just runs on choke

[dieseldod]

hi lads, chinese saw i,m working on today , went through the carb started first pull on choke . the second you take it off of choke it dies,. it will run all day long at high idle choke not missing a beat. i sprayed round the crank seals and inlet thinking it was drawing air but no. all intake and seals are tight. thing that gets me is there is no vacuum at the intake when it running on choke you can block the inlet and it doesn,t phase it one bit. weird one for me ,so i thought i,d ask the experts.

 

[ZeroJunk]

I think the high speed jet is stopped up. Nothing more.

 

[dieseldod]

i will have to pull the carb off and have a look AGAIN . thanks for that

 

[a. palmer jr.]

It's either getting too much air or not enough fuel.

 

[dieseldod]

well opened it up today carb full of fuel as normal , pulled the land h needles passages clear on both to venturi. still the same would run all day on choke and never miss a beat. the lack of vacuum at the intake is baffling me
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[Gumneck]

well opened it up today carb full of fuel as normal , pulled the land h needles passages clear on both to venturi. still the same would run all day on choke and never miss a beat. the lack of vacuum at the intake is baffling me
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Is the metering lever set correctly? Diaphragms soft and pliable?

 

[dieseldod]

yes lever set level, diaphragm is soft yes didn,t warrant me putting a new one on

 

[Gumneck]

Its leaking air somewhere or its starving for fuel.
New fuel lines and filter since carb is gone through for normal stuff.
Time to pressure/vac test

 

[rupedoggy]

Check the pulse line

 

[ericm979]

If it needs the choke to idle but runs at WFO, it's likely an air leak. The air leak is too small to affect the mixture at WFO much (until its not and you seize the engine). But at low rpm the leak has a greater effect. Secondary cause would be a fuel blockage that affects low speed running but not high speed.

 

[dieseldod]

Check the pulse line

yes pulse lines fine , it never has no bother drawing fuel to fill carb. and the carbs always full when i open it up

 

[dieseldod]

Its leaking air somewhere or its starving for fuel.
New fuel lines and filter since carb is gone through for normal stuff.
Time to pressure/vac test

yes i will psi vac test it. i should just put another carb on to see if it cures . i have at hand

 

[dieseldod]

If it needs the choke to idle but runs at WFO, it's likely an air leak. The air leak is too small to affect the mixture at WFO much (until its not and you seize the engine). But at low rpm the leak has a greater effect. Secondary cause would be a fuel blockage that affects low speed running but not high speed.

eric it doesnt run at full throttle at all it just starts great and sits running well on choke /fast idle say 4000 rpm. it just bogs as soon as the choke goes off

 

[ericm979]

eric it doesnt run at full throttle at all it just starts great and sits running well on choke /fast idle say 4000 rpm. it just bogs as soon as the choke goes off

I understood runs all day to mean you were doing work with the saw.

So yea, what I wrote was wrong for your problem.

 

[Gumneck]

Here's another quick check idea. On the fuel pump side of carb, is the screen absolutely clean. I had one a time that was not full of crud so I didn't give it a 2nd look. Once I removed the needle valve and shot carb cleaner I didn't see anything getting through. It was shellacked over. Kept on spraying and free n clear. Just watch that you dont spray the screen across the floor and spend an hour looking for it. Yep, did it.

 

[a. palmer jr.]

Like was said, you could always try another carburetor. It's fairly easy on most saws to just do a pressure test, a little more difficult to do a vacuum test, but the pressure test alone will probably tell you if you have an air leak. If this is a Chinese saw it might be difficult to find a carburetor to match the saw.

 

[lwmibc]

FWIW--I once had a 1963 Galaxy, that one morning would start and idle just fine, but if I tried to get it above idle it would die, instantly. Could start it with perfect reliability, and idle it all day--but try to do anything else--die. In exasperation I called a mechanic friend I knew, this in a mining town just south of the Yukon border in BC. He said 'Your coil has failed'.

'What??--it starts just fine!' He explained that the coil secondary turns are kept separated by a tar-like potting compound; when it fails and more serious than idle demands are made to the coil by increasing the frequency at which they have to supply a voltage that will jump the spark gap, the coil turns can short out either on the case or to each other; the spark-jumping voltage disappears. Went down to his shop and got a new coil--instant (and permanent) fix.

Who knows, it just could apply to chainsaw coils too. Never happened to me before or since; that was in 1971--in Cassiar, a town that no longer exists.

(BTW--if you're scared of asbestos--why am I still alive? My office (exploration geology) was right beside the drier exhaust, that was measured to blow out 6 tons of asbestos dust an hour.)

 

[dieseldod]

it can be running away quite the thing and i can block the intake with my thumb and it dont bother it any. it must be getting air from somewhere to run, would the base gasket be leaking? i never sprayed around there when i did the intake and crank seals i will likely delete gasket and port it a bit while i,m at it if thats the case

Here's another quick check idea. On the fuel pump side of carb, is the screen absolutely clean. I had one a time that was not full of crud so I didn't give it a 2nd look. Once I removed the needle valve and shot carb cleaner I didn't see anything getting through. It was shellacked over. Kept on spraying and free n clear. Just watch that you dont spray the screen across the floor and spend an hour looking for it. Yep, did it.

 

[dieseldod]

hi initially the screen was dirty i always take the screen out and look below, being an old duffer, i,ve spent too many hours on my knees looking for items of awkwardness like springs . its all downhill after you get your first pair of specs.

 

[dieseldod]

Like was said, you could always try another carburetor. It's fairly easy on most saws to just do a pressure test, a little more difficult to do a vacuum test, but the pressure test alone will probably tell you if you have an air leak. If this is a Chinese saw it might be difficult to find a carburetor to match the saw.

yes in have the test gear here, i have plenty carbs here the same ,just stubborn, want to fix it lol