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Old Apr 24, 2012, 04:50 AM
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Help!
How to make a new cylinder gasket

Hello, I have been running an old webra 3.5ccm engine for the last few months. It has run pretty well however recently it would not stay running and was difficult to start. I figured out it was not maintaining compression in the cylinder because of the gasket and when I removed the gasket it broke in two. I was wondering how I can make a new one at home as I am sure its near impossible to find a replacement anywhere.I read in a thread somewhere they can be made using an aluminum pop can cut to shape. I was wondering if anyone can confirm this? It seems that to make a good seal something softer than aluminum should be used but then again I don't know much. If anyone has tried this method or knows of any better methods please let me know, thanks.

-Greg
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Old Apr 24, 2012, 07:54 AM
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hello i would cut thin aluminum sheet to gasket shape, or you can use copper sheet if needed i would apply thin layer high temperature gasket silicon on outer edges of cylinder head gasket, although i think the sheet itself would be more than enough, you can check afterwards is it leaking gasses
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Old Apr 24, 2012, 07:56 AM
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Lots of the head gaskets are aluminum...it's not so necessary that the gasket be soft or hard,as long as it seals well...More importantly,it needs to be the correct thickness,within a couple of thousandths of the original.
Once you've carefully cut one out,I'd suggest pushing the head down over the gasket,on the cylinder,and rotating it back and forth to check that it's sealing.
As you spin it,that will relieve any small wrinkles that develop while you're cutting it out....If necessary use some rubbing or polishing compound to get it as smooth as possible. Clean it up well.
Bolt it down in a cross-torquing pattern about a 1/4 turn on each bolt,after contact,until theyr're all tight. That should do it..
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Old Apr 24, 2012, 08:07 AM
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For the head gasket copper or aluminum is good. I made a punch for each size bore and just cut the outside by eye. If you don't have a lathe, a divider with a knife on one side can scribe the inside hole and scissors for the outside.You want to get the right thickness and make sure that there is at least .012" headspace. If you are not blowing plugs and have .012" headspace, you may not need a head gasket at all. If you are making the paper base gasket, a grease pencil or your least favourite lipstick works as a pattern.
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Old Apr 24, 2012, 08:32 PM
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Thanks for the advice. I gave it the old "college try" (I am a college student so this term is meant literally). Anyway.. using what few tools I have at hand with me at school (an exacto knife and some heavy duty scissors) I fashioned a gasket. Unfortunately it was not effective. when I turn the prop I hear a slight leak from the cylinder so to locate the source I wet the outside of the cylinder. I then saw small bubbles come out of a spot between the cylinder case and the head as I turned the prop. Should I just wait till I am home in a few weeks and can use better tools or should I try two layers of aluminum gasket? I can post pics of my handiwork if needed. Thanks.

-Greg
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Old Apr 24, 2012, 09:18 PM
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Yes you can do that, try a two head gaskets and see what happens.
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Old Apr 24, 2012, 09:22 PM
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You could try a piece of 400 sandpaper on a piece of glass and twist the cylinder a few times on the top mating surface to at least make that flat. Sometimes the heads get twisted from uneven tightening of the bolts. A little bit of castor oil or even grease on the mating surfaces wouldn't hurt either
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Old Apr 24, 2012, 09:37 PM
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Go easy on oiling the head, cylinder top or gaskets. I have had to clean off the parts to make them basically oil free to get a good seal on some engines. The oil can form a film that prevents the parts from sealing correctly.
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Old Apr 25, 2012, 04:59 AM
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Ok, I finished the second one and put them both on. And.........it didnt work, there is still the same if not more leakage during compression. I think that my gaskets are not flat or smooth enough. They do get kind of bent and misshapen as I am making them so this may be the problem? I am screwing the screws opposite one another and a little at a time on each till they are all screwed down really tight. I have attached a picture of the gaskets I have. I figured it was ok they got bent up since they should flatten when installed right? (evidently not). Anyway I tried sanding but all I have now is a 400 grit foam sanding pad that is not very effective so I will probably try to put together a better sanding device and work them down to be a lot flatter. I really dont want to see this engine go to waste just because of a gasket so any thoughts are appreciated. Thanks.

