Big ends on a 1913 2+3/4 - urgent help please !

[phil_h]

I went out for a shakedown run today - Banbury next weekend - and had to push home after a sudden bottom end clonking
Luckily I was 'only' about a mile from home.
I 'popped off' the rear cylinder first, and it seems that the rear cylinder big end nuts have come loose.
I was able to unscrew the nuts by hand , but cant get the rod off the bolts though. (They have sort of screwdriver slots)
Is there a trick ?
I'd really like to see if the shells and crank are ok before I think about a complete engine strip right now !
That would give me a way to look in the cases too of course.
What is then the best way to secure the nuts ?
phil
pulborough, w.sx.

[eddie]

Phil,
      If your con rods are standard, you will find that they have phosphor bronze shells in the big ends. You will also find that there are 2 keep plates ( about 60 thou thick) that prevent the shells turning in the rods. The whole assembly is clamped up by 2 square headed bigend bolts - these bolts are split on the threaded end so that they can be spread to prevent the nuts from coming undone. The problem you have experienced usually happens if the bigend assembly is clamping up on the shells rather than the actual conrod. Under these conditions, if there is a period of minimal oiling, the shells overheat and spread, then after cooling, leave the bigend bolts slacker than they should be (eventually unscrewing several turns if the bolts haven't been spread). In the past, I have tinned the outside of the shells with soft solder and then assembled them in the rods. Then heat the rods while the bigend bolts are tightened - they will then be soldered into the rods and any excess solder will have been squeezed out. The mating faces of the rod and cap (and also the shells) can be lapped flat - this will ensure that the faces of the rod and cap and the shells are all clamping up equally. With this done, you can use the old keep plates (if they are re-usable) or make new (you may need to adjust the thickness to improve the fit of the bigend). Don't attempt to make the fit too neat - there needs to be enough clearance to allow oil into the bearing as it relies totally on a splash feed.
  Hope this is of some help,
     Regards,
                 Eddie.

[phil_h]

Thanks Eddie
I'll use a bit more effort pulling on the rod.
It did nip up a couple of times on the pioneer, and I know I should have taken the barrel off to inspect the damage, but have not been in very good health.
The piston has obviously been seizing, and the rings are stuck in, but the liner looks good.
I hope it will clean up sufficiently for now.
phil

[phil_h]

Anybody have a 2 3/4 engine for sale or loan by Tuesday ?
Please ?
Or an aluminium piston and rings and a set of big end bolts (and possibly shells) ?
Or one ring and a set of big end bolts ?

The rear (winter 2010/11 aluminium) piston has suffered from its rings completely gumming up with carbon - terrible coking in the head and on the piston crown, so no shortage of oil - and then the rings stuck, making it get too hot and consequently seize and pick up, 'welding' the rings into their grooves on the bottom of the piston - the top ring so badly I had to break it to get it out.
What eddie described must then have happened to cause the loose big end, and it seems that the big end bolts have been bent a touch, preventing me from doing anything there anyway without a strip down.
With Banbury at the weekend

All this not helped by:- there seemed to be plenty of oil in the cases, but on inspection, its gloop, as the drain cock had clogged up, leading me to believe there was little in the cases when I opened it ... and of course, oily gloop doesn't splash-feed anything very well

Of the thousands of bikes made for the war, there do seem to be very few still in circulation.
There seems to be more activity with the veterans down under than in the uk !

[eddie]

Phil,
       Big end bolts were available from LDMCC spares. They may also be able to help with rings as all the 350's (including post war) were 60.8mm bore.

   Regards,
                Eddie.

[Chris54]

Hi Phil

I have a spare engine, it is about 1920 with early cylinders, we built it when the 1913 bike threw a rod on the pioneer run 2014, and we used it when we done the Newforest run its mostly together but without mag carb, inlet manifold, exhaust, flywheel. we have since rebuilt the 1913 engine which is back in the bike and it completed the pioneer run this year, an evenings work should have it running again, if your interested in borrowing it please PM me

Regards Chris

[phil_h]

Well, I had an 'interesting' week last week - many thanks to Chris for the loan of his engine... and then an inlet manifold when I realised my straight one wouldn't fit his 'flat-side' engine !

