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#275394 09/19/09 3:39 pm
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I remember reading somewhere about an a10 short rod coversion. Has anyone got any info ? I'm hoping to start my cafe racer project and would like to know more.
Thanks in Advance Bill

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You could use A7 rods and shorten the barrel by 7/16 inch. You'd need A7 pushrods, of course.
It's been done - my '57 Spitfire is so modified and runs quite well.

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What mods to the barrels was there, any welding or did you just drill headbolt holes deeper and tap? I was thinking of using A65 rods.what cam are you running?
Bill

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you of course know that shortening the rod increases cylinder wall loading.what are you trying to achieve??

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Jaycee
A faster A10!My ridged is modded to the max. Twin carb head oversize valves ,alloy valve collars , mushroon adjusters ,alloy pushrods, roller conversion ,close ratio box,cam+ idlers run in needle rollers, lightened timming gears...
Some one posted an article on short rods so i thought i should have a serious look at it. I think the article came from an old chopper mag ? Any info appreciated Bill

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Bill, the only thing that shorter conrods get you is less reciprocating mass, which can help a high-revving motor and material mass saved in the barrel length. Unfortunately it does this at the expense of the piston's time in residence at the top of its stroke. This actually reduces torque which is why for a long-stroke motor, shortening the rods make no sense.

If you want to increase your power-to-weight ratio, it would be a lot easier to leave the last Ho-ho in its package or just let someone else eat that ckicken leg.

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Bill, do you have a welder? An A10 crank works fine in an A65 with A65 rods(though longer would be more ideal) but how good would the A10 be with a set of A65 cyls and head? You could then tow something with it and eat the extra chicken leg, having an extra 100cc and lightning head.


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A65 rods/cut top fin on barrel/500cc push rods/357 or 358 cam/ late barrel&crank

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Thank You Goldstar Freddie!!This is the article I've been looking for. Will study it and weigh up the pros and cons. Much appreciated Bill
Mark I was told that an A65 head and barrel had been grafted to A10 cases but when i asked for proof, photo ,the guy never got back to me. I think that conversion would be beyond my abilites.
Cheers

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This is all very interesting, but after reading this article through, isnt it describing all the changes done to A10 engine to get infamous A65 power egg ???
It looks like I got this "hot rod" engine in my bike smile

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I'm sure I saw a photo of such a motor in a very old magazine Bill, in about 1970, I have old A65 cyls but no A10 case to compare.
It would make a very unique engine if it were possible.


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For a faster A10 the only way to go is TRIbsa grin


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And so easy,too!The bolt pattern on the rear engine mounts fits the pre-unit triumph crankcase,and the primary chaincase lines up too.Did this once on a Road Rocket.
You only have to fabricate front engine-mounting plates.

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Steady on 76 thats way more blasphemus than even the heracy of the A65 top end, to those of the A10 persuasion. If Bill went such a retragrade step with a 'Triumph' downgrade, he could never look BSA men in the eye, the A65 top end would procure some raised eyebrows, and no doubt serious counciling, but probably be followed by 'How does it go?' and 'can I have a go?


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No welding and yes, the head bolt holes will need deepening. I run the -357 cam.

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Gday Mark, Ive never had a beezer bloke look me in the eye. At first I thought they were being rude but it turns out they were looking for their rods and cases after the timing side bush moved and starved the bottom end of oil! laugh
On a serious note I ran an A10 in my TRIBSA for a short while whilst using the trumpy motor in another project. It used T140 rods on an underground crank, 7:1 TR6 pistons and about 12mm milled of the last of the big fin A10 barrels. Comp was over 11:1 so I ran a 1/16 spacer under the barrels so it would run on petrol (road bike) It had the 357 cam and a much modified alum head with twin 30mm amals. It was smoother than the triumph motor but did not go anywhere as good. It did about 1000k's before the timingside bush seized on the mainshaft and wore the cases. It was still running when I took it out but had no oil pressure.


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Originally Posted by 76degree-triumph
Gday Mark, Ive never had a beezer bloke look me in the eye. At first I thought they were being rude but it turns out they were looking for their rods and cases after the timing side bush moved and starved the bottom end of oil! laugh
On a serious note I ran an A10 in my TRIBSA for a short while whilst using the trumpy motor in another project. It used T140 rods on an underground crank, 7:1 TR6 pistons and about 12mm milled of the last of the big fin A10 barrels. Comp was over 11:1 so I ran a 1/16 spacer under the barrels so it would run on petrol (road bike) It had the 357 cam and a much modified alum head with twin 30mm amals. It was smoother than the triumph motor but did not go anywhere as good. It did about 1000k's before the timingside bush seized on the mainshaft and wore the cases. It was still running when I took it out but had no oil pressure.


Yes, it requires more than a drunken monkey to put a BSA bottom end together and yes, they will get you home. Thanks for sharing.


A smattering:
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'67 Royal Star
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'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.
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"Yes, it requires more than a drunken monkey to put a BSA bottom end together and yes, they will get you home. Thanks for sharing."
A super Chimp will get a motor completed in less than an hour and a half and do a fair job, so long as you keep the peanuts up to him, steer clear of Orangatangs I wouldn't let one near my bike even to check the tyres.


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This posting degenerated quickly, didn't it?

David

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Some Triumph lads were over here stiring up trouble.


mark

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