I'm having trouble with my Husky 350 so I decided to take it apart and check the intake boot fpr any tears or holes, and I wanted to check the crankcase bolts and piston/cylinder as well. The CC bolts were not super tight so I snugged them all up. I had used a common hose clamp on the boot previously and boot/piston/cylinder all looked good. However, I sprayed carb cleaner and blew some air through the ports where the impulse hose attaches but later realized that I have no idea what is going on in there. Could I have done any damage blowing compressed air through there? Is there a way to test whether it is OK w/o pressure testing? ( I don't have a tool/gauge for that) I searched for an answer about impulse lines and found an explanation that says it connects to the carb, but in the 350 it connects to 2 places on the intake boot, If someone can explain what the impulse hose does, that would be a bonus. Thanks, Larry
Husky 350 intake boot
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The impulse hose sends a positive and negative signal from the crankcase to the carb. This works the internal fuel pump and the metering system.
Depending on how much pressure you ran through the crankcase you would run the risk of blowing the case seals out, but that would be unlikely if you didn't have the engine sealed up. Only way to be sure would be to preform a proper vac/pressure test.
Depending on how much pressure you ran through the crankcase you would run the risk of blowing the case seals out, but that would be unlikely if you didn't have the engine sealed up. Only way to be sure would be to preform a proper vac/pressure test.
One end of the impulse hose goes from inside the crankcase, the other to a fuel pump diaphragm in the carb. Blowing air into the crankcase is unlikely to hurt anything (might depend on where the piston was sitting & how much pressure). Blowing high pressure back into the carb may damage the fuel pump diaphragm. It will become apparent if thats the case & a carb kit should sort it
But neither end of the short hose goes to the carb.. Both ends connect to the intake boot.
Edit: I think I figured out how the impulse gets to the carb. Looks like there is a channel through the intake boot to where it connects to the carb. Please correct me if i'm mistaken. I'm definitely a novice here. BTW, I have a bucket full of pipe clamps and most were too wide (about 1/2") to fit in the space allowed between cylinder and boot. Only one was the right diameter and narrow enough (7/16") to fit. The Stihl clamp that is often mentioned here looks to be about 1/4" wide but they are $8-$10 and I'm a cheapskate
Edit: I think I figured out how the impulse gets to the carb. Looks like there is a channel through the intake boot to where it connects to the carb. Please correct me if i'm mistaken. I'm definitely a novice here. BTW, I have a bucket full of pipe clamps and most were too wide (about 1/2") to fit in the space allowed between cylinder and boot. Only one was the right diameter and narrow enough (7/16") to fit. The Stihl clamp that is often mentioned here looks to be about 1/4" wide but they are $8-$10 and I'm a cheapskate
I think I used a clamp for a 390xp, diet cheap on the internet, even generic ones work ok. Worm clamps suck for this application.
They probably were dirt cheap 4 years ago but the lowest price on Ebay now is $8.40 and most go for over $10. Shipping has gotten ridiculous. I agree a pipe clamp is not ideal but it will work if it is narrow enough
Some guys have gone to cv boot clamps that can be purchased in bulk or individually, available at auto parts stores. Do a Google search and you will see many options that match suit your needs and your budget.
You don't need a stihl branded one, just one that's the right size. I'm not home or I'd grab the bag the last set I got came in. Was about a year or so ago. They were a few bucks each.
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Stihl bands work just fine, but do NOT have to be made for/marked for STIHL, soon as you put those 5 letters on a part, the price triples.
Knock off band clamps work just fine.
These are somewhat odd of an impulse travel system and you are correct, the manifold forms an impulse port seal, a plastic nipple from the manifold clamp fits into that rubber seal to provide an exit/entry to the cylinder. It then exits the right side of the clamp plastic via a nipple into short 180 degree bend rubber impulse hose, back into another nipple on the carb holder and via an internal channel there to the carb.
Knock off band clamps work just fine.
These are somewhat odd of an impulse travel system and you are correct, the manifold forms an impulse port seal, a plastic nipple from the manifold clamp fits into that rubber seal to provide an exit/entry to the cylinder. It then exits the right side of the clamp plastic via a nipple into short 180 degree bend rubber impulse hose, back into another nipple on the carb holder and via an internal channel there to the carb.
This is the clamp I used on 3 of the 350 saws I rebuilt.
Make sure these 2 holes are completely open and clear on both parts marked in red. Many times I find them melted partly or fully shut, causing the engine to starve or run lean for fuel.
This will cause scoring of the piston and/or cylinder which is no good at all and will need replacement.
This will cause scoring of the piston and/or cylinder which is no good at all and will need replacement.
