Replace iron cylinder with alloy?

[Bob PA USA]

I have a mongrel of an AJS/Matchless 500. A ‘48 Matchless bottom end, with a ‘49 AJS iron barrel, with a probably ‘51 alloy head. Does anyone know if there is a way to fit an alloy cylinder to this Frankenmotor?

[clive]

Alfin made an alloy cylinder which would fit, hens teeth though.

[dave16mct]

Not sure there was a 500 'bolt on' Alfin barrell, Definately was a 350 but hard to find. The later long stroke comp alloy barrell can be made to fit but the holes in the crankcase have to be welded up and re-drilled and tapped for the through studs. Here's a video of how it's done:

Dave.

[Bob PA USA]

Cheers Dave. Are there any long stroke alloy comp barrels out there?

[Iron Head]

Interesting video Dave and fantastic workmanship. Only question it raises is where to find competition alloy barrels which seem to be few and far between as I understand it.

Iron Head

[clive]

You could try a wanted Ad Bob but i would not hold your breath whilst you are waiting. If you want to loose weight on the bike it might be easier to go on a diet instead.

[Bob PA USA]

So it's mission impossible then... 😄

[Andy51]

I have seen 2 longstroke alloy barrels on eBay US in the last 10 years or so, but missed them both, so they do turn up - if you have 10 years is so to spare! You might save 10 pounds or so, but since the bike weighs well over 300 pounds, as a percentage it is very small indeed. As Clive says, better to diet and lose the weight yourself. You can always paint the cast iron barrel with silver paint and few people would know! I saw an aluminium-colour painted barrel on a Matchless-engined, featherbed-framed special a few years ago and it looked very smart indeed; I asked him where he got a 500cc 82.5 mm bore barrel and he let me into his little secret, otherwise I would never have known. Andy

[Bob PA USA]

So I'm looking for a "500cc long stroke competition alloy barrel"?

Will there be any issue fitting to my '51 AJS alloy head?

Thank you all for the insights.

[Andy51]

The CS alloy head and barrel are held on by through bolts, whereas the roadsters use 2 sets of fasteners - studs in the crankcase holding the barrel in place, and bolts holding the head onto the barrel. For some reason these studs and bolts have different hole spacing and furthermore, the CS models used sleeve nuts whereas the roadsters used 3/8 in bolts with holes to suit. So, the roadster heads will not fit directly onto the alloy barrel - holes wrong spacing and wrong size. I do not know if there is enough 'meat' on the roadster head to mill larger holes to the right spacing - you could not use a drill as it would follow the existing holes. You take the spacing from the crankcase holes, and somewhere in Christian's archives there is a drawing and specs for the CS through bolts. I have been investigating whether I could get an alloy barrel cast using a cast iron one as a mould, but have shelved the idea for the moment. My earlier investigations indicated that the holes in the roadster head could probably be enlarged and moved to fit through bolts, but the head would need welding/building up as the pillars through which the head bolts pass would be left too thin and might crush or settle immediately or in use. Will keep members informed if I take this project further. Andy