Rock solid engine.

[orabanda]

Despite the fact that the engine was running, check that the three 5/16" primary cover screws are not touching the crankshaft when tightened (too long).

Also, that primary drive sprocket nut is not fouling primary drive cover.
Richard

[duTch]

 

.........check that the three 5/16" primary cover screws are not touching the crankshaft when tightened 9too long).......

 Also the two internal rear ones (particularly the bottom one I think) that hold the inner case to the crankcase-

[Swarfcut]

Good thoughts there, Gents, but this engine is the earlier Plunger Type, with the inner chaincase being part of the primary side crankcase casting. Long bolts only apply to the later S/A engine....the plunger does not have them.

Just wonder if sludge trap plugs ever come loose to foul the cases...evidenced by metallic shavings in the sump and a rhythmical crank speed clunk?

Swarfy.

Additional....plus bearing failure because of lack of oil pressure.

[Rex]

Sounds like a possibility. Not a lot of clearance if one does start to unwind.

[duTch]

 

......Gents, but this engine is the earlier Plunger Type, with the inner chaincase being part of the primary side crankcase casting. Long bolts only apply to the later S/A engine....the plunger does not have them.....

 True enough- I didn't read back to reference which model but the plungers chain tensioner studs are in the same or close to the S/A rear ones, so if they've been changed to longer..... as I had to, having lost the original ones.

[AdrianJ]

Starting to get somewhere at last.
The engine is now free and I can turn it with one hand with a spanner on the crankshaft.
The clutch chainwheel has been cutting into the inner timing case. (Photo attached).
It was like this when I got the bike but worse now and the are some markings on the chainwheel teeth. (photo attached)
The chain still seems OK.
I strongly suspect that the engine never seized but the clutch locked against the timing case. As soon as I got the transmission off the engine was free
I tried experimentally replacing the clutch. Tightened it sensibly and there was still wobble. I tried a bit more of a heave on the clutch nut and it suddenly freed, got another 1/2 turn off it and the wobble on the clutch has gone. It looks to me like this is the problem.
A minor irritation - as I loosened the cylinder barrel nuts two of the studs started to unwind. So I'll have to put that right.
Does the chainwheel still look OK or do I have to take out a mortgage to get one from Holland?
Regards,
Adrian.

[ellis]

Hi AdrianJ,

I have seen some much worse than yours and were still operating just fine, so i wouldn't be too concerned. I presume the needle rollers are of the correct size?
Hope this is some help to you and gets you back on the road soon.

ELLIS

[AdrianJ]

Hi Ellis,
I think they are OK. I'm hoping that if the clutch centre is tight enough it will be fine.It seems to need a lot of force to tighten it properly.
What worries me is that though the marks are worse now, some were there when I started.
I have replaced the original rollers. We will see :-)
Adrian

[duTch]

 Check that the new rollers are 1/4" x 1/4" and not 1/4" x 6mm as was used in unit construction clutches

[Swarfcut]

Adrian..Those teeth look reasonable as a try.  For new parts, C&D Autos had NOS Clutch Chainwheels, (a while ago) but there are still reasonable  numbers  of used chainwheels available on eBay.

Try tightening the big nut against the clutch centre, which should slide easily down the mainshaft splines to abut the thrust washer.

   The nut and tab washer will tighten  to clamp the clutch centre hard against the  thrust washer. A new nut and a clean up of the gearbox mainshaft thread may be required, lots of nuts get butchered, the tab washer is essential.  Correctly assembled the nut does its clamping before bottoming on the mainshaft thread. Various thickness thrust washers were originally available to align the chain and space the clutch sprocket from the chaincase. You could also loosen the gearbox/engine bolts (plus engine mountings) and try to move the box further to the drive side, moving the clutch position further away from the inner chaincase. Any circular shims to finely align the chain go between the splined crank drive sleeve and the main bearing inner race.
 In an ideal world you replace with new both sprockets and chain, or be like me and select the best of the rest for a reasonable low annual mileage runner.

To confirm duTch, the rollers are 1/4" x 1/4"

Swarfy.

[BSA_54A10]

If the clutch center will not tighten down easily check for burrs on the edges of the key ways both on the mainshaft and inside the clutch center.
Then get some Brasso and use it to lap the shaft taper to the clutch center.
It is common for one that has not been snugged up properly to wear a little ridge which prevents the hub locking onto the shaft.

[muskrat]

Plunger type Trev.
G'day Adrian.
Check the cotters (abutment rings) will fit into the thrust washer all the way without binding. Check for burrs on the shaft and center.
Cheers

[AdrianJ]

Thanks Dutch, Swarfy, Trevor and Musky,
Will check threads, rollers and burrs tomorrow and put it back together.
I have a new nut.
I've been unimpressed by the quality of a lot of new parts, including a crankshaft nut with no thread :-)
Adrian.

[Greybeard]

If the clutch center will not tighten down easily check for burrs on the edges of the key ways both on the mainshaft and inside the clutch center.
Then get some Brasso and use it to lap the shaft taper to the clutch center.
It is common for one that has not been snugged up properly to wear a little ridge which prevents the hub locking onto the shaft.

No taper on these clutches Trevor and no key ways. The shaft is splined.

[BSA_54A10]

Sorry did not realize it was a plunger box.