Clattering Cam Followers!

Slots side to side.

The forces on the follower are from the camshaft and principally fore and aft.

Lubrication channels at the side where the loads are least. 

Might account for some of the wear and noise observed. 

Looks good in the photo. Not much burnt oil on those pistons. 

Peter

Hi Nick, 

Better to set the bushes a bit lower rather than higher. Like this one projects down towards the camshaft. 

I'll be checking this is not projecting too far. Too far and the cam follower stem radius will foul the bush at full valve lift. 

Cheers. Peter 

 

Hi Nick,

Have never seen these bushes peened in place before - I don't think this was ever done at the factory!

I have heard (& John Hudson** has written about this in the past) that some folk on the production line were bashing in the cam follower guides any old how. Your pictures are the first evidence of this practice that I have come across. It makes more sense to me that its on an Electra - as the Electra was born in Plumstead & I suspect Bracebridge St had nothing to do with it.

The big clue is the gearbox which, if you look at some of the exhibits at Sammy Millers Museum, was designed for a sports Matchless (G3? or G5?) that never saw the light of day. Its main feature was a stronger Mainshaft (3/4" rather than 11/16 as on the Navi at that time).

No Staff from Birmingham were transferred to London - except John Hudson. He writes that he was appalled when he saw the follower guides being bashed in, without paying attention to their orientation. The oil drain slots must run across the frame - not front to back!

There may be some merit in the argument that aligning them 'at a slight angle' could be beneficial - pointing towards a point 3ft in front (and 3ft behind for the rear ones) - as the cam does not lift the follower centrally. The idea at the time was to ensure the followers rotated in the guides to even out the wear. Sadly, all it achieved was to make them wear at the top and bottom of their stroke. whilst leaving the mid-portion unworn.

Any tappet noise/clattering you hear is usually attributable not to loose tappets, but to the followers rattling to & fro in their guides. Replacement is the only cure. NOC spares have both in stock. The followers are expensive, as we have had them remanufactured - and it's not an easy job!

The pictures show my Electra barrels WITH Jubilee head gaskets (best fit!!) - note the slots are East-West across the engine, and the guides are about 1/2" down the bore measured from the front edge (away from the cylinder)..difficult to be exact, as they are at an angle. You can see better at the bottom of the barrel, where the guide protrudes by 3mm or so.

 

**John Hudson was the Service Manager at Norton in Birmingham. Many a Norton Owner in the day was very grateful to the ever-helpful JH, who would rebuild bikes under warranty at peoples houses while they slept - in order that the bike was ready (if possible) to take its owner to work the next day. As stated above - he was the ONLY employee to transfer South when Norton production moved to AJS/Matchless in 1963. What a shambles that was! Clapped out lathes without their operators meant that nothing lined up - as nobody knew you had to add a couple of thou here, or wedge a feeler gauge under there, etc.

I found the Jubilee Gasket made the best fit around the Electra spigotless cylinder. The Navi gasket creates a little pocket all around the top of the cylinder, and under the head. If you are struggling for +40 pistons - have you managed to locate other sizes? You may have to sleeve your barrels down to fit smaller pistons - or go out more on your existing barrel? Pistons do come up now and again - but "Murphy's Law" states they never appear when you want them. I would be wary of JP pistons, as my understanding is that they are modified car pistons. Nothing wrong with that - if they were to be used in a water cooled engine. Its because water cooled engines tend to run cooler & thermally more constant then our air-cooled engines, so their thermal coefficient of expansion is different to pistons designed to run in air-cooled engines - so, yes - try to get original pistons if you can. If you are stuck - then find an engineer that understands the problem & can advise what to do. We had such a chap in Bristol - Steve Riley (AKA Piston Broke) - but we lost him last year...damn shame, all that knowledge gone!

I've used JP pistons in my Navigator engine rebuild well aware of the poor reputation of the product.    Superficially, the pistons I bought (+0.020") looked okay. Closer examination brought up some concerns.  They where somewhat heavier than the originals,  H&G 175g, JP 210g, much heavier even comparing std. size with +0.020",  that's a bare piston. The JP gudgeon pins have a parallel (drilled) bore, I tapered each end of the pins and improved the surface finish of what was left of the parallel bore.  This brought the weights very close, H&G vs JP pin.   Ring pack the same weights. I also removed the "extraction ears" from the circlips.  I machined a small slot in the piston to aid circlip removal I lightened the piston by removing metal from the inside below the bottom ring and some from the inside of the crown.  The weight came down to close to the H&G piston. There is a "centre drill" pocket in the crown of the piston that meant that I could not take too much from the over thick crown, see photo.  I assume this pocket was to aid machining the piston.  The clearance specified by JP suggests that the correct material is used for the piston with regard to air vs water cooling.   As for the pistons being modified car pistons, firms that specialise in low volume piston manufacture will not make an individual mould for a piston.  They will have a few moulds (forging dies as well) covering the size range they deal with.  Also the mould core will be interchangable between O/A piston diameters.  Some "mix and matching" will ensure most sizes will be covered. So far I've managed about 100 miles so far, no problems with the pistons, yet.  Hardly proof of the durability of the pistons, time and miles will tell!