carb not getting fuel

[singinwoodwackr]

Uh, no, lol

I've noticed that QUITE OFTEN for just a few dollars more I can buy a Carb vs getting an OEM kit.

As suggested above check the impulse hole coming out of the engine and the impulse hose.

I'm suspecting that the issue IS NOT the carb. (after seeing all of the above)

Have you pressure/Vac tested the block?

Not yet and that is sounding like a very possible cause.

I agree it is most likely not a carb issue...especially after trying a different carb and symptoms were exactly the same.
If a bad bering it will give me the excuse to make a case cracker

Thanks for all the replies!

 

[singinwoodwackr]

Had to make the special tool

 

[singinwoodwackr]

The only leak I've found is at the spark plug. Brand new plug isn't seating. Even after cleaning...still leaks. Slight leake on the decomp as well but not nearly as much. macro lens on this phone is crap...
But, the plug seat is really buggered up.
How to fix? I don't have a lathe.

The plug threads are in bad shape as well. Even a rubber plug jammed in tight won't seal, sheesh.

 

[singinwoodwackr]

Thinking AM cyl for this one now.
The OE piston is fine...may as well re-ring it.

At least the 2 193s he gave me are ready to work . New carbs came in...all back in action.

 

[singinwoodwackr]

I think this one is solved. I couldn’t even get 10# pumped into the thing…with constant pumping. That bad an air leak would sure cause the issue.
plugged the spark plug and decomp holes with rubber plug and Teflon-taped bolt that didn’t leak. 7# of pressure holds as it should so seals are ok.

 

[Okie]

Just something I've noticed about decompression valves leaking.

When doing pressure tests on Homelite EZ's block it's common for the built in (non-replaceable) de-compression valves to leak on every one I've ever tested and the saw would start run and idle A-ok if all else was ok. MAYBE when the leak is above the piston instead of below the piston the intake applecart is not upset as much????????????

Anyway I just wanted to give you a hint to not get too excited if you see a slight de-compression valve leak.

 

[singinwoodwackr]

Just something I've noticed about decompression valves leaking.

When doing pressure tests on Homelite EZ's block it's common for the built in (non-replaceable) de-compression valves to leak on every one I've ever tested and the saw would start run and idle A-ok if all else was ok. MAYBE when the leak it above the piston instead of below the piston the intake is not upset as much????????????

Anyway I just wanted to give you a hint to not get too excited if you see a slight de-compression valve leak.

Decomp leak is very minor. Spark plug is the big one. The threads and seat are both too badly damaged to fix with what I have.

 

[Okie]

Decomp leak is very minor. Spark plug is the big one. The threads and seat are both too badly damaged to fix with what I have.

See where you are thinking After Market cylinder.

IMHO:
Heli coil is not the answer for a stripped spark plug hole.
I've heard of time serts but never used them and not a low priced install for just one after buying all required.

Few years ago I had a machinist friend that would machine and install spark plug stripped head adapters into aluminum Outboard motor heads for me Sometimes after they had been operated several hours the custom machined insert would come out with the spark plug and I would use the red permanent thread locker and all would be OK unless the engine ever overheated due to water pump failures.

 

[singinwoodwackr]

I threw on the cheap AM cyl from the other 261 carcass. We'll see.
The cyl is not something I would let out of the shop . No-name, Chinese, most likely...$40 or less...
But, just to get the thing running till I get some decent kits here.

 

[Aknutter]

Epoxy /JB / threadlocker a new spark plug in place and run it... Unless you have it welded up and rethreaded or use a timesert

 

[Chevboy0167]

I just got one of these kits last month just in case I run into the blown-out plug threads. Cheap and worth a shot.

 

[copen]

I just got one of these kits last month just in case I run into the blown-out plug threads. Cheap and worth a shot.

K-D had a similar kit some years ago, maybe still? Couple things to keep in mind. Make sure the piston is down, for obvious reasons, and use grease on the tap to catch cuttings. Take your time. They work well. Repaired a few VW heads using these but have not tried Heli-coil so I can't offer any opinions on them. Oh yeah, use locktite on the external threads.

