Vacuum leak?

[fields_mj]

It's a cheap tester from Amazon, so its my own fault. The gauge has lousy resolution on the vacuum side. I checked with a co-worker and he things he has one. If he can find it, he'll loan it to me so we'll see. Worse case, I'll wait until I can get to HF and buy theirs. If it wasn't so far away, I'd have bought theirs to begin with.

Thanks for the info on the vacuum level.

 

[fields_mj]

Well, last night it held 0.5 Bar. I need to also mark the flywheel and turn it over a few times to see if it leaks. I went through that process last night, but I didn't think about marking the fly wheel to get the piston back in the same position.

 

[SteveSr]

Well, last night it held 0.5 Bar. I need to also mark the flywheel and turn it over a few times to see if it leaks. I went through that process last night, but I didn't think about marking the fly wheel to get the piston back in the same position.

Piston position is irrelevant as the pressure will equalize rather quickly around the rings. Also as part of the vacuum and pressure test you should push/pull and rotate the crank as this may show marginal sealing/leaks that only appear when the crank is in a certain position. In fact, one test to check for leaking seals is to turn the saw up / down / and sideways to see if the idle rpm changes.

 

[Vintage Engine Repairs]

Also flex the rear handle assembly to test intake boot issues

 

[fields_mj]

Coworker brought in his tester during lunch. It's good to have a friend or two

 

[Mad Professor]

They have MityVac MV85000 on ebay for $80 shipped

https://www.ebay.com/itm/2262637595...RRjTKXKZlTjrOTiGZ5EZpyvw==|tkp:Bk9SR6jJ-qqqZA

 

[fields_mj]

Used my coworker's tester and it was much easier to use. It was really easy to pull 14 in Hg with it. It held vacuum fine until I started moving the flywheel. Then it dropped to a little more than 7 in Hg, and stayed there. No matter how I moved the flywheel around, it held at a little more than 7 in Hg. That's a little below the 0.3 bar limit. I'm thinking they are just past the point of needing replaced.

 

[lone wolf]

Used my coworker's tester and it was much easier to use. It was really easy to pull 14 in Hg with it. It held vacuum fine until I started moving the flywheel. Then it dropped to a little more than 7 in Hg, and stayed there. No matter how I moved the flywheel around, it held at a little more than 7 in Hg. That's a little below the 0.3 bar limit. I'm thinking they are just past the point of needing replaced.

Did it go back higher when rotating the flywheel back?
Did the Vac go to zero over a few minutes, or hold?
Seems like you are having trouble here. It either holds or drops it shouldn't drop at all in a minute, the flywheel will move it up and down when rotating but if it holds vac at the same number over a minute or so you are good.

 

[fields_mj]

Did it go back higher when rotating the flywheel back?
Did the Vac go to zero over a few minutes, or hold?
Seems like you are having trouble here. It either holds or drops it shouldn't drop at all in a minute, the flywheel will move it up and down when rotating but if it holds vac at the same number over a minute or so you are good.

It depended on how fast I moved the flywheel. If I did it with any speed (pulling somewhat slowly on the pull rope), the vacuum level would raise and lower as you would expect, but then always return to a little more than 7 in hg. If I moved it slowly (just moving it with my finger), the value would fluctuate slightly but again always return to 7 in hg. If I ran it up to 14 in hg, and them moved the flywheel until it started to bleed down, and then ran the vacuum back up to 14, it would still blead down to 7 without moving the flywheel any.

Based on the previous quote from the repair manual, it sounds like my oil seals have reached the point of needing replaced. They may not be in terrible shape, and it may not have contributed to the issue with my piston, but if I don't deal with the problem now I'll soon be going through this entire process again as the seals continue to degrade.

