Crankshaft end float woes… no movement, just solid with no end play!

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Soundbite

Soundbite

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Having replaced the main bearings and big end shells to my MK3 it was time to check the crankshaft’s end float once it was back in its casing.

I know this subject has been covered many times with all the options to shim to arrive at the ‘Permissible end float between 0.010"/ 0.024" in accordance with the official workshop manual. However, I’m scratching my head as to what to do when you have no movement at all. The crank continues to sit solid in the casing despite numerous attempts to mitigate the problem. I did have some generous float movement while the cases were still warm (after reinstalling the bearings for the umpteenth time) but once cooled down the crank sits solid with no end play.

Has anyone out there had the same problem… if so, how did you overcome it?
Is it safe to leave it in this state if the float appears when the engine warms up?

Here’s my Q/A check list of which I hope answers any background detail in advance:
  1. Did you check and measure the new mains to ensure they matched the originals? – I microed both and they are identical FAG main bearings specific to the MK3, including the inner races.
  2. Did you check there were no old shims stuck behind the inner races after pulling the originals? – None, and ensured the new races were driven upto the crankcheek faces with no gaps.
  3. Likewise with the outer bearings to ensure the replacements were seated correctly at the bottom of each housing without any obstructions (like old shims)? – Yes and both went in smoothly after the casings were heated then driven down to the absolute bottom.
  4. And did you ensure the crankcheeks were bolted and torqued correctly to the flywheel without any obstructions or gaps? – Yes.
  5. Did both casing halves mate together without any gaps or obstructions? – Yes.
I even tried the new bearings with the old inner races prior to removal – same issue, no end play.

I’m really at a loss here, so any constructive advice would be greatly appreciated.
 
Fast Eddie said:
I can only offer that perhaps one of the inners or outers is not fully home...
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Thanks Fast Eddie, I will have yet another crack at this (I have no choice) though I'm mindful how many times I can heat up the oil seal on the drive side without damaging it? Her Ladyship’s AGA has been very supportive when she’s out… bottom left oven at 150 degrees!
 
Soundbite said:
Thanks Fast Eddie, I will have yet another crack at this (I have no choice) though I'm mindful how many times I can heat up the oil seal on the drive side without damaging it? Her Ladyship’s AGA has been very supportive when she’s out… bottom left oven at 150 degrees!
Click to expand...
Have you checked that the crank webs are seated and secured to the flywheel to the required
torque, just a thought, hope it might help.
 
To be sure of the reason you must go inside the cases and push the crank cheek with a screwdriver and try to force it back and forth. If the screw driver moves it but a hand hold push pull does not ...
I've had this happen 2 times, Both were the result of not using C3 clearance bearings. Removed and replaced fixed it. Believe it or not it is not long ago some parts dealers still have the incorrect standard clearance bearing and are still selling them. Ihave one standard set I will never use on a norton.
The problen stems from standard bearings are engineered to be used in steel or iron housings not aluminum, which calls for MORE shrink fit so you need more internal bearing clearance.
 
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kommando said:
If you bought the mains from Norvil they will not be the required C3.
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Hi Kommando & Dynodave… thanks for your feedback. The mains were supplied by RGM in Cumbria, UK. So where are the C3 clearance bearings available please and how can you identify them as being the correct variant?
 
Soundbite said:
Hi Kommando & Dynodave… thanks for your feedback. The mains were supplied by RGM in Cumbria, UK. So where are the C3 clearance bearings available please and how can you identify them as being the correct variant?
Click to expand...
good question! Meanwhile , can someone with unused C3 bearings measure the assembled width with micrometer, so that you can cross check??
 
RGM do the C3 bearings so either your housings are on the tight side or there is another issue. Of the 3 main UK suppliers only Norvil do not do C3 mains.

Have you used Loctite on the bearing inners or outers to cure a loose fit.
 
Esmerela said:
I fitted RGM supplied FAG C3 mains in my MK3 with out any problems they do also sell the SUPERBLEND ROLLER BEARING, FAG NJ306E (STANDARD CLEARANCE CLASSIFICATION) maybe you just clicked on Superblend by mistake. could be worth checking the part numbers on your order. I would also check your crank for runout your old bearings may have had enough wear to allow for a little wiggle room.
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I ordered RGM's bottom end overhaul kit - Part No 050359... https://www.rgmnorton.co.uk/buy/bottom-end-overhaul-kit-mk3-850-commando_458.htm

I also note C3 is stamped on the bearing pictured on Andover's website https://andover-norton.co.uk/en/sho...shaft-bearing-d12-32-nm17822-nm17824-06-2114-

The stamped ID markings are currently face down in the housings, so my cases are being reheated in the oven ready for pulling (again)... I'll keep you posted once I know!
 
If you put the crank in just one side of the cases at a time is it free to turn? I wondering if it is a side play issue or a bearing diameter issue or an alignment issue.
 
Onder said:
If you put the crank in just one side of the cases at a time is it free to turn? I wondering if it is a side play issue or a bearing diameter issue or an alignment issue.
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The crank on the drive side is tighter to remove from its bearing and requires a generous tap with a soft mallet to free. You’ve got me wondering!?
 
Onder said:
...and on the TS it is free to turn?
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Yes, the timing side is not tight and moves freely away when splitting the cases. I did check and measure both inner races on the new bearings were the correct size (matched originals) and slipped in and out of their outer bearings without any excessive resistance. Perhaps the drive side bearing is out of alinement in its housing. Hmmm… more wondering!
 
Sounds like you need to remove the bearing outers again, double check for extreme cleanliness and try again to refit them following the advice already given.

Also, did you freeze the bearing outers? Some say this is the thing to do, but there’s a counter view which is that the frozen bearing will cause issues by sucking too much heat too fast out of the heated case and then expand rapidly, causing tightness before being fully seated. Heated cases and room temp bearing outers are my own preference.

And what about Kommandos loctite question? His reason for asking is that loctite can cause a bearing to tighten too much when it hardens. So, unless your bearing housing are suspect, best to avoid loctite and simply aim for scrupulous cleanliness IMHO.
 
The difference between a C3 and standard internal clearance is measured in 10's of microns. A burr or swelling on a housing can affect the internal clearance. Equally a housing slightly undersize from the factory will do that too, today's bearings are made to much closer tolerances so a tight housing with an original C3 but to top limit would function as normal but with a mid limit modern C3 could be tight.
 
OK… I’ve just dropped out the replacement bearings and noted they are not stamped with ‘C3’. They do show; ‘FAG X-life NJ306-E-XL-M1 INDIA R059-163952’ but without the ‘3C’ endorsed.

If you look at the image displayed on the AN website you can clearly see ‘NJ306E.M1.C3’ stamped.

Hmmm, even more wondering!
 
You might just reheat the tight case in an oven and let it sit. The make sure it is really loose in the case, sitting all the way to the
bottom. You have any shims in there? They are damaged?
Just trying to cover all bases. You have to start over really.
 
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