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Thread: 86R idle tuning debacle.

  1. #1
    Join Date
    Apr 2017
    Location
    Wausau Wi
    --
    116

    86R idle tuning debacle.

    Hey guys,

    So I have a few odd issue looking for some insight on. Bought a 1986 250R that had apparently been sitting for a while. The old girl starts 1st kick, idles fine and strong through the power band. Only issue was idle screw wasn't adjusting idle.

    Pulled the carb apart and this is where it gets interesting. Turns out the pilot jet and air idle ports were/are varnished solid. But it somehow still idled fine.

    Put the carb throw a couple cycles in the ultra sonic cleaner till she was clean as a whistle. Put it back together with a fresh carb kit, all factory jets(same that I pulled out) and reset the float to be closed when parallel with the bowl base (checked for flow stoppage as well, all good). Started it back up and anything less than 1/8-1/4 throttle it just dies. Lots of smoke and won't rev, clearly pig rich. Pulled apart and checked and rechecked assembly for human error, good Lord knows I'm normally at fault but no dice still pig rich and won't run.

    He's the kicker for those that can bear my long winded issue, finally say screw it and put in the original pilot (still completely clogged) and like magic the thing is back to running like a top. And the idle screw is semi working again.

    What on earth could be causing an issue like this? I'm not green on carb tuning but this has me turned around 6 ways till Sunday trying to find some logic in it.

    Sent from my SAMSUNG-SM-G891A using Tapatalk

  2. #2
    Join Date
    Jul 2009
    Location
    South Florida
    --
    6,722
    With the small jet clogged it must be using the choke circuit to make it idle . Your having to turn the choke / idle adjustment screw almost all the way up correct ?
    This is a very common problem with the 1986 PW carburetor when they simply get worn out .
    I easy solution is to buy a new PWK 36mm .

    Their are several threads on this subject and a ton of theory's but to my knowledge no body has found the fix but like I said I believe they just get worn out , body and slide .
    Last edited by shortline10; 08-16-2017 at 09:19 PM.
    78 atc 90/180cc Dickson Full Suspension
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    84 KLT 110/123cc Powroll Racer from 80s
    87 atc 125m stock
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  3. #3
    Join Date
    Jan 2017
    Location
    Fond du Lac, WI
    --
    39
    Sorry to jump in on this but have a question. Do the 34 mm keihin carbs ware out?

    Sent from my SM-G920V using Tapatalk

  4. #4
    Join Date
    Apr 2017
    Location
    Wausau Wi
    --
    116
    Quote Originally Posted by shortline10 View Post
    With the small jet clogged it must be using the choke circuit to make it idle . Your having to turn the choke / idle adjustment screw almost all the way up correct ?
    This is a very common problem with the 1986 PW carburetor when they simply get worn out .
    I easy solution is to buy a new PWK 36mm .

    Their are several threads on this subject and a ton of theory's but to my knowledge no body has found the fix but like I said I believe they just get worn out , body and slide .
    Thank you very much for the prompt response. I guess, much like how many licks it tastes to get to the center of a tootsie pop, there are just some things we will never figure out. Being you recommended the 36mm PWK do you happen to know of if it fits the factory boots (intake and air filter) with out machining?

    Rugby- we are talking about the 34mm carbs specifically.

  5. #5
    Join Date
    Jul 2009
    Location
    South Florida
    --
    6,722
    It will fit the intake side fairly easy , the air box boot will need to be heated up with a heat gun to make it fit .
    Yes the 36mm is an upgrade and if you have any mods done to the motor a 38mm will work great as well .
    78 atc 90/180cc Dickson Full Suspension
    76 ATC90/180cc Nicholson
    77 atc 90 Dickson Full Suspension
    84 KLT 110/123cc Powroll Racer from 80s
    87 atc 125m stock
    84 atc 200x Curtis Sparks
    84 atc 200x Powroll My race bike from 80's
    83 atc70/108cc Powroll blue Xmas Special
    81 atc185s HP-ATC full suspension

    Performance Shop is Open PM me for Service

    My Feedback http://www.3wheelerworld.com/showthr...ck+shortline10

  6. #6
    Join Date
    Jul 2009
    Location
    South Florida
    --
    6,722
    The 1985 34mm round bore carbs are fine , it's the 1986 pw34mm that have the issue with idling / wearing out .


    Quote Originally Posted by rugbyflanker View Post
    Sorry to jump in on this but have a question. Do the 34 mm keihin carbs ware out?

    Sent from my SM-G920V using Tapatalk
    78 atc 90/180cc Dickson Full Suspension
    76 ATC90/180cc Nicholson
    77 atc 90 Dickson Full Suspension
    84 KLT 110/123cc Powroll Racer from 80s
    87 atc 125m stock
    84 atc 200x Curtis Sparks
    84 atc 200x Powroll My race bike from 80's
    83 atc70/108cc Powroll blue Xmas Special
    81 atc185s HP-ATC full suspension

    Performance Shop is Open PM me for Service

    My Feedback http://www.3wheelerworld.com/showthr...ck+shortline10

  7. #7
    Join Date
    Apr 2017
    Location
    Wausau Wi
    --
    116
    Quote Originally Posted by shortline10 View Post
    It will fit the intake side fairly easy , the air box boot will need to be heated up with a heat gun to make it fit .
    Yes the 36mm is an upgrade and if you have any mods done to the motor a 38mm will work great as well .
    Thank you again for the knowledge, I went ahead and got a 38mm en route. Hopefully I can stop losing sleep a night again!

  8. #8
    Join Date
    Apr 2017
    Location
    Wausau Wi
    --
    116
    Just to update the thread, Got the 38MM PWK installed this morning and ll the problems have disappeared. Thank you again for the help

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