I changed my reed valves.......am i rich?

mrbluesbox · Scooby Slapper Joined: 14 Sep 2006 Karma :

Hi all

ive just put some new boyosen power reed valves on my derbi 125 gpr and need a bit of advice about re-setting up the carb.
since ive changed the reeds, it seems to idle really high (like 2.5k + revs) even after playing with the idle air screw on the carb - just cant really get it to fall much more than this.
its also revs a bit slower than before and - most noticably - the revs seem reluctant to fall when i roll off the gas - its seems to take quite a while to fall back down to the idle speed. The engine also appears to stutter slightly as the revs fall, but im guessing that its the wheels slowing and fighting the revs of the engine.
im think that i need to rejet / play with needle height, but do i go richer or leaner - infact is there any way i can check how its running.

Thanks for the advice.

Gaz.

ps - its also got a ramair filter on there so the carb was slightly upjetted by 2 valve sizes which im guessing will make a difference.
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alains · World Chat Champion Joined: 08 Jul 2004 Karma :

probably your throttle cable is too tightened , you must have 1mm of play at the cable entry in the carb . idle is set down by playing with the idle screw , not the pilot screw . the pilot screw is to adjust the the mixture in the range 0-2000 rpm , after that it has no effect , only the jetting & needle position will change that
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baldy · World Chat Champion Joined: 16 Feb 2004 Karma :

sounds like an air leak to me. Did you use new gaskets?
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mrbluesbox · Scooby Slapper Joined: 14 Sep 2006 Karma :

no - unfortunately i didnt have a new gasket so just reused the original cos it didnt seem to be damaged.
im gonna check that its properly sealed tonight and maybe get a new gasket ordered tomorrow if necessary.
would i be ok using instant-gasket-in-a-tube type stuff so seal round the original should i find that it it leaking?
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19van71 · Spanner Monkey Joined: 04 Dec 2007 Karma :

mrbluesbox · Scooby Slapper Joined: 14 Sep 2006 Karma :

an air leak is looking very much like the culpret.
didnt really have mich time to play plast night but reseated the carb and manifold and tightened all the bolts and it made a massive difference - revs were much more responsive.
gonna take it all off again and get some instant gasket on it tonight and hopefully thats gonna sort it out.
good call Smile

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Ichy · World Chat Champion Joined: 15 Jul 2005 Karma :

Did you disconnect the throttle cable?

mrbluesbox · Scooby Slapper Joined: 14 Sep 2006 Karma :

yeah - took the top off containing the slide and needle to remove the carb and made sure id placed the jets n things properly and screwed the float bowl cover back on tightely enough.
Its possible that the cable could also have been an issue.
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I seem to have misplaced my pants...................