I'm researching Norman Vanhouse who died on June 2nd this year. For those not in the know, Norman was the BSA Competitions head back in the 1950s and was also part of the 1952 BSA ISDT and Maudes Trophy campaign team which won a gold medal and the trophy after a 4500 mile jaunt across Northern Europe.

Norman also rode a BSA M20 in the war; a machine that he initially thought hopelessly inadequate, but later came to have a high regard for.

I've got an old Classic Bike magazine in which Norman talks about squeezing a maximum 110mpg from an M20 (with a bit of "popping and banging"), down to a more realistic (and consistent) 65mpg.

The method used was, it's said, to restrict the internal diameter of the needle jet with some kind of collar - which was "a bit hit and miss". Does anyone have any more info on Norman generally, and this carb mod specifically? My own M20, incidentally, is lucky to see 40mpg.

email (option): dannydefazio@sumpmagazine.com

you tight git

email (option): richardholt@rocketmail.com

Hi Danny..I have Norman Vanhouse's book 'BSA Competition History'..don't know if it is still in print and it won't tell you much about the man but you are welcome to borrow it, it's an interesting read.
Born 1916, Started his career at Ariel in the comp. dept. He was a DR for the duration the war including 9 months with the BEF.During this period he covered 98,000 miles..Then moved to Douglas Motorcycles. Joined BSA in 1952 as a sales rep ending his career in charge of Fleet sales for BSA/Triumph.
He rode as a factory trials and scrambles rider and won over 150 awards and ISDT medals.
He wrote a number of articles for the motorcycling press, the first being in 'Motor Cycling' in 1940...but you probably know all that already!...Ian

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

Hi Ian, I did have SOME of that info, but not all. So thanks for that. I take it the info comes from Norman's book. Can you confirm that?

Also, do you know anything about that carburettor modification? Hard to see how anyone squeezes 110mpg from an M20 without wrecking the engine, but 65mpg sounds more plausible (but still a bit of a stretch).

Any views?

P.S. Thanks for the offer of the loan of the book. But I think I can pick up a copy locally at an upcoming autojumble.

email (option): dannydefazio@sumpmagazine.com

Hi Danny..the info. is from the book so can be considered correct.
During the early stages of the war fuel shortage paranoia led to a number of experiments aimed at saving fuel. Basically it was a case of weaken off the mixture as much as possible (and probably restrict performance as well).
The mind boggles at how they achieved those sort of figures from the M20 but it's a fair guess that the statement 'it popped and banged a bit' was a gross understatement..substitute 'it ran like a piece of s**t' as a more accurate description. That experiment was obviously at the extreme end of 'playing about'..after all if the M20 was capable of those figures and could still run properly it would have been sold like that.
I have only had direct experience with two bikes that were actually produced with modified carb settings...the Triumph 5SW and the WD Velocette.
In both cases the jet sizes looked implausible on paper and sure enough niether bike would run properly.
Reversion to 'standard' settings solved the problem and I suspect that was exactly what happened in REME workshops at the time.
If you think about it, it was an unachievable aspiration...you can't cut down the fuel consumption of an engine and still have the same performance without some serious modifications to the basic design and a whole new way of supplying fuel such as fuel injection...Ian

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

I've clocked Danny's comments on M20 fuel consumption!
I've never bothered to work out my fuel consumption in the past, but....
I went to Warminster on Saturday with my mate Indian Tim. A total round trip of 112 miles. Riding mostly at about 50mph. I started off with a near full tank and topped it up at home to about the same capacity from a couple of cans. Nothing too accurate, but I estimate 6 litres or 1.32 gallons. My calculator comes up with 84mpg? Say I made a cock up and it was actually 7 litres. This is still 73mpg.
However my engine and gearing has been brought up to M21 (600cc) spec.
Anyone else know their fuel consumption?

Ron

email (option): ronpier@talk21.com

My 16H while being rode at 45/50 mph did about 35mpg.
I havnt done a proper calculation on my WM20, which rarley goes over 45mph, but my feeling is that it does about 40mpg
I had been bought up with tales of the fantastic economy of old British singles, so that came as a bit of a shock.
My Commando (with standard engine and twin Amal concentics), cruising at 70mph, never goes over 80mph and general riding is 45mpg
My Yamaha XT 600 (single cam, 4 valves, carburettor), does 63mpg on general riding, never going over 70mph with off road riding.
My BMW GS1200, cruising at 80mph, with bursts over a 100 and other mixed riding including low gear off road riding is doing 52.3mpg.
I think mpg is mainly to do with throttle opening and how close you are to maximum revs. My 500 side valves have their throttles about 3/4 open and arnt far from max revs most of the time, the Commando and Yamaha are usually about a 3rd open, and the BM is hardly cracked until it goes over 70mph

email (option): gasboy@btinternet .com

I haven't checked my 16H's consumption. I prefer not to fill it to the brim so I'll have to wait until it goes onto reserve as I pass a filling station but I have the impression that I can ride something over 100 miles if I put ten litres in so I wouldn't expect less than 50 mpg.

My 850 Commando usually turns in around 60 mpg - about 120 mile to reserve on a Roadster tank.

I don't wish to sound indelicate but might rider weight have a significant effect on the consumption ?

A B31 will return mid 70s to the gallon all the time over varied use but it is easily possible to get over 80mpg with a little restraint. Motorcycling Weekly tested one in the 50's and by riding very carefully got over 100mpg. My B33 has managed 78mpg on a run to the Lake District on one of the few occasions I recorded it. I think to an extent it is a case of whether the most commonly used operating speeds are in the most efficient area of the engines performance. I have never worked out the consumption exactly on a std. M21 but when I lent mine to a friend to do a Normandy tour and I took the 720 the latter did about 15-20% more to the gallon at the same speeds on the same roads...it's bigger, but not working so hard..
45-50mpg would be normal for an M20 or 21 I would have thought...I think a more accurately measured test of Rons bike would be interesting..those figures don't seem to be normal!...Ian

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

I've had umpteen cars and bikes since the early 60's and never bothered to check the consumption of any of them. But now I have a bee in my bonnet to see what I get from my M21. I'll do another more accurate check this weekend whilst on a more laboured run out over the Purbecks Hills. Ron

email (option): ronpier@talk21.com

Interesting fuel economy figures, and all seem pretty accurate to me except Ron's (sorry, Ron). I haven't got the slightest doubt about Ron's honesty and integrity, etc. So there's probably a calculation error - or Ron's got a very interesting example of an M20.

My T140s return around 50-55mpg (usually two up and moderate speeds, 55-75mph, mixed riding).

My BMW R80ST returns a measly 45mpg at best (usually two up and moderate speeds, 55-85mph, mixed riding).

My BSA M20 returns 40-45mpg, usually solo.

My old Ironhead Sportster had a best figure of 70mpg riding between Bournemouth and So'ton (interestingly, that's Ron's neck of the woods - spooky, huh?). But typically, I used to get 50-55mpg.

I'd be happy with 50mpg from my M20, especially in view of its "relaxed" performance. 40mpg sounds a little mean.

I read an account once of a Harley Sturgis (double belt drive) that was very mildly modified and returned 102mpg - albeit at around 40-50mph. And I've heard of other Harleys returning 60-70mpg.

Will be interested to see what numbers Ron gets when he buys a new calculator.

email (option): dannydefazio@sumpmagazine.com