Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board How do you...

...dual plug an A65?

Looks impossible.

konon's done it, i believe

I think you'd get more response if the thread was titled "How to double-plug an A65?"

There was a post about detonation many years ago which included details of A65 dual plugging, see This Link, apparently it is doable and was used by sidecar racers amongst others.

http://www.britbike.com/forums/ubbthreads.php/ubb/showflat/Number/584276/Searchpage/1/Main/63384/Words/%5Bimg%5D/Search/true/re-another-bsa#Post584276


i knew it was in here somewhere.

lol

couldn't find it because konon mispelled"dual"

Thanks. I searched and did not find this. Figured it would have to be through the cylinder head cover.

Wonder how it seals?

Whats your motivation for this?

As far as sealing , grommets didn’t work, lot of oil mist. Went to a rubber gasket & o- ring with metal ring fastened on top.

Racing.

So the chamber holding the plug became part of the "pressure vessel" of the motor? Now I see why peeps race triumphs. All this is done. Really informative thread thanks...

My thought was a built up tunnel with a machined surface on the cylinder headthat meets a tunnel from the top built down from the cylinder head cover with a groove with an o-ring in the middle for sealing ala Honda. The ignition wire would then have a rubber cover to keep dirt out. Two bosses fore and aft of the holes to provide sealing pressure with bolts. Alas expensive.

A second possibility was to go sideways with narrow D sized plugs through the cooling fins in the center of the head to get to the opposite cylinder and thus avoid all the through the cylinder head cover rigamarol. Has anybody done that?

Also interesting discussion of heat effects of crank expansion in this thread.

Over time I have some shim in the cup on the crank go bad and shim bits ended up in the bottom of the A65 sump. I've wondered why this was happening. My riding style is much more aggressive than the normal A65 peeps so it makes sense that on my bikes the crank is running much hotter.

The one anomaly is the Thunderbolt. I got 40000 miles out of a standard bush rebuild but the difference is that I put a lockhart oil cooler on it that many people said I didn't need. My gut told me differently. Could that have been the difference? That cooler keeps the crank from expanding so much by taking away heat from the crank and bearings with the oil and preventing crank expansion? And thus protecting the shims from being crushed by crank expansion while doing 65-70 out on the highway fully loaded?

Recently my ears perked up when I heard from a rebuilder that on A65 race motors he uses .005" of endfloat instead of the normal .0015-.003" (are those numbers right?) He didn't say it but it makes sense that he was doing this because a race motor would be subject to much high heat stress on the crank and its bearings and would need the extra end float to protect the shims from the crank expanding.

You Might look into a outrigger bearing on crank. Think Mark Parker and Allen G both use one.

Bill, I love you, man. But all the dual plug heads and belt drives in the world aren't going to make you a better racer. It's all great in theory and tons of fun to have when it all comes together but there are serious development steps to get around. Ask me how I know. My unsolicited advice is to get a reliable bike first and work hard on technique. The guys out there riding circles around us have many years more experience honing their craft than we do. A bone stock bike is going to allow you to work on Yourself more than a hot rod that you spend more time fixing than riding. As your working years are now behind you, you have an opportunity to get a lot of track time. Get on it like flys on poop!
Peace and love

DAMN......I musta REALLY liked it!!!!!!!

Gordon

At CMP last weekend, Jake, Dave Spanger and I all had fast laps right at 2:01. Difference was that Jake and Dave put down more 2:01's than I did.
All our bikes are putting out within a couple HP of each other and we're all capable of cutting a fast lap. Consistency and reliability wins.