Crank Seals

[Bootlegger1956]

First off...Hello to all and thanks for all the posts that have educated me in my new chainsaw tinkering hobby. This journey started several months ago with a Stihl 025 and a Tanaka arbor saw. Since retired I decided to heat with wood and felt I needed another saw. I mentioned this to some of my Vet buds and in short order I had a Husky 51, a 55 and a 350 all retired because they "wont run." The 51 and 55 both had low compression and scored pistons. I disassembled the 55 because it was the best looking of the pair. It is an open port 04 model with a Zama carb. After cleaning and evaluation I did a vacuum / pressure test @ 8-10" and psi. The saw seems to hold the vacuum and pressure for several minutes with little to no drop. However when I rotate the crank 10-20 revolutions I lose @ 1" of vacuum. Would this be considered an acceptable test or should I replace the crank seals. I soaped the seals and under pressure I get no leakage. There are a lot of posts about leak testing but I could not find a clear enough answer to satisfy me. I just ordered a new Meteor P&C kit and obviously dont want to risk killing it. Thanks in advance. Any advice would be appreciated. Sorry for the life story.

 

[hotshot]

Welcome aboard!

Hard to tell in your posting (no paragraphs) what your baseline vacuum was, it should be 15”Hg to start.

A 1”Hg drop, starting at 15, over several minutes is acceptable. Especially after turning the crank over so many times.

You can easily tune the carb around that.

 

[Bootlegger1956]

I was kind of under the impression that the test should be conducted at 7-10" or psi with no more than 10 psi. Remember your dealing with an infant when it comes to my chainsaw repair knowledge so I typically parrot what I read or hear. Thnx for the response.

 

[cuinrearview]

@HarleyT ???

 

[Deleted member 117362]

I was kind of under the impression that the test should be conducted at 7-10" or psi with no more than 10 psi. Remember your dealing with an infant when it comes to my chainsaw repair knowledge so I typically parrot what I read or hear. Thnx for the response.

7 is correct.

 

[HarleyT]

The needle will move some when you rotate the crank. I wouldn't worry about it much.

 

[hotshot]

I was kind of under the impression that the test should be conducted at 7-10" or psi with no more than 10 psi. Remember your dealing with an infant when it comes to my chainsaw repair knowledge so I typically parrot what I read or hear. Thnx for the response.

Correct. Negative 1 psi is roughly 2”Hg vacuum.

Small radial seals are only designed for 7 psig service. Dichtomatic seal company has an excellent guide on their website about seals.

 

[Deleted member 117362]

Check your in box.

 

[Bootlegger1956]

Thanks all for the info and tech manual. One spin of the crank does not have much impact. The drop only occurs when I spin it multiple times. I am starting to think I may be too critical and expecting zero tolerance on the leakage. I want to build both of these saws. One with the Meteor P&C and the other with a Hyway or another AM version and see which one does the best and lasts. Any advice would be appreciated. I have read a lot and watched a lot of builds on youtube and can hopefully make good decisions.

 

[rupedoggy]

I think you can make the 51 into a 55 by a simple cylinder change. Since you are buying replacement sets why not have the added displacement. This will make your comparison more valid also. Mike

 

[Deleted member 117362]

I gave up on hyway p/c kits, others will have different opinions.

 

[Bootlegger1956]

I think you can make the 51 into a 55 by a simple cylinder change. Since you are buying replacement sets why not have the added displacement. This will make your comparison more valid also. Mike

That is my plan. I just need to decide which inexpensive AM kit to use. Hyway may not be the answer. There seems to be dozens of different suppliers. Its hard to believe that they are all made by different manufacturing companies.

 

[backhoelover]

With seals bearing so cheap I would replace them. Added insurance

 

[Bootlegger1956]

With seals bearing so cheap I would replace them. Added insurance

I am trying to follow the "dont fix it if it aint broke" theory. I learned my lesson on that in the US Submarine force where we tore down the ships diesel engine to replace a vertical drive unit coupler that had .025 run out against a .020 max spec. The TWO factory replacements were worse than the original which we reinstalled in the end. Four of us worked 16 hour days for three weeks to FIX this problem. The base diesel expert who required us to effect the repair disappeared and never returned after the second factory replacement failed. That's not a dig against you backhoelover just a sea story. My concern is not the cost but my lack of experience at replacing chainsaw crank seals.