Chainsaw Repair

How To Basics - Carb Fixes + Mods - IPL and Service Manuals => How To Basics and Fixes => Topic started by: farmboy on May 01, 2013, 08:33:11 am

Title: Leaking needles
Post by: farmboy on May 01, 2013, 08:33:11 am
I'm on a run of leaking carb. needle valves.  Got 4-5 apart now won't hold pressure.  Had a few with rubber tip they won't hold either.  Carbs have been through ultrasonic cleaner.  Any redneck fix for the seats?  Seems I remember toothpaste to lap???  If so how do you?
Shep
Title: Re: Leaking needles
Post by: 660magnum on May 01, 2013, 09:46:38 am
You have to use a piece of Tygon over the lever part of the needle to hold it so you can turn the needle in the seat when using the tooth paste. Just twiddle it between your fore finger and thumb.

It just takes a very small amount of tooth paste because you have to clean that mess out when you are done.
Title: Re: Leaking needles
Post by: farmboy on May 01, 2013, 05:46:03 pm
Thanks for the confirmation on the toothpaste.
Shep
Title: Re: Leaking needles
Post by: Al Smith on May 01, 2013, 07:48:05 pm
You could also use something like rubbing compound or "Mothers" chrome polish .
Title: Re: Leaking needles
Post by: srcarr52 on May 02, 2013, 10:21:33 am
I've seen it a lot lately where it will be the upper flapper diaphragm that will be bleeding the pressure off.  I don't know if they get a little pin hole or if the cover gets warped but they bleed down when testing the pop-off pressure.  You can put grease on the needle and hold it down with your finger and the carb will still bleed pressure.  It seems to happen more on carbs with one screw holding the top cover down.  Most of the time a new flapper and gasket will take care of it.
Title: Re: Leaking needles
Post by: 660magnum on May 02, 2013, 10:44:01 am
Where is this flapper you are talking about?

Are you talking about the upstream check valve flap for the pump?
Title: Re: Leaking needles
Post by: Al Smith on May 02, 2013, 06:43:24 pm
He's probabley refering to the fuel pump check valve assembley .FWIW the soft parts of the carb just get stiff from old age or ethanol .There's nothing you can  do except replace them .

I've probabley rebuilt in excess of 100 saw carbs and never once seated a fuel shut off valve .Fact I've seldom ever replaced them .I seldom even buy the complete rebuild kits ,usually just the basic kit with the soft parts .