Author Topic: Transmission slipping at high revs and have no idea why  (Read 2011 times)

Offline owain

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Re: Transmission slipping at high revs and have no idea why
« Reply #45 on: 21.09. 2017 19:31 »
Yeah, I can confirm that the cush nut is fully tightened and pressing against the sleeve. And Yes Graybeard, I'm currently in the UK :)
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Offline Greybeard

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Re: Transmission slipping at high revs and have no idea why
« Reply #46 on: 21.09. 2017 19:55 »
The spring does not look like it is being compressed enough.

Is the cush nut fully tightened against the sleeve?


I agree. On my machine there is a definite gap between the split pin and the nut.

Offline owain

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Re: Transmission slipping at high revs and have no idea why
« Reply #47 on: 21.09. 2017 20:28 »
I can't get the nut on any tighter, there is about a 1-2mm gap between the pinbolt and cush nut. Perhaps grinding a few mm off the nut?  *conf*
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Online ellis

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Re: Transmission slipping at high revs and have no idea why
« Reply #48 on: 21.09. 2017 20:37 »
I cured my Cush drive riding over by grinding the splined sleeve down until the spring became coil bound so it would not ride over its self . As said many times before you cant be certain that all the parts on your bike may not be correct.   *smiley4*

ELLIS

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Re: Transmission slipping at high revs and have no idea why
« Reply #49 on: 21.09. 2017 20:42 »
The lobes on the engine sprocket look completely gubbed. If you can't get hold of a replacement, I most likely have one in my box of bits.
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Offline duTch

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Re: Transmission slipping at high revs and have no idea why
« Reply #50 on: 21.09. 2017 21:44 »

 I clicked through frame-by-frame, and something doesn't look right (at 0:09 it shows a gap between the spring and the sleeve much like mine, so i reckon it's not the proper diameter spring which affects the tension); Even with no spring installed, the nut should stop the sleeve from sliding further so the cam lobes should engage enough to drive (well mine does), and not pass over (not reccommended, but if yours doesn't engage, then I guess that's a substitute for a slipping clutch *conf*). Plunger and Swing arm components are physically different, and the *sliding* splines are different sizes and are not compatible, so can't mix them. Plunger model Spring-nuts are stepped so the sliding sleeve can pass over it (trying visualize that in my own mind now).
 If the spring Nut is fully tight, it *looks* in the right spot, assuming it's the proper one-hard to tell I think....perplexing, but we'll get it sorted; *dunno*
                               
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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
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Online chaterlea25

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Re: Transmission slipping at high revs and have no idea why
« Reply #51 on: 21.09. 2017 22:35 »
Hi Owain,
As far as I can see on the video, you have mismatched parts
The cam and sprocket should be a close fitting match without a gap between them
so no relative movement without the spring compressing
As said before the assembly should not be able to ride over when the nut is tight even without the spring

John
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Offline duTch

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Re: Transmission slipping at high revs and have no idea why
« Reply #52 on: 21.09. 2017 23:55 »

 I forgot to read Page 4 (this one) before I did my previous post, but just dug out my spare cush bits, and it appears that your sliding sleeve may have been shortened by at least 1/8"  *eek* .

 As can be seen in my pic the sliding sleeve hangs over the inner by ~ 0.028". You may be able to remedy (bodge) this with a packer shim on the minor diameter of the nut, but holding it in place (?- maybe with a light spring or squishy meal sleeve or similar) something to think about for a while *conf*
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
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Online ellis

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Re: Transmission slipping at high revs and have no idea why
« Reply #53 on: 22.09. 2017 00:02 »
I agree dutch, Just as I said in my post.   *work*

ELLIS

Offline duTch

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Re: Transmission slipping at high revs and have no idea why
« Reply #54 on: 22.09. 2017 00:36 »

 
Quote
but holding it in place (?- maybe with a light spring or squishy meal sleeve or similar)
...

 ... or silicon face to face


Quote
I agree dutch, Just as I said in my post.   *work*

ELLIS

 Sorry,  I might have not interpreted that properly, but I think I intended (but forgot ) to disagree with grinding any more, as I generally prefer to regenerate if possible, and was also distracted with other ideas  *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 duTch

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Re: Transmission slipping at high revs and have no idea why
« Reply #55 on: 22.09. 2017 00:59 »

 Actually Ellis - (not to be confused  with Ashley- or Shirley  *smile*), I'm still not sure which bit you ground, but I also don't like the idea of 'coilbound'....tholly *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 Klaus

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Re: Transmission slipping at high revs and have no idea why
« Reply #56 on: 22.09. 2017 09:51 »
I think the parts dont match together. It looks like a 4 loop sprocket connekted with a two loop part.

cheers Klaus


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Offline duTch

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Re: Transmission slipping at high revs and have no idea why
« Reply #57 on: 22.09. 2017 10:01 »
 Yeah Klaus, I reckon you're right *conf*.... my cross-eyes over looked that, would'na thought it possible but fairly obvious now I look harder  *bash* , but probably easier to find a two lobe one than a four lobe(?)
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

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Re: Transmission slipping at high revs and have no idea why
« Reply #58 on: 23.09. 2017 18:30 »
Righto, I've done the bodge fix for the disengaging cush drive and stuck big washer between the the end of the sprocket sleeve and the cush drive nut. My only concern is that, should the cush drive nut come loose (used loc-tite and pin bolt to keep it in place) then the washer could potentially knacker the thread on the crank....should the drive nut come loose.... :o
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Offline BSA_54A10

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Re: Transmission slipping at high revs and have no idea why
« Reply #59 on: 24.09. 2017 10:55 »
Yeah, I can confirm that the cush nut is fully tightened and pressing against the sleeve. And Yes Graybeard, I'm currently in the UK :)

Your cush drive is wrong.
You have a 4 lobe inner with a 2 lobe outer and that is a receipe for disaster.
What has been happening is the lobes have been passing over each other.
You can go either way, although the 2 lobe is a lot stronger than the 4 lobe.
They also use different springs.
The 4 lobe uses a square section spring and the 2 lobe uses a round section spring.
The square section spring comes in a dozen different lengths so finding the correct one is always a bit hit & miss.
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