Walbro WJ 105 A

[Al Smith]

I think this thing is a modification perhaps this sub division is only used on the Makita concrete saws I've spent forever on .At any rate this was the first of two I attempted to rebuild with no luck on this one .I failed to notice a welch plug that was missing .As such the discharge of the fuel pump could never have reached the metering diaphragm .It took me three rebuild kits to find one with the proper plug .
Fragile little thing I could not get it to expand so I got it in place best I could and sealed it with Loctite 271 .As soon as one application dries I'll do another with a q-tip .Might get it might not .if not I'll just get another carb as I'm tired playing patty cake with this one .

 

[jmester]

Never seen a welch plug go over top of the inlet screen.

Welch plugs usually go on the metering diaphragm side of the carb not the pump side

 

[Al Smith]

Me neither .Which is why it screwed me up . It's got a plug on the metering side too which I assume is over the idle holes .I've never once had to get under a plug although I assumed leakage on an early Zama C1Q on a Stihl 200T which I used red Locktite on . So if this gets it fine .If not I'll probably exercise my expertise in the use of profanity .

 

[Al Smith]

Well that didn't work as usual .So it's another carb because I'm done with this one .When I get one I have an anvil and an 8 pound sledge and nobody with ever need to play baby sitter to this one again ,.I might regain my composer though which I usually do after a cooling off period .

 

[Al Smith]

After a good nights sleep I'm over my grump . I may delve into this miserable POS later on today .I may not have sealed the welch plug good enough .From what I gather the plug is concaved and should fit in a very shallow shoulder in the hole and you deform it to smell it outward to seal .I could not get that thing in the hole which I might have figured .High tech Chinese stuff you know .I have some diamond lapping paper and may be able to fit things up and give it a thump with a little hammer . I've completely rebuilt entire chainsaws in less time than I 've spent on this damned carb .Humbug !

 

[jmester]

The welch plug hole will have a step for the welch plug to bottom out on. The welch plug is convex new then you punch it down till its flat.

Have you checked your high speed check valve?

 

[Al Smith]

That's the problem I could not get in the step ,too fat or eccentric .Just plain screwed up .Evidently the red Loctite didn't work . As far as checks the only ones I'm aware of are the flappers on the fuel pump diaphragm and it's new. One of those yellow fiber contraptions .However I have another that came in the kits made of a black mylar film type of material . I've never tried this type on the small carbs but have on the larger HL series Tillotsons .
In my way of thinking the larger components on the HL and HR models would be more receptive with regards to the impulse rise and fall of pressure and vacuum and there fore seal better .
If I could find a working drawing large enough to read without a magnifying device of some kind I could figure this thing out .I have the complete Tillotson book but nothing on Walbro except what I can find on the internet .Plus this bastard of a thing with the welch plug doesn't appear any place I've looked so far .If I live to 100 and never see another one of these it will be too soon .

 

[Al Smith]

I've pretty much given up on this carb .Could not get the welch plug to hold .What I did do was plug the hole using a second screen using JB cold weld .I had to go to You Tube to figure out what this fore mention check valve was . I'm not sure but it seems to be getting too much fuel .I've got another carb coming Thursday this week .What ever that check valve is supposed to do I have no idea nor can I really find much of anything about this model WJ 105 A .However the direct fit OEM they are very proud of price wise like from $75 to up to $400 . What I have coming is a WJ 131 which I may have to change the covers on to fit .

 

[DND 9000]

You are on the wrong site. This (in your pic) is the pump site of the carb. The hole where you made the JB Weld has to be free, because in there is the fuel strainer. Fuel needs to go through it to get through the inlet needle on the other site (metering site) of the carburetor. The welch plugs are always on the metering site. What you did here can`t work.

From which machine (or saw) is this carburetor?

 

[Al Smith]

Really it's different than any other I've ever seen . Where the strainer is on the other carb had a plug over it .They are identical Makita DCP 7321 concrete saws but I attempted to rebuild this one first and it was only on the second one where I saw the difference . If you look on the first picture in this thread it shows where the fuel would come in from the fuel chamber through the flapper on the fuel pump diaphragm and go to the metering diaphragm on the other side of the the carb .No other Walbro picture or diagram shows this design that I could find . Unless I don't understand the flow through this thing that is .
Now in my way of thinking I would have thought the yellow fuel pump diaphragm by the way it's made would have sealed over the area weather it had a welch plug or not above the screen but evidently not .
The other saw runs like a top after a carb rebuilt ,starts easy etc . This one farts a couple of time and dies .That tells me it's not pumping or it is leaking through some how and flooding . Thursday after the other carb gets here I'll know .Never the less I'll figure this SOB out one way or the other weather I ever use it or not . I cuss a lot but never admit defeat .

