CSR twin help

[jim griff]

Good evening all.

I'm currently sitting here typing and could easily begin to either scream or cry. I've had my 1963 AJS CSR for a few years now, (I think it's about 10-11) and have had problems that over the years I had hoped to iron out. I've had a recent issue over the summer with it becoming a poor starter, or which I bought a new carb and checked & rechecked the ignition. All good.

I recently went to check the valve clearances and found the LH pushrod broken where the steel cap fits the alloy, all was well last time I checked so I was thinking metal fatigue etc was the root cause. I ordered a set of new ones and before I fitted them noticed a score down one side of the barrel. About 2 years back I was lucky enough to find a pair of NOS Hepolite +60 8:5:1 pistons, gudgeon pins & circlips that were dated 1968 on the box. I had the barrels rebored to suit these and the crank balanced again to match.

Upon inspection I have found the inner circlip nearest the other cylinder has only one eylet, so this is the cause of the scoring, with a fragment found in the gudgeon pin recess when I removed the barrel. The barrel is scored badly on the broken circlip side and to a lesser degree on the other (where I suspect the broken piece migrated to later on).

Mad thing is apart from the bore damage and broken circlip, the pistons, rings etc are in excellent condition. I'm now looking for a used barrel bellow +60 so that I can rebore it and get it sorted.

Now in over 35 years of riding I've never experienced a broken circlip, so am I now slightly paranoid to say the least. Is it down to sheer bad luck, metal fatigue, corrosion with the parts sitting on a shelf for 45-50 years or something else? Would this have caused the pushrod to break or is this another case of fatigue?Are the two issues linked? I assume the spares scheme can supply new circlips or are hepolite ones different?

The bike is a keeper as I love it, but It's really tried my patience over the years and I had thought that all was good. It certainly didn't burn any oil from the damaged bore and didn't give any indication of a problem over the last two years.

Any thoughts or guidance would be greatly received

[SPRIDDLER]

O.K. Jim, I'll stick my neck out and go first with an imaginative guess.

[Para with my imaginative guess deleted as I've just noticed you wrote that the broken piece of circlip was inside the pin ]

Although you received the piston, pin and circlips as a complete NOS kit it may just be worth checking that the circlips are correct for the piston. Wire circlips are used in a piston where the locating groove is semi-circular, whereas the locating groove for cut/stamped out circlips is square section. Where wire circlips are used the pin should have a radius on the outside ends so that pressure on the clip tends to force it towards its groove. I assume from your comment that the circlip had eyelets that they are the stamped out type.
I only mention this because I had a circlip fail (become displaced from its groove) and badly score the cylinder bore. It was an incorrect wire circlip fitted in a piston with a square section groove.

[Duncan]

I have had hairline cracks in pushrod ends on twins, age and use the most probable cause, the do take quite a hammering over the years. New ones should be the cure for another 60 years.

[Pharisee]

Never had a push rod break but I have had a couple of occasions where the steel ends have come loose on the aluminium tube. On one occasion, it was on an almost new pushrod. On both occasions, a clean, a 'roughing up' and the application of Loctite 638 sorted it out. Be a bit wary if you fit the stainless steel pushrod tubes available from the club spares. The top end is 'swaged' in a lot and on my '55 G8, it fouled the actual pushrod. I didn't find out until some time later when I discovered the pushrod had significant wear where it had been in contact with the top of the pushrod tube.
Also suffered the circlip problem but not on an AMC machine. I bought a Triumph Bonneville, brand new from the showroom, back in 1971. After about 5000 miles it started smoking badly on one cylinder. Further investigation revealed that one of the circlips was missing, allowing the gudgeon pin to move sideways and score two grooves in the cylinder wall. Never did find the wire circlip so I have to assume that it was probably never fitted at the factory as there was no damage to the piston which there almost certainly would have been if the circlip had tried to escape between the piston and the cylinder wall.

[g5wqian]

hi jim ;
when you say push rod broken do you mean that the cap had loose from the alloy rod , if so i bought some new pushrods from club spares
about 4 years ago which this happened to .

upon inspection it looked like the caps had been loctited to the rod on assembly .

i had bought 4 rods and i had 3 fail due to caps coming loose .

i dont know who made the pushrods for the club at the time but to be honest they werent very good and lasted less than 12 months .

ian

[Mick D]

Hi

Sorry to hear of your woes, these things can be soul destroying. If you can post photos of the broken components it would help greatly with diagnosis of the possible cause.

If the push rod aluminium tube had become loose in the threaded adaptor this would lead to circumferential fretting and eventual failure, (though I'm struggling to see how the engine continued to run in this condition).

The circlip was probably broken during installation, did you use circlip pliers or just 'snick' it into place? the shock of 'snicking' it into place could have fractured the end but left it lodged in the groove. I've only ever encountered broken circlips during removal / installation, (never in service), I also always confirm correct installation by ensuring the circlip can be rotated by gentle pressure from a scriber inserted into one of the eyes.

Finally, have you considered having the damaged barrel sleeved?

Regards Mick

[Pharisee]

Finally, have you considered having the damaged barrel sleeved?

Regards Mick

T & L Engineering re-sleeved a G3 barrel for me recently. The one I had when I bought the 'basket case' G3/LS was not in very good condition, to say the least. It had been stuffed with a piece of rag and left in a damp garage for the best part of 35 years.
Anyway... Once they'd stopped laughing, the guys at T & L re-sleeved it back to STD and supplied a new piston. Only one slight hitch, the cut outs at the bottom of the barrel for con-rod clearance weren't quite deep enough and the con-rod was just in contact with the liner at one point in the cycle. It was only a couple of minutes work with a die grinder to create the necessary clearance.

cylinder-1.jpg

cylinder-2.jpg

[jim griff]

Hi all,

and thanks for the feedback. Reference the push rod, this actually sheared in two, the dural (alloy) section was completely in two halves, although the top piece broke under the hardened steel end cap and was left sitting there in the oil return well.

Regarding the circlip I used a pair of proper circlip pliers and tested it once fitted to see if it moved within it's rebate. No problem at the time whatsoever. All I can think of is that it had corroded after spending nearly 50 years on a shelf?

I've managed to secure a spare barrel at +30 thou so at least I will be able to get it bored out to fit my piston & I've ordered a new set of circlips from Jampot spares. Very Frustrating but these things are sent to try us I guess?

Jim

[MalcW]

Very Frustrating but these things are sent to try us I guess?

I've long since come to the conclusion that running an old bike is very, er, character building.

Malc

[SPRIDDLER]

All I can think of is that it had corroded after spending nearly 50 years on a shelf?

After 50yrs on a shelf you'd lose your temper

Very Frustrating but these things are sent to try us I guess?

Long swinging kick. (640x468).jpg