before I risk a tear down, my rebuilt B40 engine is tight to turn over, got the back wheel in today with chain and even with plug out in top gear, its still hard to turn over with the wheel and cant use the kick start by hand.
the clutch was fitted and it was the same to turn over, its a complete rebuild/
crank and bigend assembly new and was ok, Im thinking it may be valves need adjusting.? but I only manage to do bits and pieces to the rebuild between other work.
Hi Chaz,
Was it tight before you fitted the head?
Dave.
Dave, to be honest, I cant remember.
the motor was rebuilt by me last year, then it got fitted into the frame and youngest son had it all back to rebuild. Its been at his until he gave up on it after doing some wiring, he has been on shift 4 on 4 off, with two young kids and I work nights as well as working on my days off at the unit rebuilding and servicing bikes, I would have thought it was ok but cant remember.
will have a look at valves tomorrow asinlet cant remove cover as carb is in the way so have to make angle flange up which will cure the alignment to the air box mismatch..
Can't see how the valves would make the engine tight.
Did you turn the engine after the crank was fitted in the crankcase to make sure it wasn't tight in the cases? Did you turn the engine over after the barrel was fitted to make sure it moves ok?
Unfortunately you may have to start stripping the engine and removing components and hope it is not the crank binding in the cases.
Just out of interest, you say it is hard to turn with the back wheel. Was the bike in first gear when there will be a lot more resistance?
If the engine has been rebuilt was it totally dry? Did you use STP or similar on all the key bearings during the rebuild. May need to inject some oil into various accessible places to make sure things a aren't binding a bit
re checked the valves today, inlet was playing up, a look through the inspection showed up the inlet rocker had jumped out of the push rod. loosened the cover and reset valve clearances, now turns easier in top gear and kick start is better. just have to wait until next weekend to see if I can get it to fire.
HI THERE I HAD THE SAME PROBLEM TIGHT ENGINE , TURNED OUT TO BE TOO MANY THRUST WASHERS ON LAYSHAFT WITH NO FREE PLAY FOUND BY SLACKENING OFF TIMING COVER SLIGHTLY THEN ENGINE TURNED OVER OK SO EASY FIX REGARDS JOHNBOY .
slackened the primary chain off today, seems a bit better. I suppose being a 350without decompressor, its going to be tight any way.
now to sort the dripping primary, the joint compound one side/ grease the other didnt work. so its back to compound//compound again like I always have in the past!!
Ok, back ressurecting this problem again, I dont get to play with it as often as I would like.
Ive pulled the primary off today sprocket and clutch. the crank is still turning on the tight side, so specialists, would it be the oil pump or washers, Im pretty sure that I didnt put any thrust washers back on the rebuild.
I suppose the only way to check is pull the timing side back off.
Maybe the crank mainshafts are misaligned?
The bushing was machined by the same person that has done all my rebuilds, Brit, Jap, Italian etc Ive used for the past 40 years, and currently doing my A50 work. Although we all get off days.
One thing I am considering, would it be the possibility that the engine is a tight fit in the frame? Ive mentioned before that there are no spacers on the bottom engine mount bolt? also I did have to ream out the frame/ cases to get the front mount bolt in. might take that bck out as its a new item.
removedthe front mount bolt today, and loosened the bottom mount bolt, engine now turns over easier, not too easy but easier and on the kickstart on the ramp so by hand.
2 pictures, one the front mount and 2 the bottom mount , only has a washer each side not half inch spacers as suggested.
Ive now turned front stud down to see if it will clear easier
cant see how loosening the mounting bolts should make any difference unless the crankcase is distorted by tightening them.
I do feel though that the problem is within the engine - either crankshaft misaligned as Julian said or what I feel is more likely the shimming of the crankshaft is not right.
Bite the bullet, get the engine out and strip it down. Take off what you can in the frame to make it a bit lighter if you cant manage lifting it complete ( weighs about 35 kilos).
When I did my B40 I had a local engineering guy rebuild the bottom end. On his first attempt it was very tight and would hardly turn. Stripping it and checking he found that they had not pressed up the crankshaft sufficiently. Gave it a further squeeze and it rotated freely. It does mean an engine strip though. Same effect as having it shimmed wrong.
Are the crankcase nuts and bolts torqued up correctly? If they are not it could be the frame bolts are further compressing the crankcase halves and causing the crank to bind between the bearings.
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.
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.
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.
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?
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.
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?
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
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...
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).
By the way does fitting the spacer chamfer side in cure your primary drive alignment?
Quote from: Colin SS90 on 11 Dec, 2021, 18:34
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.
Quote from: chaz on 11 Dec, 2021, 19:33
Quote from: Colin SS90 on 11 Dec, 2021, 18:34
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
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.
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.