72 Eldorado Big End - Oopps

[Kiwi_Roy]

I ran a big end on my bike, low oil, I caught it quickly but not quick enough
Only one shell had lost its babit metal but I replaced them all.
Went over the crank with Crocus cloth but really it was fine, nothing came off.
Could an expert tell me the big end bolt torque setting, I overtorqued and stretched the bolts last time and don't want to make the same mistake.
-----
I think it spat most of the oil out the breather system, at least it's very oily around the rear of the gearbox where the breather hose ends up.
All of the seals were replaced about 4 years ago.
Thanks in advance
Roy

[Antietam Classic Cycle]

I ran a big end on my bike, low oil, I caught it quickly but not quick enough
Only one shell had lost its babit metal but I replaced them all.
Went over the crank with Crocus cloth but really it was fine, nothing came off.
Could an expert tell me the big end bolt torque setting, I overtorqued and stretched the bolts last time and don't want to make the same mistake.
Thanks in advance
Roy

Depends on which type of rod bolt you have - early or late.

Early: uses lockplates to secure the nuts: 25 ft. lbs.




Late: self-locking nuts: 33-35 ft. lbs.

[Kiwi_Roy]

Early straight shank
These are replacements from MG Cycle but the originals were the same

Ok I must have used the Late torque last time, that's how I screwed up, good to know I'm not completely stupid eh!

Thanks very Much Charlie, saved me again

[Kiwi_Roy]

Thanks Les but these bolts haven't been stretched

I think i"m good to go

[Kiwi_Roy]

Depends on which type of rod bolt you have - early or late.

Early: uses lockplates to secure the nuts: 25 ft. lbs.




Late: self-locking nuts: 33-35 ft. lbs.

So it looks like the later bolts have a larger thread, no wonder the torque is different.

[LesP]

The early bolts are shorter also and con rod is also of lighter construction but same bearing bore and eye to eye length.

[Kiwi_Roy]

It seems I spoke too soon, the big ends came in just before Christmas and I put them in the other day.
I went over the crankshaft with Crocus cloth, I did not remove the engine from the frame, just worked through the sump
I started up and the oil pressure only came up to about 10 psi, it would normally sit on 60 with cold oil.
The oil pressure must be escaping at some other point.
It still has the same clunking noise I assumed was the big end.
Sitting on the bike the noise seems to be on the right hand side, almost sounds like it's in the head area.
Any ideas what the knocking could be?
I think it must be something in the oil circuit
I had the oil pipe in the sump off. gaskets were ok
Thanks in advance
Roy

[John A]

Could be cam/lifter or piston pin if it’s high up.  Those are more of a tap tap tap though. Time for the old screwdriver to ear from engine trick  to find it.

[Kiwi_Roy]

Could be cam/lifter or piston pin if it’s high up.  Those are more of a tap tap tap though. Time for the old screwdriver to ear from engine trick  to find it.

Thanks for the reply.
The tapping noise corresponded to low oil pressure, I thought it must be the pump one of the 4 big bearings or the camshaft bearings.
One of the big end shells showed sign of having lost metal. Are the lifters getting direct lube as well, I thought they would be splashed like the piston pin, there must be a significant oil leak to drop the pressure so.
The bearing at each end of the cam shaft has a lube supply of course and each head
I am monitoring the pressure at the banjo on the right head, it always ran 50 - 60 at speed. 60 at idle when cold but only 10 now

[Antietam Classic Cycle]

You had the "oil pipe in the sump off", but did you check operation of the oil pressure relief valve built into it? The oprv should "pop off" at ~ 60 psi.

While you had the rods off, it would have been a good idea to run a probe through the oil holes of the rod journal to ascertain how much sludge is in the trap.

[Kiwi_Roy]

You had the "oil pipe in the sump off", but did you check operation of the oil pressure relief valve built into it? The oprv should "pop off" at ~ 60 psi.

