Britbike forum

Classic British Spares Klempf British PartsBaxter Cycle BritBike Sponsor SteadfastCyclesSRM Engineering Lucas Classic Motorcycle Industrial tec supply Hepolite Pistons The Bonneville ShopLowbrow Customs

Upgrade your membership to: Premium Membership | Gold Membership | Life Membership | Vendor Membership | Site Sponsor Membership
Member Spotlight
Boomer
Boomer
Orygone
Posts: 3,616
Joined: February 2011
ShoutChat
Comment Guidelines: Do post respectful and insightful comments. Don't flame, hate, spam.
Top Posters(30 Days)
quinten 95
Rohan 65
Top Likes Received (30 Days)
quinten 14
Newest Members
yornocT120R, robert wilby, Jonah A, paulski, DAMadd
11,837 Registered Users
Who's Online Now
5 members (Lannis, DavidP, HughdeMann, garbln, DPO), 23 guests, and 78 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Page 1 of 2 1 2
Joined: Feb 2007
Posts: 2,731
Likes: 55
Britbike forum member
OP Offline
Britbike forum member
Joined: Feb 2007
Posts: 2,731
Likes: 55
Perhaps I should be on the competition board but I thought I'd query the BSA collective first.

The Hornet Race bike Transmission (67 frame and a 71 motor) has left me High and Dry for two races now and i'm am unhappy.

What is going on: The transmission is dragging in neutral. I miss diagnosed the problem as the wrong shim on the layshaft but what I think is happening is gear(s) are push down the shaft toward the primary side and loading the shim on the primary side. I can feel something slipping which I thought was the Newby jumping a tooth but I think its in the transmission. As soon as I feel the slip in WOT I know that soon the bike will be dragging down on power.

When I remove the shim the rear wheel spins freely so when last I was there we machined a shim that would allow the wheel to spin freely. After one lap at Little Taledega today the bike is dragging again and now I cannot find CR2nd and CR3rd. Things are obviously out of position and STD1st and STD4th gears does not a race bike make.

I'm also running a Bob Newby Clutch and the SRM outrigger bearing. Fellow racer Mike Baker suggests I find the spec of where the fixed gears are supposed to be along the Lay Shaft and I can see the wisdom in that but I am worried that I am going to walk the gears around again in race conditions and end up with dragging and miss shifts. So any advise on how to accurately trouble shoot and attack this problem would be greatly appreciated.

Thanks in Advance.
SG - resting at wits end.

Last edited by Semper Gumby; 09/05/21 9:07 pm.
BSA on eBay
Joined: Jan 2014
Posts: 1,604
Likes: 175
N
Britbike forum member
Offline
Britbike forum member
N
Joined: Jan 2014
Posts: 1,604
Likes: 175
Not familiar with belt drives but setting up the a65 box property is a fair procedure.
Make sure all the bearings and bushes are in good nick.
Make sure the outrigger is true to the mainshaft run for a start.
Make sure the camplate is in good condition and is the late type. Ditto the plunger
some people remove the point on the plunger end, a good idea. Some people
polish the cam plates and remove all the burrs, a good idea. Some people
shim the camplate in the end housing, a good idea.
Ditto with forks.
Setup and set layshft endfloat..
Although it's difficult to do, check the need for either moving the mainshaft or shimming
the top gear. This really involves some trial and error and fine measuring of gear
engagement etc, bit of a pig to do without having a cutaway box but does pay off.
As a sidecar racer for some years using these old lumps, i went through the learning
curves of a65 gearboxes, they are a crap box but can be made reasonable with loads
of time and patience.

Joined: Jan 2014
Posts: 1,604
Likes: 175
N
Britbike forum member
Offline
Britbike forum member
N
Joined: Jan 2014
Posts: 1,604
Likes: 175
By the way, why did you bother using a close 3rd?
The only time they are any use is on about one circuit in 100.
Close 1st and 2nd are the ones to have. With GOOD dogs.

Last edited by NickL; 09/05/21 11:13 pm.
Joined: Apr 2005
Posts: 2,822
Likes: 41
M
Britbike forum member
Offline
Britbike forum member
M
Joined: Apr 2005
Posts: 2,822
Likes: 41
You can weld the selector tracks if shimming doesn't get full engagement on all gears, and a ball ended plunger is good. But it sounds like a problem I've not had and I think you should look at everything it could possibly be.

