Carburetor good or bad?

[cdntbone303]

How do I know if a carb is no longer good for a rebuild? I have a older model Husqy 61 I can’t get to run right. Low is too rich and high there isn’t enough turning in left to get at recommend max rpm. Carb has not been rebuilt yet. Compression is 135lbs

 

[pioneerguy600]

If the tuning screws, H & L still have good tight threads then I rebuild them, had 2 in 40 years that would not work correctly after a full rebuild.

 

[Ozhoo]

Welcome to AS. Remove and inspect the adjustment needles. If they've been deformed it'll be obvious. If you have a pump, apply 7psi to the fuel inlet and submerge the carb in a bowl of water. It should hold pressure, if not, pull the metering side and troubleshoot the inlet needle/spring/lever... then report back.

 

[cus_deluxe]

sounds like stiff metering diaphragm?

 

[cdntbone303]

Thank’s all for the replies. I have some investigating to do

 

[Ted Jenkins]

If the tuning screws, H & L still have good tight threads then I rebuild them, had 2 in 40 years that would not work correctly after a full rebuild.

I have to agree with Pioneer on this one. Recently I threw a carburetor in the carb box because it suddenly died, but it was one in maybe 40 or so that did this. It is possible for some of the passages to get plugged, but not many. Thanks

 

[stihl86]

If the tuning screws, H & L still have good tight threads then I rebuild them, had 2 in 40 years that would not work correctly after a full rebuild.

What a memory.

 

[Conquistador3]

If the carburetor just doesn't want to run right after a good cleaner bath and a rebuild, just replace it. Life's too short to waste time on this kind of stuff.
If the membranes are installed correctly, the carburetor spent at least 6 hours in a bath, the main jet has been set using a Walbro/Zama gauge (tip: if you haven't got a set, just buy it) and the adjustment screws are set right you have done all that could be done. With aftermarket carburetors as cheap as they are nowadays it literally makes no sense to waste more time and money, and if you want a 100% original saw you can just buy a used genuine carburetor down the road while you keep on working. I think an aftermarket carburetor for a 61 is $15 or so. If China Post doesn't send your order to the South Pole first, of course.

Some carburetors (Walbro WT and Zama RB series to say but two of the most notorious) seem to be very much hit and miss: either they work with new membranes and gaskets or you can just throw them away. I don't repair as much stuff as I used to but I throw away one or two carburetors every year, mostly Walbro. Buying cheap aftermarket carburetors just makes so much sense if repair kits don't work.

 

[cdntbone303]

If the carburetor just doesn't want to run right after a good cleaner bath and a rebuild, just replace it. Life's too short to waste time on this kind of stuff.
If the membranes are installed correctly, the carburetor spent at least 6 hours in a bath, the main jet has been set using a Walbro/Zama gauge (tip: if you haven't got a set, just buy it) and the adjustment screws are set right you have done all that could be done. With aftermarket carburetors as cheap as they are nowadays it literally makes no sense to waste more time and money, and if you want a 100% original saw you can just buy a used genuine carburetor down the road while you keep on working. I think an aftermarket carburetor for a 61 is $15 or so. If China Post doesn't send your order to the South Pole first, of course.

Some carburetors (Walbro WT and Zama RB series to say but two of the most notorious) seem to be very much hit and miss: either they work with new membranes and gaskets or you can just throw them away. I don't repair as much stuff as I used to but I throw away one or two carburetors every year, mostly Walbro. Buying cheap aftermarket carburetors just makes so much sense if repair kits don't work.

I had installed 2 aftermarket carbs on 2 other 61’s and one is hard to start because the choke only opens halfway/won’t idle well after taking it up to max rpm the idle is never consistent enough to stay running I have to readjust the idle again and again, and the other wouldn’t start at all. Both having spark and excellent compression. So I have their original Tillotson HS carbs soaking in cleaner waiting to be rebuilt. Do I have to adjust the main jet on these?

 

[Conquistador3]

I've had a couple of defective aftermarket carburetors over the years: both of them were Walbro WT clones so it can happen more than once. I was refunded both times so I only lost time. Intriguingly enough one had troubles idling and the other required setting the H adjuster continously.

To get back at your Tillotson carburetors, you should make sure the little metering lever/arm over the main needle (#7 here https://tillotson.ie/wp-content/uploads/2015/07/HSPartsList.pdf ) is set properly. It can really drive you nuts; don't ask how I know.
Tillotson hasn't got a metering gauge available like Walbro and Zama do, but you can manufacture one yourself with a strip of sheet metal or stiff plastic about 3/4" wide. The metering lever needs to be flush with the bottom of the bowl: you can adjust it by turning very slowly the retaining screw (#9 on the diagram above).

