Carburetor tuning on muffs

[tphoyt]

Ideally you should completely dissemble the carbs and clean thoroughly and reassemble with new own kits.
If your in a pinch you could try removing the needle just unscrew it nothing to worry about and spray some carb cleaner in there. To reinstall the needle screw it in until lightly seated and back it out 1 1/4 turns to start and adjust from there.
Best

 

[Toshi]

I will check the 3 points that you mentioned also. Thank you !

Perhaps the screw was backed out so far, that it didn't make any real difference to the Mixture, or there was some gunk/gum/varnish in the passages that were restricting the flow and the needle wasn't making any change in the range you turned it.
Another possibility is that the Middle carb wasn't fully closed, and that certainly will affect the idle circuit

 

[Toshi]

Yes, sir !
Thank you.

Ideally you should completely dissemble the carbs and clean thoroughly and reassemble with new own kits.
If your in a pinch you could try removing the needle just unscrew it nothing to worry about and spray some carb cleaner in there. To reinstall the needle screw it in until lightly seated and back it out 1 1/4 turns to start and adjust from there.
Best

 

[Toshi]

I removed the needle valve and sprayed good amount of carb cleaner and let it soaked for a while and sprayed again. The tip of the needle valve looked fine to me. I checked the spark in the middle carb and it was fine.
Still, rpm wouldn’t change even when I turn the screw all the way in or back out 4turns or so. While engine is off, I unscrews the screw on the bottom of the middle carb and fuel came out, so I think the carb is getting fuel.

I will do compression test again just to check, but if the compression is fine, I have no clue what to check next.
Any advice is really appreciated.
Thank you very much.

Ideally you should completely dissemble the carbs and clean thoroughly and reassemble with new own kits.
If your in a pinch you could try removing the needle just unscrew it nothing to worry about and spray some carb cleaner in there. To reinstall the needle screw it in until lightly seated and back it out 1 1/4 turns to start and adjust from there.
Best

 

[saltchuckmatt]

I removed the needle valve and sprayed good amount of carb cleaner and let it soaked for a while and sprayed again. The tip of the needle valve looked fine to me. I checked the spark in the middle carb and it was fine.
Still, rpm wouldn’t change even when I turn the screw all the way in or back out 4turns or so. While engine is off, I unscrews the screw on the bottom of the middle carb and fuel came out, so I think the carb is getting fuel.

I will do compression test again just to check, but if the compression is fine, I have no clue what to check next.
Any advice is really appreciated.
Thank you very much.

Did you look down in the carb and see if the butter fly valves is completely closed like previously discussed?

Is that middle spark plug wet?

You say you checked for spark, did you check for GOOD Spark?
Adjustable spark arc tester with a nice crisp blue spark.

 

[tphoyt]

I can’t find your original post.
Is this by chance the same cylinder that was scored that caused the rebuild in the first place?

 

[Toshi]

Yes. Butterfly valve is completely closed at idle for the middle carb.

I checked the spark plug today and it wasn’t wet. I’ll recheck tomorrow, though.

I don’t have an adjustable spark tester and I have ignition tester like the picture attached here. The brightness of the tester for the middle carb was the same as the other two (top and bottom carb).

I just checked fuel lines and I felt some resistance to blow air when it’s slightly bent on the fuel hose with smaller diameter. This hose goes to the upper portion of the middle carb. Maybe this hose could be an issue?

Did you look down in the carb and see if the butter fly valves is completely closed like previously discussed?

Is that middle spark plug wet?

You say you checked for spark, did you check for GOOD Spark?
Adjustable spark arc tester with a nice crisp blue spark.

 

[Toshi]

Yes. The middle cylinder was scored and I honed it. I also honed the other two cylinders and now the compressions are the same and 105 psi or so.

I can’t find your original post.
Is this by chance the same cylinder that was scored that caused the rebuild in the first place?

 

[tphoyt]

Well if that carb is not supplying fuel it’s not supplying oil either.
I think you really need to dive in and find out what’s going on before running it again.

 

[Toshi]

Before rebuilding the engine, I disabled VRO and use pre-mix (fuel: oil = 50 : 1)

Well if that carb is not supplying fuel it’s not supplying oil either.
I think you really need to dive in and find out what’s going on before running it again.

 

[tphoyt]

If that mix is not reaching that cylinder your running it without oil.

 

[saltchuckmatt]

Before rebuilding the engine, I disabled VRO and use pre-mix (fuel: oil = 50 : 1)

Did you check your reed valves when you rebuilt your motor?

 

[jimmbo]

While a possibility, Reed failure is very rare.
Spray some premix into the middle carb and note how the engine responds

 

[Toshi]

Yes. They are in good shape.

Did you check your reed valves when you rebuilt your motor?

 

[Toshi]

Yes, sir. I will do that tomorrow.

While a possibility, Reed failure is very rare.
Spray some premix into the middle carb and note how the engine responds

 

[jimmbo]

Yes, sir. I will do that tomorrow.

Mix the premix at 16:1, just to insure it gets enough oil to spin a bit after you quit spraying, in case the carb is delivering no fuel to that cylinder.

 

[ct1762@gmail.com]

I removed the needle valve and sprayed good amount of carb cleaner and let it soaked for a while and sprayed again. The tip of the needle valve looked fine to me. I checked the spark in the middle carb and it was fine.
Still, rpm wouldn’t change even when I turn the screw all the way in or back out 4turns or so. While engine is off, I unscrews the screw on the bottom of the middle carb and fuel came out, so I think the carb is getting fuel.

I will do compression test again just to check, but if the compression is fine, I have no clue what to check next.
Any advice is really appreciated.
Thank you very much.

you had asked how you tell if the middle carb or any carb is taking fuel... either put your hand over the carb to choke it, or squirt some premix with a syringe into it. no change=no fire. simple.

 

[Toshi]

I couldn’t get out of work till late. And it’s too tale to turn on the engine now. I don’t want to get a complain from my neighbor…

I will spray 16:1 to the middle carb tomorrow and see how it goes.

In the mean time, I checked all fuel lines to make sure they are all air right and shorten the main fuel line from gas tank hoping if it helps somehow.
I noticed I haven’t put a plug into the oil outlet of disabled VRO, so I did.
Maybe weak VRO could be causing this issue?

I also switched spark plug of the mid carb with the top one to rule out spark plug isn’t causing a problem.

I will keep posting here tomorrow.

Thank you very much all.

 

[Toshi]

Got it. Thank you !

you had asked how you tell if the middle carb or any carb is taking fuel... either put your hand over the carb to choke it, or squirt some premix with a syringe into it. no change=no fire. simple.

 

[jimmbo]

I couldn’t get out of work till late. And it’s too tale to turn on the engine now. I don’t want to get a complain from my neighbor…

I will spray 16:1 to the middle carb tomorrow and see how it goes.

In the mean time, I checked all fuel lines to make sure they are all air right and shorten the main fuel line from gas tank hoping if it helps somehow.
I noticed I haven’t put a plug into the oil outlet of disabled VRO, so I did.
Maybe weak VRO could be causing this issue?

I also switched spark plug of the mid carb with the top one to rule out spark plug isn’t causing a problem.

I will keep posting here tomorrow.

Thank you very much all.

All the carbs are fed the same Fuel mix that the VRO supplies, so the only way a Cylinder by itself, would be affected, would be an Leaky Pulse/Vacuum Line between the Pump and the Crankcase.