We had a broken battery terminal that at low rpm felt like the transmission was jamming when it was low voltage to the ignition, the fixed terminal fixed the transmission that we thought was at fault. I think it was retarding or something felt like the brakes were on, and we suspected the transmission.

I think it freed up at rpm when the alternator put in enough voltage, but we thought the trans was trying to lockup at low rpm.

You can set the G/box up and check it out of the bike.

Last edited by Mark Parker; 09/05/21 11:36 pm.

mark
Joined: Aug 2001
Posts: 5,826
Likes: 169
G
Britbike forum member
Offline
Britbike forum member
G
Joined: Aug 2001
Posts: 5,826
Likes: 169
make sure the shafts are straight, check them for run out between centres .
Do what nick says , particularly the advice on ratios, close 1st and 2nd, std 3rd.

Your set up std 1st, close 2nd , close 3rd is not great, the gap between 2nd and 3rd is too much.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Joined: Feb 2007
Posts: 2,731
Likes: 55
Britbike forum member
OP Offline
Britbike forum member
Joined: Feb 2007
Posts: 2,731
Likes: 55
Interesting.

Time to get the box out on the bench then...Thanks Nick.

As to selection of std Vs.cr gears I don't yet feel qualified to comment yet...

Last edited by Semper Gumby; 09/06/21 2:21 am.
Joined: Apr 2005
Posts: 2,822
Likes: 41
M
Britbike forum member
Offline
Britbike forum member
M
Joined: Apr 2005
Posts: 2,822
Likes: 41
Getting off the line for short races is talked about in the US quite a bit. I don't know if std 1st addresses that effectively because I've never tried it, but we use 20-40 with C/r 1st on a 750 And 20-38 on another C/r with 17" wheel, and neither take much to get going, or probably more to the point is once they get on the boil a straight should sort out who goes in front anyway? Getting good drive after you get away would be what I'd concentrate on, you still need to get away smartly without breaking anything, but a harder drive will soon round you up.

Wide gaps between high gears does people no favours. I watched video of Phantom's lovely Triumph with a big std 4-5th gap up a long straight, shifting into it meant bikes just keeping with him came past every lap, Kawasaki triple I think. That 4-5th gap is far bigger than a std BSA 3rd and 4th which is very good. Quaife made an A65 5speed with worse ratios than the 4 speed, big gap to top like the Triumph? Getting it right like the PES box helps the motor at every change. I think the C/r BSA 3rd was for 500s at Daytona trying to keep near peak power. I think the PES 4th is near that but with an extra gear and 1st is a little lower than the C/r 1st because it's spread over 5. The C/r 1st and 2nd make the 4speed very nice. But the taper on the main-shaft isn't great.

[Linked Image from i.postimg.cc]


mark
1 member likes this: gavin eisler
Joined: Oct 2009
Posts: 630
Likes: 19
P
Britbike forum member
Offline
Britbike forum member
P
Joined: Oct 2009
Posts: 630
Likes: 19
A bit fiddly would be an understatement but this sounds like a 'new' problem. I found that the outrigger plate can be tricky to set up. The fit has to be perfect otherwise it will drag. Since we use a dry clutch I found that no plate works fine on the 'gas' bike. Admittedly, we do not have to make hundreds of gearchanges like you guys do. I have used both cr and std on it. With careful shimming they have worked well. The 'fuel' bike uses a carefully set up out rigger and has the dogs undercut. This has been relatively trouble free for many years. Keep us posted! PRT

Joined: Jan 2006
Posts: 2,309
Likes: 49
M
Britbike forum member
Offline
Britbike forum member
M
Joined: Jan 2006
Posts: 2,309
Likes: 49
I think the cr v std debate is not really the issue that needs to be addressed at this point. Bill takes the disappointment at the track well but if he can't get this bike sorted soon I fear my friend throwing in the towel. With the rear wheel raised bike in neutral, grabbing and turning the wheel feels like lifting weights. Much resistance. When he told me that it was fixed by grinding a shim smaller I knew it was not a true fix. Shims do not grow. I have known Triumph gearboxes where press fit gears have "migrated" on the shafts. Is it possible that could happen to a A65 causing a clearance to tighten up? Are there specs/ measurements of where gears should be on shaft? Something has moved, that much is obvious. Most likely scenario?
Thanks from a racer that would like to see a BSA finish a weekend without drama.