I am yet to test an ultrasonic cleaner on these carburetors but if you have one available you may want to try that route: I keep on hearing excellent things about them.

 

[Cliff R]

Tillotson carbs are very well made and it's rare to find one that isn't serviceable.

I've had to remove the Welch plugs on a few that refused to work correctly after rebuilding no matter how long they were in the ultra-sonic cleaner or how much carb cleaner and compressed air you pushed thru them.

Have had a couple that needed a little work where the linkage is staked on the end of the shaft where the link from the throttle hooks up. One was my 480CD It started acting a little funny right off idle and sometimes refused to idle all the way back down. I discovered the linkage was loose and ended up brazing it in place. That repair was done about 35 years ago and it's been rock solid ever since.

Also interesting and almost amazing is that the carb has never had a kit put in it, and still has the original fuel line. I did replace the tank vent back around 2003.......Cliff

 

[cdntbone303]

Today I split the covers off the 2 aftermarket chinese carbs I had replaced the original Tillotsons with and found that the smaller 7/32 welch plugs have a pin size hole in the center on both of them. Is it me or does this defeat the purpose of a welch plug? Probably the reason why I couldn’t tune the one saw that I could get running. By the way both original Tillotson HS’s soaked for 26hrs with welch plugs removed I blew then out with my compressor and then I rebuilt with new kits but lacked 7/32 welch plugs so I hammered them flat and put gasket maker in crevice from where I punched them to remove to seal, then making sure everything was level/aligned and the saws still wouldn’t run right.

 

[rupedoggy]

I don't see a hole in the welsh plug. There is one in the jet and supposed to be there. BTW that is a forky type fulcurm and may need the type diaphragm that has the little "tit" on it to slide onto the fork. Mike

 

[Conquistador3]

Today I split the covers off the 2 aftermarket chinese carbs I had replaced the original Tillotsons with and found that the smaller 7/32 welch plugs have a pin size hole in the center on both of them. Is it me or does this defeat the purpose of a welch plug? Probably the reason why I couldn’t tune the one saw that I could get running. By the way both original Tillotson HS’s soaked for 26hrs with welch plugs removed I blew then out with my compressor and then I rebuilt with new kits but lacked 7/32 welch plugs so I hammered them flat and put gasket maker in crevice from where I punched them to remove to seal, then making sure everything was level/aligned and the saws still wouldn’t run right. View attachment 787856

The welch plug is the silver one at the top, the brass-colored one is what Tillotson grandiosly called "metering-nozzle valve". A jet for us earthlings.
Also try these baseline settings: turn both adjustment needles in ("tighten" them) until they are gently seated. From there undo the L one full turn and the H one ¾ of a turn. Let the saw idle until it's warmed up and then you can try adjusting it.

At this point however I would move my attention to the fuel lines, if you haven't yet, especially if the previous owner had the bad habit of storing the saw with fuel in it. One that's leaking or turning to goo can really ruin your day...

 

[cdntbone303]

Finished 1 of 2 husqy 61’s today turned out both crankseals were bad on that one. Took a few tries at the carburetor to get it to run right. Leaky 7/32 welch plug should have known better to change instead of resusing. I didn’t have any to fit so I machined a larger plug to fit that I had extra in my carb kits. Second one I believe I have it right too but the aftermarket muffler split in half from the vibration as I was tuning the carb. Would motoseal be good to glue the muffler together? It is an empty can type with 2 round channels for muffler bolts and below that 2 holes where the front bracket fastens on. The factory had used some sort of hard glue but it wasn’t enough to hold it together.

 

[rupedoggy]

The factory had used some sort of hard glue

The factory never glued mufflers

 

[Conquistador3]

If both crankshaft seals were leaking I would advise to check piston and crankshaft bearings conditions: it means the saw ran lean for a pretty long time. Perhaps nothing to worry about, but it's better to err on the safe side and also explains why no amount of carburetor adjustment seemed to help.
As far as the muffler goes... the previous owner(s) left you a present following his attempts at "tuning". How sweet. An aftermarket muffler for those old Huskies is $15, maybe less, but if you are in a hurry order from a source outside China: the Lunar New Year is next Saturday, meaning the whole of China will go on vacation on Monday and not be back until early February.

 

[cdntbone303]

The factory never glued mufflers

It is a Chinese aftermarket, not original.

 

[rupedoggy]

There are hundreds of member here and they have bought thousands of Chinese parts. I will ask "has anyone had a muffler that was glued?"

 

[pioneerguy600]

Nope, never.