Author Topic: Small Journal Crank  (Read 4228 times)

Offline Rocket Racer

  • Wise & Enlightened
  • *
  • Join Date: Jun 2009
  • Posts: 1430
  • Karma: 16
  • A kiwi with a racing A10 rig and too many projects
    • NZ Classic Sidecar Racing
Re: Small Journal Crank
« Reply #15 on: 30.09. 2009 22:42 »
Sorry my link didnt quite work, if you search for threads there involving my user "atlas" you should be able to get to my profile and access my public album.
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
New Zealand

Offline Rocket Racer

  • Wise & Enlightened
  • *
  • Join Date: Jun 2009
  • Posts: 1430
  • Karma: 16
  • A kiwi with a racing A10 rig and too many projects
    • NZ Classic Sidecar Racing
Re: Small Journal Crank
« Reply #16 on: 30.09. 2009 22:48 »
One of the main things I'm intending to do is keep the reciprocating masses as light as possible, so will avoid heavy rods and pistons, if you look at the original BSA pistons they are lovely and light unlike many modern ones. I'm guessing that most modern manufacturers make too many different sizes from one mould so piston wall thickness can be  pretty clunky if the piston happens to be at the wrong end of a size range. Everytime you go up an oversize the piston wall thickness gets greater and the piston heavier.
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
New Zealand

Online muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Join Date: Jul 2009
  • Posts: 8262
  • Karma: 106
  • Lake Conjola NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: Small Journal Crank
« Reply #17 on: 01.10. 2009 14:29 »
G'day RR, if you use the SJ keep the comp under 10:1 and revs under 7000. I snapped a few SJ's in my 57 A7SS racer. 357 is good on petrol but 356 is better on Methanol and will run on 10:1. I used roller conversion in mine with no probs there, if useing bush do not use white metal go for solid PB. Lighten push rods (alloy), rockers (replace springs with shims) and valve spring collars. For sidecar work do not lighten flywheel. I also through bolted the head & barrels (thick flange). Tuning for speed is my bible. Good luck.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Online RichardL

  • Outside Chicago, IL
  • Wise & Enlightened
  • *
  • Join Date: Nov 2007
  • Posts: 5062
  • Karma: 48
Re: Small Journal Crank
« Reply #18 on: 01.10. 2009 15:15 »
Not that I am tuning for speed or intentionally built for it, but my '55 A10 has been 9:1 with a 356 since I bought it in 1973. Can I assume, from your use of a 356 with 10:1, that my cam/compression match is a good one, even if a later Super Rocket with 9:1 came from the factory with a 357?

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020 (if it's not cancelled and we are free to move about by then). Watch website at https://www.gentlemansride.com for details.

Offline olev

  • Brisbane, Australia
  • Resident Legend
  • *****
  • Join Date: Sep 2008
  • Posts: 510
  • Karma: 3
Re: Small Journal Crank
« Reply #19 on: 01.10. 2009 15:53 »
Gday rocky,
A month or so ago there was a pile of A7 and A10 parts for sale on 'Trade me"
There were a few cranks in the pile.
I didn't see the end of the auction so he might not have sold them. There is no feedback on the sale anyhow.
He seems to be flogging off a lot of BSA stuff from a deceased estate.
He currently has an ad in Trade me for 'BSA B31 Parts' so you may be able to contact him through that. He is in Timaru, Oamaru and his seller name is AKD11.
Just thought it was worth pointing out in case you missed it.
cheers
lots of sheep down there

Online muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Join Date: Jul 2009
  • Posts: 8262
  • Karma: 106
  • Lake Conjola NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: Small Journal Crank
« Reply #20 on: 01.10. 2009 20:50 »
G'day Richard L,
                     the 357 gives a stronger top end and coupled with the SR's bigger valves it comes "on" at about 5000 - 5500 rpm. The 356 gives better torque down low which would suit RR's racing chair.
RR will you be using petrol or methanol ? Either way a long inlet tract ( from valve to end of velocity stack 11" ) and a smallish ( 1 1/8" ) carb will work.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline Rocket Racer

  • Wise & Enlightened
  • *
  • Join Date: Jun 2009
  • Posts: 1430
  • Karma: 16
  • A kiwi with a racing A10 rig and too many projects
    • NZ Classic Sidecar Racing
Re: Small Journal Crank
« Reply #21 on: 01.10. 2009 22:20 »
I was planning to stick to race gas to keep it simple for carb set up, with a 357, but do have both a 356 on the shelf which was what was in the early road rockets and came out of this one.
Was hoping to run 9:1, but realistically the well used pair of BSA stamped 8.5:1 which came out of this motor may well get reused as they have some life left in. Seems easier to find 10.5:1 in hepolites but not too keen to overload the crank.
I've got an 1 3/8" (30mm) 10TT9 with two float chambers (was planning to run a swill pot to offset any fuel bias on corners), its slightly bigger than I wanted, but should do the job and a nice bit of bling for the bike.
The solid plain bush sounds like the business, I'll get one through Mike who is mentioned in one of the threads as soon as I've checked the state of the crank which was still standard but well used when stripped down.
I have an article (avail in pdf 4mb) on a NZ A10 sidecar racer which mentions briefly that the BSA technical department in 1954 (David Munro) recommended that a new location hole be drilled in the timed breather to give a 30 degree retard. I'd be interested to know if any competition A7/A10 users have modified their timed breathers...
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
New Zealand

Online muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Join Date: Jul 2009
  • Posts: 8262
  • Karma: 106
  • Lake Conjola NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: Small Journal Crank
« Reply #22 on: 02.10. 2009 08:14 »
G'day RR, I would go the 357 with a 30mm feeding two pots with moderate comp. I used 2 X 32's on the A7 on methanol with very short intake (7"), it wouldn't pull the skin off a rice custard under 4500 rpm, but from 6000 to 8000 hold on.I did away with the timed breather all together and vented out the inner timing cover to where the dynamo should be with 1/2" hose to the oil tank then to the catch bottle, also vented the rockers.
Are you going to use the mag or electric ignition ?
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline Rocket Racer

  • Wise & Enlightened
  • *
  • Join Date: Jun 2009
  • Posts: 1430
  • Karma: 16
  • A kiwi with a racing A10 rig and too many projects
    • NZ Classic Sidecar Racing
Re: Small Journal Crank
« Reply #23 on: 02.10. 2009 22:24 »
The k2f mag that came with the motor is missing some bits and obviously not been used in quite a while. I'm not a fan of old mag's, well most things lucas that the british bikes put up with in the day. So will probably be leaving it on the shelf. If my budget can be extended that far I'd like to put one of those new BT-H electronic mags on it, I've got one on my B33 and its been worth its weight so far, unlike a brand new joe hunt I ran on my norton a few years back that gave me nothing but grief. The BT-H  mags arent cheap but are at least new and appear well made.
I was planning to put an oil filter where the dizzy went. I like your idea re the breathing, have also yet to decide whether to run twin pipes or a 2 : 1 which would reduce weight.
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
New Zealand