 

[DND 9000]

If you look on the first picture in this thread it shows where the fuel would come in from the fuel chamber through the flapper on the fuel pump diaphragm and go to the metering diaphragm on the other side of the the carb .

That`s right.

This is the carburetor Walbro WJ 105 A from the IPL drawing. You can clearly see the fuel strainer (part 257) and where it belongs to on the drawing. On you first message (with picture in this thread), the fuel strainer can be seen in place. In your last picture you filled this place with JB Weld. This has to be free, otherwise the fuel can`t flow through it. The welch plug (part 258) belongs to the other (metering side) of the carburetor. It can also be seen in the IPL drawing.

I have attached the complete carburetor section of the IPL.

 

[DND 9000]

I looked again at your pictures, specially the one with the wood stick. I see the path you show there and I`m confused if there should really be this plug. I can`t believe that, it`s also not shown on the IPL drawing. ??? Weird design.

 

[Al Smith]

The fact none of that has never been seen on any drawings I have seen is the point I'm trying to make .I also should make reference to the replacement welch plug right next to the filter hole in the first picture I could not get to stay in the hole because the shoulder was only about 10-12 thou thick .That plug is much smaller than the plug on the flip side where the metering diaphragm is .----unless this particular model was specifically made for Makita for this model which is entirely possible . The question might be why ?

 

[Al Smith]

The new carb got the job done ,seems to run just fine .It is a Walbro WJ 181-1 which is slightly different .I had to change the cover over the metering diaphragm and use the slightly shorter idle screw to get it to fit .It's also a odd one .Has a partial plate choke which is spring loaded and once set opens the throttle plate up a tad .Pops off by hitting the throttle .
Now what I don't know is what in the world this nipple does on the diaphragm cover .Unless whatever it actually goes on uses a tube going to the air filter housing like a so called intella carb used by Stihl .

 

[DND 9000]

Yes it is the compensating feature that connects to the clean air filter side.

 

[Al Smith]

I might mention on the replacement carb it did not have a welch plug over the strainer but it did have a fuel pump that used the older buna-n type of diaphragm .I know it's a debatable subject but I've had better luck with this type on the smaller carbs than the yellow type whatever they are made of .
As far as the old carb I've never been whipped by one yet and when I regain my composure I'll delve into this no good SOB until figure it out . I had one on an 042 Stihl that pissed me off so bad I shelved the dang thing for 2 years . I got it after a cooling off period .

 

[Al Smith]

After I got that thing running I noticed on a spool up it was jumping the spark to ground .The reason I didn't see that before is it would not run long enough to spool up .With a mag the faster it turns obviously the higher rpm's the voltage goes up to a point of coil saturation . With a limited coil of course at a certain predetermined speed it "crow bars " the circuitry limiting the speed .In this case 9200 RPM's .I'm not sure on this coil if the spark plug wire can be changed or not .If not I'll give it a good coat of gyliptal or urethane .

 

[Al Smith]

I tested the compression and as I had thought it was low .100 PSI on one and 75 on the other . I'll give them a run next spring when it's not as cold out like well drillers behind .It might come up or it might not and if not a new ring in each .Single ring pistons about 10 bucks a pop . I have no idea how long they have sat unused .Hard to say, gummed up. stuck rings maybe or just plain worn out . The things smoke a lot so it's hard to say what the insides look like but I've seen that before and some times after some run time they clean up .

 

[bmp01]

I have a Makita DPC6410 that's playing up, acts like it has a big air leak and it seized its previous top end - so it's in bits for pressure and vacuum testing.

The carb is on the bench - its WJ 105 607, thats how I got to this thread ....

What do we reckon, Welch plug over the strainer or not ? Shall I open it up for a look-see? From the IPL I cant see any reason for the plug - the pump diaphragm looks like it seals over the filter recess in any case.

Just so long as there is no acclerator jet in the WJ 105 .....

 

[bmp01]

Well, as part of the investigation to fix my DPC6410 concrete saw I took the carb apart. The gauze filter was a little blocked but otherwise it's healthy. I have to say, a very nicely made carb, full of nice crisp machining.

No sign of a Welch plug over the filter. I notice a slight 'chamfer' around the filter hole (looking through microscope) but this is the cast surface, not a machined feature, there is no shoulder to accomodate a plug in this one. Picture attached...

I wonder if the OP's 2 off WJ105A carbs had a little modification since leaving the factory? Why wouId you do that though?