Rebuilding the Walbro WT-3 carburetor, issues

[Opihi59]

I have read on this forum somewhere that a very significant percentage of poorly running saw problems can be addressed by carb rebuilds; I suppose it would follow that continued problems after this can be due to improper carb rebuilds as well.

Encouraged by the successful rebuild of my Zama C1Q EL7 Husqvarna carb, I decided to dig into my Walbro WT-3 Carb. I had picked up kits for both at the local small engine repair place where I get my Tygon line. I replaced both sides of the carb, there was some gunk in there I cleaned with carb cleaner and wiped it down, blew out passages, etc. Replaced the needle valve and assembly. Put all back together but cannot get the previously running (a bit rough, but running) saw going because it floods out and dumps raw gas/mix out the exhaust. I have viewed a number of video rebuilds prior to doing this, took notes during my tear down etc so have it all back together with the right diaphragms, gaskets, needle valve assembly back properly--but since it floods, I am suspicious of the needle valve aspect of the rebuild. I feel it is back together properly, just floods.

Suggestions from the Walbro carb crew? Thanks. Sorry, I know this is out of character but I don't have any pictures to show. :msp_sad:

 

[Eccentric]

There's a non-serviceable check valve in the body of those carbs. You can damage them with compressed air. May be your issue my friend...

 

[DSS]

First thing I'd check is the metering lever height. If it's too high it will flood. Make sure you have the gaskets and diaphrams in the right order.

Or sometimes you just miss a piece of crud in there, and have to blow them out again.

 

[DSS]

Or what Aaron said too, sometimes compressed air is not your friend.

 

[Eccentric]

Sometimes those damn WT/WAT carbs just won't behave either...

 

[griffonks]

I had a similar problem with a Walbro carburetor rebuild earlier this spring. I bought a kit online from an ebay seller and after the rebuild it poured gas into the exhaust. I tore it apart again and the metering level was right. I emailed the seller of the kit and he sent me a different metering valve. The first valve had a material on the tip (different colors) that was different than the second and it did not seal. The second valve sealed fine. Problem solved. Someone posted that there was a test for non-sealing metering valves but I don't remember it....

This was in a Ryobi trimmer, my Stihl trimmer was down and I needed a replacement fast. The Ryobi is worthless but at-least it's not in the landfill yet. I'll sell it next spring on the CraigsList.

 

[DSS]

I had a buddys Wt 194 on an 026 that wouldn't tune right, lean, fat, no idle, hard start...replaced it with the carb from mine and it ran like a dream.

Apparently some WT's were bad from the factory, and no amount of kits or cleaning will fix them.

 

[Opihi59]

I do suppose I could go back to the orig needle and see if that makes a change, but they sure looked right by comparison. As far as air blowing, I dialed way back on the air pressure, and didn't directly stuff the tip in any passages. Nonetheless, not knowing about the non-serviceable check valve, I could have boogered the whole thing up. I'll start looking around for a new WT-3 I suppose but will keep diddling with this thing.

And of course, I'll keep accepting recommendations.

 

[Eccentric]

I do suppose I could go back to the orig needle and see if that makes a change, but they sure looked right by comparison. As far as air blowing, I dialed way back on the air pressure, and didn't directly stuff the tip in any passages. Nonetheless, not knowing about the non-serviceable check valve, I could have boogered the whole thing up. I'll start looking around for a new WT-3 I suppose but will keep diddling with this thing.

And of course, I'll keep accepting recommendations.

You probably didn't damage it then. There may be some crap lodged in the check valve now though. Some guys have reported success reviving these carbs with LONG soaks, and ultrasonic cleaners. Sometimes they just won't behave though. When I worked in shops, we'd often just replace the damn thing if it didn't wake right up with a quick flush and a kit. In a shop, time is money.

 

[heimannm]

You can check the metering needle by pressurzing the fuel inlet and checking to see if it holds pressure. I have a device similar to the pressure bulb the doctor uses on the blood pressure cuff with a gauge that will pump up to about 12 PSI and is equipped with a check valve to hold it.

If you don't have one of those, use your compressed air and a regulator (no more than 10 PSI!) to pressurize the carburetor. You can either put a little fuel, carb cleaner, oil, etc. around the needle to watch for for bubbles, or submerge it in a container of water, solvent, your choice, and see if it still leaks. Sometimes the needle and seat can be made to work by gently lapping it with a little tooth paste, rubbing compound, or even valve lapping compound.

