Nice picture, is that you, Henk ?
Somewhere in France ?

Yes that's me.

Henk.

email (option): ahum@quicknet.nl

And I'm further back trying to catch up:blush: Ron

email (option): ronpier@talk21.com

Those M24 cams seem to work well, Henk.

M24 cams !! Is that a thing ? I mean is that an option ? Go fast(er) mod..... ?

Nice photo Henk

email (option): wadeschields@mindspring.com

I guess it's the M21 crank that does the trick. Lots of difference between an M20 and an M21 engine and there are just standard M20 cams in that engine.

Henk.

email (option): ahum@quicknet.nl

It's why I fitted an M21 crank to those crankcases I got from you Henk. It's still going strong and I still have that new B33 piston for maybe another day. I still don't ride much over 50mph, but the extra acceleration and pulling power is just nice to have. Ron

email (option): ronpier@talk21.com

I played with almost every combination of cams and there are lot of them
For my riding I found GS touring cams gave the best combination of (Lack) of acceleration & ( lack ) of power .
You need a good sense of humour to enjoy riding an M20 .
B & M series cams interchange so when you add all of the B series cams there are an almost endless combination.
You can play around to get peak power right up to top of the 5000 rpm rev range right down to around 600 rpm and very where in between ,
Fit a good gasket on the timing cover & you will find you can swap cams in under 10 minutes so go for a ride with a big bag of cams.
Also remember you can also swap the position so run an inlet as exhaust & visa versa.
Proper M20 cams are identical inlet & exhaust .

email (option): bsansw1@tpg.com.au

Cam changes by themselves will provide limited, if any, improvements depending on the cams selected....They don't work in isolation from the other aspects of the engine design that govern (and limit) performance and aren't intended to...

The best boost in bottom end and mid range power without altering anything else is to increase the engines capacity...The 720cc 'M20' has considerably better bottom end and midrange power and will also pull taller gearing than a standard engine but the improvement decreases rapidly towards the upper third of the range due to the breathing limitations imposed by the cams, ports, carb size, inlet valve size, low compression ratio, the heavy crank and the low upper rev limit. However, fuel consumption is improved due to the fact the engine is not being run so much in the lower gears, particularly up hills..That level of improvement may well satisfy most WD M20 users....

At the end of the day, from a simplistic viewpoint, tuning is only about getting better cylinder filling, and thus more fuel/air mixture and a 'bigger bang' as a result....To substantially improve a side valve like the M20, which is effectively a stationary engine that they added wheels to, each feature needs to be considered with alterations to improve breathing as the target...There's no single 'magic bullet' unfortunately....Ian

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

I agree with ian, i came to this conclusion many years ago. I played around with a unlined cylinder and bored it out as much as i could to fit either a VW or Jag piston i cannot remember which. I do remember that i had to bore the little end bush till it was very thin. I also had to take a couple of mm off the crown. I played around with all sorts of goldstar cams. Same as Ian said not much more top speed but loads of pulling power with a 24 engine and 19 gearbox sprocket. 4 off us went over to watch the TT on our M20s i had the big bore engine fitted to mine. I thrashed it around all week but half way through the week i noticed oil on the dynamo and the mag. The cylinder was so thin and porous at the back that oil was working its way through the cylinder casting. Back home i just change it to M21 flywheels and piston and fitted the standard cams. Engine is still like that now but its sat on the garage floor as i have fitted a special long stroke M33 engine to the bike. Big bore cylinder and piston is still on the shelf, cams went a long time ago.

Oil trough the cyl casting....have you even heard of that (!)
Changing to an OHV engine seems indeed a much better idea.

The OHV motors are better in both performance and fuel economy...Even the B31 produces 30% more power than the M20 and will do over 50% more to the gallon....However, doing some work on the SV engine helps a lot, particularly if you travel any distance on your WD bike yet want it to retain it's original appearance and general feel...Ian

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