Author Topic: A7 Timing side bearing upgrade  (Read 1125 times)

Offline Bsa Nut

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A7 Timing side bearing upgrade
« on: 24.11. 2016 17:09 »
What is the general opinion of upgrading the timing side bronze bush with the needle bearing conversions??
Worth the money??
Anyone in the States recommended to do the machining/fitment??
Approx cost??

Thanks in advance!
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Online RichardL

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Re: A7 Timing side bearing upgrade
« Reply #1 on: 24.11. 2016 18:10 »
I think you should ask SRM if they have agreements with any US shop. I know of one shop who advertises the work but, unfortunately, I wouldn't let them work on my engine again. Sad, because there are so few shops specializing in this. If you share who SRM suggests, I'll PM if it's a match with my warning and why. Not going to blast them in open forum.

Richarx L.
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Offline Bsa Nut

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Re: A7 Timing side bearing upgrade
« Reply #2 on: 25.11. 2016 00:44 »
May fit the new bushing accordingly and rock on.
;)
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Offline BSA_54A10

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Re: A7 Timing side bearing upgrade
« Reply #3 on: 25.11. 2016 10:01 »
Unless you are racing the std bush is more than adequate.
The fact that there are thousands of A 10's still running around 50+ years later should tell you it is a good set up.
Now if you are running an RR or SR, things might be different.
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Offline coater87

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Re: A7 Timing side bearing upgrade
« Reply #4 on: 25.11. 2016 11:36 »
 There was a shop on the far east coast advertising this last year at $1400.00 for the conversion. Now add in shipping cost and what-not and it is not a price to be sniffed at.

 Richard, I think Frank might have died, I dont see his ads anymore.

 Lee
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Offline Topdad

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Re: A7 Timing side bearing upgrade
« Reply #5 on: 25.11. 2016 12:14 »
Hi BSAnut , how you doing . re your question When I put my A10 back on the road I decided on the conversion as I wanted to make sure it out lasted me ,that was 10 yrs ago and still great , costly but IMHO worth it , cheers Bob
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Online a101960

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Re: A7 Timing side bearing upgrade
« Reply #6 on: 25.11. 2016 12:55 »
Quote
Unless you are racing the std bush is more than adequate.
The fact that there are thousands of A 10's still running around 50+ years later should tell you it is a good set up.
Now if you are running an RR or SR, things might be different.
BSA_54A10, I have to agree with you. There is a picture featured in Roy Bacons BSA TWINS AND TRIPLES book captioned "A very well used police flash which covered 120,000 miles on the original crankshaft" No doubt many of you will already have read the book and be aware of this. Of course police motorcycles were all well maintained and had regular oil changes, but as far as I am aware no additional external oil fliters were fitted, and of course all those years ago the bikes would have been run using straight oils. Interestingly  enough despite the alleged A10 plain bearing “Achilles heal“problem, A10s appear to be regarded as solid reliable motorcycles in most of the press reviews that I have read. The roller bearing conversion concept was a product of the BSA competition shop inspired by Les Mason originally for the unit twins as a result of racing experience, but it was not adopted for production bikes, no doubt due to the cost of re-tooling. There is no doubt that this is a good mod for racing bikes, and I do not doubt that it is beneficial for road bikes, but the original plain bearing has served well for many years. Regular oil changes are the key to reliability.
John
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Offline Bsa Nut

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Re: A7 Timing side bearing upgrade
« Reply #7 on: 25.11. 2016 14:40 »
Thanks everyone....I've seen prices from $1400-$2300 for the conversion.
The bushing is about $80.00, with the balance I'll buy lots of fresh oil. LOL
This is just an old Star Twin...wont see but a few thousand miles a year.
;)
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Online KiwiGF

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Re: A7 Timing side bearing upgrade
« Reply #8 on: 25.11. 2016 18:35 »
Urban myth around here is that reputation of a bad main bearing design has resulted from poor attempts to replace them when the engine had its first overhaul, failing to clean out sludge traps of grit afterwards, and not grinding a radius on the big end journals. Some tips below,which are elsewhere on this forum, and it's worth reading up on this topic.

Line bore the new journal
Bore the case if the housing is oval or worn, then fit a "one of" oversize o.d. bearing.
Only grind the minimum of the crank to make it round, then machine the bush to suit.
Get the end float correct afterwards, using a single thick Shim is best.




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Online muskrat

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Re: A7 Timing side bearing upgrade
« Reply #9 on: 25.11. 2016 19:41 »
I tend to agree. The first thing I did to my A7SS race motor was to convert to roller and still works very well 25 years later (I check the oil pressure gauge more than the speedo).
 My plunger got a new bush 33 years ago and still good.
Cheers
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Offline BSA_54A10

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Re: A7 Timing side bearing upgrade
« Reply #10 on: 26.11. 2016 12:37 »
Ill put it this way.
Rhett bought a cheap A 65 with 20,000 is miles on the clocl.
He go it cheap because when hot the oil pressure lamp wold stay on till a bit over 1500 rpm.
He bought a back up bike which he sold some 15 years latter as he realised his bottom end was going to outlive him. and it did ( almost ).
Rhett works a funny shift, 8 days on 4 days off and only rode the BSA for fun.
he changed the oil almost every time he used it and ended up selling the bike some 25 or so years latter with over 80,000 miles on the clock, and the same bodgy bearing with low oil pressure when hot.
The next owner threw a rod within a year.

I have a theory about the "weak crank" storys that all seem to eminate from the USA.
If you run an A65 at or above redline for any length of time you blow oil out the exhaust and out the breather.
So what I have always assumed to have happened is on one of the long strail highways the USA riders opened it up and left it there, eventually blowing all of the oil out the breather.
When running Penzol in my A65 to Goulburn flat out to a rally I was about to miss the start off, I blew the entire contents of the oil tank out of the overflow/breather tube.
That was in the days when you could do 100 mph plus all the way Sydney to Goulburn.
Had I not stopped for fuel at Merulan and noticed everything on the back was oily we would have blown the engine before we got to the TT rally
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Offline Clive54bsa

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Re: A7 Timing side bearing upgrade
« Reply #11 on: 27.11. 2016 00:44 »
I spent a lot of money having the SRM bearing conversion done. The bearing broke up after 13,000 miles, I bought a new one from Canada, the suppliers told me a 1% failure rate is acceptable. I rebuilt my '54 Golden Flash with the standard bush, and after over 8000 miles it's perfect. My feeling is, if I was going to race it or use my bike as every day transportation, and lived on the west coast of Wales, I would consider it. But as a pleasure bike and changing oil as frequently as 500 miles, don't bother.
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Offline Rocket Racer

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Re: A7 Timing side bearing upgrade
« Reply #12 on: 13.12. 2016 04:12 »
The star twin's are such sweet motors, a bush is the way to go: these are thin flange small journal motors not known for giving trouble if the sludge trap and oil is clean.
 save your money  ;) .

If it was a 650 race engine a timing side conversion is a good idea.
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