Villiers 75cc Lt Weight aluminium eng - crankshaft tight

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Antbr123
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Villiers 75cc Lt Weight aluminium eng - crankshaft tight

Hi guys,

Struggling with my Villiers 75cc Lt Weight Aluminium engine.  It has a mechanical governor mechanism fitted.  Some odd balls found when restoring (previous bodge jobs)...but here is a general question.

How tight should the crankshaft be after the crankcase bolts has been tightened?  Valves have been lapped and re-are fitted, head is off.  The only thing that I can think is that in tightening down the crank case, it is putting undue pressure onto the end of the camshaft drive.  Currently, I need two hands strength of grip to turn it so that the piston goes up and down! Is that normal?

I attach some images......

regards,

Tony

wristpin
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Joined: 23/05/2012 - 22:09
The crank should have some

The crank should have some end float. That is, with everything bolted up you should be able to feel some longitudinal movement usually controlled by the thickness / number of gaskets at either the crankcase drive cover end or if applicable the removable bearing cover at the mag end. A quick look at the Lightweight manual has no mention of a figure for end float so I would guess between 7 and 10 thou.  There is a mention of “ if shims are fitted” they should be refitted but no mention of removing one or more to obtain end float. 

Is your case cover gasket a genuine Villiers item or home made?

EDIT. Further reading suggests that your engine may have ball bearing mains. While preload, ( squeezing) of the bearings should be avoided to allow a smooth and free running rotation of the crank a specific amount of end float should not be necessary.

Have you had the crank right out of the engine, if so make sure that it is fully home in the magside bearing and that the bearing itself is fully home in its housing. Same goes for the PTO side bearing , just in case it shifted during dismantling.

 

Antbr123
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Thank you Wristpin.  I can

Thank you Wristpin.  I can feel longitudinal movement in the shaft.  I just cannot turn it easily, unless I loosen off the crankcase bolts, which defeats the purpose of sealing the gasket, thereby risking sump oil leaking.  Either,

1. The case is gripping the end of the camshaft, or pushing the camshaft because it is overtightened, or

2. The only other thought that came to mind is that the oil seal in the crankcase cover is hard rubber and is naturally stiff on the shaft,  or

3.  Most unlikely of all, the bearing in the crankcase housing is in the wrong position, ie push into the crankcase cover too far, thereby allowing the case to be tightened too far.

The crankcase is genuine and not homemade or bodged in anyway. I have verified that I have set the timing marks on the camgear and crank drive and the valves are opening correctly.  

regards,

Tony

Antbr123 (Tony)
Consider grass in terms of how you would like to be treated yourself - and you won't go wrong!

wristpin
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I think that my edit to my

I think that my edit to my original post more or less covers your last one but perhaps it’s time to go off piste a bit.  Soft faced hammer and give each end of the crank a sharp tap in turn . Not too heavy to avoid the risk of peening /  brinelling any ball bearings. Any better? If not loosen all the cover bolts half a turn then tap all round the cover and re-tighten .

hortimech
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If the crankshaft turns

If the crankshaft turns easily before you tighten the cover screws, but is very tight after they are tightened, then something is binding. There should be a certain amount of crankshaft end float, not a large amount though, probably somewhere between 3 - 10 thou.

In a situation like this, I would remove the piston and conrod, along with the camshaft, then refit the cover and see if it still goes tight when the screws are tightened, if it does, you know where to look. If not, refit the piston/conrod and try again, if it is still free turning, refit the camshaft and try again. I think you get the idea, keep readding items until it goes tight, the crankshaft must rotate easily.

 

Antbr123
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Sometimes, the simplest and

Sometimes, the simplest and not most obvious solution solves the problem

I took the engine to an old-timer lawnmower engineer.  He looked at it, tightened 2 bolts into the crankcase cover and then wandered off into his head-high mountain of mowers and emerged with a 4kg copper hammer.  He proceed to hit the crankshaft 2 sharp blows from the flywheel end and looked at me with a twinkle in his eye.  He said "I think you will find that it will be free now" and sure enough it was.  Total time = 5 seconds.  Cost = nothing, but I felt so small and embarrassed, even though I had done everything right.

But a salutary lesson was learnt.  I am adding a 4kg copper hammer to my arsenal of tools for future judicious use.

Antbr123 (Tony)
Consider grass in terms of how you would like to be treated yourself - and you won't go wrong!