I was under the impression that an air leak would cause erratic idling, over-revving, inability to tune the carb etc. Is it possible for an air leak to cause a bogging condition? Even though the saw will idle fine?
Air leak question
- Thread starter Armosh
- Start date
Help Support Arborist Forum:
Timber MacFallen
ArboristSite Operative
Sure, if air starts rushing in from somewhere other than the carb you won't have enough fuel to compensate.
This a general question or are you having problems with a saw? First thing I’d check is the piston. If it’s scored checking anything else is kind of a waste of time.
Both actually. I am working on a husky 141. Did the piston and cylinder. Starts, idles fine. Wont rev, just bog and stall. But it was my impression if it was an air leak it would idle erratically and over rev, not bog. I've rebuilt and cleaned the carb, coil is good, plug is good too. Might have to rig up something to block off the intake and exhaust and pressure and vac test it. I'm a newbie and just trying to learn.
+1, leaking intakes cause bogging & then the engine dies off when throttled up.
Did you replace the little impulse seal tube on the intake?, those get squashed down over time & leak 90% of the time.
https://www.ereplacementparts.com/impulse-pipe-p-621538.html
Did you replace the little impulse seal tube on the intake?, those get squashed down over time & leak 90% of the time.
https://www.ereplacementparts.com/impulse-pipe-p-621538.html
Open the L screw 1/4 turn and see if it gets rid of the bog
vac/pressure test would be a good idea, have you adjusted the carb at all?
Both the intake boot and the impulse tube were replaced when I did the piston and cylinder. The old impulse tube was cracked pretty bad and the carb partition impulse end was melted and slightly deformed so that was replaced too. I did indeed try to tune the low jet which settled the idle but it just doesn't seem to want to rev at all. Also tried turning the high jet 2 1/2 turns out with no change. I opened up the carb again to double check my work and decided to replace the needle and lever arm. Put it back on and it helped slightly, can almost coax it to slowly rev up but then starts to bog and die. Almost like its running out of fuel. Also should mention the fuel filter and fuel line were also replaced. It originally came to me with a heavily scored piston and cylinder. The ring on the exhaust side was completely embedded into the piston.
The owner told me it was spitting and sputtering when he last used it and wouldn't restart. He said the fuel filter had broken off the fuel line so he replaced both and still no go. Compression tested at 55 or so psi. I thought a fuel filter falling off shouldn't score it like that and then when I saw the badly split impulse pipe and melted tip of the carb extension I assumed between that and a dull chain did her in.
Also a side note: absolutely garbage design on the impulse and intake boot.
What saw is it?
Husky 141 LE
- Joined
- Jul 19, 2019
- Messages
- 4,546
- Reaction score
- 9,204
You are not starting from a "great" place. 
That whole family of 36's and 40's of various guises right up to the 40-45-49 saws are all pretty average in the air sealing of the intake tract when they get a bit of age about them.
By all means, rig something up to pressure test it- you do not need a mityvac to test a saw- they are just nice to own.
Bits of inner tube and muffler/carb back on will seal- internal impulse and no decomp kind of narrow down your entry point to the spark plug hole- remove the porcelain from an old plug and epoxy in a tube air can travel through in its place and you are away laughing.
That whole family of 36's and 40's of various guises right up to the 40-45-49 saws are all pretty average in the air sealing of the intake tract when they get a bit of age about them.
By all means, rig something up to pressure test it- you do not need a mityvac to test a saw- they are just nice to own.
Bits of inner tube and muffler/carb back on will seal- internal impulse and no decomp kind of narrow down your entry point to the spark plug hole- remove the porcelain from an old plug and epoxy in a tube air can travel through in its place and you are away laughing.
Try spray carb cleaner on the crank seals when running.
The seals are a crap design and crap material. I have replaced all of them along with crank bearings in about a dozen saws in that line. The rubber hardens then the crank wears them down.....= air leak.
The seals are a crap design and crap material. I have replaced all of them along with crank bearings in about a dozen saws in that line. The rubber hardens then the crank wears them down.....= air leak.
55 for compression?
- Joined
- Jul 19, 2019
- Messages
- 4,546
- Reaction score
- 9,204
Easy to get with an automotive tester- not a specific small engine tester.
I remember the 141LE to have the aluminized muffler with the small rear outlet.
I'd guess the muffler is not allowing the engine to rev up .
^^^^^ Very possible...... The cheap aftermarket mufflers work and fit well with a bar side fish gill outlet that can be bent open a bit for better flow. I have installed many.
OEM
Aftermarket
https://www.ebay.com/itm/3231545955...2TSmeQ=|tkp:Bk9SR9zp9874Yg&LH_ItemCondition=3
OEM
Aftermarket
https://www.ebay.com/itm/3231545955...2TSmeQ=|tkp:Bk9SR9zp9874Yg&LH_ItemCondition=3
That is one of my suspicions. I ordered a cheap hollow muffler to try. Haven't figured out a way to block off the intake and exhaust yet to test it but I did start it and tried flipping it on its side to see if the idle would change. Nothing, didn't matter what orientation I put it in, idle doesn't change. At this point I'm just honestly curious to see what the problem is so I can learn from it. It's driving me crazy.
You can run it for a bit without the muffler just don’t stick your finger in there lol. In a pinch I use carb spray with a tube on it to try and pinpoint a leak. Spraying near the carb/throttle shaft can give a false positive
If I start it up and set it down and just let it idle it will eventually die after about 30 or so seconds, like it is running out of fuel. Choke it and starts right back up and can repeat it. I also noticed that when you start it choked and push in the choke lever it will indeed run on high idle until you blip the throttle to settle into a normal idle. It then will bog if you try to rev it up.