1 member likes this: Gary E
Joined: Feb 2007
Posts: 2,731
Likes: 55
Britbike forum member
OP Offline
Britbike forum member
Joined: Feb 2007
Posts: 2,731
Likes: 55
I'll start another thread on the CR Vs Std ratio gears later. I do want to visit that topic - it was a complete surprise! Right now I'm more concerned with starting and finishing races.

In the early days of this bike I had a stock clutch and chain which ment I had a Cush drive.

NickL - could this be part of my problem. The Newby and the outrigger have no Cush drive which may be hard on the box. I got away with this on the Thunderbolt (not a racer) I think because with the QPD belt drive I didn't have the out rigger bearing. So the flexing main shaft with the belt acted as a "cush" drive?

I'm not at all adverse to going back to the stock clutch and chain as I am quite comfortable keeping the the chain oiled properly now. Its only those cursed rollers that make it such a pain. Is there a chain basket with a one piece roller bearing so I could have a cush drive again?

OR putting on a cush drive rear wheel (and having to machine bits to get it to align).

Taking the day off. Transmission comes out tomorrow.

Last edited by Semper Gumby; 09/06/21 2:36 pm.
Joined: Feb 2007
Posts: 2,731
Likes: 55
Britbike forum member
OP Offline
Britbike forum member
Joined: Feb 2007
Posts: 2,731
Likes: 55
Going on right now. This is all moot until I get the transmission out and see what is going on but....

https://www.britbike.com/forums/ubbthreads.php/topics/846199/1

Joined: Aug 2001
Posts: 488
Likes: 2
K
Britbike forum member
Offline
Britbike forum member
K
Joined: Aug 2001
Posts: 488
Likes: 2
I have a Yamaha that will jump out of low gear , and the back wheel turns hard like in two gears at the same time. I’m sure you’ve already checked , but possibly a shifting fork is bent?


1968 BSA Firebird
1200 Sportster
XS 1100
1972 Rickman 125
Joined: Feb 2007
Posts: 2,731
Likes: 55
Britbike forum member
OP Offline
Britbike forum member
Joined: Feb 2007
Posts: 2,731
Likes: 55
Thanks K. Not yet but Yes. Tomorrow will check all that.

Joined: Mar 2011
Posts: 236
Likes: 10
L
Britbike forum member
Offline
Britbike forum member
L
Joined: Mar 2011
Posts: 236
Likes: 10
Originally Posted by Semper Gumby
As soon as I feel the slip in WOT I know that soon the bike will be dragging down on power.

if the gearbox is consuming so much power at WOT then it must heat up considerably. all energy not delivered at the rear wheel is turned into heat in the gearbox. as these components aren't very big they'll heat up. so if this happens again I would check the gearbox oil temperature and see what readings you get.

Joined: Aug 2001
Posts: 5,826
Likes: 169
G
Britbike forum member
Offline
Britbike forum member
G
Joined: Aug 2001
Posts: 5,826
Likes: 169
It seems like one of the fixed gears has moved on a shaft, if this is the case, then you need to find out why , there shouldnt be side loads on the gears if they all line up properly, i dont think the belt drive / newby clutch has anything to do with it.

i fitted an outrigger when I put in the 5 speed , same as Marks, havent had any issues with it, I did add a few more screws, and fitted them all with studlock.

possibly the sleeve gear bush is tight that would give drag in neutral.It would be OK in 4th when its direct drive,, and get more draggy in the lower gears.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
2 members like this: Allan G, pushrod tom
Joined: May 2013
Posts: 8,194
Likes: 182
A
Britbike forum member
Offline
Britbike forum member
A
Joined: May 2013
Posts: 8,194
Likes: 182
Originally Posted by gavin eisler
It seems like one of the fixed gears has moved on a shaft, if this is the case, then you need to find out why , there shouldnt be side loads on the gears if they all line up properly, i dont think the belt drive / newby clutch has anything to do with it.

i fitted an outrigger when I put in the 5 speed , same as Marks, havent had any issues with it, I did add a few more screws, and fitted them all with studlock.

possibly the sleeve gear bush is tight that would give drag in neutral.It would be OK in 4th when its direct drive,, and get more draggy in the lower gears.

