Walbro HD199 Fix

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wcorey

wcorey

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drill a 1/8 " hole in the center of the metering cover.
set the lever level with the carb body,
you need at least 15 psi of popoff
report back with your results

Wow, I leave for 24 hrs and come back to 5 pages of new nothing… No one has even tried this yet?

I have a couple hours to play around this morning, so, drilled the hole, lever was ok, checked pop off and it was ‘at least’ 15psi.
Fired it up. No change that I can notice. Tried the other carb, still no change.
Still wonder if the problems I'm experiencing are 'other than the usual issues'...

But...
Pop off pressure on these things is insane. When I played around changing it previously, I didn’t actually measure it,
just changed spring tension around some.
Had I bothered to check the numbers, it would have raised some flags.

How close do I need to be to 'at least' 15psi?
Seems it would either need a mere wisp of a spring or I’d need to increase the area of the needle seat/passage (pretty small on these).
Or am I missing something obvious here?


Having a keen perception of the obvious is an under-rated skill…
 
Mastermind

Mastermind

Work Saw Specialist
Joined
Nov 21, 2009
Messages
36,449
Location
Tennessee
Wow, I leave for 24 hrs and come back to 5 pages of new nothing… No one has even tried this yet?

I have a couple hours to play around this morning, so, drilled the hole, lever was ok, checked pop off and it was ‘at least’ 15psi.
Fired it up. No change that I can notice. Tried the other carb, still no change.
Still wonder if the problems I'm experiencing are 'other than the usual issues'...

But...
Pop off pressure on these things is insane. When I played around changing it previously, I didn’t actually measure it,
just changed spring tension around some.
Had I bothered to check the numbers, it would have raised some flags.

How close do I need to be to 'at least' 15psi?
Seems it would either need a mere wisp of a spring or I’d need to increase the area of the needle seat/passage (pretty small on these).
Or am I missing something obvious here?


Having a keen perception of the obvious is an under-rated skill…

I've ported six cylinders in the last 48 hours........nope, I ain't played with any carbs. If I need carb work I send it out most of the time......keep trucking. I'm watching.
 
Justsaws

Justsaws

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Mar 3, 2006
Messages
4,825
Location
Zanesville Ohio
Walbro's suggestions.

Reseat should occur around 10psi less than the pop off. Reseat is more important than pop off until pop off is way wrong.

Fuel pump produces 5-7 psi.

Atmo is 14.7 at sea level.

Pop off pressure will vary carb to carb.

Lots of folks drilled atmo vents in the covers.

Zama suggests that you not bother testing pop off, you could damage some carb parts.
 
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