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BSA A10 gearbox high rev problems #714358
11/09/17 9:58 am
11/09/17 9:58 am
Joined: Sep 2015
Posts: 4
northern germany
G
gunnix Offline OP
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gunnix  Offline OP
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Joined: Sep 2015
Posts: 4
northern germany
Hello everybody
Since I am a newbe in asking questions in a forum, I hope I am doing it right.
If not, please tell me.
I am riding a side car racer based on a BSA M20/A10 with an engine one cylinder, dohc 600cc and approx 65hp at 8500 rpm.
In my A10 std gearbox above 7000 rpm sometimes gears slip out and I am not able to get in any gear.
Sometimes the gear slips out and jumps in again (awefull noise!!!).

Is there anything I can do?
I changed the layshat to goldie type with needle rollers, and the main shaft wit one needle roller and one bush on the drive side side - no change.
The gears itself dont look worn.

Greetings from
Gunnar


in progress: BSA/Jawa 620cc supercharged sidecar racer
BSA/Jawa 600cc sidecar racer
BSA super Rocket
BSA B33 sidecar
Ariel VH
Triumph 6T custom
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Re: BSA A10 gearbox high rev problems [Re: gunnix] #714381
11/09/17 3:06 pm
11/09/17 3:06 pm
Joined: Sep 2008
Posts: 845
Edgewater, Md
B
Blown Income Offline

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Blown Income  Offline

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B
Joined: Sep 2008
Posts: 845
Edgewater, Md
Gunnar,

I think the best thing you could do would to have the gears undercut. This would keep the gears pulling together while engaged.


1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1970 Triumph TR6C
1972 BSA Lightning LSR Bike
1974 Triumph T150V
Re: BSA A10 gearbox high rev problems [Re: Blown Income] #714480
11/10/17 12:44 pm
11/10/17 12:44 pm
Joined: Sep 2015
Posts: 4
northern germany
G
gunnix Offline OP
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gunnix  Offline OP
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Joined: Sep 2015
Posts: 4
northern germany
Thank you very much for the information.
Is it normal to happen if the gears are not undercut?


in progress: BSA/Jawa 620cc supercharged sidecar racer
BSA/Jawa 600cc sidecar racer
BSA super Rocket
BSA B33 sidecar
Ariel VH
Triumph 6T custom
Re: BSA A10 gearbox high rev problems [Re: gunnix] #714492
11/10/17 2:24 pm
11/10/17 2:24 pm
Joined: Aug 2015
Posts: 1,240
Bolton Lancs UK
A
Andy Higham Offline
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Andy Higham  Offline
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A
Joined: Aug 2015
Posts: 1,240
Bolton Lancs UK
I don't want to rain on your parade but undercutting an A10 gearbox is almost impossible.
Only the layshaft 2nd and 3rd gears have "dogs" but they are rounded section and locate into rounded blind holes


BSA B31 500cc "Stargazer"
Greeves 200cc "Blue Meanie"
Greeves 350
Greeves 360 Challenger
Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500cc sprint/LSR bike "Deofol"
Jawa 500cc "Llareggub"
2003 Aprilia RSV Mille "Lo Stregone"
'35 OK Supreme
'36 OK Supreme
Re: BSA A10 gearbox high rev problems [Re: gunnix] #714493
11/10/17 2:27 pm
11/10/17 2:27 pm
Joined: Aug 2015
Posts: 1,240
Bolton Lancs UK
A
Andy Higham Offline
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Andy Higham  Offline
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A
Joined: Aug 2015
Posts: 1,240
Bolton Lancs UK
For racing I would either fit a Nova 5 speed cluster http://www.novaracing.co.uk/ManufacturerBSA.html
or a TTI gearbox http://www.ttindustries.com/bsa_gearbox.html


BSA B31 500cc "Stargazer"
Greeves 200cc "Blue Meanie"
Greeves 350
Greeves 360 Challenger
Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500cc sprint/LSR bike "Deofol"
Jawa 500cc "Llareggub"
2003 Aprilia RSV Mille "Lo Stregone"
'35 OK Supreme
'36 OK Supreme
Re: BSA A10 gearbox high rev problems [Re: gunnix] #714591
11/11/17 2:45 am
11/11/17 2:45 am
Joined: Nov 2005
Posts: 762
Riverside, CA.
N
noisy norton Offline
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noisy norton  Offline
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N
Joined: Nov 2005
Posts: 762
Riverside, CA.
The real solution is to scrap the BSA box and find an AMC box. Impossible to break.


God rides a Triumph but wishes it was a Norton.
Re: BSA A10 gearbox high rev problems [Re: NickL] #714604
11/11/17 10:17 am
11/11/17 10:17 am
Joined: Aug 2014
Posts: 1,657
OZ
Triless Online content
BritBike Forum member
Triless  Online Content
BritBike Forum member
Joined: Aug 2014
Posts: 1,657
OZ
Yep, reminds me of something I once read about the poor old Matchless gearbox........ " designed for a thirty horsepower world and ending up in a sixty horsepower one !"

