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[Howzie]

Hi all,

Anybody with advice as to checking the correct operation of the oil pressure relief valve on a 1959 250cc Clipper, at what point (pressure)should the spring loaded ball valve lift!

Also how do you check that the spring loaded ball is seated Ok! if not,what do you use to re-seat it.

Cheers all.

[trevorch]

Hi Howzi,

Did you remove the right side outer cover to expose the alternator?

Does yours have a small brass plate held on with 4 cheese head screws and stamped "do not remove"?

If so, it is like mine what and I might be able to help a little.

Have you found an original manual for the Clipper?

Cheers, Trevr

[Howzie]

Hi Trevorch,

Thanks for the reply, yes we do have the same pile of old junk for an engine.

Just done about 600miles after a full rebore, right pain in the but that was.

i'am ready for an oil change and before I do I was wanting to make sure that there was no oil pressure issues.

There does not seem to be a lot of oil inside the rocker box cover, when I check, trying to play it safe if you now what I mean.

Cheers.

[Mark M]

Howzie, as long as oil is returning to the tank and it's not wet sumping (and the fact you've done 600 miles suggests no problems on this front?) then all is well. You won't see much oil when you remove the rocker cover, as long as there is evidence of it in there, it's ok. To double check, run the engine with rocker cover in place and gently loosen the 2 feed bolts on the head, you should see a slight weep of oil when engine running, that is normal.
REgards, Mark

[Les H]

Howzie. First the oil pressure valve ball can be re-seated by a LIGHTLY tapping the ball into it's seat. Oil pressure for plain bearings on the twins is blown off at around 60PSI so its likely that pressure would be chosen for the Clipper. Later engines have no OPRV so maybe they relied on pump face lift to relieve excess pressure? The only test access after the filter is at the bottom of the filter before the oil is routed round to the crankshaft. With cold thick oil you might be able to measure the lift off by turning the engine quickly by the kickstart (plug out), but you will need some kind of conical seal on the gauge and hold it in position on the bottom outlet hole of the filter chamber. As you will be blocking the oil passage completely, the pressure will rise quickly to its blow off point. To measure the running pressure (Big end wear indicator) you will require a modified engine cover with some kind of test drilling to the outside.
BTW...have you seen this engine overhaul write up: http://www.hitchcocksmotorcycles.com/pi ... usader.pdf

[Howzie]

Many thanks,

One & all for your swift replies, your expertize & comments are greatly appreciated.

Just back from the shed Les H, found my old lump hammer, make sure that spring loaded ball valve gives no trouble.

The reason I asked the question was this, went on a 35 mile trip up country, a certain part of the road has a slight incline nothing to worry about I thought. It goes on for about a mile or so, I had been at a steady 40/45mph up till then, so I give the throttle a little more, by the time I reached the top the machine was just about packing in, I had to shut off the throttle & let the bike coast into a layby, by which time the machine was belching smoke out the crankcase relief valve and the engine was very very hot. was taken home by the breakdown van. checked the oil level next day, on the high side perhaps next checked the spark plug bit on the white side so I screwed the air mix in a half a turn, kicked the pile of s**t over and the bloody thing fired up! and has been OK since! was the machine running hot due to weak mixture or was there an oil problem.
Wonderful Bloody Enfields.


Cheers.

[trevorch]

If you remove the little brass plate, I seem to remember the ball bearing and the spring pop out, so that was why it said do not remove, but of course if the engine is being stripped it is of no consequence. when I rebuilt my engine, I found the crankshaft oil way was full of drilling swarf, but I had to remove the plugs in the crank web to get at it. They were lodged in the crank pin. Despite this the bearing was still in good condition. My favourite 250. White plug my need something like a bigger main jet to be safe. Had mine fitted with a goldie, sounded almost as loud as a Bullet, but smoother running less vibration.
Good luck

[Dennis C]

Hi Howzie
From your description it sounds like the bike is running lean causing the overheating and a partial seizure of the piston.

If you were on or about full throttle up the hill a bigger main jet would be in order or if under 3/4 throttle lift the needle.

[Dennis C]

Sorry forgot to say the mixture screw only affects the mixture at idle speeds and wont make the bike run any richer when riding.

[Les H]

It sounds as if the machine had all but seized up. At 600 miles you are still running in? Maybe the piston is a little short of clearance and you need another 500 miles at least to loose some of the tightness, otherwise as per Dennis, the mixture seems too weak, or the ignition too retarded. I don't think it is oil shortage as the big end will quickly seize solid in only a few hundred yards if oil is not circulating. I can't imagine that the relief valve is stuck open, it is a simple device. For your own reassurance, you could always check oil is being flung out of the big end by running the engine with the sump plug removed and collect the oil, but don't expect to see pints per minute coming out. I would make sure the bike was running with a much richer mixture slightly richer than normal for running in a still tight engine as it will run far cooler. The plug should not look white, just verging on very slighty sooty would be better at this stage. Screwing in the pilot air screw will make no difference at all with the mixture strength when running at 1/4 gas or more. As your piston has suffered a slight seizure you might well get a bit of extra piston slap on a cold start up from now on but this will have to be accepted....nowt you can do!