Friday, 12 September 2014

Make your own gaskets!

I've made gaskets in the past for any smaller bikes I owned and would just cut up Rice Krispies boxes or similar and roughly cut a shape out of the cardboard. Probably not the best material but it usually worked ok on the succession of rough-but-reliable Honda CD 200 Benlys I owned, as well as a gutless Superdream, and the first Guzzi Lodola I owned about 20 years ago. Pre-internet days it just wasn't so easy as it is today when a package ordered the day before flops onto your doormat. Even living in London, just to find a gasket that you needed urgently was difficult, and usually my bikes were my only transport and had to be kept running. It was a case of make do and mend.

But even today the cost of gaskets for the small Guzzi singles I like to work on are ridiculous, especially as they have to usually come from Italy, with the associated costs of postage. And even then, you'll get a complete gasket set, and you'll be left with loads of gaskets you may never use, unless you're fond of doing a complete engine stripdown every time. So fed, up with shelling out, I've decided to make my own from now on when possible (and of course, it's not always possible depending on the gasket required and the job it does) but for rocker gaskets and similar, it's pretty simple. Recently I managed to get hold of a single rocker gasket for the Moto Guzzi Lodola 175 I am presently working on, and decided to do a copy from it. I decided to get the proper tools this time round too, so Ebay, it was easy and cheap to find gasket paper and a metric punch set, better than trying to cut decent round holes with a blade like I'd do in the past. Now this is no 'master class' in making your own gasket, but what worked for me...

Moto Guzzi Lodola 175 rocker cover, for which the gasket is required

This is the new shop-bought gasket I used as a pattern

The rocker cover should be spotless, with any old gasket removed. I usually soak the old gasket if really stuck on with WD40 or similar, then use a blade scraper to remove all the material.

This is the remains of some old silicon someone has used to try and seal the valve cover in the past, and looks like the Italian equivalent of Hylomar or similar. Everyone has their own opinion, and gasket sealants have their use on certain parts of a motor, but all a rocker cover on a small (or big) Guzzi needs is a gasket coated lightly with grease. It seals well, and can also be reused.

Having measured the thickness of the new gasket with a digital vernier, I decided to use the 0.40mm sheet, which is nearest to the approx. 0.43mm of the new gasket. .02mm amongst friends is nothing in this case.

In the past, I'd try and make an impression of the shape of the rocker cover required by pressing the cover hard on the card, or you can also put a thin film of grease on the rocker cover's mating surfaces.

The result is enough of a shape to then trace around with a pencil, as above. But in my case, I've already got a gasket to copy, so it's easier to tape it down securely, and draw round it with a sharp pencil. Try and be as accurate as possible.

This is the punch set I bought - was only about five quid on Ebay and seems ok quality.

Find the correct the size punch for the holes in the gasket. These were 7mm in diameter.

Line up the punch accurately on your template and hit the punch firmly with a hammer - the holes are much more accurate if you punch them first go, so don't be shy. I had the gasket paper on a cutting board to do this.

Once I punched all the holes needed, I lined the pattern gasket on top to check everything lined up - so far, so good.

Then this is the bit that requires patience, a steady hand, and a scalpel with a new or very sharp blade. I've tried with a Stanley knife in the past but found it too unwieldy. A surgeon's scalpel is lighter and easier to hold. Cut around your pencil template as carefully and accurately as possible. You might want to tape the gasket paper down again, but I'm ok with just holding it, leaving it free to spin round when required when cutting. I also prefer to cut the outside of the gasket first, as it's more important that this is particularly accurate, compared to the inside, which can't be seen.

Then just repeat, cutting round the inside too. Don't rush it, because you'll be pissed off if you tear it at the last stage - been there, done it. Once finished, it's looking good.

Now, because you're a human being and not a laser-guided cutting robot, there will be bits that don't really line up so well. No problem, just go back and trim 'em off. The important part is that the holes line up, as does the gasket that will be covering/sealing the metal mating faces on the rocker cover, and cylinder head.

It all lines up fine on the rocker cover.

It's also important to check the gasket lines up properly on the other surface, in this case the Guzzi Lodola 175's cylinder head. Check the cam chain!

Now, grease the gasket thoroughly. That means so it soaks in to the gasket well, not so that it's dripping off in great big gobs - a light film is sufficient.

Gasket greased, and in place on the Guzzi's cylinder head.

I always always use Coppereaze on bolt threads where the application is appropriate. This practice was beaten into me when I worked in motorcycle shops years ago.

I then tend to put the cover lightly in place with a few bolts just placed into their threads by hand, to check the gasket is sitting correctly and the holes all line up. Be gentle, you really don't want to to tear your paper masterpiece at this late stage! 

Once happy with how it all sits, I then use a ratchet to tighten all the bolts down. 
I do them hand tight, and nicely nipped up..

Job done, and looks okay - the proof will be when I start the bike up next. 
All this took about 30 minutes from start to end, and was also thoroughly satisfying to do. It saves money, but more importantly, is just so much more convenient - you can get on and doa  job on the bike without waiting from parcels from aborad. The varying thicknesses of gasket paper also means you can use it for various applications, carbs, covers, etc etc.

Got any of your own tips, or did we do something wrong? Get in touch here


Anonymous said...

Good Info, A lot of times when you buy gaskets kits for vintage bike, you ended up with brittle dried out old stock that un-usable. I have seen some gasket companies that use a C&C machine to cut gaskets for any bike they have a program for.

ITALIAN MOTOR magazine said...

I agree - I haven't bought any NOS gaskets for many years now, though I do still have a stock for my big Guzzis that I dip into every now and again, if they're any good. Otherwise I'll buy new or make them. No doubt new gaskets are CNC cut nowadays, they are usually pretty accurate (should be for the $$$)