What's the problem with the post war Big 4's they seem cheap. Is it just the age, lack of girders, etc or is there a snag with them.

Cheers Pat

I don't believe that there are any special problems. They were a reliable sidecar tug.

The 634cc Big 4 was re-introduced in 1947 and this used the 82x120 1938 pattern engine with the performance improvements developed for the WD model.

However, for 1948, in common with the rest of the range, there was a new engine which used flat tappets instead of the lever followers and the stroke was reduced to 113mm giving 597cc. These engines had alloy heads and the detachable alloy valve tappet housing which resembles a pair of old fashioned clay chimney pots and they're often referred to as the 'Chimney Pot' motor.

They did lose some of the vintage feel but somehow the styling doesn't seem to work as well as it did with the tall ohv engines. They always look a bit dumpy and staid to my eyes.

I'd assume that 1950s M20 / M21 prices are somewhat lower than wartime or pre-war models ?

Thanks Rik, I was after a long stroke one so will have to look for a pre 48. The one on milweb looks like a lot of work and I assume the parts are harder to find than M20/M21 bits. The other plan was an excentric crankpin to stroke out an M21 to 127mm plus one of Ians 90mm pistons taking it to about 820cc. In my dreams!!!!

Cheers Pat

Did the driven wheel combination have a diff of some sort or was the drive only engaged off road . It would steer like a cow otherwise.

Cheers Pat

Parts are indeed hard to find for the swd Big 4 (probably 'cause Lex has got 'em all ! ) It's a very specific military vehicle. If you just want a 120mm stroke Norton then you'll find ordinary civilian pre-war Big 4s for less than the cost of the WD version.

The WD types have no diff which is why the dogs were cut off prior to them being sold-off (mostly)

I don't have all the parts, just a lot of them!!
The army not only cut the drives, a lot more:



But why not buy a Panther, longstroke and OHV, and something different.

Cheers,

Lex

email (option): welbike@welbike.net

Is that your museum of horrors Lex? I like that you have plated all the fixings.
No diff Pat. Just clunk and go and hope for not many corners Ron

email (option): ronpier@talk21.com