Debugging 066 work saw carb

[JIMG]

Well, I am satisfied with how this revived 066 work saw is working except for the problem of stalling when going from full throttle to idle. I can tune it to hold an idle fine, it cuts with the full 36" bar, full comp chain buried fine. I believe the L is about 3/4 out or so and the H maybe a bit less. I put a carb kit in it. The kit had no replacement screen or welch plugs, though.
Any Ideas/opinions?

 

[Canadian farm boy]

Check the height of your metering lever and maybe check your pop off pressure.
Did you use a genuine carb kit or a Chinese kit?
Did you change the metering lever spring or reuse the original?

 

[Stump Shot]

Open up the idle speed screw a bit and recheck the idle mixture might just fatten it a bit to bring idle back down and rev up should be normal.

 

[JIMG]

Check the height of your metering lever and maybe check your pop off pressure.
Did you use a genuine carb kit or a Chinese kit?
Did you change the metering lever spring or reuse the original?

I used a Walbro K15-WJ kit. If the kit had one I would have used the spring. I cant remember if one was included. I checked the lever height with the walbro height setting W shaped tool thing. It was good.
The saw acts like it's flooding after I let up on full throttle. If I carefully feather the throttle for a few seconds I can get it back to a good stable idle that it will hold indefinitely. It winds up no problem.
How do I check "pop off" pressure?

 

[jacob j.]

Which WJ carb is it? Most of the WJ carbs used in the 064 and 066 series started at one full turn out on both the low and high needles for the factory settings.

Checking pop-off is pretty easy - you can do it through the fuel inlet barb with a small manual pressure pump with a gauge. I use a Mityvac.

 

[huskihl]

Guessing the H and/or L screw are too far out

 

[drf256]

Did you vacuum test the saw?

A small vacuum leak can be turned out at idle, but many times it throws off the rest of the tune.

The other thing to check is the nozzle check valve. That stops the wet side from pulling air into the metering chamber from the carb bore. A bad one would cause all sorts of weird problems from bad idle to poor running when transitioning from different throttle plate positions.

I’d Vac test the saw, check that the carb holds pressure, and then try another carb on it-if that’s possible.

 

[srcarr52]

Sounds like low pop off pressure or a needle/seat that isn't sealing correctly.

 

[JIMG]

The case passed a pressure test after assembly.
I just had time to disassemble and clean up the needle end, gave the spring a little tug, checked height and reassembled. Pop off pressure about 16. Does that seem within normal?
Returned to idle from wot ok with 1 turn out on both needles after that. It may have been something like a little bit of old gasket material.
I will be running it for a few hours in some oak soon. That should show if this was the issue.
I tuned it on site while cutting the other day to barely clean up with the bar buried. I just checked and the low was at 3/4 and the high was at 1/2 turn out.
That could have been bad.
The carb is a wj39.

 

[Stump Shot]

The case passed a pressure test after assembly.
I just had time to disassemble and clean up the needle end, gave the spring a little tug, checked height and reassembled. Pop off pressure about 16. Does that seem within normal?
Returned to idle from wot ok with 1 turn out on both needles after that. It may have been something like a little bit of old gasket material.
I will be running it for a few hours in some oak soon. That should show if this was the issue.
I tuned it on site while cutting the other day to barely clean up with the bar buried. I just checked and the low was at 3/4 and the high was at 1/2 turn out.
That could have been bad.
The carb is a wj39.

Pressure test carb to 7psi/0.5bar at the fuel inlet and see if it holds. If it leaks down the leak will need to found and corrected. Leaky inlet, bad gasket seal etc..
If you have a genuine Walbro inlet lever spring your pop off should be fine, if not it may be worth checking while you have the
pressure tester there.
If it does physically look and see that the throttle plate is slightly cracked open, if not it will need adjusted open slightly and your
tune reset. Sometimes they are just not getting enough air at low speed to make the transition(like pulling the choke out) In other
words the relationship between the idle speed and idle mixture screws is off kilter.

 

[srcarr52]

I normally pressure test the carb with the diaphragm off so you can bump the lever and see if the needle reseats properly.

Also when testing pop off it should pop and then reseal before it drops below ~5psi.

If it doesn't its usually the lever fork slightly kicking the needle to one side which causes it to not complete seal back up.

 

[JIMG]

I thought I had this one figured but not so much.
Working cutting today I was not able to get the saw past 12k with the H turned all the way in.
I made a sort of uneducated guess and plugged the brass hole at bottom left. The saw would not hold a steady tune after that. I cleared the hole out and called it a day.
Above I mistakenly said this was a wj39. It's a wj35A c4.
I'm about to order a new one of those Hutzl wj69 walbros. If anyone has experience with using one of those I would be much obliged to hear about it.

 

[huskihl]

The Tillotson HS320A is a good replacement carb

 

[JIMG]

Thanks for the tip. Price on one is close to an "OEM" walbro wj69 sold through FarmerTec. Any one care to share experience with using one of these?

 

[huskihl]

Thanks for the tip. Price on one is close to an "OEM" walbro wj69 sold through FarmerTec. Any one care to share experience with using one of these?

I don’t think I’d trust anything through Farmertec to actually be OEM. Maybe a second or a blem item. The Tillotson above is probably a better carburetor than the OEM Walbro anyway.

 

[Dolkitafreak]

I don’t think I’d trust anything through Farmertec to actually be OEM. Maybe a second or a blem item. The Tillotson above is probably a better carburetor than the OEM Walbro anyway.

You have a pic of 320 metering side? I’m familiar with HS and WJ but trying to see which ones have undesirable features.

 

[JIMG]

Thanks again, Kevin,
Here's a pic of one like I just ordered.
Amazon had em cheapest.

 

[huskihl]

You have a pic of 320 metering side? I’m familiar with HS and WJ but trying to see which ones have undesirable features.

I don’t. I replaced a couple in 660’s a few years ago with them but never looked inside

 

[Maintenance Chief]

The farmertech carburetor for the 066 I got had throttle plate alignment issues.
I did swap it out for the oem walbro throttle plate and fixed my idle problem.
The original carburetor was just worn out from years of use.

 

[srcarr52]

The farmertech carburetor for the 066 I got had throttle plate alignment issues.
I did swap it out for the oem walbro throttle plate and fixed my idle problem.
The original carburetor was just worn out from years of use.

The notch wasn't inline with the idle jets?