MS 361 dies out after creeping on the throttle a bit… need some help with tuning

[singinwoodwackr]

Yup I don’t get people bashing all the aftermarket carbs, like you said, there’s not much to them once you understand how they work.

I’ll try some more tuning stuff and hopefully that works, really hoping it’s not an air leak. If it’s an air leak I just don’t understand that since it pasted the vacuum and pressure test.

And, if it’s an air leak then how is the thing able to idle for minutes on end on upside down on its side or any position? Just hoping I’ll be able to figure it out and it doesn’t burn up the saw, seems like it Has to be a minor air leak if anything. I’ll try replacing the impulse hose line as well since that is hardened up.

Did you test just the carb? Off the saw

 

[ZeroJunk]

Whatever works for you the individual, what works for me works for me, I don`t try to persuade others.

I'm not trying to persuade anybody either. If it was a pristine saw I would put an OEM on it. If it's an old work dog I'
d probably use something cheap.

I have just used too many aftermarket carbs to automatically assume that is the issue when 90% or better of the time they work fine.

Seems like on here any time somebody says aftermarket carb automatically that is the problem.

In the meantime, I have a stack of bad OEM Stihl carbs sitting on a shelf that came out of the box bad.

 

[buzz sawyer]

Just a thought - why not try the OEM carb? Maybe the broken L screw is set correctly? I would even swap gaskets from the replacement or buy a kit for the OEM if needed.

 

[2-StrokeDude]

Did you test just the carb? Off the saw

You mean like pressure test? I have not done that and I have never done that, so how would I go about that?

 

[bwalker]

Just can’t justify buying $100 Walbro carb for a saw that I’m not gonna use a whole lot, I don’t use chainsaws a huge amount. When I got the saw the L screw adjustment was broken off so the old carb is junk otherwise I would 100% be using the OEM one. I’ve got an ultrasonic cleaner so I’d be able to get it like brand new. It’s just a shame that the screws busted off on the old one.

So your time is worthless?

 

[singinwoodwackr]

You mean like pressure test? I have not done that and I have never done that, so how would I go about that?

Hook it up to the miti via the fuel nipple. Many of the air leaks I've come across were in the carb.

 

[Vintage Engine Repairs]

Just can’t justify buying $100 Walbro carb for a saw that I’m not gonna use a whole lot, I don’t use chainsaws a huge amount. When I got the saw the L screw adjustment was broken off so the old carb is junk otherwise I would 100% be using the OEM one. I’ve got an ultrasonic cleaner so I’d be able to get it like brand new. It’s just a shame that the screws busted off on the old one.

Use a dremel and cut the broken end off square, then use that same cutoff wheel to make a flat head slot in it. I have done it countless times in brass on much smaller needles which is even more tricky.

Edit, if it’s broken below the surface of the body of the carb, drill a hole in the needle, use an easy out to get it out and then cut the flat in it. This covers both eventualities.

 

[singinwoodwackr]

or...once you get the broken needle out, replace it. they are available from any Stihl dealer

 

[2-StrokeDude]

Ok guys, here is an update on this issue.

I re-did the pressure/vac test with all the proper Stihl block off tools and the saw held pressure and vac perfectly. Also tested the carb I had on the saw and it held pressure. But after looking at the order I placed on HL Supply for some parts including the carb, it seems the carb is a Farmertec. Crap. No wonder I could not get the saw tuned!

So I ordered the next best carb next to OEM that I could find. I got a Proline Parts carb from sawzilla that fits. I am installing the Proline carb today so hopefully it will work well. I contacted the seller on sawzilla and they said they have very low defect rates on their carbs. When I rebuilt the saw I put some Proline brand crankshaft bearings in the saw and they seem like very high quality. On the website it says they are not made in China. They looked and rolled just as good as the OEM ones.

Hopefully the Proline carb is better, I'll let you guys know what happens with it in case someone needs to use this thread in the future.

 

[2-StrokeDude]

Ok guys, here is an update on this issue.

I re-did the pressure/vac test with all the proper Stihl block off tools and the saw held pressure and vac perfectly. Also tested the carb I had on the saw and it held pressure. But after looking at the order I placed on HL Supply for some parts including the carb, it seems the carb is a Farmertec. Crap. No wonder I could not get the saw tuned!

So I ordered the next best carb next to OEM that I could find. I got a Proline Parts carb from sawzilla that fits. I am installing the Proline carb today so hopefully it will work well. I contacted the seller on sawzilla and they said they have very low defect rates on their carbs. When I rebuilt the saw I put some Proline brand crankshaft bearings in the saw and they seem like very high quality. On the website it says they are not made in China. They looked and rolled just as good as the OEM ones.