 

[lone wolf]

It depended on how fast I moved the flywheel. If I did it with any speed (pulling somewhat slowly on the pull rope), the vacuum level would raise and lower as you would expect, but then always return to a little more than 7 in hg. If I moved it slowly (just moving it with my finger), the value would fluctuate slightly but again always return to 7 in hg. If I ran it up to 14 in hg, and them moved the flywheel until it started to bleed down, and then ran the vacuum back up to 14, it would still blead down to 7 without moving the flywheel any.

Based on the previous quote from the repair manual, it sounds like my oil seals have reached the point of needing replaced. They may not be in terrible shape, and it may not have contributed to the issue with my piston, but if I don't deal with the problem now I'll soon be going through this entire process again as the seals continue to degrade.

Like I said, put grease heavily in the inner lips and see what changes. Change them and be done with it.

 

[fields_mj]

That's where I'm at with it. I think the cost of the parts is going to be around $50, and it's questionable at best so I'm going to get them changed and be done with it.

If I'm replacing the seals and bearings, what parts do I need? Looking at the parts breakdown/diagram, it looks like I need 2 different bearings, 2 different seals, and a gasket for the 2 halves of the case. Is that correct?

 

[SteveSr]

That's where I'm at with it. I think the cost of the parts is going to be around $50, and it's questionable at best so I'm going to get them changed and be done with it.

If I'm replacing the seals and bearings, what parts do I need? Looking at the parts breakdown/diagram, it looks like I need 2 different bearings, 2 different seals, and a gasket for the 2 halves of the case. Is that correct?

The seals will come with the complete gasket set for less than just the seals alone. The IPL should give you gasket set part number.

 

[Mad Professor]

That's where I'm at with it. I think the cost of the parts is going to be around $50, and it's questionable at best so I'm going to get them changed and be done with it.

If I'm replacing the seals and bearings, what parts do I need? Looking at the parts breakdown/diagram, it looks like I need 2 different bearings, 2 different seals, and a gasket for the 2 halves of the case. Is that correct?

If bearings are in good shape you can get by with seals and save a lot of work.

Get the OEM gasket set.

 

[fields_mj]

The seals will come with the complete gasket set for less than just the seals alone. The IPL should give you gasket set part number.

Complete cost for an OEM gasket set from my dealer was $13.49. Total cost for both bearings was under $22. They should get here on Monday.

Interestingly enough, while I had them on the phone, I priced repair parts for my 064. At one point it had an 066 top end on it. A guy rebuilt it for me once before, but I can't remember if he took it back to an 064, or if he used an 066 for the top end, so I priced pistons for both. The 064 piston is $98 which is only a few dollars more than what they charged me for the 036 piston. However, an 066 piston is only $44. I guess Stihl must make a BUNCH of 54mm 066 pistons...

 

[Mad Professor]

Complete cost for an OEM gasket set from my dealer was $13.49. Total cost for both bearings was under $22. They should get here on Monday.

Interestingly enough, while I had them on the phone, I priced repair parts for my 064. At one point it had an 066 top end on it. A guy rebuilt it for me once before, but I can't remember if he took it back to an 064, or if he used an 066 for the top end, so I priced pistons for both. The 064 piston is $98 which is only a few dollars more than what they charged me for the 036 piston. However, an 066 piston is only $44. I guess Stihl must make a BUNCH of 54mm 066 pistons...

Time to get a spare for my 066!

Do you have tools to split cases/pull install bearings?

 

[fields_mj]

Time to get a spare for my 066!

Do you have tools to split cases/pull install bearings?

No. I have a co-worker who works on 2 cycles as a hobby who has the tools and substantially more experience doing it than me (which is zero). He's offered to do my 036 as well as my 064 for me.

 

[mbret2004]

What kind of tester is it?


Stihl says 0.5bar or 7psi vacuum. If it continues to loose vacuum over time it is also no good.

If vacuum, in/hg, isn't given, you need to double the psi to get proper vacuum number. The conversion is approximately double the psi. So, 7psi = 14 in/hg. Yes, vacuum First!