The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Rich on 19.05. 2013 18:38
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Will araldite fix this?
Large journal crank required
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HI Rich,
The cause of the disaster is almost certainly down to incorrect grind radius when the crank was ground previously
*sad2* *sad2* *sad2*
Sorry cant help with a crank, they come up on fleabay fairly regularly but are getting very expensive *ex* *ex*
HTH
John
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Not the recommended way to remove the sludge trap ;)
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Bugga, but the cam still looks OK, how about the cases?
I agree with John, bad radius. They should be 80-90 thou and almost a mirror finish.
Cheers.
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Cases, conrods all ok.
just over a year ago, at Shepton Mallet I sold a large journal crank on -30thou thinking I would no longer need them, but kept my thick flange barrels in case I ever did, wrong decision.
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I'd get the rods checked for alignment.
Cheers
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OMG!
That is awful. I hope you are able to source a crank quickly. What speed were you doing when it failed?
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I have a crank I picked up as a spare from ebay but I have not measured it so it probably needs a grind, I could measure it if you have not sourced one yet. I think I paid £100 odd quid for it a couple of months ago
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Even tho the exact thing happened to me on an LJ crank (59 Super Rocket) over 35 years ago so this looks horribly familiar.....I concluded it was the incorrect radius at the edge of the journal.....the machine shop I used to regrind the ends on that crank did not seem to be aware how important that was, although to be fair, I did not either, so did not give the shop the instructions on radius required, or check the crank after the grind.
One thing to remember when buying a crank, it's generally not possible to correct an incorrect radius, once the metal is gone, you can't put it back!
On my SJ crank the machinest just did the best he could given on the prior grinds the radius had been made a bit small, and I only wanted a grind down to the next undersize.
Out of interest, does anyone know if this same mode of failure occurs on SJ cranks? Or is it just a problem with LJ?
From what I've heard, contrary to popular opinion, the SJ crank is not THAT much more prone to failure than the LJ, even under race conditions.
The SJ has wider journals than the LJ, so big end bearing area is not that much different to the LJ, and the SJ has a smaller sludge/oil supply drilling through the journal (not that that part of the journal adds much strength anyway).
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Thats a bad bit of luck there. Hope it didn't take too much out with it.
Regarding small-journal cranks.....yes, they do fail in the same way! I had one go in a similar manner on my first A10 many years ago. Funny enough, nothing came apart, just locked up. Wasn't until it came to splitting the cases that the breakage became apparent.
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Yep, had two A7 SJ's go. One on the right and one on the left. But wasn't doing your average road speeds *eek*.
Cheers.
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I have only just aquired this bike, previous owner now passed away, however apparently he had a problem whilst riding in France but managed to get back to blighty, and the engine was turning over ok, but a low down small clunk could be heard, if you look at how it has broken, when it was all together it was sort of keyed and turned ok.
Biker boy where are you situated, as I may need the crank, I am just waiting for another person to look in his workshop and should know later today. I expected to have to have a regrind on all journals on any replacement as would not be able to afford one that was completley done, that way a bit out of the pocket bit by bit.
I will be checking the rods for alignment today, but initially they look ok, as previously stated the enginge was turning over ok but had this slight clunk, so in one way it was lucky as I think the crank just cracked in stages, looking at the stress marks on the break and stayed together.
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Looking at that pic again, dont you just love the way the sludge-trap-plug threads end exactly under the fillet radius? *eek*
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Biker boy I have sent a PM to you
Regards Richard
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Got it and replied :)
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There is actually a crank on ebay uk
http://www.ebay.com/itm/ws/eBayI:SAPI.dll?ViewItem&item=350800104671&ssPageName=ADME:B:SS:US:1123
Sincerely Rudolf
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Thanks now on my watch list, just need to check to see if A7 and A10 are the same.
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LJ's only come in A10, same with TF barrels. Do you need A7 or A10?
Cheers
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A10 large journal
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Rich
Keep an eye on that crank that's a great price, will ring you over the weekend
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any idea what time over the weekend?
As for the ebay crank you can bet your last dollar that the price will increase and if I bid someone will have a snipe on it, I have been unlucky with Ebay and prefer to buy at a fixed price, that way you know if you will get the part that is required.
Speak to you soon
Regards
Richard
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less than two hours left and the price has soared but I am still hanging in £162 how much further have I gone? time will tell
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What did I tell you, I had a high bid on the crank as to be honest I was willing to pay for a crank on standard just needing a first regrind, but in the last 2 seconds a bid £5 higher than mine won it.
I am still looking for an A10 crank and would prefer not to rely on Flea bay
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opps = ouch = bugga. Those cranks are getting pricey, $350AU. Did you use a sniper? I've been beaten a few times by $1.
Cheers
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no but I bet the guy that won it did,one will turn up sometime, meanwhile the bike will stay on the ramp in the workshop waiting.
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http://www.ebay.com.au/itm/BSA-A10-SUPER-ROCKET-GOLD-STAR-BIG-BEARING-CRANK-/140986475876?pt=UK_Motorcycle_Parts_13&hash=item20d372e564
Cheers
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already made an offer as £250 is a lit of money when you add the cost of egrind and a bush and in line boring, I still do not like Ebay
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well I had my offer rejected so I bit the bullet and paid £250 + £15 carraige, I hope it is worth it when it arrives, Biker Boy will know what I mean
left hand footrest tube next part to source
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HI All
The splines are well worn on that crank *sad2*
They can be built up and remachined, I have had SRM do this on a couple of cranks
John
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It will be going to a machine shop in Witney, whatever needs doing he will do and at a cost a bit less than SRM would charge and the job will be as good, plus the fact I can get it there without having to post it.
Thanks for pointing that out, a big cloud has just appeared over me to add further to my depression.
As I had decided not to buy any more bikes and also sell some just to keep the B25 and my Hinkley Triumph,just over a year ago at Shepton Mallett auto jumble I sold a large journal crank in good overall condition just needed a regrind for a lot less than I have paid, however without a crank I have a bike that is useless.
The good news is that I was told yesterday that the thick flange barrells I have also in good condition with no broken fins could be worth £3.50 to £4.50.
Should I part with those and a matched set of genuine super rocket crankcases to pay for all the work?
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Keep the barrels. Remember you thought you'd never need that crank. *problem*
Cheers
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If the Machine shop asks, the crank material is EN40B.
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Thanks
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Rich
Glad you got sorted I have been away all week so never got chance to check that crank. Don't sell the barrels or the cases, unless you need the money, they are only going to go up in price *smile*
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just am update as John pointed out the splines were worn, anyway when it arrived it was well worn and the main roller bearing just slid on and off the shaft so that needed grinding and resleeving as well, the total cost made this crank no go,as the guy who was selling it was aware of the worn splines, by implication when we were conversing, he had no choice but to offer me a full refund including the P&P as it was a buy it now,all because he put no description about the wear on the crank, in fact he put no details other than what the big end and main journal sizes were. EBay even sent me a pre paid label FOC to return it by Parcel force and informed me the seller has to refund within 3 days of receiving the crank back.
So once again I wait for the ever elusive crank
This transaction remind me of my late fathers favorite saying "fools rush in where others dare not" at my age you think I would have known better.