New guy and A7 landspeed record build

[dan daughenbaugh]

I cant say I know anything about A7's, but given they put late A10 cranks into A65's, I suspect that an A50 or A65 would go nicely into an A7 and provide a LJ crank, something I believe they never had on the A7.
I recall the A7 and A50/A65 stroke is what 1/2mm different?
I recently had a look at a "genuine" daytona A7ss motor and it had a very thick flange, something I wasnt aware of. I believe they did quite a lot of special parts for those...race rods etc.
Nice to hear people wanting to get their beesa twins flying!

Interesting.  I'm building an A7 rigid roadracer (long-term project).  If you have a choice, use later pre-unit cases and large-journal crank.  What are limitations on internal engine modifications?  Can bore/stroke be altered?  My advice would be to spend your money on building a strong bottom end and then on cam/flowing the head.  If you wanna go fast, you'll have to spend some money.
I agree, that would work with only a few mods. The timing side bushes are different size, the a65 being larger so it would have to be machined down to fit the a7/10. Also the conn rods are different lengths from the early motors to the late ones. Dont think that would affect this swap though because were talking large journal cranks here. I found this all this out when I was doing research for an 850cc a65 Im building with an lj a10 crank, Volkswagen diesel cylinder liners, and BSA 441 victor special pistons (79.mm)

[Rocket Racer]

Dan,
not sure what you had planned for that front loop, but my 10cents worth is to suggest you convert it into a rigid. Not sure how that would handle bonneville, but the daytona a7 specials were bb32r framed and that frame is for intents and purposes the same as the swing arm frame at the front loop, but missing the back half of the loop.

I had one made by a mate and its much lighter than the swing arm frame. However I race it on smooth race tracks not bumpy sand or salt flats
Cheers
Tim

Here she is as it sits. The frame is a 58 it had been hacked apart by someone long ago. I traded a guy on another board a triumph cotton spool hub for it. The frame looked like it had been sitting in water for years, the lower tubes had holes that you could fit your thumb in. I cut out the bad sections and welded in new with slugs for strength. Front end is a 60's ( purists close your eyes ) honda unit for weight it has an aluminum top tree and 33mm tubes for a wide selection of clipons

[beezalex]

I cant say I know anything about A7's, but given they put late A10 cranks into A65's, I suspect that an A50 or A65 would go nicely into an A7 and provide a LJ crank, something I believe they never had on the A7.
I recall the A7 and A50/A65 stroke is what 1/2mm different?
I recently had a look at a "genuine" daytona A7ss motor and it had a very thick flange, something I wasnt aware of. I believe they did quite a lot of special parts for those...race rods etc.
Nice to hear people wanting to get their beesa twins flying!

Interesting.  I'm building an A7 rigid roadracer (long-term project).  If you have a choice, use later pre-unit cases and large-journal crank.  What are limitations on internal engine modifications?  Can bore/stroke be altered?  My advice would be to spend your money on building a strong bottom end and then on cam/flowing the head.  If you wanna go fast, you'll have to spend some money.

I agree, that would work with only a few mods. The timing side bushes are different size, the a65 being larger so it would have to be machined down to fit the a7/10. Also the conn rods are different lengths from the early motors to the late ones. Dont think that would affect this swap though because were talking large journal cranks here. I found this all this out when I was doing research for an 850cc a65 Im building with an lj a10 crank, Volkswagen diesel cylinder liners, and BSA 441 victor special pistons (79.mm)

That's kind of why I asked about the limits on modifications for the class you're running.  I will be using an A65 crankshaft offset ground to de-stroke it to stock to meet class requirements for AHRMA class C racing.  Standard A7, even SS pistons don't look great, so my plan is to use Triple pistons, which are more readily available and have a much better crown shape.  This also allows me to stay within bore limits for the class. Deck height also works out well with triple rods and pistons, with only minor skimming needed...depending on compression ratio.

[muskrat]

G'day all,
               I never got that far as to use an A65 crank, but I did use trident pistons. To make it work with an A7 crank I had to shorten A10 rods by 2.5 mm, this gave me a comp ratio of about 13:1 to run on methanol. But I did snap a few cranks !!
I think the drive side mains is different as well, and also the length for the alt rotor.
The other problem is holding the barrels down. Horrible sound of the rockerbox hitting the bottom of the tank !! If you want I can show you how I through bolted the head to the cases. Pics attached.
Down here in classic racing we are allowed 5% oversize (525cc), those pistons gave me 524cc.
Good luck, cheers

[dan daughenbaugh]

You guys got me thinking now! The class is limited to .050 overbore but it says internal modifications are unlimited. Makes me think about using one of the 7 a65 cranks I have and getting it offset ground, use the a50/65 rods and pistons. A few questions though.
Are the rocket 3 and a7 and a50 wrist pin sizes the same?
Muskrat, you said you shortened a10 rods, how? Are the a10 and a7 rods different lengths? Could you have used a compression plate under the barrel as well.
It also appears that a50 pistons stock are 65.5 i could use then in .020 to get me to std a7 size.
Does anyone know any of the compression heights of the above?

