First ever carb rebuild idles very fast

[dylanjustice]

I was given an old Husky L65, and told it was "a bit hard to keep running". It had great compression and started up easy after I cleaned it out, but it was indeed hard to set a low idle that wouldn't promptly stall.

I did my very first carb kit on it, and now it idles way too fast, even with the idle screw backed all the way out. I've checked everything I can think of and everything Dr. Google has suggested. I'm here looking for suggestions on what to check next!

Here's what I've checked:

- blocked the intake and outlet with rubber and leakdown tested (through the plug hole; there's no impulse line). Pressurized to 10psi, it dropped to 7 in maybe 2 minutes. I'm not set up for a vacuum test yet, but I will if that's indicated.
- triple checked order of gaskets, diaphrams, and flapper membranes
- pressure tested the new intake needle (and verified length/throw is pretty close to that of the old needle)
- carb is a Tillotson HS, the metering lever is supposed to be level with the flat surface of the carb. Bent it down 1-2mm below that, no joy.
- the throttle butterfly *appears* to be seating correctly

What else can I check? It feels like there must be air getting past the throttle butterfly, but how can I test (and/or fix!) that?

 

[J D]

Set the metering level back to where it should be & check pop off pressure on the fuel line.
What do you have the L & H set at? Have you tried winding the L out a bit?

 

[J D]

Also check the T screw is what the throttle is actually stopping against... if a spring or linkage or cable isn't right it may not be returning all the way once installed

 

[dylanjustice]

Thanks for all that! Metering lever is now readjusted, that was just a test to see if if helped things.

1. Pop-off pressure: Didn't know about this! It's about 15 psi. It seems like it's slowly closing by around 8-9 psi.

2. Mixture: I've been working with both needles at 1.25 turns out. I've played with the L screw, but no reasonable setting lowers the idle appreciably.

3. Throttle return: I'm working with the cover off and the linkages removed. I feel reasonable tension on the throttle return spring, and if I hold the carb up I don't see any light through the throat (except for the little half-moon at the bottom).

 

[J D]

Pop off is good.
L screw should definitely be having an effect... I'd be cleaning those passages out again as there's a good chance you still have a bit of something lodged in there.
Check needles too.
Did you remove any welch plugs?