Oh happy day....

[MG]

Good morning gents,

Be warned, long sad story ahead, lots of ranting and yammering and no happy ending to top it off.

Went for a 200 mile trip yesterday, and after getting soaking wet in sudden heavy rains, myself and the Flash had to take shelter for nearly an hour in a bus shelter as it started to hail, in the middle of nowhere.

Well, according to Mr. Knopfler, there will be sunshine after rain, so after it had stopped raining I continued my trip, wet but happy.

On the way back home however I noticed a quiet, but still evident rattling, metallic sound, especially at overrun, obviously coming from the drive side of the engine.
I stopped, checked for loose bolts or parts, couldn't find any, so started the engine and again heard what sounded very much like tappet noise.
However, engine power seemed fine, everything was working, so I decided to ride her home gently. The rattling sound got worse and worse, so I was glad to finally arrive back home safely.

Spent the rest of the day looking for the source of that sound, valve adjustment, dynamo chain, primary drive, etc. Nothing prooved to be the culprit, so I took off the sump plate and here's what I found in there:

http://img717.imageshack.us/img717/5749/blech.jpg


Having found these, I checked the conrod bearings with a screwdriver through the plug holes and found the lhs to have extensive play. OMG!
After this find I had to get myself a glass of red wine and started to think where these crumpled pieces of soft, thin (around 4 thou) sheet metal could come from. I still had absolutely no idea.
Well, after burning the midnight oil and the rest of the wine bottle I had the engine out and apart, and guess what I found:

http://img823.imageshack.us/img823/3466/buchselehre.jpg

The small end bush had obviously come loose in the conrod and rotated around. It has a play of more than 4 thou ALL AROUND!!! So there's the same amount of vertical and horizontal play, the conrod hole has not become oval!

What struck me immediately was a little groove that had obviously been machined into the conrod small end in axial direction. I can't remember having seen this on any rod before???

http://img638.imageshack.us/img638/4449/pleuelnut.jpg


When I bought the bike, the PO had the crank reground and I remembered him telling about new small end bushes he had bought and had fitted by his engine guy.
To me, it looks like some smartarse had "fixed" the loose bush with a piece of thin sheet metal, using the groove as an anti-twist measure.
 

Has anyone ever seen a groove like that in a BSA rod before? Any ideas where else these metal parts could come from? I am absolutely sure I didn't drop anything into the engine while assembling and always had every opening covered when not working on it, so I can definitely rule that out.

[fido]

Oh dear  Looks like you will need to measure up and examine everything in the engine if that's the sort of bodge they carried out. Is the thickness of the chewed bits consistent with the gap you measured?

[Brian]

Not a nice feeling when this sort of thing happens.

I would say there was a good chance the pieces of metal were wrapped around the little end bush to take up the gap.

The slot in the rod would have been made by someone using a hacksaw to slot the old bush to remove it.

Unfortunately you are going to have to dismantle the complete engine and have a very close look if this is the standard of workmanship by the bloke who did the engine.

Good luck with it.

[MG]

Thanks for your sympathy, guys.

Brian's hacksaw theory sounds good.
The thickness of the crumpled bits is very close to what the amount of play in the rod is.

When rebuilding, I have double- and triple checked and measured everything on the engine, the play in the big end and main bearings, the reground crank itself, I fitted new bearing shells, refaced folllowers, a new cam, new conrod bolts and nuts, had it rebored with new pistons, had the head reconditioned, etc., etc., the list is almost endless.

BUT: I have checked the play of the gudgeon pins in the small end bushes, which was absolutely fine. However, I have not seen the (most likely) bodge with the sheet metal around the small end bush, although I spent hours polishing the rods.
Who would think of something like that...
ARRRGHHHHH!!!  

I pulled the engine apart completely last night anyway, after I found the loose bush. The timing side bush and big end play look fine, but I have yet to take the rods off and measure the crank.

[fido]

I would press out the other little end bush to check if that is similarly shimmed.

[MG]

Yep, absolutely. Will do so.

[Hubie]

What cheap dodgy way to get rid of small end play and noise.  Makes you wonder doesn't it!

[MG]

What cheap dodgy way to get rid of small end play and noise.  Makes you wonder doesn't it!

"wonder" is not quite the word to describe my reaction....


However, I pressed the second bush out and this was absolutely okay, nice and tight. Had to heat the rod to get it out with reasonable pressure.

The big ends and timing side bearing are fine at least, zero wear on cams and followers, pistons and bores are as new, with the hone marks still visible. That engine would have had many many more miles in it.

I think I will go for a quick spin on the A7 now to get rid of my frustration. Good to have another bike in reserve.

[RichardL]

Marcus,

Sorry to herar of your woe, but impressed by how fast you got the engine out and apart. By the way "5-Hour Energy" is not the name of a wine.

Before seeing the rods, my first thought was crankshaft shims, but the reasoning seems right with regard to the small-end bushes.

If you end up replacing rods, you might find it ineresting to look at the MAP/SRM forged billet versions. They don't use bronze bushes, but just run the gudgeon pins through the aluminum small end, with the strength of the forged aluminum doing the job. 1600 miles on mine, thus far (what's that you hear, it's not the front door, it's me knocking wood -- my bow to superstition).

Richard L.

[MG]

Richard, the crank shims had been my first thought as well after removing the sump gauze, but the bearing race sits tightly on the shaft and the shim's okay.

As meanwhile I've ended up with a CR of almost 9.5:1 I guess this would be a good opportunity to go for a large journal crank and some new SRM rods. Running the gudgeon pins in the rod without bushes works pretty well on the AMC twins (and many lawn mower engines  ), so no concerns here from my side.
One part less that could cause grief (q.e.d.).

Taking the engine out of the s'arm frame and apart is a matter of maybe 1.5 hours, 2 if the darn crankshaft pinion won't come off. If you have the mounting bolts the right way 'round, the primary chaincase and clutch can stay in place, which saves a lot of time and work.
So no need for "5-Hour-Energy", the stuff that really "Gives you wings" is produced and canned here in Austria anyway!!!

At least the Shooting Star's running fine, some knocks on wood for me as well please, Richard.

Cheers, Markus

[A10Boy]

Markus, I think SRM can bore your rods and fit an over sized small end bush, unless I dreamed it...

[MG]

Well, as luck would have it, I just bought a large journal crank on ebay from a guy in Solihull.
This means I will need a pair of new rods to suit as well.

Thanks mate!

[A10Boy]

Yes ha ha. Which ones will you go for, SRM, Lightning or what?

[MG]

No idea yet, just had a look at the MAP ones, SRM's seem to be unavailable at the moment.

Any recommendations?

[chaterlea25]

HI Marcus,
I sympathise with your probs,
I have found through long and sometimes bitter experience that the one thing you dont dismantle /check /replace, or remove every stud and bearing that will be the first to give trouble

I would NOT use that rod again, "definitely hacksaw""  the BAST**D !!!!!

I have a long story regarding the "SR thing" thats spent the last 6 months on my workbench, it was bought from a "restorer/dealer" for top dollar and has proved to be totally knackered!!!
I have had to totally recondition the engine, fit the correct head, sort the mag and carb, the dynamo was full of rust!!
The gearbox needed 4 gears + bushes and seals etc, sprockets, chains
A complete clutch as well
All this ever before the poor guy ever gets to take it out for a spin!!!!
I should have it running this week and will put up a few pics of it

Anyway keep us informed of your progress
Best Regards
John O R