JAP 2a flywheel removal

[davidbliss]

Grahame, I have an idea what someone has done, the flywheel nut should be done up quite tight without the need of locktite, and with it being held in position with the roll pin and flywheel locktited sort of sends shivers down my back. and it could be penny has dropped. Right the crankshaft should be pulled up tight against that mag sides bearing, So it should be crank inner face up against, bearing, spacer, points cam and then flywheel all locked up tight with the nut, so you should have four parts to fit flywheel side yours wasn’t pulled up tight hence roll pin. I think what some would say is a non mechanical person has attacked or lost a bit it could even be on the impeller side loosing some shims that adjust clearance on the back side. Now if the flywheel wasn’t on at that time being messed with at the pump side they would have drawn the crankshaft threw some bit, then it looks to me they then fitted the flywheel later and on what should have been able to do is pull the nut up tight but in-doing so would have pulled the crank threw locking the impeller up against the back face, So I would remove pump housing and unscrew the impeller. Sort out the flywheel and hopefully be able to pull up tight and still turn the flywheel someone has lost something.

[sidevalve5]

Am thinking very much along the same lines. The pulley should be done up tight against the flywheel, the roll pin prevents that. There is a strong possibility that if it is pulled tight it will pull the crank slightly towards the flywheel end. Am going to grind in the valves, so the stator plate has to come off. Will also get the deposits in the flywheel hole and shaft flattened off so I can get near to H7 h6 or js6 in the Limits and Fits tables. Should then be able to put the flywheel on and off relatively easily and see where the problem lies. Can try it with the roll pin and without, tightening the pulley. I think this is a factory bodge and if so, it was done for a reason. It could have also been a method to prevent over-tightening by ham-fisted ‘mechanics’ after the matter was raised. It could have been only done for a small production run, then decided to drop the idea. All I do know is that I do not want to damage an engine that has done little work from new.

[andyfrost]

H7 h6 or js6 , forgive my ignorance , but what exactly does that mean.

Andy.

[andyfrost]

Grahame , one more question , and it may sound off topic , when you removed the flywheel , was the large thick felt seal present around the stator plate.

Andy.

[sidevalve5]

H7 is a transition fit, where it’s not a sliding fit, but not a press fit either. The flywheel should fit over the shaft and come off again with very little effort. But have some resistance to rotational turning.

There was no felt seal around the edge of the stator plate.

Believe the engine cowl has never come off since it left the Alcon works. So anything that is unusual was done by the JAP factory or possibly Alcon. The steel key has two grooves either side of it, so was designed to shear if the engine stopped suddenly. Modern engines have an alloy key that does the same. Have you or David seen keys like that on a 2a before, because I have not. Could be that the roll pin mod was specified by Alcon, but only for a short while. If the pulley was tight against the flywheel, the key would not shear as designed. Will take photos of the key and the sheared Villiers crank that I have mentioned in a previous post. That was broken by a pump sucking up a stone.

[andyfrost]

I’ll have to wait for an accurate close-up of the key before passing judgement. No felt seal present is a further indicator that your engine has been apart before and been tampered with.

Andy.

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