Unfortunately, once everything mechanical was going ok, the engine still wasn't running properly, and got worse when hot...
so I changed plugs, even though the colour on the old ones looked good, and that made no difference, so I looked at the points, even though it always starts easily, hot or cold (once inlet leaks are sorted  ), and saw a gap of well over a mm
Running the engine with the cover off gave a very pretty light show though
Hmm, so the recent drop off in performance hasn't just been the fault of the pistons, as I am pretty sure it would have been intermittently retarded and hence running hotter due to the clapped condenser.

So, to cut a long story short, I had to adapt my wife's Triumph so my long legs would fit under the bars, and used that for Banbury.

[phil_h]

So, the dismantling has resumed to find that the rear rod has bent its eyes and shells.
The club doesn't list any spares, except for the big end bolts.

Anyone know where I can get a complete rod assembly please ?

And the front piston has also got far too hot and smeared itself everywhere, just not as badly as the rear.
What a waste of time getting them sorted out was to only last 4 seasons - and its left me with oversize bores.
Admittedly, the engine must have been running hot with the timing so out of spec - I found the broken points face sitting in the mag when I took out the contact breaker assembly !

[eddie]

Phil,
        Firstly, I think it's a little unjust to infer that the 'Club pistons' were at fault when, in fact, the timing must have been erratic and the major cause of the overheating and subsequent piston damage - which then, probably, resulted in excess stress on the bigends.
     Anyway, regarding the need for a replacement conrod - in the past I have managed to resurrect conrods that have suffered in this way. The rods are made of a relatively soft steel, and providing there are no signs of any cracks, can probably be pulled back into shape. First of all, turn up a steel plug to fit the bigend eye of the good conrod, then tweak the damaged bigend until it fits neatly on the plug (you may need to 'blue up' the plug and scrape the eye to get it perfectly round). With the 2 halves of the rod a good fit on the plug, carefully dress up the joint faces. With this done, clamp the 2 halves onto the plug to determine what thickness the 2 new keep plates need to be. At this point, you can make new shells to suit - leave enough clearance on the bore (say 3-4 thou) so that oil can get in and lubricate the bearing. A tight bearing will eventually nip up, and on cooling, will curl tighter around the pin - making the problem even worse.
   If pistons are proving to be a problem to find, Postwar Mk type pistons can be modified to fit - my TT 2¾ was fitted with them back in the '70's, and has now done thousands of miles without any problems.
  Good luck with the repairs,
   Regards,
                 Eddie.

[phil_h]

Thanks Eddie (again)...
Resurrecting a conrod ! 
I hadn't considered that - but after all, they have to be fairly soft in order to bend as they have, and there are no signs of cracks.
Any recommendations on where to get some suitable bronze bar for the shells ?
I understand that having the right amount of lead in the alloy is important.

Mk pistons ?
I have absolutely no information on Mk models.
Could you elaborate please, as it does sound quite fitting to use pistons from a later model

[eddie]

Phil,
       I have always used PB2 phosphor bronze for the shells. For me, the local supplier is Advanced Alloys at Boyatt Wood, Eastleigh, Hants. They have always been happy to supply small amounts.
  The Mark piston conversion on my bike was, as I said, done in the early 70's for the previous owner by a Club member who no longer has the facilities to repeat the exercise. Without stripping my engine, I cant give any specific dimensions, but I know it involved reducing the compression height, shortening the skirt to remove the bottom ring groove. then sleeving the gudgeon pin bosses down to 3/8". Finally the skirts were drilled to improve their lubrication. These were the sort of lengths owners went to in the days before repro pistons became available!

  Regards,
               Eddie.

[phil_h]

Haha !
That's not a quick fix is it 
It definitely sounds easier to buy a cnc lathe and machine some of bert pol's pistons !
(Same job can then be done more easily for other people but it would take a week to clear out my garage so I could get my old lathe out and a new one in )
Unfortunately for me, bert only has 1 blank casting in stock just now