Walbro WT Metering arm setting Question

[jeffpack1957]

So I'm rebuilding a WT carb from a Stihl 011AVT. From reading here, set the valve/arm height to .065.

Using the arm that was already in the saw, which knowing my Dad, it was never rebuilt, is a stock arm. Its less than .065.
I need to look again, but I think its set around .060 just with the arm at current height. Maybe between 055 and .060, I dont recall now.

As an amateur machinist with a full machine shop, I got to looking at the play on the arm in a 10x optical comparator as it lifts the valve, and theres a bunch of slop between the pin/arm/and metering valve (where arm engages valve) itself.

I can adjust to the required height, but theres so much slop in all that, it doesnt make sense for it to be between .065-.075 when there so much slop.

I didnt measure, but theres gotta easily be .005-.010 in slop, and thats probably being generous.

Thoughts?

 

[2StrokeFondler]

If the old one isn't worn, reuse it .

 

[jeffpack1957]

If the old one isn't worn, reuse it .

I wouldn't know what worn is on that arm. The whole setup is pretty sloppy

 

[2StrokeFondler]

I wouldn't know what worn is on that arm. The whole setup is pretty sloppy

It wears where the metal knob on the diaphragm touches the arm. If you can't see obvious wear it's probably good to go.
Also, it's not necessary to be spot on. Slop is okay.
Did you get an OEM kit from Stihl or Walbro?

 

[heimannm]

The metering lever does not actually lift the needle, it just takes the pressure off of it and the fuel pressure opens the needle valve and the fuel flows through.

The metering lever should be set about 0.065" below the body of the carburetor, Walbro makes a simple little gauge to make this task easier.



If the metering lever is too low, the engine may starve for fuel if the metering diaphragm cannot press on it to allow the valve to open. If the lever is too high the engine may run too rich or even flood if the metering diaphragm is pressing on the lever so the needle valve cannot seat properly.

It is always a good idea to pressure test the carburetor before reinstalling it to insure the metering needle is properly seated and will hold 7-10 PSI.

Mark

 

[jeffpack1957]

It wears where the metal knob on the diaphragm touches the arm. If you can't see obvious wear it's probably good to go.
Also, it's not necessary to be spot on. Slop is okay.
Did you get an OEM kit from Stihl or Walbro?

I just got some kit off of amazon, 2 sets. From what I read, here, dont bother replacing the Welsh plug.

 

[jeffpack1957]

The metering lever does not actually lift the needle, it just takes the pressure off of it and the fuel pressure opens the needle valve and the fuel flows through.

The metering lever should be set about 0.065" below the body of the carburetor, Walbro makes a simple little gauge to make this task easier.

View attachment 1198633

If the metering lever is too low, the engine may starve for fuel if the metering diaphragm cannot press on it to allow the valve to open. If the lever is too high the engine may run too rich or even flood if the metering diaphragm is pressing on the lever so the needle valve cannot seat properly.

It is always a good idea to pressure test the carburetor before reinstalling it to insure the metering needle is properly seated and will hold 7-10 PSI.

Mark

I've got the gage coming, but several hundred dollars of precision stuff in my machine shop I already know its not set from factory at .065

 

[Okie]

You have to also pay close attention to the little knob that rests on the lever. They are slightly different lengths/sizes in some kits. Compare their size to the OEM one in the carb BEFORE installing.

 

[jeffpack1957]

Damn I misread the above post, I assumed you meant post diameter of the diaphragm, but you meant height

If its any small victory, pressure tested good, held 7psi, do I need to worry about looking at it again?

 

[stihltech]

One way to check is with a pressure test with the metering side on and off. Should be the same. This is where the long or short center post on the diaphragm come into play.

 

[jeffpack1957]

One way to check is with a pressure test with the metering side on and off. Should be the same. This is where the long or short center post on the diaphragm come into play.

not following, theres only one pressure test connection. How do I turn on/off metering side?

 

[epo]

not following, theres only one pressure test connection. How do I turn on/off metering side?

By checking first with the metering diaphragm (and gasket) installed, and then by unscrewing the cover and removing the diaphragm.

 

[jeffpack1957]

By checking first with the metering diaphragm (and gasket) installed, and then by unscrewing the cover and removing the diaphragm.