[dan daughenbaugh]

G'day all,
               I never got that far as to use an A65 crank, but I did use trident pistons. To make it work with an A7 crank I had to shorten A10 rods by 2.5 mm, this gave me a comp ratio of about 13:1 to run on methanol. But I did snap a few cranks !!
I think the drive side mains is different as well, and also the length for the alt rotor.
The other problem is holding the barrels down. Horrible sound of the rockerbox hitting the bottom of the tank !! If you want I can show you how I through bolted the head to the cases. Pics attached.
Down here in classic racing we are allowed 5% oversize (525cc), those pistons gave me 524cc.
Good luck, cheers

Muskrat, also how far in "the hole" were your 13-1 pistons

[muskrat]

G'day Dan,
                 A7 rods are 6", A10 are 6 1/2". To shorten I just milled off the said amount from the mating surfaces on the rod and cap then bored it back to size.Remember there is crush on the shells, can't remember exactly but about 2 thou.
I had to use two sealing washers under the spark plugs to stop the pistons closing the gap. A comp plate of more that 0.060" will lift the followers too far from the cam.
I will have a look at my notes and parts down in the man cave tonight.
Cheers

[trevinoz]

Musky,
              Aren't A65 rods 6" long? If so, that would save a lot of buggering about.
Trev.

[muskrat]

G'day Trevor,
                      It would, but back then I only had small journal A7 cranks.
In Dan's case it would probably work but I don't know if there is a difference in pin to crown height between A& and A50.
The barrels could be sleeved to take the std A50 pistons, that way there is no need to de-stroke the crank.
All my books are in the man cave.
Cheers

[dan daughenbaugh]

Well through a bunch of more research I think I have found 2 workable combos.
I could use an a50/65 crank at 74mm stroke and have it offset ground 72.6 mm. Then use the stock rods from the a50 and 20 thou over pistons. This would make it the same bore stroke combo as the later a7's and give me a stronger bottom end and keep me within class rules and have a better selection of pistons. This assumes that there is an undersize available for the rod when its been offset ground and machining the timing side bush too and the deck heights of the motors are the same.
Or it looks like the rocket 3 pistons have the same sized wrist pins as the stock a7 so they would go right on. Just have to check the compression height. And the bottom end would be a bit weaker

[trickytree]

.....This assumes that there is an undersize available for the rod...........

Personally I wouldnt be putting stock 50+ year old con rods in a performance motor so why not just have suitable rods custom made?

[beezalex]

Well through a bunch of more research I think I have found 2 workable combos.
I could use an a50/65 crank at 74mm stroke and have it offset ground 72.6 mm. Then use the stock rods from the a50 and 20 thou over pistons. This would make it the same bore stroke combo as the later a7's and give me a stronger bottom end and keep me within class rules and have a better selection of pistons.

Yes, stronger bottom end is the idea, but there isn't encessarily a better selection with A50 pistons.  Have you looked lately?  Triples are another story, with 67mm standard bore (Well within the overbore limit) being plentiful and the crowns being a better shape, they are IMHO the way to go.

And if you want to turn some revs, ditch the stock rods and go with aftermarket. Carillos are indestructible and MAP and Thunder rods get high marks from others.

[charlieb1954]

hi all,
       being reading this thread with intrest, i used to go sprinting in the uk, lyme, saltburn, houghton castle, etc.have 3 bikes with bsa plunger engines in, favirite is a norton navigator with 500 engine.
       i also have a royal enfield gt with a very much modified a7 plunger in it heres the spec
   a65 crank, was worn out so was reground to suit triumph rods , t120, only needed small amount of material removing then std shells fitted. i fitted the roller bearing to bush side at same time, fitted rocket 3 pistons, with spitfire cam, had to recess the piston cutaways to get clearance, and fit 3mm spacer under barrel, i removed the camshaft retainers to allow tappets to drop, lengthened pushrods, bike goes likehell    hope this helps   charlieb
  never knew a 358 cam exsisted, over here only got 356,rocket,or 357 spitfire would like to see the profile of a 358 or even buy on    charlieb

[beezalex]

Thanks for the input, charlie.  Nice to know someone's already done this.  I assume this worked well?

[charlieb1954]

goes very well; the roller timing side bearing really makes differance, smoother, quicker on the mark, and the big ends got oil, i have blown the odd oil seal feeding the modified crank quill out off the housing so now use the metal housed ones with a drop of locktite, job sorted. like the through bolt idea, never seen that before, got to help the 650 thin flange barrells on some of my other bikes stay on, great idea  thanks