Stihl 461 no idle or low jet

[sledneck22]

I have a 461 that I rebuilt and had running excellent. I sold it to my cousin and now it has a problem after months of use. The saw will start and run as long as you give it throttle. It’ll slowly rev up until getting high jet then runs like it should until it comes down in rpm to a point where it needs low jet. Then if you don’t keep the throttle open it just dies.
Obviously I adjusted the low jet up and down and there’s no change. Took the carb apart, cleaned it all. Removed the low jet blew and cleaned out all those passages and exact same problem.
Things I’ve checked.
Carb cleaned and gone through.
Metering valve set and sealing.
Spark plug changed.
New clutch and drum and bearing.
Checked the spark plug wire for grounds.
Checked the internals. No piston or cylinder wear, all look new.
New fuel filter and fuel line.
New impulse line.
Intake boot is in place and not leaking.
Set the coil to flywheel with a business card.
New air filter….

Idk what’s next. My only thoughts are the carb is somehow messed up or the coil needs to be replaced.

Thoughts my semi expert friends?

 

[cus_deluxe]

did u check the actual throttle arm adjustment?

 

[sledneck22]

did u check the actual throttle arm adjustment?

Yeah. That looks fine

 

[Woodslasher]

I have a 461 that I rebuilt and had running excellent. I sold it to my cousin and now it has a problem after months of use. The saw will start and run as long as you give it throttle. It’ll slowly rev up until getting high jet then runs like it should until it comes down in rpm to a point where it needs low jet. Then if you don’t keep the throttle open it just dies.
Obviously I adjusted the low jet up and down and there’s no change. Took the carb apart, cleaned it all. Removed the low jet blew and cleaned out all those passages and exact same problem.
Things I’ve checked.
Carb cleaned and gone through.
Metering valve set and sealing.
Spark plug changed.
New clutch and drum and bearing.
Checked the spark plug wire for grounds.
Checked the internals. No piston or cylinder wear, all look new.
New fuel filter and fuel line.
New impulse line.
Intake boot is in place and not leaking.
Set the coil to flywheel with a business card.
New air filter….

Idk what’s next. My only thoughts are the carb is somehow messed up or the coil needs to be replaced.

Thoughts my semi expert friends?

Have you pressure tested it yet? Do you have another coil to try on it?

 

[jacob j.]

Those symptoms are what I get when I leave an impulse line unhooked.

Have you gone through the low circuit on the carb? You may need to pull the welch plugs.

 

[sledneck22]

Have you pressure tested it yet? Do you have another coil to try on it?

It passed pressure when I sold it but haven’t checked since and no I don’t have another coil to try. I guess I need to rule out the pressure test and Welch plug passages.

 

[huskihl]

Could also be the brass main nozzle. If you punch it out you can hook your vac/pres tester to it. From the venturi side, it should hold pressure

 

[heimannm]

Good call there Kevin. If it is flooding at low speeds it does indeed sound like the nozzle/check valve.

slednek - Do you have to hold the throttle open to restart like it is flooded? If yes then you need to investigate the nozzle/check valve.

Mark

P.S. Mini Mac's and PM6's with the MDC carburetor are notorious for this...

 

[Mastermind]

If you need a coil let me know.

 

[Al Smith]

Just a thought for what it 's worth .On occasion some bit of crud makes it through the fuel filter and past the screen in the carb .Could be anything ,dirt,chip of wood fiber etc . Soaking in carb cleaner or blowing out with compressed air may or may not get it .What will get it is punching a skinny wire torch cleaner like for on a cutting torch .I have a set that has wires not much larger than a human hair .It helps to have a drawing of the actual carb which you can find on whoever made the carb's web site to determine where those passages actually are .

 

[Stump Shot]

I have a 461 that I rebuilt and had running excellent. I sold it to my cousin and now it has a problem after months of use. The saw will start and run as long as you give it throttle. It’ll slowly rev up until getting high jet then runs like it should until it comes down in rpm to a point where it needs low jet. Then if you don’t keep the throttle open it just dies.
Obviously I adjusted the low jet up and down and there’s no change. Took the carb apart, cleaned it all. Removed the low jet blew and cleaned out all those passages and exact same problem.
Things I’ve checked.
Carb cleaned and gone through.
Metering valve set and sealing.
Spark plug changed.
New clutch and drum and bearing.
Checked the spark plug wire for grounds.
Checked the internals. No piston or cylinder wear, all look new.
New fuel filter and fuel line.
New impulse line.
Intake boot is in place and not leaking.
Set the coil to flywheel with a business card.
New air filter….

