My 4G Restoration Blog

[Jon P Fudge]

Thank you Paul, I’m sure once I get into this I will be asking lots of questions. Merry Christmas to all. Jon Fudge

[nevhunter]

That camshaft has been running displaced one way. It has an unworn section on the same side of each cam. While this hasn't directly caused all the wear it doesn't help longevity of the shaft if a it can be assembled this way . The camshaft lobes are one of the most critically lubricated parts or most 4 stroke motors. They need some friction modifier to prevent scuffing. Nev

[paul.wirdnam]

For Paul Wirdnam,
I have a camshaft which you can have free of charge if you wish. I classed it as knackered but it is an awful lot better than the one in your photos!

Thanks for your offer Paul but looks like I will not need to take it up as I visited our mutual friend Peter Batten yesterday. I knew he had some good manifolds and barrel/piston set that has only done 500 miles (long story), but in the end, I came away with all his 4G spares (photo below) including those two camshafts sitting on another barrel.

[pappleton]

Mmm, Almost enough to start another 4G there Paul...
Oh nurse! Nurse! I think it's time for my medication
BR, Paul

[paul.jameson]

Paul,
That looks to me like a very sound course of action.

Paul

[paul.wirdnam]

Now that I restored the thread on the end of the crankshaft, I've been mocking it up to check it all bolts together OK. Didn't want to keep taking the coupling gear on and off the shaft, so there are two tubular spacers of the same overall length as the coupling gear in the photo below:



It all seems to fit OK when I assemble this crank in the crankcases and put the inner cover on etc, but I'm puzzled by the oil seal arrangement. From memory, in the photo below, the steel disc was against the coupling gear facing outwards and then the rubber seal was sitting on the thread of the coupling gear against the steel disc and then finally the inner race of the cover roller bearing was fitted before the inner cover goes on.

Have I got that right and, if so, how does this seal anything? What is the purpose of the steel ring?

[roger.fellows]

Seals against the back of the coupling gear cover to prevent your primary case filling with engine oil I think, Paul. .... should have said against the coupling gear cover roller inner face.

[paul.wirdnam]

Seals against the back of the coupling gear cover to prevent your primary case filling with engine oil I think, Paul. .... should have said against the coupling gear cover roller inner face.

Do you why the steel disc is needed Roger? Is the actually oil seal then between the revolving rubber seal and the edge of the non-rotating outrace in the cover?

[roger.fellows]

Sorry Paul, I should read the whole question. The seal has to be where you say .... at least until PJ comes back with the correct answer. I'd guess that they could source an oil seal which did not take up enough room, so they padded it out.

[paul.jameson]

I think Roger, you could well be right about padding out the oil seal. But the order of assembly is coupling gear onto crank, then steel washer then oil seal. If you put some oil on the inner face of the oil seal, fit it, then run round the threads between coupling gear and oil seal with a jeweller's screwdriver you can seat the oil seal right to the back of the recess, against the steel washer and coupling gear. The front lip of the oil seal goes against the outer of the bearing in the coupling gear cover. Again, a bit of oil helps it seat.

Does the oil seal work? Is it necessary?

On my first (1948) 4G I didn't have the oil seal, or any problems. When I built my present (1936 built but 1937 model year) 4G I didn't fit an oil seal. Why would I? Then I found that the sheer volume of oil coming into the primary case on this bike made fitting one imperative. It stopped the flow of oil into the primary case at a stroke. So they do work. No, I can't tell you whether or why you might need one on your particular bike.