+1

I’d treat the slipping in top as a separate issue. When I bought my 3rd clutch off Bob I discussed the need for the race clutch on my 823 over the standard clutch with the 5 plate conversion (3x thinner plates) he said there was no difference and I believe him. I have a race clutch also, wider belt etc. The standard clutch with 5 plates has taken a hammering, it’s been tested in the attempt to break it… it won’t. The only
Time it’s slipped is when the clutch nut hasn’t held up to the job and loosened off, then sheered the key and spun on the shaft. The same nut covered over 10,000 miles under my ownership and it wasn’t a new nut.

……….…………


If the box selects neutral better when the thinner shim is at the drive side of the box then there cannot be good alignment with the gears and the selector forks within the cam plate.

You “should” use the thinnest shim only on the timing side of the layshaft, then shim accordingly on the drive side until you have the smallest amount of play. Too much play and the box will jump out of gear.

However, it might be worth fitting the next size shim up on the timing side then shim to suit on the drive side and try again.

A cut away box would be nice, but you would have to shim that box accordingly also. (Least you would on the drive side)


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (now rebuilt)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Joined: Aug 2001
Posts: 5,826
Likes: 169
G
Britbike forum member
Offline
Britbike forum member
G
Joined: Aug 2001
Posts: 5,826
Likes: 169
As lemans said, drag creates heat, something is bent? , shafts or selector forks or both, what was the lay shaft end float on assembly?
Caveat , I could be totally wrong. A bearing perhaps, I could come over and help , but it would take a while.

Last edited by gavin eisler; 09/07/21 10:11 pm.

71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Joined: Apr 2005
Posts: 2,822
Likes: 41
M
Britbike forum member
Offline
Britbike forum member
M
Joined: Apr 2005
Posts: 2,822
Likes: 41
The beauty of these gearboxes is that they are a cassette. They can be inspected out of the case. Assuming you shim end float out of the lay shaft hold it and check gear engagement, the sliding gear may not go right in both ways so you can weld a track and file it to get it. But you problem is bigger than that so look closely at everything. Everything around the belt as well.


mark
1 member likes this: gavin eisler
Joined: Feb 2007
Posts: 2,731
Likes: 55
Britbike forum member
OP Offline
Britbike forum member
Joined: Feb 2007
Posts: 2,731
Likes: 55
Wow. What a day... OK - the Layshaft is straight. I forgot to check the main shaft - will check tomorrow.

OK riddle me this because this is what I found.

The only CR gears in the box are the 2nd gear set - every thing else is Standard. This is a surprise because what I had asked for was CR 2nd and 3rd with STD 1st and of course STD 4th.

But what had been done was the 2nd gear set was in the 3rd gear position and the 3rd gear set was in the 2nd gear position. These gears were switched to the opposite shafts to work. So 2nd gears were matched to each other but were on opposite shafts. Same with the 3rd gears. So I sort of had a Close ratio 2nd and 3rd but I don't know exactly what the Maths are for this. It hurts my brain just typing this.

So you will all be happy to know that I now have the STD 3rd in the correct position and the CR2nd in the correct position.

I don't know if this will fix the layshaft top gear popping off the the primary side of the layshaft or not (I suspect this will happen again but who knows until you twist the wrist?)

So now I have STD 1st CR 2nd STD 3rd and STD 4th which is pretty close to what you all said I should have anyway!

Y'all heard of anything like this before other than the wrong gears got put on the wrong shafts when the main shaft timing side bearing got replaced?

Oh and I have new shift forks in place. And I am getting real good at assembling a transmission and installing. I cannot tell you how many times I counted teeth on gears today but after the first hour I was mumbling unintelligible stuff that sounded like numbers. When I caught a look at the other mechanic in the room, he had a crooked smile on his face suggesting he rather enjoyed watching someone else doing this.


