Stihl 07 (1961-1965) Rebuild Process.

[Vintage Engine Repairs]

Did you coat your base gasket on both sides with a sealer? Did you check the crankcase deck for true/flat surface?

Hey yes both surfaces got checked for flatness with glass and feeler gauge. I didn’t use any sealant on the gasket mate no. The leak seems to be within the matrix of the gasket itself rather than the mating surfaces.

 

[Vintage Engine Repairs]

As the gasket ages, the gasket can dry out, shrink, and by the sounds of it in this case, begin to shrink away from the metal matrix that is sandwiched between them.
Older gaskes could often have such things as linseed oil in them to give them malleability, over time this dries out and or hardens.

Suggest a few heat cycles and a re torque, if that dosent help, get some permatex no3 non hardening aviation gasket, get it warm, ie crack the lid of it, put it in hot water to allow it to get nice and warm, mix well so its evenly mixed and runny, and whilst pulling vacum, apply it via a syringe to be taken up into the matrix of the gasket and fill the voids.

Thanks for the suggestion mate. I can do that. The annoying thing is that I can’t test it for leaks anywhere else as it’s leaking so much from there. Will continue to re resemble and see how things go.

 

[Vintage Engine Repairs]

Or, ditch the old, dried-out, junky gasket and make a new one. Cylinder gaskets are not hard to duplicate and these old saws are pretty generous with top end clearances.

Hey Cb, these can’t be made from normal paper, they are super thick. I was advised against it by my local stihl dealer as they said thick gaskets require reenforcing? I don’t know, but this was why I waited 9 weeks to continue this build while waiting for it to arrive from USA lol. Regarding clearance, you are right, the squish is massive lol.

 

[cbfarmall]

If you've got massive 'squish' then you have plenty of room for a thinner, modern style gasket. If you fret that it 'changes' your timing numbers, just remember what you are working on. Likely, you wouldn't notice a difference. How many experts on this forum brag about base gasket deletes? What is really the difference between that and a thinner gasket here?

Good luck.

 

[PV Hiker]

Seems like you had to wait 9 weeks for the gasket then there are not many gaskets out there available. The one you did get as @trains mentioned is not the same gasket as it was made. If it was made years ago time was not on your side. The edge where the metal is could have shrunk or hardened enough to have a path for a leak to travel.

You said it was also leaking out of the bolt holes, so by using vacume to suck in sealer I'm sure sealer would not flow in enough to seal. Some older gaskets did require a tack coat to aid in sealing to with mating surfaces. Some needed to ruff up the surface.

You might need to find a similar material and thickness to work with. The metal is helping the thicker material keep shape under torque and heat cycles. It is a old saw do you need the thicker gasket, and if not would it cause a side effect being thinner (higher compression, can't pull it over?).

 

[pioneerguy600]

Hey yes both surfaces got checked for flatness with glass and feeler gauge. I didn’t use any sealant on the gasket mate no. The leak seems to be within the matrix of the gasket itself rather than the mating surfaces.

After seeing your post on my big screen I could see the gasket is massively thick, no idea what its made from but its likely to be deteriorated material, very old at this time frame. It could be fixed but making one would be simpler.

 

[PV Hiker]

Have you tried applying vacuum to see how much it leaks? If holds vacuum a few heat cycles and re touqeing could work. Or gasket is compromised being old and will always leak between the layers.

 

[Yukon Stihl]

Dry gaskets...
no sealer on any surface.
If you really wanted to use the thick gasket you could seal the inner edge with dirko and pressure it up to force the dirko into the gasket.
I would make a new paper one,and enjoy a little extra power from the reduced squish.

 

[Vintage Engine Repairs]

Lifted the head off to see superficial delamination and a fine crack in one area. 60 year NOS is showing its age.

I cleaned the mating surfaces, bolts, refitted the loose bolt with red loctite. Nuts and washers cleaned. Not sure where to go from here.

I’m considering applying a thin coating of dirko over the gasket and reusing it. This seems like a viable option and ensures non meshed gasket don’t squish too much and affect transfer, intake and exhaust timing.
Thoughts?

The alternative of making a gasket from high temp material is something I can do. I suppose the key is to refit this one, check squish, get new gasket material and interchange a couple of layers and torque down the cylinder and check squish, add and remove layers until the squish is the same?

 

[PV Hiker]

If that is the original gasket that came off and can put it on the same way it came off. I think the dirko can fill in the imperfections and cracks by using it on both sides. If you torque the four bolts down evenly in multiple steps to insure no edge loading it might just work. Give it a try let it set up to cure the dirko before testing for leaks. Re check the torque after the dirko cures.

Don't have new gasket material to make a new one. It's only your time, give it a go.

 

[Vintage Engine Repairs]

This is the NOS gasket

ok my plan...

NOS gasket Crushes to 1.5mm

I have 0.8mm gasket material and I know that under 8nm of torque it crushes just shy of .2mm

Two layers of this gasket will make 1.6mm. Add to that a thin film of Dirko on each of the mating surfaces will likly bring this to around 1.8mm.

Torqued down, I’d estimate to be somewhere around 1.5mm which should maintain, with reasonable accuracy, the same degree of squish.

The gasket material I have and used for the cylinder is just standard stuff, not high temp. This said, with the dirko and it’s insulation it should hold up to cylinder temps of around 200c. I could stick some into the oven to see..

 

[PV Hiker]

Stacking two gaskets together might ruff up the two surfaces and dirko the interface. I would be concerned at the thin sections you might get the material to spit out ( blow out when torque down). The metal gasket gives it shape and strength to prevent it from spitting out .

Just some random thoughts. May work out but not sure. If clamping forces are good and gasket holds shape stacked. Win.....

 

[PV Hiker]

Is there room out side the cylinder that you can make the gasket a little wider at the thin sections? Might give the material a bit more strength.

No worries I just over think things........

 

[Vintage Engine Repairs]

Is there room out side the cylinder that you can make the gasket a little wider at the thin sections? Might give the material a bit more strength.

No worries I just over think things........

Yes slightly. I’m testing this paper gasket material, watch this space will update in half hour!

No worries I just over think things........

we must be related!

 

[Vintage Engine Repairs]

Ok, current gasket material won’t do-

tested it at 220-249c for 40 minutes. Weight dropped by .1g which is no big deal, but because incredibly brittle.

 

[Bob Hedgecutter]

You know you can buy all kinds of gasket material in all kinds of grades and all kinds of thicknesses eh?
Go buy a sheet of something like Permaseal double sided manifold gasket and cut one out to suit- it is an old saw- not a NASA rocket.

 

[Tony ray]

Farmertech sell those gaskets for 41cents each.

 

[Bob Hedgecutter]

Farmertech sell those gaskets for 41cents each.

Perfect!

 

[Vintage Engine Repairs]

Farmertech sell those gaskets for 41cents each.

Thanks for the heads up Tony. I used a few clone parts in the first couple weeks of chainsaw rebuilding when I started last year. I didn’t know any better then, but shortly thereafter, I began to understand more about the Chinese Knockoffs and also my experience on the quality (lack there of) to know I’d rather not support or purchase from them. None the less, thank you!

 

[Yukon Stihl]

Just take the jug and install it without the gasket and check the squish,being an old saw there will be a metric buttload of squish.
Once you have the squish without a gasket get the appropriate thickness of gasket material to put the squish where you want it,anything over 20 thou will work.
like it was mentioned this is an old chainsaw not a rocket...
Mind you i have a few old chainsaws that are Rockets...Hmmm