While you had the rods off, it would have been a good idea to run a probe through the oil holes of the rod journal to ascertain how much sludge is in the trap.

No, I didn't check the relief Valve, it had been running 60 that morning so I assumed when I fixed the Big Ends it would run 60 again, I was wrong obviously.
I took the plug out of the trap 4 years ago and cleaned it right out, don't I have to remove the crankshaft to clean it again or can you just measure what's there through a hole.
It still doesn't explain the tapping noise on the Right side.
Thank-you for responding.

[Tom H]

The tapping noise. Are you sure you adjusted the valves correctly?

Oil pressure. The oil pipe in the sump, could it be in backward? I'm not sure it can, maybe Charlie can answer that?

Good luck,
Tom

[Antietam Classic Cycle]

No, I didn't check the relief Valve, it had been running 60 that morning so I assumed when I fixed the Big Ends it would run 60 again, I was wrong obviously.
I took the plug out of the trap 4 years ago and cleaned it right out, don't I have to remove the crankshaft to clean it again or can you just measure what's there through a hole.
It still doesn't explain the tapping noise on the Right side.
Thank-you for responding.

A chunk of something could have lodged itself in the oprv, holding the valve open. Doesn't take much.

I didn't know you had the crank out and cleaned the sludge trap. Likely not an issue then.

[moto-uno]

  While you were at this task , did you have a chance to check the pistons ? If they seized for a moment or so they
frequently become distorted and fitment becomes rather loose . My experience has been they stay noisy even when
hot . Mine were somewhere between 004"to .005" . I didn't believe this was enough to cause the noise , so I removed
them and center punched both front and back skirts with numerous punch marks and for a few hundred kilometers it
was actually quiet again . Proof enough for me that it doesn't take a lot of extra clearance to generate noise . Hope it's
not this as they're kinda pricey anymore .  Peter

[Kiwi_Roy]

No 4 years ago I had the crank out, less than 10k miles ago
No, I didn't pull the pistons but they slid up and down like I would expect, not seized, I will do a compression test tomorrow.
Yes Tom H, the valves should be ok, I didn't touch the tappets

[TOMB]

I had a similar problem.

Replaced the original connecting rod I had refurbished and installed standard big end bearings.

Once assembled  I tried to turn the crank to see if it was binging. YES IT WAS. Would not rotate.

Pulled the bearings mic.  them up, my crankshaft is standard size - verified. The new bearings were marked as standard -

Verified,  measured them , they were 1s/t undersize in the wrong package.

Good thing i had extra new bearings , i installed them  and crank rotated -Verified.

 I don't remember if you stated that your crank is standard size or first undersized but if undersize and you installed standard size you can / will generate some noise.

And your oil pressure will be low due to much clearance between the rod journal and con rod bearing.

Keep us posted

TOMB

[Kiwi_Roy]

I believe the bearings are standard size, thats what I ordered 4 years ago and again last month, I didn't use plastigauge on them this time as it was too awkward working through the sump but I could not detect any play.
They are not tight at all the crank turns easily from the generator belt pulley.
I will do a compression test tomorrow if it warms up enough and take another listen to the Knock.

[moto-uno]

  My remarks earlier concerning a temporary seizure ( of the pistons ) actually didn't impact moving them through the cylinders .
The slight marks on the cylinder didn't look particularly bad , nor did the piston skirt ( small area of slight discolouration ) , certainly
nothing like what used to be seen in seized high performance 2 stroke pistons . But it did cause the piston to collapse enough
to give it that above mentioned clearance and noise. Feel isn't accurate enough. Just a suggestion to make sure it doesn't generate the noise after restarting.
That significant oil pressure lose is troubling though . An extra thou or two over standard clearance on any of the bearing surfaces
woudn't lead to this . The stuck oil pressure relief valve suggested earlier deserves double checking . A check while running is to load
the engine heavily ( keeping revs low ) this will frequently add a noticeable knocking if it's really loose rod bearings . Good luck and please
keep us notified .  Peter