Matchless 450cc ?

[Eamonn]

I've received the following email:



Help!! Wondering if anyone can help identify this bike Stripped the head of an eBay find which looks to have used for short circuit racing in its day with the following

1949 16M cases with cast iron barrel, ally head Bore 82.22mm on +20 Stroke 85.5mm I made that 454cc

Inlet valve 42.51mm
Exhaust valve 42.72mm !!
Carb inlet 1.05" 26.65mm
Exhaust down pipe OD 1.75"

So smallish carb, large bore exhaust and exhaust valve With competition Plug NGK N8 EV

Anyone throw any light on this please!!



If anyone has thoughts on this, I will pass on to the originator.
Many thanks.

[Rob Harknett]

82.5 bore is 498 cc, sounds like the 347 cc 16M is fitted with a 498 cc top end.

[Stan Palmer]

But the stroke of a standard long stroke was 93mm, not 85.5. Either a miss-measurement or a non standard stroke. That would make it around the 454cc mentioned.
Stan

[Chazzyb]

I'm sure I read of a mod in the dim and distant using a Triumph piston to do this. May not have been that capacity; 410 springs to mind.

[Rob Harknett]

But the stroke of a standard long stroke was 93mm, not 85.5. Either a miss-measurement or a non standard stroke. That would make it around the 454cc mentioned.
Stan

I was puzzled about the stroke being 85.5 Stan 350 & 500 AJS have 93, so have no idea why the bike in question has 82.5
1958 comp engines had 85.5 stroke

[Chazzyb]

85.5mm is the stroke of a lightweight 350...

[Stan Palmer]

Is it even possible to put lightweight flywheels etc into longstroke 350 cases ?
I can't imagine it would be easy to change the stroke of a standard crank set, and if you did a lot of work why would you choose an odd capacity like 454 ?
Len Hutty (sadly deceased at a young age) had a magnificent 410 Matchless for classic trials. In fact he built two as somebody liked his first one so much they stole it.
Sorry to digress from the original topic, just that he was so good to watch on that bike.
I don't know how the 410 is achieved, there are plenty of them about though.

I'd forgotten Lens name, while finding it on Google I came across mention of "escaped" works Trials bikes. These were usually AJS but my 1957 was a Matchless. I have never considered it a full works bike, though it was registered by AMC all their top stars rode AJS. I think their scrambles boys were given trials bikes for training, mine was purported to be from a Scottish rider who's name I have long forgotten. It wasnt Gordon Mclaughli. What was interesting is the google article mentioned various elektron bits they fitted. The top yoke on my bike was, I think also the front hub. I could never get any kind of polish on either part, my dad (who knew about such things) confirmed they were not aluminium. Not important as I sold the bike for £30 in 1967.


Stan

[Rob Harknett]

I'm sure I read of a mod in the dim and distant using a Triumph piston to do this. May not have been that capacity; 410 springs to mind.

I seem to recall a member who sold parts to make 410 cc comp engine at Jampot rallies Stan.

[Rob Harknett]

Is it even possible to put lightweight flywheels etc into longstroke 350 cases ?
I can't imagine it would be easy to change the stroke of a standard crank set, and if you did a lot of work why would you choose an odd capacity like 454 ?
Len Hutty (sadly deceased at a young age) had a magnificent 410 Matchless for classic trials. In fact he built two as somebody liked his first one so much they stole it.
Sorry to digress from the original topic, just that he was so good to watch on that bike.
I don't know how the 410 is achieved, there are plenty of them about though.

I'd forgotten Lens name, while finding it on Google I came across mention of "escaped" works Trials bikes. These were usually AJS but my 1957 was a Matchless. I have never considered it a full works bike, though it was registered by AMC all their top stars rode AJS. I think their scrambles boys were given trials bikes for training, mine was purported to be from a Scottish rider who's name I have long forgotten. It wasnt Gordon Mclaughli. What was interesting is the google article mentioned various elektron bits they fitted. The top yoke on my bike was, I think also the front hub. I could never get any kind of polish on either part, my dad (who knew about such things) confirmed they were not aluminium. Not important as I sold the bike for £30 in 1967.


Stan

http://www.jampot.com/article_read.asp?id=163 Does this relate to your comment Stan

[Chazzyb]

Is it even possible to put lightweight flywheels etc into longstroke 350 cases ?
I can't imagine it would be easy to change the stroke of a standard crank set, and if you did a lot of work why would you choose an odd capacity like 454 ?

Odd capacity? That's the result of 82.5mm (long stroke 500) on a lightweight 350 (or short stroke heavyweight) crank's stroke. Perhaps someone was cheating in competitions, all hidden inside an old iron 350 heavyweight's skin.

Surely no-one would do that...