Apologies in advance, this may all have been discussed previously. I have checked but couldn't find what I needed so thought I'd ask again.
I'm starting to rebuild my engine and have a few questions:
1. When fitting the drive side and timing side bearings onto the crankshaft, they are tight, but I believe I will be able to tap these onto the the shaft. Should these be quite tight or a sliding fit? Judging by the current tightness I feel I'd need a puller to remove the bearings from the shaft again.
2. When fitting the oil flinger to the drive side, should the inner bearing be pressed tight against the flywheel? I don't need to allow for any space?
3. Am I correct that I'll also need to press the timing side inner bearing tight against the flywheel? If so, does this leave the con rod correctly centered? I'm assuming I'll need to carefully tap the crank cases onto the shafts because of the ball joints?
4. Would you recommend adding any thread-lock to the crank pin locking washer screws, or just tighten them up?
1) I always follow the description from a BSA publication I had years ago when it comes to the fit of the inner bearings...That said the bearings should push on by hand but not be slack...To achieve this, tight (or new) mainshafts should be reduced by hand with emery cloth strip to achieve the fit described....It's worked for me in scores of engines...
2)The oil flinger should be flat (not worn or distorted) where it fits against the face of the shoulder on the flywheel. The bearing inner is then pushed up against it...
3)Both bearing inners fit against the flywheel shoulder, taking into account the note at (2) about the flinger plate...With a flat flinger plate and the correct spacer between the drive side main bearings the crank will be correctly positioned within the crank case when the shock absorber nut is tightened...The spacer between the bearings should be unworn on the ends and measure up at 1.000"- 1.010" in length...The crank assembly is pulled up and locked in position against the outer drive side main bearing (which is fixed in the crankcase by the circlip) when the shock absorber nut is fully tightened...
4)Personally, I never Loctite the big end locking plate screws...Just use a screwdriver of the correct size and do them up tight...
My own personal preference for the bearing fit on the main shafts:
Outer ball bearings - hard push fit. If you need to bash the cases to get them together, it is too tight.
Inner roller bearings - press fit and should require some tapping to get them on to the shaft. If they slide on, I either replace the shaft or loctite the bearing on.
Thans fir your response. I'm assuming you just reduce the crank shaft size towards the ends to allow a greater clearance for the roller bearings?
Glenn
No I don't touch the shafts to make the diameter smaller. A little too tight is OK.
If you have shafts made to the correct dimensions, not bodged or worn out and good quality bearings, everything should fit together as is. BSA when making the bikes did not have someone modifying the shaft diameter to make the bearings fit. The motor went together as fast as possible.
On these old bikes, I mainly have to deal with main shafts that are too small from years of abuse and bearings spinning. If the roller bearings are a little too loose, I loctite them on. It the ball bearings are too loose, I replace the shaft as you can't loctite the balls on or you can never get the motor apart again without great difficulty.
