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Re: Off Topic - A10 Timing Side Bush Replacement

Hi Dean

Thanks for this.

I had a trawl through this website.

It's very good. However, I couldn't find the tolerances for that bush. End float seems to be under 3 thou.

I will post something, but feel starting a thread on the timing side bush is a bit like starting a thread on what is the best oil to use. All the regulars will have seen it before and probably a bit bored of it.

Regards

Pat

email (option): sacombsashtrees@hotmail.com

Re: Off Topic - A10 Timing Side Bush Replacement

Pat, I don't think you should worry, I've never found them to have that kind of attitude.
I hope you find your answer (says he somewhhat red faced as a long term multiple A10 owner!)

An alternative is to ask SRM, I have also found them pretty helpful and again have many years A10 engineering experience.

Re: Off Topic - A10 Timing Side Bush Replacement

Patrick Meagher
Hi Dean

Thanks for this.

I had a trawl through this website.

It's very good. However, I couldn't find the tolerances for that bush. End float seems to be under 3 thou.

I will post something, but feel starting a thread on the timing side bush is a bit like starting a thread on what is the best oil to use. All the regulars will have seen it before and probably a bit bored of it.

Regards

Pat

Then ask.
It helps if you start with " I have been searching the old threads but can not seem to find one with the tollerance for the bush mentioned "
Then one of 3 things will happen.
1) musky will direct you to the appropriate previous thread
2) You will start an arguement amongst the members about what the clearence should be
3) you will get 200 answers, none of which will answer your question.

Where ever possible I turn up my own bushes from 85-5-5-5 gunmetal.
It seems to work best for me.
Trev in Oz relines old again with 85-5-5-5.
Measure your crank very carefully because a very slight out of round will eat a bush in no time flat as will a slight skew in the alignment between the holes in the cases or if it not in line with the crank.

email (option): bsansw1@tpg.com.au

Re: Off Topic - A10 Timing Side Bush Replacement

Thanks Trevor.

I think I will go for 1.5 thou between bush and crank and fit a spin on filter on the oil return line.

Regards

Pat

email (option): sacombsashtrees@hotmail.com

Re: Off Topic - A10 Timing Side Bush Replacement

End float should be .003"...Shims should be fitted behind the bearing against the flywheel cheek...Check the end float with a DTI after the crank is fitted to the cases...

Years ago when I had many A7s and A10s I kept an old bearing the bore of which I opened out slightly with a flap wheel to ease the fit on the crank...That made the job easy and avoided the risk of damaging a new bearing.

SRM also supply good quality bushes as well as their more expensive end feed conversion but I guess they are not in the habit of offering that as a first option...Ian

email (option): ian@wright52.plus.com

Re: Off Topic - A10 Timing Side Bush Replacement

Hi Ian

The cases and crank are at a local firm just now for accurate measuring.

From there, I will know what undersize I/D bush to get from SRM (I am going for a solid phosphor bronze bush). I will go for one that has plenty of material for the guy to work down to.

I want the minimum off the crank and bore the bush to fit.

He can use the old drive side bearing for the shimming (good idea of yours).

I have done this job twice (badly and without the correct measuring tools), must be in excess of 30 years ago now and the bike has been sitting on its bearings in the barn since then.

The problem with the conversion is that you end up persuading yourself that since you have spent so much you might has well go for the full monty e.g. buying one of their pumps.

Regards

Pat

email (option): sacombsashtrees@hotmail.com

Re: Off Topic - A10 Timing Side Bush Replacement

The original 'end feed conversion' was developed by BSA for Chris Vincents factory sidecar bikes which as you can imagine worked under pretty extreme loads...

This was picked up by Devimead who offered the conversion to A65 owners as an upgrade to the oil supply for road use. There has always been some debate about the necessity of this conversion and one chap I knew who ran a business specialising in A65s wouldn't fit them. He argued that a correctly fitted bush made of the correct material and oil changes at the correct intervals was sufficient..His own daily bike was an 850cc Lightning which he ran thus equipped for years, which at least indicated he may have been right...

My own view is that the problem of exploding A65s is a fault in the con rod material/design...not the oil supply. Personal experience during the autopsy of the two I blew up indicated that was the problem....

Regarding A10s they didn't even have a problem, being renowned in their day as a high mileage bike..I knew an old boy in Plymouth who had a Gold Flash that had done over 200,000 miles from new and had never had the bottom end stripped down...I also did scores of thousands of miles on various A10s and A7s...The only timing side bush failure I had was with an RGS which had been built with odd crankcase halves and I ran two bushes before realising what the issue actually was...crank misalignment...

Devimead sold out to Steve Mc.Farlane and SRM came into being (his initials)..After some years he sold out to the current SRM management who retained the name....

Business is business and under their control the conversion was also offered for unit Triumph engines fitted with a bush as standard...Another engine that didn't really have a problem with the bush in the first place...

Like wise with upgraded oil pumps...There was no deficiency in the oil supply of an A10 that indicated a pump fault...

What you have to remember is that SRM (and any other business selling 'upgrades') are looking for business, so any opportunity taken to play on peoples worries will produce beneficial results for them...

I'm not a member of the flat earth society and have upgraded certain aspects of many, if not most, of the bikes I have owned both with my own mods. and bought in products. However, the first consideration before buying should be is there actually a problem that needs solving?...

It shouldn't be assumed that all such upgrades are needed just because they are being offered.....

Personally I think the classic bike media are also complicit in this possible deceit...In the back of the classic bike guide for example, I remember reading the comment...'BSA A7/A10. One of BSAs best sellers from the 50s, benefits from bottom end conversion'....If you read that again it is actually a contradictory statement.. It's suggesting one of BSAs best sellers had a basic fault....Hmmm....

