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Needle Valve Settings for Walbro LMG Carb


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  #1  
Old 04-07-2010, 02:16 PM
Oberon67 Oberon67 is offline
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Default Needle Valve Settings for Walbro LMG Carb

I have a rebuild kit on order for the carb on my Clinton-powered tiller. The carb is a Walbro LMG with choke.

When I get the rebuild done, there are two needle valves in particular I'm concerned about. One is in the middle of the float bowl and points upward. The other is on the left side of the carb, next to the engine intake.

How should I set these screws so the engine can start and run?

Thanks in advance...
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Old 04-07-2010, 11:20 PM
manioso manioso is offline
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Default Re: Needle Valve Settings for Walbro LMG Carb

The needle on the bottom of the float bowl is the main jet, and initial setting is to tighten gently, then turn out 1 1/2 turn. The jet on the side of the carb is the idle mixture, and it is set at 1 1/4 turns. In both cases be sure you tighten gently. If you force too hard, you will damage the needle tip, making carb difficult if not impossible to adjust properly.

When you disassemble carb be sure to replace main nozzle with the replacement nozzle provided in the kit. Do not reuse the original main nozzle. The original is cross drilled at the factory after assembly to provide fuel passages. When you unscrew and then replace you'll never get it clocked exactly right and fuel flow will be compromised.

The replacement nozzle has an annular undercut, permitting fuel flow no matter where the nozzle finally tightens up.
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Old 04-08-2010, 09:32 AM
Oberon67 Oberon67 is offline
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Default Re: Needle Valve Settings for Walbro LMG Carb

After reviewing the parts kit I got in the mail last night, I realized that it came with the main jet needle and the nut that secures the bottom of the float bowl (which also is the mounting point for the main jet needle), but it did not include the main jet (the needle valve seat).

So it's back to parts scrounging for me. I did find this on e-Bay... it's part number 182 37... but I don't know if it's the right jet for a Walbro LMG.

I get the impression that, given the amount of dead gas and varnish and dust and tank rust that has been through this machine during its life, a new jet is mandatory. How can I find out which is the correct part?
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Old 04-30-2010, 02:17 PM
tasturbo86 tasturbo86 is offline
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Default Re: Needle Valve Settings for Walbro LMG Carb

I am aware of the jet replacement recommendation above, but I have never found the correct kit for rebuilding these carbs. I usually just replace the gaskets and that gets me going.
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Old 05-13-2012, 09:50 PM
martinf martinf is offline
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Default Re: Needle Valve Settings for Walbro LMG Carb

Quote:
Originally Posted by manioso View Post
Do not reuse the original main nozzle. The original is cross drilled at the factory after assembly to provide fuel passages. When you unscrew and then replace you'll never get it clocked exactly right and fuel flow will be compromised.

The replacement nozzle has an annular undercut, permitting fuel flow no matter where the nozzle finally tightens up.
Wow. SO this is what's going on with my clinton LMG 4 carb problem!! I've been messing with this thing all day and could not get enough fule flow unless I was half-choking the dang thing. i cleaned the carb and soaked and cleaned and routed out every passage way...and still not enough fuel.

SO, my question is: what is the deal with the cross0drilled passageways? Do they need to line up to holes in the main jet hole in the carb body. I can't quite picture what's going on here. And, the most important question...how do you line the holes back up? I'm not up for getting a rebuild kit with the improved main jet. Certainly there's a way to line it up!
Sure would appreciate any help here.
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Old 05-14-2012, 12:53 PM
Road Torpedo Road Torpedo is offline
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Default Re: Needle Valve Settings for Walbro LMG Carb

They took care of the main jet problem by under-cutting a shallow circular groove in that area were that hole is in the jet. The part that so called "wouldnt" line back up.

This can be acomplished EASILY by someone with a lathe and a squared cut off tool. You would just ease the tool into the peice ti'll a shallow groove was aparent in that area.

That was enough to do the job.

The replacement jets were nothing more BUT that, with a groove.
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Old 05-14-2012, 01:59 PM
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OTTO-Sawyer OTTO-Sawyer is offline
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Default Re: Needle Valve Settings for Walbro LMG Carb

If you don't have access to a lathe, you can carefully file a groove in it that would do the same thing.
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