Diagnosing An Air Leak

[blsnelling]

This is a commercially used 346XP that I built several years ago. It's seen a lot of heavy use. The customer stated that it idled high an a new carb didn't help. When I got the saw I fired it up and played with the tune. It idled a little high, but not too bad. More significantly, the low side wouldn't tune and run quite right. I pulled the muffler and checked the piston. It looked great. I pulled the carb and found the impulse line had a significant hole in it. I thought I had found the problem. I replace the line and it didn't run/tune any better. So, I set the saw up for a vac/pressure test. I simply put the hose in my mouth and blew and could hear a significant air leak. It takes a BAD leak to be able to hear it that easily. I immediately knew I had a bad PTO side crank seal leaking. Thankfully, the user knew not to continue using the saw and took it out of service before any damage was done. Below is a video showing you what it looked like.

 

[FamilyTradition]

Nice job, glad it wasn't ruined. Max.

 

[stihlaficionado]

Good to see you're posting again, Brad

 

[blsnelling]

Good to see you're posting again, Brad

Don't get used to it I go back under the knife tomorrow morning for a 4th and unplanned operation. Hopefully this will be the last.

 

[Canyon Angler]

Useful information, thanks for posting.

 

[Jacob J.]

Don't get used to it I go back under the knife tomorrow morning for a 4th and unplanned operation. Hopefully this will be the last.

I thought they removed your unborn twin last time?

 

[Wood Doctor]

Worn out crank shaft seals cause lots of problems. They can even lead to bad bearings and many service manuals say to replace the bearings while you are at it. Normally I avoid that unless I can see that the bearings are shot.

Good post, Brad.

 

[SeMoTony]

Don't get used to it I go back under the knife tomorrow morning for a 4th and unplanned operation. Hopefully this will be the last.

Hopefully you recover to the point of doing all that you did before the surgeon started practicing his needle point on you.
Wishing you good health

 

[old CB]

All the best to you Brad. You're one of those who've really made this place worthwhile. Let's see you back and healthy.

 

[MG porting]

This is a commercially used 346XP that I built several years ago. It's seen a lot of heavy use. The customer stated that it idled high an a new carb didn't help. When I got the saw I fired it up and played with the tune. It idled a little high, but not too bad. More significantly, the low side wouldn't tune and run quite right. I pulled the muffler and checked the piston. It looked great. I pulled the carb and found the impulse line had a significant hole in it. I thought I had found the problem. I replace the line and it didn't run/tune any better. So, I set the saw up for a vac/pressure test. I simply put the hose in my mouth and blew and could hear a significant air leak. It takes a BAD leak to be able to hear it that easily. I immediately knew I had a bad PTO side crank seal leaking. Thankfully, the user knew not to continue using the saw and took it out of service before any damage was done. Below is a video showing you what it looked like.

Wow that was one heck of a bad seal.

 

[Wood Doctor]

Wow that was one heck of a bad seal.

I have a Husky 350 that could be doing this. New top end and intake manifold solved nothing. It tries to start and dies instantly. I've also noticed some traces of fuel making it to the inside bottom of the case.

 

[MG porting]

I have a Husky 350 that could be doing this. New top end and intake manifold solved nothing. It tries to start and dies instantly. I've also noticed some traces of fuel making it to the inside bottom of the case.

Yea I'd be checking your crank seals that's for sure if you've done all that and nothing has changed be sure to check them bearings out to.

 

[blsnelling]

I have a Husky 350 that could be doing this. New top end and intake manifold solved nothing. It tries to start and dies instantly. I've also noticed some traces of fuel making it to the inside bottom of the case.

An air leak usually make a saw idle too high.