Re: BSA A10 gearbox high rev problems [Re: gunnix] #714662
11/11/17 9:06 pm
11/11/17 9:06 pm
Joined: Aug 2015
Posts: 1,240
Bolton Lancs UK
A
Andy Higham Offline
BritBike Forum member
Andy Higham  Offline
BritBike Forum member
A
Joined: Aug 2015
Posts: 1,240
Bolton Lancs UK
Years ago I used an AMC gearbox on a sprint bike, supercharged (28psi) 500cc Weslake speedway engine and a 6,5" wide rear slick. First drop of the clutch would bend the gearbox mainshaft making the clutch run out by about 2mm. subsequent runs would sometimes pull it straight, it never went worse


BSA B31 500cc "Stargazer"
Greeves 200cc "Blue Meanie"
Greeves 350
Greeves 360 Challenger
Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500cc sprint/LSR bike "Deofol"
Jawa 500cc "Llareggub"
2003 Aprilia RSV Mille "Lo Stregone"
'35 OK Supreme
'36 OK Supreme
Re: BSA A10 gearbox high rev problems [Re: gunnix] #714724
11/12/17 11:17 am
11/12/17 11:17 am
Joined: Sep 2008
Posts: 845
Edgewater, Md
B
Blown Income Offline

BritBike Forum member
Blown Income  Offline

BritBike Forum member
B
Joined: Sep 2008
Posts: 845
Edgewater, Md
I've done 118 mph in Ohio and just over 120 mph at Bonneville with my A10. I have the scrambles ratio box fitted and have not had a problem at high speed with it jumping out of gear. The Nova 5 speed box's are great but do cost a lot. You may want to check the current setup on your gearbox to make sure you do not have excessive play on the mainshaft, the bearing may be worn out causing too much "end float" allowing top gear to not fully engage.


1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1970 Triumph TR6C
1972 BSA Lightning LSR Bike
1974 Triumph T150V
Re: BSA A10 gearbox high rev problems [Re: gunnix] #714826
11/12/17 9:41 pm
11/12/17 9:41 pm
Joined: Aug 2015
Posts: 1,240
Bolton Lancs UK
A
Andy Higham Offline
BritBike Forum member
Andy Higham  Offline
BritBike Forum member
A
Joined: Aug 2015
Posts: 1,240
Bolton Lancs UK
Racing sidecars are brutal on gearboxes, when drifting around corners the tyre is slipping and gripping which puts shock loads into the gearbox


BSA B31 500cc "Stargazer"
Greeves 200cc "Blue Meanie"
Greeves 350
Greeves 360 Challenger
Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500cc sprint/LSR bike "Deofol"
Jawa 500cc "Llareggub"
2003 Aprilia RSV Mille "Lo Stregone"
'35 OK Supreme
'36 OK Supreme
Re: BSA A10 gearbox high rev problems [Re: gunnix] #714846
11/13/17 12:29 am
11/13/17 12:29 am
Joined: Sep 2008
Posts: 845
Edgewater, Md
B
Blown Income Offline

BritBike Forum member
Blown Income  Offline

BritBike Forum member
B
Joined: Sep 2008
Posts: 845
Edgewater, Md
I could see that, straight line racing we dont really have the side loading. I guess the best plan of attack would be to upgrade to the Nova 5 speed box.


1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1970 Triumph TR6C
1972 BSA Lightning LSR Bike
1974 Triumph T150V
Re: BSA A10 gearbox high rev problems [Re: gunnix] #723475
01/27/18 11:13 pm
01/27/18 11:13 pm
Joined: Feb 2015
Posts: 135
UK
F
flowboy Offline
BritBike Forum member
flowboy  Offline
BritBike Forum member
F
Joined: Feb 2015
Posts: 135
UK
Wow Gunnix that sounds like an interesting motor! 600cc DOHC M20/A10. That is a strange combination! I hope it has a wild nickname..

I've raced Goldstars - with anything from 30 to about 45 hp & never had jumping out of gear problems with a BSA box unless the gears were worn. It does suggest your gears are more worn than you think. On the other hand you're putting a lot more power through it!
The Nova 5 speed cluster is good (I think about £2k last time I looked & I think they also make a 6 speed) The TTI equivalent is over £3K for a 6 speed once you've imported it to the UK but I've only raced a Norton TTI box - very nice but not cheap...
I would suggest the Triumph 5 speed but suspect that may be more fragile than the BSA.
Regarding wear on the mainshaft did you fit a crowded needle roller? The caged ones which are often supplied these days are not up to the task, particularly what you are doing to it!. There is a thread on this in the goldstar forum. The mainshafts are available new from Autocycle but you probably know this.
Seems like you might need a heavy duty box from some other machine...


na

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