid rpm's it misses. If I shut the bike off and don't turn the petcock off, the right carb overflows. It also gets hot really fast.

    What I have done: Cleaned the carbs, changed spark plugs and gapped them properly.

    What I will be doing: Rebuilding the carbs, clean the gas tank, try and figure out why it doesn't run right!

    Any help would be greatly appreciated!
     
  2. DaisyCutter

    DaisyCutter

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    It sounds like a fuel issue to me. I'd start by cleaning the carb and and adjusting the float. Also maybe bumping the clip one notch closer toward the pointy end of the needle (if she still misbehaves after the cleaning). ;)
     

  3. nsb22

    nsb22 TEAM OAF

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    I cleaned the carbs right after I got them, that's when I noticed that the right carb float needle was sticking alittle bit.

    I'm afraid you lost me on the clip towards the tip of the needle part though!

    Thanks,

    Also, I think it is the right or front, whichever it is, that is missing.
     
  4. DaisyCutter

    DaisyCutter

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    Did you clean and inspect both the slow/pilot jet and the main jet? (These are the little brass thingys with the holes in them that screw into the carb).

    The slow/pilot jet influence low end fuel delivery. To adjust the amount of fuel delivered, you switch out jets (A bigger number means more fuel)



    The taper and diameter of the needle (the big long needle in the middle of your carb, connected ot the throttle) controls how much fuel your engine gets at midrange. The clip has ~5 notches that it can snap into. The higher the needle sits (moving the clip to the pointy end), the more fuel your engine gets at midrange.



    The main jet controls the high rev fuel delivery. Like the slow jet you need to change them out, no adjustment. To adjust the amount of fuel delivered, you switch out jets (A bigger number means more fuel).



    If your bike is running hot, that's a sign that it's lean, and needs more fuel.

    If your the carb has no clogged jets, AND your bike has no air leaks, then the easy option to richen up the midrange is to move the needle clip.



    FYI, If your intake boot is cracked, then the engine can suck in extra air and lean itself out. Check the intake boot for cracks.


    Odds are that the needle clip position is not the root cause. But it WILL influence the way your bike runs in the midrange and can be a good diagnosis tool, and temporary fix.


    Look at the jets really really close.



    EDIT: To set the float level. Pull the bowl off the carb. Tild the carb back/forth so that gravity is opening and closeing seat. Observe the angle of the float arm as the seat closes, it should be PARALLEL to the edge of the bowl. If not, bend the small tab to make it close when the float arm is parallel. This is a general rule, and works pretty well.

    Linkys:

    http://oldmanhonda.com/MC/Rcarbs.html

    http://www.dansmc.com/carbs.htm




    ;)
     
  5. nsb22

    nsb22 TEAM OAF

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    Thining back on it now, the jets may have been clogged! I've got two rebuild kits coming, so hopefully that will help. I was wondering about the air cut-off valves as well, on of them had some rust color to it.

    I checked the boots and they are fine! I had a KZ440LTD that wouldn't go over 55mph, and right before I sold it, to help buy the wife a car, I noticed that the boots on that were cracking pretty good.

    Thanks,