 

[singinwoodwackr]

So, tried the cyl from the other carcass even though it is probably from a $35 kit. .
No change. It did "run" longer than before with a bit of gas into the carb directly but 2 sec rather than 1...gee...
Next door neighbor is a bit of a 2-stroke wiz so he brought over his carb tools. We got both of the carbs to hold pressure so that ain't the problem.
He thinks the needle valves are not opening when they should.
I've ordered a couple cheap carbs to try. More when they get here.

Sometimes there is a good reason people throw out a saw .

 

[Vintage Engine Repairs]

The very in-depth video I sent earlier of how to go through every part of a carb, have you
followed it?

 

[Automender]

So, tried the cyl from the other carcass even though it is probably from a $35 kit. .
No change. It did "run" longer than before with a bit of gas into the carb directly but 2 sec rather than 1...gee...
Next door neighbor is a bit of a 2-stroke wiz so he brought over his carb tools. We got both of the carbs to hold pressure so that ain't the problem.
He thinks the needle valves are not opening when they should.
I've ordered a couple cheap carbs to try. More when they get here.

Sometimes there is a good reason people throw out a saw .

I have pressure tested a few carbs and I found that the one on my Husqvarna had a pop off pressure of about 10 psi but the one on my Stihl would not pop at pressure of 20 psi and more. You would think if you put enough pressure on the inlet needle it would lift. The Stihl ran fine anyway. One thing I did notice that the one side of the diagram was vented to atmosphere and any little suction on that vent would open the needle valve.

 

[Vintage Engine Repairs]

I have pressure tested a few carbs and I found that the one on my Husqvarna had a pop off pressure of about 10 psi but the one on my Stihl would not pop at pressure of 20 psi and more. You would think if you put enough pressure on the inlet needle it would lift. The Stihl ran fine anyway. One thing I did notice that the one side of the diagram was vented to atmosphere and any little suction on that vent would open the needle valve.

Few things, although pop off pressure does have an effect on carb tuning, Zama no longer recommends testing it for anything more than its ability to hold off 10 psi - more pressure than will typically come from the fuel pump and or pressure that builds in the tank.

I haven’t given my carbs any special attention to pop off pressure honestly, other than what is mentioned by zama




Secondly that drilling in the metering diaphragm just ensures the diaphragm is acting against atmospheric pressure (vented). Some carbs go one step further and have a snorkel that will create the cover to the metering chamber and then extend into the air filter housing.

Zama calls these “Compensating carburettors”. In that case, the outside of the diaphragm is no longer under atmospheric pressure, but a slight vacuum that it has to actuate against every time it is lowered against the metering lever. It’s to stop an overly rich fuel condition when the air filter is dirty.

 

[Okie]

I've noticed what Zama says about checking pop off pressure. I've seen some little carbs on chainsaws and weed eaters that would not ever pop off at 20 plus pounds but would run good on the engine.
I started paying attention to the holding pressure for 15-30 seconds as mentiioned by Zama and like to see them hold 5 lbs but have seen some run good when they leak down and hold 3 lbs. On the type that have the vent hole in the plate I can use a small blunt tip punch through the hole and operate the needle diaphragm gently to see the bleed off and reseal of the needle valve.

 

[singinwoodwackr]

The very in-depth video I sent earlier of how to go through every part of a carb, have you
followed it?

 

[singinwoodwackr]

Yes but should watch it again.

 

[singinwoodwackr]

So, what, exactly, does the impulse port do? Vacuum or pressure?
I tried a little oil in the port, then crank a few times. I wouldn't say oil spirts out but there was some slight movement. (The oil just flows down). Tried a dab of grease and that popped right out with a pull. The port is clear into the cyl. I tred covering the port with my thumb and cranking and didn't feel any vac or pressure. Should there be enough to feel?
Impulse port on the carb is also clear.
I'm not going to futz with the carbs any more for now...gonna wait for the new to arrive.

If the new AM carb works ill tear into the old again.