Personally I would argue that is not the case....People are assuming it is, based on various magazine articles, a lack of experience of the particular engine and chatter at the clubhouse...

If as stated, the timing side bush is really so problematic and the end feed conversion is really so necessary why, as a supposedly honest supplier, are SRM still selling them?..

It's actually because they know that the bush will work and that not everyone is prepared to pay for their conversion...and at the end of the day they still want that customer...Ian:laughing:

email (option): ian@wright52.plus.com

Re: Off Topic - A10 Timing Side Bush Replacement

Gees Ian,
You and I are in agreement again.
Interesting that you had bottom end failures as all I have known about were from the USA .
I put most of these & the A65 ones down to ring flutter allowing oil to litterally blow out the exhaust when running WFO for long periods as is the want of Americans, particularly on the West Coast with single straits longer than the UK is wide.
I never thought about this till talking to Prof Falco and his analogy between riding positions & saddles on horses makes perfect sense to me as I do some thing similar depending upon which side of the hill I am riding .
The one & only case of left rod exitus I know of down here was on a bike owned by a very fast rider and when he pulled down the engine there was almost no oil in the tank ,but it was dripping out of the pipes.
He had been "dragging" some one on a rice burner for miles of expressway when it happened when he backed off to enter the fuel station.

And yes a plain Tin-lead babbit slippers was not a good idea in a short stroke high compression engine and I always recommend not using NOS slippers when people rebuild bottom ends.

Never seen an A10 throw a rod.
Have seen a few A 7's fitted to go-carts do this but the 9000 rpm probably had more to do with that.

Too much oil and too much oil pressure can be just as destructive as not enough .
And double ditto on the business that fuel the hype of the ignorant encouraging them to print misinformation to the uninformed.
Valve seat replacements for unleaded fuels is the perfect example.
Something that only happened in aircraft under lean burn conditions at high altitude being extrapolated to rich running engines at sea level.

email (option): bsansw1@tpg.com.au

Re: Off Topic - A10 Timing Side Bush Replacement

A quote on the A10 from Classic Bike Guide Feb 2018:

"SRM main bearing and uprated oil pump conversion are plusses when looking to buy".

A quote on the A65:

"Specialist engineering sorts suspect bottom end oiling, as in all BSA twins".

Regards

Pat

email (option): sacombsashtrees@hotmail.com

Re: Off Topic - A10 Timing Side Bush Replacement

Quotes from journalists...and from journalists who may well never have ridden or owned either bike or really examined and thought about anything regarding the design and construction of the engines mentioned...

What journalists do generally is talk to a few people in the trade and an 'expert' or two and then sift through the answers they get to create an article...
The resulting article is therefore constructed largely from the knowledge, opinion, experience and crucially, bias and possible vested interest of others...That makes checking the facts a bit hard for the writer...

It has to be said that it's a system that works OK generally but has the inbuilt weakness that the accuracy, truth and logic received by the writer depends entirely on those they choose to talk to...Additionally, I feel information provided by experts who have something to sell should, logically, be treated with caution and thoroughly checked...

I tend to read old copies of the Blue 'un and Green 'un when seeking enlightenment...Back in those days the journos were often ex industry men or were keen clubmen and riders who knew the practice and theory of their subject and crucially, were passing on 'first hand' information based on their own experience...

I believe that's why the older magazines contained much more hard technical information as opposed to the 'riding impressions' so prevalent in todays publications..

I read an article in one well known magazine written by a so called 'tech' (how I hate that expression) on the use of measuring equipment. It was memorable only for its inaccuracies (ironic or what?) and was plainly written by someone who didn't fully understand the subject...

Sadly, whilst someone well versed in a subject will soon see through a 'fake' expert, those less familiar will simply absorb the information provided as fact...

Eventually the whole thing becomes part of 'folk lore' knowledge, is enshrined as fact and the person that disagrees with the accepted wisdom is written off as an eccentric (at best)........

That brings us neatly back to timing side bushes..:laughing: ...Ian

email (option): ian@wright52.plus.com

Re: Off Topic - A10 Timing Side Bush Replacement

Bloody hell Ian,
Agreeing with you twice in the same thread, unheard of.
I stopped buying all modern "Classic Bike Mags" back in the 90's for just that reason.
All eye candy and no brain food.
Even worse was an article that requoted some lines from an 80's motorcycle magazine.
"BSA was doomed to failure, there is no way they could make modern motorcycles to close tollerances using all of that worn out machinery that was so old all of the calibration marks had worn off "
Who ever wrote that story has never worked a capstain lathe like the one in the accompaning photo clearing showing no markings.

In the 80's I was an occasional contributor to all 3 local motorcycle magazines.
AMCN was written by full time motorcyclists, usually racers.
The others were written by by people many of who could not ride.
The editor of Two Wheels ( which has just closed down ) was also a sub editor of Surfing Aust, Cricket Aust & Ski Slopes.
There was no full time motorcycle staff, apart from the testers ( and some of them did both cars & bikes ) every one else contributed to 2 , 3 ,4, or 5 other titles.

email (option): bsansw1@tpg.com.au

Re: Off Topic - A10 Timing Side Bush Replacement

['Bloody hell Ian, Agreeing with you twice in the same thread, unheard of...']

:laughing: :laughing: ...Maybe you're mellowing out in your old age...I wouldn't worry though, it's probably a passing phase and normal service will be resumed on the next topic of discussion...Ian:volcano:

email (option): ian@wright52.plus.com

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