Husqvarna 136

[Menessis]

My Old Husqvarna 136 didn't get much use in the past few years. I need that saw running this summer though.

But it has other ideas. I starts right up and runs great for a couple of seconds and quits abruptly. After restarting a bunch of times I could get it to run wide open by opening the choke just right. I got it warmed up doing that but as soon as I open the choke it quits.

OK So I checked for a plugged fuel filter. And found the fuel line had broken off the filter. I replaced the fuel line and used the original filter. I don't think its plugged. In the mean time I got a carb kit and did the work on Sunday. But it still won't idle. It's as if I hadn't done anything to it.

I noticed that I could see air bubbles in the fuel line (since its brand new). Some times thats an indication of a plugged fuel filter. But when the carb kit came and I pulled the fuel line off to pull the carb there was air pressure in the tank and a lot of fuel streamed out of the fuel line. So now I'm wondering if the vent is plugged?

I'm kinda going around in circles at this point. I'm trying to think of a safe way to run the saw with the gas cap off or loose to see if it runs properly.

Any Ideas of what I should try at this point?

Thanks
Mike

 

[Bob Hedgecutter]

If the filter was off the fuel line- odd are a lot of crud has been pulled into the carb.
Every time you open the tank to fill, bits of "stuff" fall in and build up in the tank- the filter keeps them in the tank and out of the system- filter falls off, crud goes in.

So if you are up to it- strip and clean the carb- could just be a heap of muck sitting on the fine filter screen inside the carb- other side of needle valve- or it might be in a gallery somewhere.
Do not blow anything out with high pressure compressed air- carb cleaner is much healthier and an ultra sonic cleaner even better.

You might want to go as far as fitting a new carb kit to freshen it up. E fuel is hell on the componentry inside small carbs.

 

[Menessis]

Ya I did the carb kit already... there was a lot of debris on the screen in the carb.

The bubbles are weird I think. Also I don't understand why there is pressure on the gas tank?

 

[Bob Hedgecutter]

Bubbles in the fuel line can mean the filter is sitting above fuel level, ledged within the tank up high- not sitting on the bottom of the tank.
Personally for all they cost- I would be replacing the filter.

Pressure blows out- vacuum sucks in. If the breather is not working, a vacuum forms within the tank as air cannot pass through the breather to replace the used fuel. There is no real way for an intact saw tank to build pressure apart from excessive heat and expansion of the fuel into vapour.

 

[Bob Hedgecutter]

Ya I did the carb kit already... there was a lot of debris on the screen in the carb.

The bubbles are weird I think. Also I don't understand why there is pressure on the gas tank?

If you have done a carb kit, are sure the internals of the carb are clean, have fuel flow from tank to combustion chamber- then more than likely you have an air leak- close the choke and you decrease the air volume- correct?
So if you can only get it to run on choke and you are sure the carb is good- an air leak elsewhere is a likely culprit.

 

[Menessis]

Ya I didn't change the gasket. I see another common problem is a poor joint in the impulse pipe. That is what makes it pump fuel.

 

[Bob Hedgecutter]

They do leak there commonly- but the horrid wee thinks leak everywhere- crank seals, engine pan, impulse, carb plate to cylinder......

Proper pressure and vacuum test is the only way to be dead sure it is not sucking air from somewhere.

 

[Menessis]

So what do make of the positive pressure in the fuel tank.

 

[Bob Hedgecutter]

So what do make of the positive pressure in the fuel tank.

Very little- unless I was there to judge it myself.
I mean what can you see that will somehow pump air under pressure in to the fuel tank?

 

[Menessis]

I'm wondering if the vent is plugged. If the vent is open there shouldn't be any pressure build up due to temp change??

 

[Bob Hedgecutter]

The vent is one way- lets air in to replace fuel used- but does not let air out.

 

[Menessis]

Ohhhhhh....I see. Didn't know that little tid bit. Thanks Bob.

 

[Menessis]

From bad to worse. Got an impulse kit today. I noticed fuel in the cylinder. Enough to dump out and wipe up the puddle on the floor. I did check the order and orientation of the carb rebuild kit before I put it back in.
Installed kit.....wont start. It's flooding right away. Didn't do that before. It floods so quick there is gas coming out the muffler!

So I may have inadvertently changed the adjustment on the needle valve. This is the only thing I can think of?? Sadly I don't have the "W" tool to make that adjustment.

 

[Bob Hedgecutter]

Okay- ah the 136, or 36, or 41 or even 141- the saws I have grown to hate.

You do not "need" the W tool per say- tongue of the lever flush with the gasket less carb body with a straight edge (steel ruler) laying over.
The kit you got- underside of the diaphragm- straight nipple of nipple with a groove in it?
Gasket on correct side of diaphragm?

Another good check is to pull the muffler and check the piston is not all scored to bits- no compression means no fire and no fire + continued rope pulling means a flooded condition.

 

[Menessis]

OK Cool....I was hoping you would tell me a method of adjusting the needle. You agree that's what's going on here now. When this all started it was starved for fuel!

 

[Menessis]

I had to take a break.....I was getting to annoyed LOL

I'm not sure of what you mean here "straight nipple of nipple with a groove in it?"

I think I can take this apart and put it back blind folded at this point

 

[Bob Hedgecutter]

Underside of the diaphragm there is a flange with a nipple that engages the metering lever- a plain nipple sits on the metering lever.
The nipple with the groove sits in a fork in the metering lever.
WT 136 carb should be a flat nipple and lever- if a grooved nipple diaphragm is used and sits upon the lever it will be holding it permanently open.

With the diaphragm and gasket removed and a straight edge laid over the carb body- on the WT the needle should NOT contact the straight edge and indeed be a few thou lower than the straight edge- WT setting on the tool is the middle of the W inverted.
You can fold a bit of pop can or similar over your straight edge and use that to measure the needle lever- or feeler gauges.

 

[Menessis]

OK. Thanks again Bob. Stay tuned I will go give that a try right now.

 

[Menessis]

OK Bob.....it's picture time. What's wrong with this picture?

 

[Menessis]

OH....I forgot. While apart I did have a look at the piston. Not a mark on it.

Also You can see the middle extends past the outer arms quite a bit.

I compared the new and old parts. They are identical as far as the adjustments would go. (by eye) The old lever has that detent that can be seen in the pic