Hopefully the Proline carb is better, I'll let you guys know what happens with it in case someone needs to use this thread in the future.

Well I put the Proline carb on yesterday and it is a lot better! It doesn’t die out like it use to. Definitely helps to have a quality carb!

The one weird thing is after adjusting the carb, the L and H screw seem to be really sensitive. After tuning the L screw it is only like 1/2 to 3/4 of a turn out from the starting point. The H screw is pretty similar and is at like maybe 3/4 to 1 turn. I’ve made sure both screws are set a little rich and upon testing the H screw setting it is just 4 stroking a little bit.

Do you think I should be concerned on how little adjustment is on the screws? Maybe it is just specifically this aftermarket carb design?

I’ve found on most carbs I’ve tuned the setting will be at least 1 1/2 to 1 3/4 turns so it’s just odd to me.

 

[Old2stroke]

Expect it with AM carbs. They may have different tapers and different thread pitch from OEM ones

 

[pioneerguy600]

The engine will determine where the screws/needles are set and the Am carbs are not exact replicas of the OEM carb, poor copies mostly.

 

[Vintage Engine Repairs]

It starts and runs, that’s a very good result with clone carburettors.

 

[Gumneck]

Interesting read here and that's a win for you figuring it out.

Now that you got it running well, If it were me, I would go back through the OEM carb and if needed swap gaskets and diaphragms or just replace them with new. Dont worry about the High speed screw yet, Put it back on and see if it runs well with that one. If so, then you can see if you can get that High speed needle out. Unless its corroded in tight, I bet a couple of picks on each side of the screw parts and the carb set gingerly in a vice could be used to slowly back that needle out. Its worth trying.

 

[2-StrokeDude]

Interesting read here and that's a win for you figuring it out.

Now that you got it running well, If it were me, I would go back through the OEM carb and if needed swap gaskets and diaphragms or just replace them with new. Dont worry about the High speed screw yet, Put it back on and see if it runs well with that one. If so, then you can see if you can get that High speed needle out. Unless its corroded in tight, I bet a couple of picks on each side of the screw parts and the carb set gingerly in a vice could be used to slowly back that needle out. Its worth trying.

Yes I am glad it is running well now. I have thought the same thing on the OEM carb, I will try getting that screw out of there, but it is buried in deep. I may need to try and get an easy out, but there is not much material to grab onto anymore.

 

[Gumneck]

Yes I am glad it is running well now. I have thought the same thing on the OEM carb, I will try getting that screw out of there, but it is buried in deep. I may need to try and get an easy out, but there is not much material to grab onto anymore.

I think it will be worth it too. I'm thinking that a tiny tiny drill bit, drill a hole in the center. Make another punch just on each side of hole and drill each again. No need to drill deep just enough to get a flat head screwdriver into the slot you create.

 

[SteveSr]

Yes I am glad it is running well now. I have thought the same thing on the OEM carb, I will try getting that screw out of there, but it is buried in deep. I may need to try and get an easy out, but there is not much material to grab onto anymore.

Have you tried gluing an extension onto the stub with epoxy putty?

 

[Old2stroke]

Nice to get the OEM carb repaired but don't do it thinking you will be getting a better carb. If the AM one works fine and the engine responds to the adjustment screws like it should (regardless of the actual settings) you have a good one. What do you think wears out in a carb? The gaskets, diaphragms and check valves are the same material and quality that you would find in an OEM carb or an OEM repair kit and will have the same lifetime. There is a lot of AM carb bashing on this forum because a few of them will be defective and can't be made to work right but if you get a good one, it will perform as well as an OEM one and you won't need a special tool to adjust the mixture screws.
AM ignition coils now, there's an item that deserves a good bashing.

 

[JG33MC]

First off, Merry Christmas to all of you guys!!

So I’ve got my MS 361 all rebuilt and running well, chopped a couple of small pines down with it and cut up some logs and it runs really good! However, I keep having this issue with it where if I’m cutting just little twigs on a log before chopping it up, I just use the throttle slightly to get through it, after letting off the gas, it just dies out. Then when trying to restart it, it will either take one pull to start it back up or I’ll have to choke it and lock the throttle to get it started up again, even if it is warm. I’ve tried adjusting the L screw on the carb a bit and it’s not seem to do a whole lot. I’ve got the L screw set a little rich. Any ideas what could be causing this?

L Screw is set at 1 1/4 turns and the H screw is set at 1 1/2.

Hoping this isn’t an air leak since I vacuum/ pressure tested this chainsaw after the rebuild which I posted about and it passed both of them. It idles great and will idle for minutes on end if it doesn’t die out after letting off the throttle.
View attachment 1138419

 

[JG33MC]

Have you checked that the fuel tank vent isn't clogged.