If it is not the metering needle, check to make sure the fuel pump cover is properly sealing the fuel pump diaphragm/gasket, again the dunk in the solvent while pressurizing the carburetor will tell...

Mark

 

[Opihi59]

You probably didn't damage it then. There may be some crap lodged in the check valve now though. Some guys have reported success reviving these carbs with LONG soaks, and ultrasonic cleaners. Sometimes they just won't behave though. When I worked in shops, we'd often just replace the damn thing if it didn't wake right up with a quick flush and a kit. In a shop, time is money.

Well, if you happen to know a direct replacement for this, I could use a PN. Searsparts has one PN for the no longer available carb, and looking at ereplacementparts it is no longer available there either. I am guessing there are a lot of different versions/applications for the WT-3 though, and they could all be different variations and multiple configurations. I'm going to go pull the needle again and do a swap.

 

[Opihi59]

Alright--so another hour of fiddling with the "15 minute job." I didn't have a sphygmomanometer bulb in my tool bag, so I got a piece of fuel line and blew thru that without resistance. Heimannm suggested that. I laid everything out again, since I was losing confidence in my rebuild and figured out where the air was blowing thru and why. Then I noticed a very very very (have I said very yet?) subtle difference in the reed valve sheet I had selected out of the pack of 15 gaskets etc of which I only needed to use 4. I had the wrong one which had an opening across a channel that the original one didn't. This let gas straight across to dump down the intake. Booo. Reassembled and whatever pressure I can blow with my lungs didn't leak thru.

At any rate, swapped that out and I am back in bidness. Can't really rip too much as the neighbor's baby is napping-I checked first but in a bit I believe I can do more than an idle in my closed (choke, cough) garage and a few braps of the throttle. It runs, you all helped me trouble-shoot the problem, and now I have 2 of the 5 in my pile to fix running again.

It's akin to that "one of these things is not like the other...................."

Thanks everyone.

 

[Eccentric]

Well, if you happen to know a direct replacement for this, I could use a PN. Searsparts has one PN for the no longer available carb, and looking at ereplacementparts it is no longer available there either. I am guessing there are a lot of different versions/applications for the WT-3 though, and they could all be different variations and multiple configurations. I'm going to go pull the needle again and do a swap.

If I still worked at Sears I'd have been able to help you with that. There were several WA and WT Wallys on the parts shelf. Sometimes we'd come accross a machine that specified a carb that was NLA. We could usually find another carb that had the same throttle shaft and choke arms as the original and make it work.

Alright--so another hour of fiddling with the "15 minute job." I didn't have a sphygmomanometer bulb in my tool bag, so I got a piece of fuel line and blew thru that without resistance. Heimannm suggested that. I laid everything out again, since I was losing confidence in my rebuild and figured out where the air was blowing thru and why. Then I noticed a very very very (have I said very yet?) subtle difference in the reed valve sheet I had selected out of the pack of 15 gaskets etc of which I only needed to use 4. I had the wrong one which had an opening across a channel that the original one didn't. This let gas straight across to dump down the intake. Booo. Reassembled and whatever pressure I can blow with my lungs didn't leak thru.

At any rate, swapped that out and I am back in bidness. Can't really rip too much as the neighbor's baby is napping-I checked first but in a bit I believe I can do more than an idle in my closed (choke, cough) garage and a few braps of the throttle. It runs, you all helped me trouble-shoot the problem, and now I have 2 of the 5 in my pile to fix running again.

It's akin to that "one of these things is not like the other...................."

Thanks everyone.

Glad you got it back in business.

 

[Opihi59]

If I still worked at Sears I'd have been able to help you with that. There were several WA and WT Wallys on the parts shelf. Sometimes we'd come accross a machine that specified a carb that was NLA. We could usually find another carb that had the same throttle shaft and choke arms as the original and make it work.



Glad you got it back in business.

Yes, me too. I had that sinking feeling that I had totally messed that one up. Wish you worked at the Sears parts place here in Mapunapuna, seems like when I go down there it's more like going to the DMV. The parts counter man really has to know a lot and when I need car parts I like to ask for the same counter man every time. You should have seen the vacuous expression I got when I tried to order a collet for my die grinder from Sears a little while back.