I'm just finishing off a rebuild on one of those engines...It looks nice but it's no Gold Star...There are a number of things that preclude too much tuning and some parts are basically impossible to find...
It's certainly a nice looking, rare engine though and historically interesting...Ian
email (option): ian@wright52.plus.com
It's certainly a nice looking, rare engine though and historically interesting...Ian
[/quote]Ian,
Would be nice to see some pics of the engine before you finish it. Never seen one close up.
Tim W
email (option): t.j.walker@btinternet.com
That picture comes from the internet (via the forum) and was taken in my workshop when I first had the engine...
I wouldn't think the engine would fit with the flat bottomed tank...
In 'standard' specification the standard BSA cams were used, though I have read Gruppo Velox did make cams for competition use and entered their bikes in the Italian long distance road events at the time...
Frankly, with the standard M20 flywheels fitted it wouldn't have been much of a performer and I can only imagine this was addressed in the more 'sporty' versions....
The ports and valves are of reasonable proportions..In fact the standard engine seems to be a little 'over ported' for the bottom end specification.
Compression ratio is also moderate, with a flat top piston fitted in conjunction with a hemispherical head...
The valve springs are of an unusual design I haven't come across before...a form of 'hairpin' springs...
I think it is unlikely this engine will make any more power, and possibly not as much, as a B33....So in the 20-23BHP range probably...
That would equate to 75-85mph on the road probably...the latter figure possibly being a little optimistic...
Drawbacks from the point of view of really getting that power figure up..?
1)The overly long M20 conrod which is a little weak for a high revving engine (assuming the flywheels were lightened to get the revs and gas speed up)
2)The fact that the kit was designed to fit straight onto an M20 bottom end endows it with its greatest weakness from the performance point of view (I suspect)....
The M20 cam followers are fitted 'vertically' into the crankcases to line up with the vertically fitted valves...
However, the rocker arms of the conversion do not align with the cam followers directly. The result is that the pushrods operate at an angle to the followers and tappet adjusters.
I suspect this could cause problems with flexing of the pushrods and possibly even keeping them in place if the revs were substantially increased to improve gas speed and the valve spring pressures were also increased to suit the more radical cam forms employed as part of a tuning programme....Ian
email (option): ian@wright52.plus.com
I'll post some current pictures of the engine sometime over the next few days...Ian
email (option): ian@wright52.plus.com