Can't Get PW80 Idle Down?

Discussion in 'Pit Bikes & Mini's' started by razorboy, Nov 4, 2005.



  1. razorboy

    razorboy Rookie DRN Member

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    Hey Fellas,
    Well, the PW80 that I revived is running but it idles high and I cannot seem to get it to come down.
    It has a new Wiseco piston, new jug and head gaskets, carbs cleaned, air filter IN place, no mods to airfilter box or exhaust, new sparkplug (correct gap) etc. I have moved the needle to every position with no difference and the airscrew is set to 2 turns out from seated (I have moved this around as well.). There is another screw (phillips top) that sits very close to the air feed tube, is this an idle adjust? Currently it is all the way in and it makes no difference. Oh, and the throttle cable is slacked as far as it can go so everything closes up when released.
    I guess it seems like there could be an air leak somewhere but I have no idea where?


    Any insight is appreciated

    Cheers
    Bernie
  2. FruDaddy

    FruDaddy Member DRN Member

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    It could be the pilot jet. As far as the adjustment screws, when standing on the left side and looking at the bike, the pilot air screw is in the middle about 1/2 -3/4 inch above the bowl and the throttle stop screw is on it's left right next to the inlet duct. I think this is the one you are asking about. All the way in would definitely cause a high idle. Bring it out a bunch. Your pilot screw should not be more than 3 turns from lightly seated, and you should start at 1 1/2 turns out. After you get the idle down, you adjust the air screw to achieve the highest idle speed, then readjust the throttle stop. I think that the baseline on the needle is the third slot, but it should not affect the idle. You might also take a look at the reed.
  3. razorboy

    razorboy Rookie DRN Member

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    Ahhh, that's good advice. I never thought of the reed being a problem and I did NOT change that. I'll take a look at it tonight and adjust the throttle stop and airscrew as per your advice. I'll post to let you know if I got any change out of it.

    Thanx
    Bernie
  4. razorboy

    razorboy Rookie DRN Member

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    I reset the pilot air screw to 1.5 turns out. I turned the throttle stop screw out a bunch and it made no difference. Even when I have the screw almost wound all the way out, the idle is still zoomin'. I checked the reeds and they look fine?

    I forgot to mention (and this may be important) that the cylinder has been bored out with a larger diameter piston from Wiseco. So, will the increase in bore size cause this problem if I am still running the same jets? Bare with me as I am still new to the 2-stroke scene.

    Cheers
    Bernie
  5. FruDaddy

    FruDaddy Member DRN Member

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    Yeah, more volume should require more fuel, If it is a small overbore, probably just a size or two. First, check your throttle cable, if it is routed incorrectly, adjusted too tight, or sticking, it will hold the carb open. If that's the case, the idle screw does NOTHING.
  6. splatt

    splatt Resident mental case

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    You also want to check where the carb mounts up they can come loose there and cause an air leak.

    Steve
  7. blan

    blan Rookie DRN Member

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    slide may be in wrong

    I have seen situations like this where the slide in the carb was actually put in 180 degrees off. Meaning the groove in the slide actually gets caught up on the idle adjustment screw instead of sliding on the fixed pin where it is supposed to. The groove should be facing a fixed pin, while the side of the slide with a beveled indentation faces the idle screw side. Hope that does it. Also consider an air leak if the idle wavers up and down inconsistently.
  8. razorboy

    razorboy Rookie DRN Member

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    Sorry to say that so far, no resolution.
    I will up the jet size next week but could that be the cause of a high idle? I think it is the 2nd over bore that they did to clean up the cylinder but I'll have to check.
    The throttle cable is wobbling with looseness and the slide IS in the correct orientation. I actually did get that one wrong once and the bike would not start at all.

    I appreciate the assistance even though I am not gettin' any love outta this thing yet.......!

    Bernie
  9. FruDaddy

    FruDaddy Member DRN Member

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    Just for fun, make sure that the needle fell into the hole, and make sure it falls all the way in. An air leak between the carb and jug would cause the bike to go lean, so I don't think that's where the problem is. Air leaks before the carb should be negated in the carb. Have you checke the float for leaks, or the needle and seat for wear. Also, make sure the choke isn't sticking. These things will cause the bike to run rich, I am actually out of ideas concerning the idle speed, but if the carb is dumping too much fuel, it could hide a downstream air leak.
  10. Jasle

    Jasle Sponsoring Member

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    typically the big bores pull more vaccuum and pull more fuel too. I've had to go down in jets with big bores. I'd check the carb as mentioned then I'd go for an air leak...especially since you were working on the bike. broken reeds typically make it hard to start and take away bottom end power. I've not seen one cause a high idle situation.

    Squirt some carb cleaner around the intake and reeds. Then at the bottom of your clyinder. Since you just dropped a cylinder on i'd guess it has the leak there. Did you use some type of sealant on the gasket. #4yamabond??? I have found about 90% of the problems that come in after someone else has worked on the bike are caused by the work done on the bike...so start looking at whatever you just did to the bike...topend!
  11. razorboy

    razorboy Rookie DRN Member

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    Hi Folks,
    I put that project on the back burner for a couple of weeks but I am poking at it again now.
    I sprayed some starting fluid around various areas last night and didn't get any change. I thought the idle actually went up a litttle at one point but that's the reverse of what I expected. Shouldn't the idle have gone down?
    What if the choke wasn't closing all the way down? Its hard to tell with the way the choke is on this little guy.
    Could it just be a pooched carb?

    I will be working on it again tonight so any info is always appreciated.

    Cheers
    Bernie
  12. bubbyb

    bubbyb Rookie DRN Member

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    i had that same problem with a 200 cc blaster and as it turned out my crank shaft seal was leaking and letting in more air than it needed .hope this helps
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