I have been building a 720cc WM20 and want to share what I've learned so far. Ian has extended me generous guidance, and I've followed his lead for the most part. Combustion chamber work was derived from Harley KR experience. Here's the crank, a steel M21, lightened and polished, with a NOS polished rod.



Most of the work has gone into the cylinder and the head. Starting with a non-liner late-type barrel I ordered 90mm JE pistons based on Ian's design but with a pop-up crown fitted with TotalSeal gapless rings.

The valves are from Manley, stainless steel Nascar-type custom ordered parts with .3405" stems requiring bronze inserts to fit standard M20 guides. The intake is 2", exhaust is standard at 1.625 on Ian's recommendation, Heads are coated with Cerakote Piston Coat ceramic insulation, the intake on the top only, the exhaust on the exposed part stem and the entire head.



The cylinder has an intake relief tract and the intake valve sits lower than the exhaust, which is a long story in itself. The lip of the cylinder bore is radiused to just above the top of the ring travel. The pop-up piston protrusion is in the approximate installed position.



The head was professionally welded up. I had 2 done, and botched one. Got the mirror-image valve positions wrong and it will need more fill welding if it's ever to be used. I removed enough from the cylinder and head to get a 7:1 compression ratio as Ian suggests.







That's it for now. Final assembly awaits the correct valve keepers and springs, on order from Manley Valve.

Jeff

email (option): jjbandoo@aol.com

Hi Jeff,

Very Impressive work!

Good luck,
Noam.

email (option): noam10@gmail.com

Fantastic stuff, I hope it goes as well as it looks

email (option): horror@blueyonder.co.uk

Sorry my Photobucket mistake loaded the photos as a slide show and took up so much disc space. Not the only mistake I've made in this project.

Jeff

email (option): jjbandoo@aol.com

Hi Jeff...It's all looking very nice...What did you do with the inlet port in the end and what was your final choice of cams??. Where you have coated the skirt of the piston don't forget to check that it still has sufficient skirt clearance after coating (which you probably have done already!)..Ian

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

That is an owesome job Jef i hoop turns out well

email (option): evandeweerthof@yahoo.com

So when are you starting selling the exchange conversion kits?

email (option): cruiserchooser@hotmail.co.uk

I will have a spare piston and 2 pairs of the custom valves to offer, but life is too short to repeat all the handwork on the head and cylinder!

Jeff

email (option): jjbandoo@aol.com

I've finally got the piston Ian provided for me last year into my M21 after a complete rebuild over the winter. I was out yesterday bouncing along the back roads of Bavaria to start the running in process. Only managed 100 miles before my rear end started to complain, but it's a start.

Cheers
Pete

email (option): petercomley@web.de

Hi Jeff,

If you would like to sell the spares,
I may be interested..

Cheers,
Noam.

email (option): noam10@gmail.com

Jeff
compliments on the work.
There was a stealth 16H at our NZ Norton owners rally earlier in the year which reportedly had a large intake valve, raised comp, releived head at intake, radiused edge to the bore - and it was hard to imagine you were trying to keep pace with a sidevalve.
With your extra profiling and extra capacity yours should be a blast.
Iain

Awesome Jeff! Great to see your project progressing along.

Are you going to go with an updraft carb? You staying with the 289 Amal? Can't really tell from your pictures, but is the head the aluminum M21?

Kevin

Kevin, chaps,

The head is the later alloy type. I learned TIG welding to fix some broken fins and then coated the outside of the head and cylinder with another Cerakote product ( http://www.cerakotehightemp.com/finishes/ ), Arctic Black, said to dissipate heat.

I took the intake port out to 32mm to match a 10TT9 carb bored out to that diameter. The carb I'm using is on the bench in the first photo. At a casual glance it looks just like the original 89! ;-)

Cams are Goldie touring cams. After running-in I may go hotter.

Jeff

email (option): jjbandoo@aol.com