Air Leak Question

[xpress]

Good evening all. I have a question about the potential causes of an air leak. I have a 2006 PS5100.... I know I know. The saw was a great runner and I don't want to give up on it yet. I can't get the carb to hold a tune and I think I have narrowed it down to an air leak. I vacuum tested the saw and it held so I am hoping the seals are good. I rebuilt the carb but once it gets hot it will start grabbing air.

I have researched these and other threads endlessly but I still have a few questions. First, should I target the area where the carb boot attaches to the cylinder and assume the heat is compromising this connection? I haven't pressure tested the system as I am concerned I might force air through this area and chase a false lead. It looks like I can't get to the spring that holds the boot on without pulling the cylinder out on this particular saw. Does anybody have any tricks to doing this without separating the piston and cylinder?

Sorry for the lengthy post but I was hoping someone has run into this problem in the past. I have already added the support ring on the carb side but it didn't help. It's extremely annoying that I can figure out this problem but I have been having a blast running my modded 032AV! If anyone has run into something similar on this saw let me know.

Thanks,

Eric

 

[DSS]

I've never worked on one of those, but with the saw idling on the bench, spray some WD 40 where you suspect the air leak. If the idle changes, you found it.

 

[xpress]

I will give that a shot tomorrow morning. It's tough to find because everything seems fine when she's cold. The carb is finicky to start with so there is very little margin of error to work with. Thanks for the tip. I will report back what I find.

 

[BIG JAKE]

Of course, a vac and pressure test is the best way to find problems. But here is a link that might help:

http://www.arboristsite.com/chainsaw/46766.htm

Good luck

 

[xpress]

Thanks for that link. That was actually one I missed. I never thought about that connection but it is a weak one. I will keep my fingers crossed that it is that easy!

 

[rmh3481]

You can find leaks at the intake, the flange where the cylinder meets the case and the main bearing oil seals. Any of these areas can leak, and the cylinder gasket is often overlooked. You will need to pressurize the case with the intake and exhaust plugged. Remove the carb. Use a strap of rubber between the muffler and the exhaust, and use a buffer or a cork at the intake. Fit your pressure pump to the pulse line or through the spark plug adapter.

If it holds 5psi for 20 minutes its considered sealed. Spin the crank with your fingertips to check for flat spots on the crank seals.

 

[Pendagator]

I have one of these saws- so far so good. I remember reading that on early models, a metal ring was missing on the air boot. I don't remember all the details, but it was a couple dollar part that solved a lot of folks problems. Also, I think Dolmar came out with a technical update to help idling. I think they had a new air filter and a sticker to cover a hole on the carb that improved idling. The post are buried here somewhere, I remember them.

Hope this helps.

 

[xpress]

Thanks. The top of my carb does have the open vent hole. I have already added the metal support ring Dolmar issued. This one is tricky as when it's cold and sealed it responds as it should. Once it heats up and in the cut, it starts to wail, which led me to believe I was dealing with an expansion or heat related issue since it will hold a good vacuum when cold.

I am headed out now to try to heat it up and spray some wd40 around the intake boot and see what happens. It also appears, unless I'm missing something, I need to pull the whole cylinder to get to this connection should it prove faulty.

 

[xpress]

problem solved

Just wanted to finish out this thread and thank everyone who replied with ideas. I tried all ideas this morning and while staring at this saw in disgust it occurred to me that maybe the air leak was a symptom and not the problem. So, I don't know what made me do it but I removed the fuel filter and that was it. No more leak. I can't believe I overlooked such a simple thing but I did. Of course this might not be the end of the story but she's running great now.

So IMO being a real man means admitting your mistakes instead of slinking away so no one will notice...besides, if you can't face your mistakes head on you're liable to encounter lots more frustration and a long slow painful learning curve! Thanks to all those who replied.

Eric