Author Topic: Srm timing side big bush conversion  (Read 1141 times)

Offline Will

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Srm timing side big bush conversion
« on: 20.06. 2016 21:01 »
Hi just stripping my engine down and removed bush it has to much play , funny thing is measuring up crank it's 1.49 od ringing round no one does this size my crank appears to be to big , the big ends are standard a friend has told me he remembers srm doing a big bush conversion alongside the bearing conversion in early days ?????? anyone else remember this here are couple of pics of present bush

Offline muskrat

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Re: Srm timing side big bush conversion
« Reply #1 on: 20.06. 2016 21:11 »
That's an A65 size -0.010". A10 is 1.375".
The PO either modified a A65 crank or sleeved the A10 crank.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
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Muskys Plunger A7

Offline Will

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Re: Srm timing side big bush conversion
« Reply #2 on: 20.06. 2016 21:15 »
Ahh what size do the a65 come in the crank hasn't got sleeve , but the bush doesn't have the steel sleeve as normal , did the a65 come with small  big end journals 👍

Online RichardL

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Re: Srm timing side big bush conversion
« Reply #3 on: 21.06. 2016 14:11 »
measuring up crank it's 1.49 od ringing round

I'm not quite sure what you mean by the expression "ringing round". If you mean that, by measuring with a micrometer, the timing-side journal is 1.490" in diameter, then it's right around 0.009" undersized for an A65. That's too big for an A10, so, we must assume the journal has been ground down and the bushing replaced and reamed. An engine with 0.009" timing-side bush clearance would die pretty quick, I think.The tape measure in the picture isn't really infomative.

Quote
the big ends are standard

Did you measure the big ends with a micrometer? Standard for the A65, and later A10s, would be 1.687".

Richard L.

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Offline a101960

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Re: Srm timing side big bush conversion
« Reply #4 on: 21.06. 2016 16:51 »
Quote
I'm not quite sure what you mean by the expression "ringing round".
I think that you will find that expression means telephoning various suppliers to enquire what sizes they have in stock.

Offline Will

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Re: Srm timing side big bush conversion
« Reply #5 on: 21.06. 2016 17:39 »
Quote
I'm not quite sure what you mean by the expression "ringing round".
I think that you will find that expression means telephoning various suppliers to enquire what sizes they have in stock.


That's right a101960 , I measured with digital vernier not perfect but good enough the machinist will be more accurate

Online RichardL

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Re: Srm timing side big bush conversion
« Reply #6 on: 21.06. 2016 17:55 »
Quote
I'm not quite sure what you mean by the expression "ringing round".
I think that you will find that expression means telephoning various suppliers to enquire what sizes they have in stock.

I guess I was confused by Will's economical use of  punctuation. *smile*

Richard L
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline Will

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Re: Srm timing side big bush conversion
« Reply #7 on: 21.06. 2016 19:01 »
Quote
I'm not quite sure what you mean by the expression "ringing round".
I think that you will find that expression means telephoning various suppliers to enquire what sizes they have in stock.

I guess I was confused by Will's econimical use of  punctuation. *smile*

Richard L

It's been said before Richard 👍

Offline muskrat

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Re: Srm timing side big bush conversion
« Reply #8 on: 21.06. 2016 20:54 »
Now to add more confusion. OK that's the bush (std A65), now what's the size of the crank main journal?
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Offline Will

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Re: Srm timing side big bush conversion
« Reply #9 on: 21.06. 2016 21:56 »
Now to add more confusion. OK that's the bush (std A65), now what's the size of the crank main journal?
Cheers

Main timing side 1.49   crank is small journal std shells ?? I have found info about srm doing a similar conversion before they did the needle bearing conversion , a friend has a old srm catalogue with a description in it

Offline muskrat

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Re: Srm timing side big bush conversion
« Reply #10 on: 22.06. 2016 10:03 »
So the crank main journal must either be sleeved or built up with weld and ground back.
See if you can get a copy off your mate. I'd be very interested to see how it's done.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Offline Will

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Re: Srm timing side big bush conversion
« Reply #11 on: 24.06. 2016 19:08 »
Hi just heard back from srm it was a conversion they offered when they were based in Cardiff , the crank was sleeved then machined and a bush made to spec , they have said they will make a bush up for me , I will try and copy the info and post on here 👍

Offline muskrat

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Re: Srm timing side big bush conversion
« Reply #12 on: 24.06. 2016 23:07 »
Thanks Will. I wonder why they did that. I can't see that by sleeving the journal it would be any stronger (still relying on the parent metal and radii). Building up with weld and grinding back would be a bit stronger but I'd be worried about what the heat would do. But then all of my crank breakages have been at the crankpin  *red*.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Offline duTch

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Re: Srm timing side big bush conversion
« Reply #13 on: 24.06. 2016 23:59 »

 
Quote
...I wonder why they did that....
My two bobs worth is it gives a greater surface area to bear on
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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Offline Will

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Re: Srm timing side big bush conversion
« Reply #14 on: 26.06. 2016 11:46 »
Hi Muskrat took some pics today you will have to enlarge it to read or I can email you pics 👍