After lots of hunting I found a barrel with reasonable fins, apart from some butchery in an attempt to gain some performance.
The first job was to degrease it before blasting as much rust of it as I could.
Then came the most risky part, getting it powder coated.
Yes I hear you, but if the painter broke some fins the expensive work would be waisted.
The polyester powder smokes and softens when you first run the engine. If not touched or got wet it will harden up.

This is a non linered version and it takes a while to bore it to liner size. Why did I decide to liner it?, because I could.

One I made earlier.
https://pesltd.uk/?product=66-0088l

I decided to cut the recesses for the valve seats in the mill as well as the liner recess. The valve seats were a brand I hadn't tried before and I was worried they would be hard to cut.



The new liner was pressed in using about five tonnes of pressure to seat it.
Bored undersized and finished honed with no greater error of 0.005mm ovality and taper. (at least the bore is euro 6 spec)




I decided to make some new valve guide tooling. Despite what is in various manuals the valve guides must be pushed in and out from the bottom. Pushing from the top can ruin the barrel.
I also produced a depth stop to make life easier.
I might run off a half dozen sets if there is any interest.



The valve guide tooling.



Precision valve seat cutting. I only cut aerodynamic profiles, it's daft not to when you have the best kit for the job.
It's too fragile for an engine jobbing shop, so never really caught on.





Just needs a clean before building.

Not forgetting the nice new piston I designed for it.



https://pesltd.uk/?product=66-1190PES

Mark

email (option): pes.sales@btconnect.com

Amazing work, Mark! Great to see!

And very different of what I do in my small workshop with mostly hand tools and a Super 7 Myford, :smile:

BR Michiel

Not sure about the fitting of the guides, though...

Original guides have a very small taper and the top is slightly bigger in diameter than the bottom which would logically mean they have to be pressed in from the top.....but open to your view off course...

BR Michiel

I've had several barrels powdercoated and, in my experience, to get a reasonable life out of the coating I suggest you don't run the engine.

I don't think the powder coating is going to last too long in the exhaust port area. On a hot day and the bike ridden hard, I have measured the exhaust port temp at 575 degrees F. And the cylinder head I have seen get up to 500 degrees F.

Your valve seat cutter, I have never seen on like this? What is it?

I usually grind the seats as that is the tooling I have.

"Original guides have a very small taper and the top is slightly bigger in diameter than the bottom"

Michiel, I expect any taper you've found on a valve guide is a manufacturing error.

Mark

email (option): pes.sales@btconnect.com

"I've had several barrels powdercoated and, in my experience, to get a reasonable life out of the coating I suggest you don't run the engine."

I've done a lot of air cooled aluminium heads and barrels without any problems, but you do have to take time to drive the volatiles out Dean.
I also over bake them to help with removing the volatiles.

Mark

email (option): pes.sales@btconnect.com

"Your valve seat cutter, I have never seen on like this? What is it?

I usually grind the seats as that is the tooling I have."

We'll see what happens with the powder Bruce.
The seat cutter is the Mira Centronic system. Sadly no longer in production, though the tooling is.
It measures the inside of the valve guide to calculate the true center.

I've used many stone grinding systems over the years and they all have issues.
This is the only one I would spend money on, but still the pilot system lets it down.

https://www.fondera.co.uk/assets/peg_valve-seat-grinders.pdf

Mark

email (option): pes.sales@btconnect.com

"I expect any taper you've found on a valve guide is a manufacturing error."

Don't think so, Mark...they are all tapered in the same direction, the bottom, (the side with the larger chamfer) is a fraction smaller, average approx. 0.1 mm.

So the guides have a top and bottom, the exhaust is a bit longer and on top has a small chamber bored in to protect the valve from the heat.

Cannot measure the holes in the barrel but think they are tapered also.

When fitted from the top the guide goes in much further than from the bottom, so fitting from top and following the manual is very critical..., sure others who have dealt with this will confirm.

No press needed, I found they fit quite easily from top with a reduced brass punch and hammer.

Please look into it, you warn for a ruined barrel, but actually, I think your advice increases the risk.

BR Michiel

Yes Micheal you are correct about the taper on the guides, but the bore is Parallel.
A serious mistake in my opinion.
When new I can see the ease of assembly, unfortunately once used it would be very hard to clean the relief in port side of the bore.
Funnily enough I'm quoting on the manufacture of valve guides for a much older engine and they have parallel guides.

You live and learn.

BTW, my guides pressed in with easy.

Mark

email (option): pes.sales@btconnect.com

['A serious mistake in my opinion']....Perhaps not theoretically perfect but not a serious mistake...I bought a one owner M21 with 112,00 miles on it years back and it had had three exhaust and two inlet guides guides in that time...One I built has now completed around 60,000 miles with no replacement guides to date and it's still running...
Ditto Deans comments about powder coating...Been there, done that and burnt off the results...It doesn't last long if the bike is used and will also burn off the cylinder head. Usefull if you want to know where the hot spots are though:laughing: ....Saying that there are now some high temperature powders but I've yet to look at their effective temperature ranges after coating..If you could get the barrel clean enough ceramic coating would be the answer I'd have thought....Powder coating will last fairly well on the much cooler running OHV B31/33 motors and I would say it's a practical finish for them which I routinely use...
Details of the valve guide dimensions are in the M20 standards book... (.624"/.625" tapering to .626"/.627")...So, a .001"-.003" taper along the length which equates to a very shallow angle....Ian

email (option): ian@wright52.plus.com

To find such a large taper on the outside of the guide was a shock to me Ian, you live and learn every day.
I've still not got a registration number for the bike, it seems they want to inspect the "running" bike.
That should be taking place at the end of the month.
I think I will try painting the head with epoxy primer and topped with 2k acrylic paint.
If it doesn't work, I guess it can be removed again.

Mark

email (option): pes.sales@btconnect.com

Mark I've just been through the DVLA age related process for this bike which also involved an inspection. (One of many over 37 years) I've never had to run an engine before and in several cases the bike wasn't at the running stage. The bike should be fairly complete and "original"!!!???. The inspector is only there to check the numbers and make sure there is nothing suspicious.

I only ever spray my barrels and heads with VHT rattle cans which is easy to touch up with "Pot Black" when it burns off. Stove enameling is an option, but I don't think they used it on WM20's

This bike is running fine now, but was not running 3 weeks ago for the inspection. Ron

email (option): ronpier@talk21.com

Yes, my T120R was checked long before it was running (or fully completed)...Ian

email (option): ian@wright52.plus.com

Strangely they must think me untrustworthy as it clearly states it must be running.

Mark

email (option): pes.sales@btconnect.com

Interesting that they state it must be a runner. I've recently registered two 1970's TY250 Yamaha trials bikes, the chap who inspected them really wasn't bothered about me running them, he just took a few pictures of the whole bikes and frame / engine numbers. Seems to me there is absolutely nothing to worry about as long as the bike is what you say it is. I had both log books and reg numbers back in less than 10 days for both bikes.
Some people clearly take the mickey, I got talking to the inspector and he showed me several pictures of a Triumph Cub trials bike which he had just inspected. It was quite obvious - And he knew it, that the bike had no original parts except the crankcases, frame,forks,wheels and tank were all brand new. He just shrugged his shoulders when I asked him what the DVLA would make of it when he submitted the pictures.Your M20 will be no problem !