Idk what’s next. My only thoughts are the carb is somehow messed up or the coil needs to be replaced.

Thoughts my semi expert friends?

Try opening the throttle with the throttle idle speed screw so as it's way too high in rpm and slowly bring it back down to a normal idle speed and see what happens and report back.

 

[pwheel]

I have a 461 that I rebuilt and had running excellent. I sold it to my cousin and now it has a problem after months of use. The saw will start and run as long as you give it throttle. It’ll slowly rev up until getting high jet then runs like it should until it comes down in rpm to a point where it needs low jet. Then if you don’t keep the throttle open it just dies.
Obviously I adjusted the low jet up and down and there’s no change. Took the carb apart, cleaned it all. Removed the low jet blew and cleaned out all those passages and exact same problem.

Earlier this year, my low-hour 461 out of the blue decided to die at idle. After re-tuning & scratching my head for a week with no improvement (to either my head or the saw LOL), took the carburetor apart and give it to the Stihl shop to cook in the ultrasonic tank & replace diaphragms. Fixed. The tech said that the metering diaphragm seemed stiff.

 

[Al Smith]

The tech said that the metering diaphragm seemed stiff.

For some reason some soft components of the carbs goes to hell faster than others . Might be the gasoline for all I know . If I get into to one I rebuild it .Kits aren't that expensive .Fact I've got one right now on a Partner ,fickle as a teen aged prom queen .I have no idea how long that carb had sat unused before I bought the saw .Fix it,forget it at least for a time .

 

[sledneck22]

first, thank you all for the insight. Started back on this today. Pressure tested the saw again today. Passed just like before. So I’m good from intake boot around to impulse. So it’s cool or carb. To a break for a beer cuz it’s fuggin hot. Gonna tear more into carb now.

 

[sledneck22]

Just went through the carb. Thin wired everything I could. Checked the nozzle/check valve. Readjusted everything correctly. Same problem. Will start with hi adle engaged. Struggle to gain any rpm’s while holding wide open. Eventually. 5-6 second it takes off and high speed runs like it should. You feather the throttle back off and when hi jet runs out it just pukes and dies.
I have to believe it’s the carb. It does look like the head of the low jet adjuster is bent so that tells me the needle could be buggered. Wasn’t like that before when it left my shop. Didn’t look like the needle end of the adjustment screw was bent but who knows.

Anyone beg to disagree a new or used carb would correct the issue or is there belief maybe the coil still not hot enough at low rpm?

 

[Stump Shot]

Just went through the carb. Thin wired everything I could. Checked the nozzle/check valve. Readjusted everything correctly. Same problem. Will start with hi adle engaged. Struggle to gain any rpm’s while holding wide open. Eventually. 5-6 second it takes off and high speed runs like it should. You feather the throttle back off and when hi jet runs out it just pukes and dies.
I have to believe it’s the carb. It does look like the head of the low jet adjuster is bent so that tells me the needle could be buggered. Wasn’t like that before when it left my shop. Didn’t look like the needle end of the adjustment screw was bent but who knows.

Anyone beg to disagree a new or used carb would correct the issue or is there belief maybe the coil still not hot enough at low rpm?

If the coil will fire in the open air at a 5-6mm air gap, it will fire under compression when running.
You could pressure check the carburetor to either .5 Bar or 7 psi and see if it holds pressure. If it leaks down in under a minute your carb definitely has a problem.
If your low speed adjustment screw is damaged, this could also be a problem especially when it's misaligned inside where you can not see.
I had a 372 come through with such a thing and it would not run right until I replaced the adjustable jet with a new one.

 

[sledneck22]

I pressure tested the fuel line and impulse line in the carb and it held pressure for 15 minutes each.

 

[sledneck22]

I have a feeling that low jet got damaged when I had him adjust the low when it got warmer.

 

[Mastermind]

Surely someone has a carb they can Rob a needle out of for you. I don't think I have anything for that carb though.

 

[huskihl]

Surely someone has a carb they can Rob a needle out of for you. I don't think I have anything for that carb though.

The only two carbs I’ve ever thrown away were an HD 50 and an HD 17. Couldn’t get the low speed circuit to work in either one lol.