Friday, January 23, 2009

Bottom end start point

Bearing outer finally arrived so I was able to commence the bottom end rebuild. A dry fit (well it wasn't, I f*cked up in haste and went for assembly) revealed negative crank endfloat as the bearing outer lip was in contact with the side of the crank and the thrust washer was slightly off centre. The thrust washer is held in place by the bearing inner sleave and as this had not been tightened home I was able to re position it.

I took 5thou off the face of the bearing using the side of a gind disc in a disc griner and a micrometer (in hindsight I should have allowed about 2 more) re-fitted the outer race in the crankcase using the oven and tried again.

I cleaned off all the bearings and the surfaces using pre-wipe and put Hylomar on the crankcase faces. The sump plug was given a final tighten an pop marked with a punch to keep it in place. The shaft on the drive side never locked onto the inner bearing at any time so I decided to loctite this. Mistake.

The cases were always fiddly to get flush and in line and by the time I was in place the loctite had set with the bearing 5mm out of place. I spent hours making a puller to pull the shaft through the bearing. Just as well the Hylomar doesn't set.

All in place and bolts tightened. I used the engine mounting bolt to nip up that area because if you dont you wont have uniform pressure all around the casing.

The reason I said I should possibly have gone for a few more thou is because the assembly turns but you would need to put on the drive gear on the shaft to turn it because it is not totally free. ( no prizes for perpetutal motion).

I am going to chance that when the drive gear/rotor and the timing gear/oil pump worm screw are all tightened along the shaft it will pull the whole crank/bearing into place. There are no gaskets used yet so if I'm not happy when thats done I'll take it apart and take the few thou off.

I have not assembled an engine for 30 years and cannot remember what the acceptable tolerance for the turning of the flywheel should be. Will it bed in when run, or cause problems. If you have experience of this please comment.

Big Tip: The reason for the alternator cable being in place already is because to get through the to grommets you need a 90 degree turn. Put it in first. I defy anyone to be able to do that with a 6 core cable when the cases are assembled. I used 6 core because my Boyer ignition will not allow me to take a feed for lights from it's circuit so I am doubling up the cables to see if I can take a feed from source. I spoke to Boyer and they said this shoul be feasible. We'll see later.

Best of Luck.

Edit: Left it alone for a while and had a rethink. When I looked at it again, as I was turning crank the needle roller rolled itself out of the shell and I found it ran freer.

This is more like alignment than endfloat so looked carefully at the cases and could see a noticeable misalignment at the joint where the base gasket would sit. I slackened off all the bolts/ nuts and put the needle roller back in place. I then put on the barrell and head and tightened them to level the joint and then re tightened the crankcase nuts/bolts. Perfect. The crank now runs in the bearings as it should and after putting on the oil pump worm and timing gear I tightened that side. Waiting for the driver side oil seal so I can tighten up that side and should be ready then to continue.

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