Disaster

[mark]

Finally got the 55 Road Rocket registered after a 2 year restoration, Took it around the block a couple of times, made sure that there were no obvious issues then took off on its first trip. With 10 miles showing on the speedo an ominous knocking noise was heard from the engine and the bike was trailered home. Upon stripping the engine it was found that one big end journal had peeled away its surface, destroying the bearing  and circulating a fair bit of material through the engine. It appears that the journal had been built up some time in its past, the chap that did the machining on the crank commented at the time that it looked like it had been built up but thought that it would be fine. I am now trying to source a big journal crank and have put a few feelers out but if any forum members here in Australia can assist it would be much appreciated
Regards
Mark

[muskrat]

G'day Mark,
                any luck finding a crank yet ? Don't often see them here but do turn up on ebay in the US now and then. Expect to pay around the $250 + mark and post from US would be another $150 or so. This one just finished but didn't reach reserve 220814899707 .
 Might be worth grinding yours back and building back up properly.
Cheers.

[Hubie]

G'day mate,

I bought one of Terry Kennedy (forum member here) a while ago.  First class item from a first class bloke, he informed me that he's only doing plunger and rigid frame BSA'a now but does has some swingarm stuff.  Might be worth sending him a PM.  Where in Melbourne are you mate?  I thought I was the only one on the forum from Melbourne!

Cheers,
Hubie.

[mark]

Hi there Muskrat and Hubie, I have tracked down a couple of cranks but both have the timing side main already ground down 20thou and I'm hanging out for one that will clean up to suit my "new" bush at 1.3665". I am waiting for Mike Reilly to get back from overseas to see what he has and then I will get the one that best suits me. Another one available has standard big ends but the timing side is -40 thou, this wouldn't matter if I was going to replace the bush but I'm trying not to as it is new. As far as building it up, I'm a bit wary as it looks like that is what failed and the 2 people I have contacted about a possible repair have both had reservations. I will try to contact Terry as well.  Hubie, I am at Hurstbridge.
Regards
Mark

[terryk]

I sold a couple of LJ cranks a while back with some swingarm A10 stuff but they were on last grind. I only have one LJ crank left but its with a super rocket basket case. I do have swingarm A10 parts that I'm selling if you are chasing anything email me. I also have bits for BSA bantam,M20/21,B31/33, A7/10.

Put BSA parts in the email subject or I could junk it.
gflash11@hotmail.com

[mark]

Got a Crank from Mike, standard big ends and timing side which means I won't have to replace the bush. Hopefully it will be back on the road in a couple of weeks.
Mark

[A10Boy]

Mark

standard big ends and timing side which means I won't have to replace the bush

Presumably you have an undersize bush and there is enough meat there to line bore back to STD?

[mark]

The ruined crank was ground to -8 thou and the bush machined accordingly, that is why I was hanging out for one that could be machined to the same dimensions. Hopefully this one will do the job.
Mark

[A10Boy]

Yes, but you're not going to machine the crank to fit the bush, you're going to machine the bush to fit the crank right? The crank journal might need a slight grind to clean it up of course.

[muskrat]

Mark I tend to agree with Andy. Why waste the extra life of your new crank just for the sake of a bush. Throw a new std bush in and get another 50K out of her.
Cheers

[mark]

Sorry for the delay in replying but I've just done a 10 day jaunt to Birdsville and back (only us Aussies will know where that is). I never really expected to get a crank that was still standard size but wanted one that would at least clean up to the same size as the other. When I said standard I meant that it hadn't been machined before but it will need to be machined true and it seems that there will only be a couple of thou difference between it and the original one, so there isn't much point in machining a new bush for such a small saving. 
regards
Mark

[orabanda]

Hi Mark,
Are you intending to use the existing timing bush (the one that was installed when the crank failed)?

Richard

[mark]

Richard, yes the intention is to use the existing bush as it is new and doesn't appear to have suffered whan the crank failed. As I mentioned earlier, it has only done 10 miles. The engineer doing the work for me has measured it all and has said that the new crank will machine up to suit the existing bush and will have needed to be machined fairly closely to that size (-8 thou) anyway. The original bush was machined to suit the original crank after it had been cleaned up but I feel that it will be easier to only get the crank machined rather than take the minimum off the crank and machine a new bush as well. Do you see a problem?

Mark

[orabanda]

Mark,
It is possible that the new bush is now out of shape (oval) or the bore (surface) is damaged because of the crankshaft journal failure. I would be surprised if it wasn't.

The required clearance between bush and journal is 0.0015", with 0.003" being the wear limit. I have dismantled running engines with a lot more clearance (up to 0.008"), but oil pressure will be lost at the greater clearances, and the risk of throwing a rod is increased.

If you have enough material on the crankshaft journal, I would be tempted to get the machinist to clean up the bore (take a lick out) so that you know it is concentric, and has a very fine finish. THEN grind the crank to 0.0015" clearance.

Richard

[mark]

Excellent suggestion Richard. I will speak to him tonight.

Mark

[A10Boy]

Given that cranks are now a limited resource, and bushes can be easily made, it makes sense to grind the minimum from the crank journal [enough to clean it up], and machine whatever is required to get to the  1 1/2 thou clearance from the bush. If the bush doesnt have enough meat to do this, replacements are cheap.

[orabanda]

In this instance, 6 of one, half a dozen of the other.
Hence my qualification "If you have enough material on the crankshaft journal......."

If either the bush is not machined true, or replaced, there will be tears!

Richard

[A10Boy]

Mark, good luck with whichever way you choose.

[mark]

Thanks guys, Will let you know how it turns out.
Mark

[mark]

Well it's finally on the road. The crank turned out well, we used the existing bush. Treated it to some new pistons as the bore had some light corrosion marks that the honing didn't quite remove. This turned out to be disaster #2. The pistons came from a well known Melbourne supplier of British motorcycle parts and he said that he had never had a problem with them. The ring gap on one ring was 25 thou and a couple of others were also too big so I exchanged them for better ones.  It pumped so much oil past the rings that it was dripping from the exhaust. He begrudgingly gave me another pair of oil rings which did exactly the same thing. I should have been alarmed when the rings seemed to come from a drawer of rings and not supplied as part of a piston set. So I bit the bullet and ordered a set of Wiseco forged Pistons from Cake St Classics which were promptly installed and all is good. Took it for a run today and no problems. Off to the National BSA rally next weekend in South Australia which should run it in nicely. Any one else going?

Mark