1970 Lightning big end replacement

[PeterR]

Hi, the timing side big end on my 1970 Lightning has failed and I need to strip the engine down to get access to the crankshaft to replace both bearings (might need a regrind but hopefully not).  Can someone advise me whether I need to dismantle the timing side and gearbox selectors to be able to split the crankcase?  I know I need to remove the clutch, rotor etc on the drive side.  The gearbox side of things is working fine so I would prefer to dismantle this unless I need to. 
Thanks for any advice.
PeterR

[DAVE BRADY]

Hi PeterR,

The gearbox 'cassette' can stay in place as it is all attached to the inner plate.  The only parts that are disturbed are the kickstart and gear selector. 
Obviously the inner timing cover comes off to give access the crank pinion nut etc.  The gearbox oil will have to be drained.
If your gears have been selecting properly then mark the position of the spring and cup  so that you can get it back the same as it was.  Keep the outer side of the spring as the outer side.

Dave.

[PeterR]

Hi Dave, thanks for the reply.  That is pretty much what i understood but it was really helpful to have a more expert response.
Peter

[PeterR]

Hi all, I am getting on with dismantling the engine on my 1970 BSA A65 to replace the big ends.  To be able to split the cases I have managed to remove all of the various components using a universal puller except for the clutch sleeve which I think is on a taper with a key to the gearbox mainshaft (see attached photo).  Despite using a fair bit of torque and some heat I cannot get the sleve off.  I am reluctant to use too much force/heat and risk damage but I am at a loss as to what I should try next.  I have removed the bolts and bite joining the cases and they are ready to come apart except for the clutch sleeve.  Any suggestions would be gratefully appreciated.
Cheers
PeterR

[Spaceman]

The normal way to remove the clutch centre is to leave it assembled and then use extractor 61-3766 to pull it off the shaft. If you attempt it the way you have been doing you could distort the clutch sleeve.

[DAVE BRADY]

Hi,

As Spaceman suggests, the proper puller is the way to go if the sleeve is to be undamaged for re-use.
The taper is the primary method of holding the sleeve on to the shaft and it often needs to be 'shocked' free.  With the proper puller fully screwed in to the sleeve and tightened it will be necessary to deliver some sharp whacks on the puller bolt to shock the taper.  You may find that you have to retighten the puller in the sleeve after the first whack to keep it tight - the thread is quite fine and easily damaged.  A bit of heat will also help but not too much. 
When the sleeve pops off the taper it can go with a bit of a 'crack' so be prepared.

Dave.

[PeterR]

Thanks Spaceman & Dave, I have been able to order a proper clutch extractor so hopefully that will solve the problem.  Your advice is much appreciated.

[PeterR]

Hi everyone,
I have successfully removed the clutch sleeve (was incredibly tight and which finally succumbed with heat and the puller with a bit of a bang!).  So I have split the cases, accessed the crankshaft and taken apart the conrods. The first photo shows what I found when I started by removing the sump plate.  Once i removed the barrels I knew that the right (timing) side big end had failed but what I found was surprising (and ugly).  The second photo shows the upper shell bearings, timing side on the right and drive side on the left.  Based on the amount of play in the timing side bearing I was expecting the bearing to be very damaged but it is only the top shell.  The bottom shell has some light scoring but looks serviceable.  However, the timing side top shell is also damaged, although not as severely and there was no discernible play in the initial investigation.  There is some minor marking to both the upper and lower faces of the conrod journals, but no scoring.
I have had quite a few bikes over my 50 or so years riding, but certainly don't regard myself as a technician other than having learned to proceed with caution. So I appreciate and acknowledge suggestions from those with greater expertise!
Keep riding.
Peter R

[DAVE BRADY]

Hi Peter,

I think you can safely say that they are knackered.
The detritus on the sump gauze is undoubtedly the bearing material from the shells - check for ferrous material with a magnet.
Fatigue caused by very high mileage, poor oil supply in both flow and pressure, poor quality oil and oil not changed often enough can cause this either singly or in combination.  It is the drive side that suffers usually the most as it is last to get oil and is more susceptible to restricted flow caused by a full sludge trap.
The top shells take the hammer of combustion and seem to fare the worst as you can see but no matter how serviceable the other shells look they are scrap as well.
The big concern is the condition of the crank.  Even if it looks perfect once measured you will probably find that it will be at the limit of serviceable tolerance so a regrind will be needed.
I have just gone through this process on my high mileage A65.  Haver a look my post 'should I or shouldn't I'
if you are interested.

Dave.

[Bess]

Hi,
    The Mahle site has a very good article on shell failure, link here (you will need to copy and paste the link in your browser as they are extensions):

chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.mahle-aftermarket.com/media/local-media-north-america/pdfs-&-thumbnails/catalogs-and-literature/engine-bearings/ceb-2-1114-engine-bearing-failures-brochure.pdf

Although a Clevite article shows the results of a bent or twisted con rod better, I had shells similar so I changed the con rods, image attached.



Best wishes...

[PeterR]

Thanks again Bess & Dave, especially for the Mahle bearing failure document.   It seems that what has happened to both big end bearings is failure of the aluminium lining rather than a problem of misalignment of connecting rods etc.  The Clevite guidelines emphasis the importance of identifying the problem rather than simply repair/replacement of the damaged components, so that is where I am now.  This engine was rebuilt less that 10k miles ago, so there is clearly a problem rather than just wear.  One theory that I have is the petrol taps don't seal properly so it is possible that during extended periods when the bike is not being used petrol is making its way past the float needles and into the cylinders.  I hadn't noticed a strong smell of petrol in the oil but perhaps there doesn't need to be much for the oil to be contaminated?  I have taken out the sludge trap an it is fairly clean.  I will in any case check all of the oil pathways in case there has been a constriction but any other suggestions would be most welcome.

[DAVE BRADY]

Hi,

With the sludge trap being fairly clean it suggests that there has been poor flow/pressure.  Both can be caused by badly worn oil pump, weak or stuck oil pressure release valve, wrong clearance on last regrind, low quality oil.  A worn or ill fitting timing side bush will allow a lot of oil to escape and never reach the big ends and cause low oil pressure.  Also, poor quality big end shells will suffer premature wear and failure.
I would think that a small amount of petrol getting in to the cylinders would cause problems with the bores rather than the big ends.  As well as the taps leaking, the carb. float needle would also have to be not working properly.
Any sign of bore damage? 

Dave.

[PeterR]

Hi Dave, sorry to be so long in unfolding this story!  Yes there is bore damage to the timing side but this was caused by the gudgeon pin circlip that came adrift and was caught between the piston and liner.  I recovered the pieces (mostly inside the gudgeon pin), but none of these seem to have migrated to the crankcase.  The scoring to the bore was not as bad as you might expect but will require a rebore.  There is also minor damage to the piston.  So whether the circlip problem was a significant factor in the big end(s) failure or not is a question I can't answer with certainty, but I am inclined to think not.  Happy to hear other views of course.

[PeterR]

Sorry, wrong image!

[DAVE BRADY]

Hi,

Yes, unlikely for the circlip to have impacted on the big ends.  It is a pain when such a small component can cause such damage and I find it best to replace all the circlips every time I remove them unless unavoidable.  They are very cheap compared to a rebore and new pistons.  As your engine has not done many miles and assuming it had new pistons fitted when built, it could be that the circlip was not quite fitted correctly or perhaps the gauge of the wire is slightly too big.  This would cause the clip to sit high in the groove and be more likely to get pushed out of place by the gudgeon pin.  Did the others sit properly in the groove?

Dave.