MK11 square re-build do`s and don`ts!

[john.bebb]

Brian - thanks for the info - plz - where the blazes do you mount the oil filter? - any chance of a pic? - I'd like to see how you've done the plumbing.

Not visible from my thumbnail pic but I've the higher capacily Mk11 oil tank fitted (speedo cable routed through a brazed in tube) so there's less room...
I'll squeeze it in somewhere but the ground clearance ain't exactly liberal at the best of times.

Plugc; - I run BH7S - Boyer 12v electonic ignition with Kirby Rowbotham pointless distributor conversion, the carb is an Amal 626 ... so it's not quite std!

I intend to fit new cylinder liners so will address clearances & tapers as required.

Thanks again, John

[Brian.Fosh]

Hi John.

The filter mounts under /in front of the gearbox, mounted sideways between the two lower frame tubes. The bracket sits on the clutch side and allows just enough room to unscrew the filter before its top touches the frame tube on the other side... completely out of sight. The rubber return oil pipe leaves the engine in the normal way via its copper manifold, curving instead in front of the frame middle down tube, then downwards on to the filter manifold, not far from the gearbox sprocket. It may help to shorten the manifold pipe. Thence the oil returns from the adjacent,upwards pointing stub on the screw-on filter manifold... back to the oil tank by a route that brings it alongside the oil return pipe as it first leaves the engine.

Draganfly make an ok bracket these days. It''s a little flimsy but works fine. My first bike with this mod was on the rear cover of one of the reprints Bob Curries Classic Motorcycles of the fifties books, the one with a black cover and a Vincent on the front. That also had an Amal.

Regards,

Brian

[simon.holyfield]

This might help:

http://ariel-square-four.blogspot.co.uk ... r.html?m=0

[Brian.Fosh]

Well done Simon. I forgot about your on-line record.. I used this quite a lot during my own rebuild.

As part of my recent unplanned 1500-mile strip down, I discovered the crinkle-finish enamel on my filter housing was flaking off internally with the largest flake about half the size of a postage stamp semi-blocking the "out" side. The paint seems to detach from the mazak style alloy with effects of oil & heat. I don't think it was related to my oil pressure loss.. which i'm pretty sure was down to an unseated ball in the crank-shaft end.. none-the-less, i scraped off all the paint on the inside of the housing, which is brittle but flaked away easily just using my finger nail.

Regards, Brian.

[john.bebb]

... Hi Brian & other Guys... fitting such "oil filters" does not appear to be too beneficial... or what the blazes was preventing the ball from seating???

... think about it!

[paul.jameson]

John,

I am a little uncertain as to what you mean by the ball not seating on a Mk II Square which has a gear type oil pump and hence no balls to seat in the oil pump. Perhaps you could clarify.
The Mk I and MK II crankcases differ in terms of the spacing of the cylinder studs. You can convert a Mk I crankcase to Mk II spec by alteration of this spacing to suit, but it is not for the unskilled.

[Brian.Fosh]

I'm satisfied the oil filter is well worth fitting. My oil stays golden coloured, with no blackening at all.

If I gave the impression it was debris holding the mk1 ball off its seat, that is not what I intended. I don't think my crank-end valve was being held open by muck. I think it was possibly an air-trap... and we know the Morgo's are prone to this... hence the priming hole in them.


The pressure drops to around 15-20psi when the oil is very hot, say after a brisk 20-30 miles, but only at tickover, but runs normally at 50psi

I've seen it drop to 25 during normal running, and then recover and hold at 50psi thereafter after revving and changing down and then back up.
I'm suspicious the ball was being flung sideways by centrifugal force off its seat, possibly aided by increased flow from the Morgo pump pushing it back further than the standard pump.

Regards, Brian.

[nevhunter]

Worth rectifying I would think. Is a different type of valve and seat possible?. Idling pressure doesn't mean much and it should quickly respond with rev increase. Nev

[john.bebb]

Paul - crossed balls! (... can be a painful occurence!) - I was referring to the (Brian Fosh) pressure relief ball valve.
Brian; - "ball was being flung sideways by centrifugal force" - no way - the implication is fallacious - think about the physics!

All; - not all Squares were fitted with oil pressure gauges... and I doubt any ever went to the NPL for calibration & certification

Cheers, John

[PhillSpain]

I fitted the oil filter mod but found it very difficult for maintenance and oil hose security.
I re fitted it in the tool box with two BSA A10 oil pipes.
Changing filter and checking hoses couldn't be easier.

Oil filter re location

Oil filter new connections