B40 tight engine

[Colin SS90]

With everything torqued up there should be 0.003"/0.005" of crankshaft end float (Rupert Ratio). If you pull and push the crank by hand you should feel slight movement.

[AdrianS]

As above re end float.
I have learnt over the years to double check everything during an engine rebuild.
Check the end float before sealing the cases, check again after. Check engine turns after fitting anything to the crankshaft. Check gearbox turns, check it turns after primary drive chain fitted. Check engine turns over easily before fitting barrel, check again after etc etc.
It's always a ball ache to end up in the situation you are in but I do feel you need to strip the engine and start again ( checking that the bearings are properly seated first when cases are apart)
At least you know that all the internals are clean and you are not dealing with an unknown engine.

[chaz]

I have said before, there are no shims on the crank inside , none on disassembly, none on assembly.
Ive loosened clutch today and gearbox inner case, the crank turns easy by hand.

Having now re consulted Ruperts book, Ive re checked the alignment of the primary chain. The clutch has been off a couple of times and looking atthe parts book there is no shimming behind the clutch but the front chain sprocket has different sized spacers available,
my problem is, Ive around 1/8" difference from the cover face to the chain plates .the front sprocket is higher than the chainwheel.
the sprocket has only .040" clearance to the boss of the crank oil seal housing, so cant really go back any further, which means the only option is to bring the clutch basket out, which will then not sit on the taper. The gearbox was not pulled apart when stripped and should all be shimmed correctly.
this can only be the reason for the tightness, although, turning a few thou off the front engine mount stud, still wont let the stud pass through casing and frame mounts.

[Colin SS90]

Maybe the gearbox main shaft is not fully seated in the gearbox bearing, or the bearing not fully seated in it's housing? This would explain your clutch alignment problem and the tightness when the gearbox cover is tightened up. Perhaps tapping the timing side of the gearbox main shaft may move the clutch and improve the alignment.
Also, does the front chain sprocket have equal bosses on both sides?

[chaz]

Hi Colin
just pulled the box out to check its all in the correct place, ready to look next week.
the front sprocket has the longer boss outward  already, if inward would be worse on alignment, I checked that on assembly.

[chaz]

found a few minutes to play today.
with no primary or inner timing cover the crank can be turned over by hand , gets harder when valves start moving as expected, Ive put the gearbox and inner case back on and its tightened up, still without primary on.
I think I can rule out crank and oil pump so its inner cover pressing on timing gears possibly?

another question, spacer on crank that sits in oil seal, is it chamfer in towards engine or face out to sprocket?

[Colin SS90]

Hi,
Looks like either the crankshaft nut holding the half time gear is fouling the casing or the camshaft bushes are pinching the camshaft. The nut fouling should show as witness marks on the cover or nut face, there should be end float on the camshaft (pull and push end of camshaft). Have you put new camshaft bushes in? If you have the top hat Bush face may need machining.

Extract from BSA service sheet 422 - chamfered side inwards. Link below.

https://www.bsaunitsingles.com/Archives/Owners_Manuals/C15%20&%20B40%20Service%20Sheets%20Book%2000-4082%20x.pdf

Cheers hope this helps, Colin

[chaz]

thanks Colin.
Ive run off copies of the sheets before but missed the page, Ive got the chamfer on the outside!!!

yes, the bushes were all replaced, so, looks like its strip it again.. best way to check is unscrew the inner cover until it all turns freely then.
good job christmas is comming as Ive got a fortnight off so should be able tosort and get finished ready for the A50 next year. Providing my engineer gets the cases and crank back to me, he has had them for a year!!   thanks covid...

[Colin SS90]

I would take off the timing cover and reassemble it minus gearbox and camshaft to check for easy engine turning. By leaving the gearbox out it makes assembly easier.
If easy, reassemble with camshaft and check for easy engine turning. If tight, loosen screws and put 0.010" feeler gauges at three places between joint faces and lightly nip up screws and check for easy engine turning. If easy, check camshaft end float and this should allow you to work out how much to remove from the cam top hat Bush face (0.010" less end float).

[Colin SS90]

By the way does fitting the spacer chamfer side in cure your primary drive alignment?

[chaz]

By the way does fitting the spacer chamfer side in cure your primary drive alignment?

not tried yet,too many leaves to hoover up at home and although I have tried last week, its a tight fit on the splines and seal and with not much sticking out, it wont pull with magnets so have to find another way to get it to move.

[chaz]

By the way does fitting the spacer chamfer side in cure your primary drive alignment?

not tried yet,too many leaves to hoover up at home and although I have tried last week, its a tight fit on the splines and seal and with not much sticking out, it wont pull with magnets so have to find another way to get it to move.

only concentrated on inner cover today, micrometer blued the gear and sure enough .002/.003 thou , enough to tighten it all up. next job to get the face of the bush skimmed, .006/.008 should do it. then back together

[Colin SS90]

Glad to hear that you've found the cause and have solved the problem. Regarding removing the spacer, what about supergluing two bolts to it and pulling them with two pairs of  pliers? You may want to file the heads flat to improve the contact areas.

[chaz]

seriously getting fed up with this bike.
put the milling head over on the lathe and skimmed the face of the bush what I thought was needed. Took back up and with the aid of micrometer blue , the crank now turns over freely sorted...
putting the screws back in , managed to strip one, luckilly the screw was a bit short so left it in. Trying to fit the electronic ignition had to file clearance on the back to allow the wires and heatshrink to go through the outer cover. on, off all good.
went to put the outer on with some gasket goo, now the bl**dy cover wont go over  the kickstart shaft, so tight that trying to getthe cover back off, Ive pulled the shaft back out.
short of getting the bike off of the ramp and laying it on the side, it means taking the middle case back off..
hey, ho, well, I suppose i can helicoil the stripped hole now, but why the shaft wont go through the bearing now???
and still not got round to the crank bush.