Author Topic: Transmission slipping at high revs and have no idea why  (Read 2010 times)

Offline duTch

  • Ricketty Rocketty Golden Flashback
  • Wise & Enlightened
  • *
  • Join Date: Oct 2011
  • Posts: 4540
  • Karma: 41
Re: Transmission slipping at high revs and have no idea why
« Reply #30 on: 17.09. 2017 23:42 »

 John,  there's no plates in it.
 The pics are purely for demonstration to show the absolute extremity of pressure plate travel, (which won't happen with plates in ) , in answer to TT's question and to satisfy my own curiosity and also provide a possible answer to Owains dilemma... *smile*
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline owain

  • A's Best Friend
  • ***
  • Join Date: Mar 2017
  • Posts: 128
  • Karma: 2
Re: Transmission slipping at high revs and have no idea why
« Reply #31 on: 18.09. 2017 19:09 »
Well, I've cleaned all the plates (friction and plain) in petrol and used 400 grit wet sand paper on a piece of glass. Also placed 2 washers into each of the clutch spring sleeves. Didn't make any difference.

I'm pretty tired of disassembling and reassembling the entire transmission everytime I made a small alteration. So I left the transmission case and clutch cover off and had a look at the transmission when it's running...The clutch is working fine....What is not working very well is the shock absorber, with heavy load (given some throttle) the spring immediately compresses and transmission is lost. When I placed the shock absorber spring onto the crank spindle during the rebuilding of the engine, it went on very easily. I had to really struggle to compress the spring and get the nut onto my B33 but this spring went on with no squeezing needed at all. Surely this indicates that the spring is well passed it's due date?
Sweden & North Wales
'50 BSA A10
'69 BSA A75R

Online chaterlea25

  • Wise & Enlightened
  • *
  • Join Date: Jun 2009
  • Posts: 3175
  • Karma: 45
Re: Transmission slipping at high revs and have no idea why
« Reply #32 on: 18.09. 2017 19:41 »
Hi Owain,
WTF  *????* *????* *????*

Its a wonder that the crank or something has not broken????
If the crankshaft nut is fully tightened, which it should be *ex* tightened to 65ft/lbs
The cush drive assembly should not be able to "slip" even if there was no spring there

If the bike has been run with the nut not tightened fully any shims that are fitted to set the crank end float
can and will break up *sad2*

John
1961 Super Rocket
1963 RGS (ongoing)

Offline muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Join Date: Jul 2009
  • Posts: 8160
  • Karma: 106
  • Lake Conjola NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: Transmission slipping at high revs and have no idea why
« Reply #33 on: 18.09. 2017 20:55 »
G'day owain.
Something very amiss in there. The spring is either shot or the wrong one. There are 3 springs listed for our A's. 67-2052 = long stroke A7's,
67-2062 = plungers 50-57 and s/a 54, 67-1136 = s/a  55-62. I can't say the correct lengths but someone will.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Online Triton Thrasher

  • Scotland
  • Wise & Enlightened
  • *
  • Join Date: Feb 2009
  • Posts: 1478
  • Karma: 20
Re: Transmission slipping at high revs and have no idea why
« Reply #34 on: 18.09. 2017 20:59 »
If the cush drive cams were jumping over each other, that should have been noisy.

Offline duTch

  • Ricketty Rocketty Golden Flashback
  • Wise & Enlightened
  • *
  • Join Date: Oct 2011
  • Posts: 4540
  • Karma: 41
Re: Transmission slipping at high revs and have no idea why
« Reply #35 on: 18.09. 2017 23:45 »

 I busted a spring a couple of years ago, and was still able to ride around for a while with no dramas until I got around to having a bo-peep...
 
 I think it was making a bit of a clunk when I rolled it over with the kicker, but nothing much else untoward.....so having said that, I know the cams will still still engage without any spring at all, but can't remember if it still engages with a loose nut.

 Even though I ordered a new spring of the correct number, I think I was sent the wrong one (for S/A), or it's just crap- shorter and a bigger diameter , so it doesn't sit on the sliding /fixed sleeves comfortably (in fact I used a short length of SS exhaust pipe to sleeve over the sliding bush and nut, these sleeves don't spin or slide- just 'space'), so I now have some lash and a clunk at times when engaging kicker, and or in and out of the 'dead-spot' between power-on/power-off- otherwise it rides around without drama- (except the previous mentioned minor slippage), but WILL change it when I find a better one(note to self).