Question: How much should the end float be on the Layshaft?

Last edited by Semper Gumby; 09/08/21 12:42 am.
Joined: Feb 2007
Posts: 2,731
Likes: 55
Britbike forum member
OP Offline
Britbike forum member
Joined: Feb 2007
Posts: 2,731
Likes: 55
Patron Saint of BSA gearBoxes

Cont Von Count.jpg
Joined: Apr 2007
Posts: 903
Likes: 15
Life member
Offline
Life member
Joined: Apr 2007
Posts: 903
Likes: 15
Sounds like an attempt at a cheap solution. I think you now have a good starting point. Like others, I'll suggest that you now need the CR 1st set. Rabers or Morrie's Place had CR gears recently. Dont remember which way around it was though, but worth checking.

When I swapped out my STD for CR second I requested the same clearance between the pressed on gear and the freely rotating captured gear (2nd gear?) that is on the layshaft (#34 & #35 in parts book diagram). Might be worth checking that clearance. It wasnt much but would need to be there. I'd have to look back into my notes to see what it was. I think you are saying that the resistance is there hot, so could it be loss of clearance there as the gears get hot? If no resistance when cold that would support that. The question might also be how fixed are the pressed on gears on the shaft, because if knocked sideways there might be some binding?

Good luck. I think others have provided good guidance. Starting from a known point is always good.

Regards


BSA 1969 A65F
BSA 1966 A65H
Triumph 1968 T120
Kawasaki A1R
& too many projects!
Joined: Feb 2007
Posts: 2,731
Likes: 55
Britbike forum member
OP Offline
Britbike forum member
Joined: Feb 2007
Posts: 2,731
Likes: 55
Hi BB. Thanks. Yes the Layshaft top gear and second gear have clearance between them. It wasn't physically possible to make them bind together.

Another vote for CR 1st! There is a formula in the workshop Manual. Time to do Maths to see what you guys are talking about...

But if I do CR 1st I'll be left on the line by everybody (those Triumph guys) unless I drop the size of the Counter shaft sprocket. Then I will loose top speed?

Last edited by Semper Gumby; 09/08/21 2:30 am.
Joined: Aug 2001
Posts: 5,826
Likes: 169
G
Britbike forum member
Offline
Britbike forum member
G
Joined: Aug 2001
Posts: 5,826
Likes: 169
layshaft endfloat should be " just perceptible" ~ 0.003".


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Joined: Apr 2005
Posts: 2,822
Likes: 41
M
Britbike forum member
Offline
Britbike forum member
M
Joined: Apr 2005
Posts: 2,822
Likes: 41
Virtually no end float on the lay shaft. Just perceptible.

What gearing are you running? Are you allowed to use 34mm carbs?

I cannot see why mixing the gear pairs would do what you describe unless they are miss matched but that would be a bit hard to put together.

The lay shaft top gear should not move nor have reason to move. What pushes it? Was that big diameter sliding gear in the 3rd position on the main shaft pushing it? But it's only 23t instead of 22t isn't it and should not get it? It's only 2mm bigger? Can 3rd lay shaft gear push it?


mark
Joined: Feb 2007
Posts: 2,731
Likes: 55
Britbike forum member
OP Offline
Britbike forum member
Joined: Feb 2007
Posts: 2,731
Likes: 55
Yes Mark. The SECOND gear could push the layshaft Top - but why?

If the dogs on the sliding layshaft Third were worn (rounded) and not sharp then it could push a bit if it didn't go cleanly into the second gear?

Is there somebody who can re weld the dogs and make them sharp again? Heat treat or Nitritde?



There is somebody I must call...

Last edited by Semper Gumby; 09/08/21 2:17 pm.
Page 1 of 2 1 2

Moderated by  Allan G, Jon W. Whitley 

Link Copied to Clipboard
Job CycleBritish Cycle SupplyMorries PlaceKlempf British PartsPodtronicVintage MagazineBSA Unit SinglesBritBike SponsorBritish Tools & FastenersBritBike SponsorBritBike Sponsor






© 1996-2021 britbike.com
Powered by UBB.threads™ PHP Forum Software 7.7.5