-Greg
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Old Apr 25, 2012, 06:42 AM
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To work properly , the aluminum gaskets need to be dead soft aluminum . Can stock etc if actually pretty hard as the aluminum is work hardened during the extrusion process . You can anneal the aluminum for better results. Copper head gaskets work very well . Copper should be annealed to dead soft for best results as well . Copper is very easily anneal with a propane torch .
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Old Apr 25, 2012, 07:37 AM
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Greg,

I know the Glo Star very well, it was my first engine with throttle in the sixties,
Some facts I see maybe you can use.

First it can be interesting to observe the most important surface of the head, the small surface that makes contact with the cilinder surface.You need a loupe for that so you can observe if the surface is undisturbed on that location.
If there is a small "channel" in the aluminum of the head it will never fit. When I see the photograph there is one location with questionmark, the red circle. A channel, or some damage can be ten times smaller to give you problems even as small as a human hair!! To clean such a surface you need the lathe IMO.

Second important point is, be carefull with the threads not overtighten them. It has to be fit with the normal torques!!
Especially the longer two srews (front and back) do fit in the crankcase aluminum!!

Third point, look at the photograph, maybe it is easier to make a gasket of model yellow or blue. Blue would better for the head, but the yellow you can try but have to be carefull with torque of the bolts Important for the choice is the cilinder surface, so can you make a photograph of the top of the cilinder, I do not remember the shape of that surface anymore. Not even if a gasket was needed in the past!!!!????

BTW interesting detail of the carburetor spraybar, two nozzles so have attention for the position!

Cees
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Old Apr 25, 2012, 08:16 AM
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Quote:
Originally Posted by Taurus Flyer View Post
Greg,

I know the Glo Star very well, it was my first engine with throttle in the sixties,
Some facts I see maybe you can use.

First it can be interesting to observe the most important surface of the head, the small surface that makes contact with the cilinder surface.You need a loupe for that so you can observe if the surface is undisturbed on that location.
If there is a small "channel" in the aluminum of the head it will never fit. When I see the photograph there is one location with questionmark, the red circle. A channel, or some damage can be ten times smaller to give you problems even as small as a human hair!! To clean such a surface you need the lathe IMO.

Second important point is, be carefull with the threads not overtighten them. It has to be fit with the normal torques!!
Especially the longer two srews (front and back) do fit in the crankcase aluminum!!

Third point, look at the photograph, maybe it is easier to make a gasket of model yellow or blue. Blue would better for the head, but the yellow you can try but have to be carefull with torque of the bolts Important for the choice is the cilinder surface, so can you make a photograph of the top of the cilinder, I do not remember the shape of that surface anymore. Not even if a gasket was needed in the past!!!!????

BTW interesting detail of the carburetor spraybar, two nozzles so have attention for the position!

Cees
This is a NIB GloStar from my collection, if you do look carefully you can actually see the gasket used on the cylinder head. Some pictures also of Graupners tiny heat resistant sheets they sell, used to be called Oilit in the past. I mentionned it recently, do get one of those punch-pliers used for making extra holes in leather belts. Very cheap. Can life be any simpler ?
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Old Apr 25, 2012, 08:32 AM
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Thanks Reginald, I hear a little bell!!

Yes, it will be the original gasket material of the Glo Star wasn't metal!! Because that I cannot remember.

And when it was THAT material it was indeed much thicker and I start to remember seeing you photograph, you could see it, it was brown ( of oil, and you could put your nails in it)!!
I know there was (also) a gasket between the cilinder and the crankcase and I (nearly) never dismantled my engines, only when it was really needed.
Of the Glo Star the head AND cilinder can be removed in one piece and that was for most service activities better by loosen the two longer screws.


Of course this is very important to know for Greg, I think the original material is needed because it is flexible and thicker!!!




Cees
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Old Apr 25, 2012, 09:19 AM
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Maybe you could try a shim that doesn't go under the bolt pattern, like a conventional shim. It will give more pressure and be concentrated where it needs to be. Just a ring trimmed to the inside dimension of the bolt pattern, being careful to not overtighten the bolts. The head does look pretty thin. Or try the material previously mentioned.
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Old Apr 25, 2012, 09:24 AM
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aspeed

I did show that in post 12 the yellow example but as Reginald did show the original material wasn't metal probably.
The surfaces and head maybe are not machined for metal gaskets, that's where I am afraid of!
There is also a risk now to disturb the head and the gasket was thicker as the normaly used metal.

I did look for a picture of that period. Glo Star in Action

Cees
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