I guess I'm being dense, if I check with diaphragm on, wouldnt that be the same as it taken off?

I've got so much time into this thing already, it had better work, had to get carb tester, all new rubber vibration stuff, replace solid handle, carb kit, tune up kit (filter, plug, etc).

With my luck i'll have an oil pump problem

 

[heimannm]

If it holds pressure fully assembled there is no need to disassemble and test again. If you were working from scratch, testing first with the metering diaphragm and cover off (holds pressure) and on (doesn't hold pressure) would let you know the projection on the metering diaphragm is too long. Of course, you can always use your calipers to measure the old and the new diphragms and compare. I have found them anywhere from 0.110 to 0.135" in the WT/WAT kits and occasionally have to file one down a bit to make it work satisfactorily.

Mark

 

[Bigjimmythunder]

I just got some kit off of amazon, 2 sets. From what I read, here, dont bother replacing the Welsh plug.

Just a quick note about the Welsh plugs

I have 2 x 009L and a 010 (same series as the 011)

All 3 of them had carburettor issues when i bought them, none of them would idle properly and had problems adjusting the low needle

After getting carby kits i changed out all the gaskets and also popped the Welsh plugs and cleaned the low and idle ports. They are so small they can easily clog up and restrict the fuel flow. I used a set of micro drills to clean them out (Dont drill them out any larger but just use to push/clean out any debris)

Now they all idle perfectly and i have been able to adjust the low and high screws. I love the 009Ls such a great sound from the reed valve 41cc engine the 010 is like meh! Its okay but doesn't make me smile like the 009Ls

After learning exactly how a carburettor works I have been able to get all my saws running perfectly, even my vintage 1963 Stihl 07 (Tillotson not Walbro)
Have a read here
https://www.helifreak.com/showthread.php?t=326599

Not exactly chainsaw related but still about Walbro carburettors

 

[jeffpack1957]

Just a quick note about the Welsh plugs

I have 2 x 009L and a 010 (same series as the 011)

All 3 of them had carburettor issues when i bought them, none of them would idle properly and had problems adjusting the low needle

After getting carby kits i changed out all the gaskets and also popped the Welsh plugs and cleaned the low and idle ports. They are so small they can easily clog up and restrict the fuel flow. I used a set of micro drills to clean them out (Dont drill them out any larger but just use to push/clean out any debris)

Now they all idle perfectly and i have been able to adjust the low and high screws. I love the 009Ls such a great sound from the reed valve 41cc engine the 010 is like meh! Its okay but doesn't make me smile like the 009Ls

After learning exactly how a carburettor works I have been able to get all my saws running perfectly, even my vintage 1963 Stihl 07 (Tillotson not Walbro)
Have a read here
https://www.helifreak.com/showthread.php?t=326599

Not exactly chainsaw related but still about Walbro carburettors

The purist in me would do the plugs too, but for the moment I wanna just get it running. Its had a pretty easy life, the screen was clean, so I'm hoping any internal gunk isnt there.

Finally got it together, just gotta mix some fuel. Just fighting the trigger right now.

 

[jeffpack1957]

well, thought I had it together, throttle cable doesnt work. I really dont know whats going on. cable is in the handle properly, but the trigger pull doesn't move the carb arm. This things been super frustrating.

 

[2StrokeFondler]

well, thought I had it together, throttle cable doesnt work. I really dont know whats going on. cable is in the handle properly, but the trigger pull doesn't move the carb arm. This things been super frustrating.

Don't remember exactly how it worked, but usually the outer, black part should push against something in the handle so the inner cable actually moves.

 

[Okie]

Some Walbro carb info I had filed for reference.

Good service testing info in both links.


https://video.search.yahoo.com/sear...b100cee33f514470a662eeb1fb1976b6&action=click



Walbro HDC Carburetor Full Disassembly, Check Valve Replacement & Testing (youtube.com)

 

[jeffpack1957]

Don't remember exactly how it worked, but usually the outer, black part should push against something in the handle so the inner cable actually moves.

It appears the cable in handle is too long, so trigger at full throttle barely moves the arm on carb. I have cable in correct hole on the arm

This damned saw is driving me crazy, this should have been the easy part