 I did a rant about it at the time- a search might find it, I'll try that later if need be.....but I don't think that's the problem of the clutch breaking loose; maybe owain you just over-charged the engine when you re-built it *smile*
 

Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline owain

  • A's Best Friend
  • ***
  • Join Date: Mar 2017
  • Posts: 128
  • Karma: 2
Re: Transmission slipping at high revs and have no idea why
« Reply #36 on: 19.09. 2017 15:04 »
I ordered a new spring from Draganfly (67-2062). It hasn't been making much of a noise tbh. It was only when I drove the bike around without the transmission cover on that I noticed it and only visually as well. Either way this spring seems well off, I have a feeling that I may accidentally placed the A10 shock absorber spring into my Triumph unit engine as I was rebuilding both engines simultaneously and in a messy workshop :S
Sweden & North Wales
'50 BSA A10
'69 BSA A75R

Offline duTch

  • Ricketty Rocketty Golden Flashback
  • Wise & Enlightened
  • *
  • Join Date: Oct 2011
  • Posts: 4540
  • Karma: 41
Re: Transmission slipping at high revs and have no idea why
« Reply #37 on: 20.09. 2017 10:54 »

 
Quote
........, I have a feeling that I may accidentally placed the A10 shock absorber spring into my Triumph unit engine......

  I've only owned one of them, and it was a T100R (Daytona) but I didn't think the Unit models had a cush-drive that you coud mix it...*dunno*
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline owain

  • A's Best Friend
  • ***
  • Join Date: Mar 2017
  • Posts: 128
  • Karma: 2
Re: Transmission slipping at high revs and have no idea why
« Reply #38 on: 20.09. 2017 21:28 »
Ah you're right dutch. I guess it's just a spent spring then...or just a bad mechanic ;)
Sweden & North Wales
'50 BSA A10
'69 BSA A75R

Offline owain

  • A's Best Friend
  • ***
  • Join Date: Mar 2017
  • Posts: 128
  • Karma: 2
Re: Transmission slipping at high revs and have no idea why
« Reply #39 on: 21.09. 2017 17:03 »
Righto, new engine shock spring arrived today. No difference in height with the old spring. The cush drive cam is still sliding over the on the sprocket. Starting the bike is now an issue as a forceful kick causes the cush drive cam to disengage immediately. The only thing I can think of now is that the cush drive cam and sprocket (type with 2 lobes on it) are badly worn. It does look visibly worn on inspection with heat marks at the top of each lobe and with one side of each lobe uni-laterally different in profile. Being a cheap bugger, I tried using a dremel to exaggerate the profile of the lobes on both the sprocket and cush drive cam, hoping that it would make it harder for them to slide past each other...no luck.

Is this a common problem with 2 lobe cush drives? Is there anywhere that I can get a new cush drive/sprocket and do you think this could be the solution?
Sweden & North Wales
'50 BSA A10
'69 BSA A75R

Offline Greybeard

  • Jack of all trades; master of none.
  • Wise & Enlightened
  • *
  • Join Date: Feb 2011
  • Posts: 5912
  • Karma: 32
Re: Transmission slipping at high revs and have no idea why
« Reply #40 on: 21.09. 2017 17:43 »
Try Andrew at Priory Magneto's. I may have this wrong but aren't you currently in the UK?

Online JulianS

  • 1962 A10
  • Resident Legend
  • *****
  • Join Date: Mar 2017
  • Posts: 960
  • Karma: 20
Re: Transmission slipping at high revs and have no idea why
« Reply #41 on: 21.09. 2017 18:05 »
Can you post photo of your assembly?

Online Triton Thrasher

  • Scotland
  • Wise & Enlightened
  • *
  • Join Date: Feb 2009
  • Posts: 1478
  • Karma: 20
Re: Transmission slipping at high revs and have no idea why
« Reply #42 on: 21.09. 2017 18:23 »
Can you post photo of your assembly?

Good idea.  Sounds like a mis-match of parts.

Offline owain

  • A's Best Friend
  • ***
  • Join Date: Mar 2017
  • Posts: 128
  • Karma: 2
Re: Transmission slipping at high revs and have no idea why
« Reply #43 on: 21.09. 2017 19:00 »
It won't seem to post any images on this thread :S. I recorded this video though, if that helps.
https://www.youtube.com/watch?v=-TvrxRBItd4
Sweden & North Wales
'50 BSA A10
'69 BSA A75R

Online JulianS

  • 1962 A10
  • Resident Legend
  • *****
  • Join Date: Mar 2017
  • Posts: 960
  • Karma: 20
Re: Transmission slipping at high revs and have no idea why
« Reply #44 on: 21.09. 2017 19:22 »
The spring does not look like it is being compressed enough.

Is the cush nut fully tightened against the sleeve?