G5 lack of oil to head

cbranni · Post by **cbranni** » Sun Dec 12, 2010 2:52 pm

Hello all, I need some help!!!..........Lightweight G5 350 1961........bought this bike as a non runner looks like previous owner started to restore it but lost interest, there were no electrics, everything was loose fit, lots of stuff missing, near enough a basket case, but I needed something to keep me busy through the winter, so I stripped down the engine, big end was sound, small end was shot and replaced, fitted new seal and screw 010138 to oil pump (warning! the JSL screw was .030" too long), new oil filter also fitted.
Fired the engine up and it started quite easily, ok its running bit rough but no nasty noises, oil returning to tank, all seems fine but I cant get any oil up to the head, engine has run for at least 30 mins, and no sign of oil.
Oil ways in head and pot are clear, oil way in crankcase seems clear,I had a G5 45 years ago and it used go through exhaust valves and guides like they were going out of fashion, so I'm very concerned.
Any advice would be very helpful, many thanks
Colin

BigAl350 · Post by **BigAl350** » Sun Dec 12, 2010 4:36 pm

Hi Colin,

If all the oilways are clear then there's a good chance it's something to do with the oil pump, although these are usually pretty fault-free.

The oil is supplied to the top end from the front oil pump housing and of course the pump plunger does its job by rotation and reciprocation - so maybe it's not doing one of these properly? A likely, and known, problem here is related to wear in the guide pin which engages in an annular slot in the oil-pump plunger. A small flat worn at the top end of this pin can completely stop oil flow to the top end. Have a look at it - or just replace it as it's cheap (part number 010079, GUIDE SCREW PIN; £1.95 from JSL).
Cheers,

AlEdited by - BigAl350 on 12 Dec 2010 10:18:10 PM

cbranni · Post by **cbranni** » Sun Dec 12, 2010 5:02 pm

Thanks for the reply Al.......I changed the pin and the screw just to be sure, the original was in good condition ie no flat spot, I've got day off tomorrow and gut feeling tells me to check the oil way in the crank case again, but don't want to pull cylinder and head off again, If I took rocker box off and put airline down oil way I should see air bubbles in oil tank, that would mean oil way is clear, does that make sense to anyone?
Colin

BigAl350 · Post by **BigAl350** » Sun Dec 12, 2010 10:16 pm

Then you seem to have checked all the main causes of problems in this area. But it's certainly worth checking your idea, Colin, and it should work as described.

As for other things...There's also a small hole close to the big hole where the oil returns to the (internal) tank which you might want to check that it's clear. Otherwise, make sure the cap over the oil-pump plunger is nicely tightened-up and that there are no (air) leaks there - new gasket and all that.

And don't give up!

Cheers, Al

cbranni · Post by **cbranni** » Sun Dec 12, 2010 10:49 pm

Thanks Al again...what size is this hole, I cant remember seeing one when I had the oil tank off, and what is its purpose, and the cap? is this the one hidden by the gearbox or the other end of pump, if you follow me.
Colin

BigAl350 · Post by **BigAl350** » Mon Dec 13, 2010 5:37 am

It's been a while since I was rummaging in that area Colin, and all my spare crankcases are in my garage a couple of miles away but I recall on one of my G5 engines there was a small, angled hole between the inside of the oil tank and the inner crankcase which must be clear (it may possibly be a breather). It's above and to one side of the big return hole. However, if it was blocked I don't think you'd see oil returning as well as you have.

The cap I mean is the one hidden by the gearbox. It has either a gasket or an O ring and must seal properly to allow the system to work properly.

Have you checked that the pump plunger is actually doing its reciprocating and rotating job? You can stick your finger on the end of the plunger whilst turning the engine over. It only moves a few mm in and out (on my G5 anyway!) but this works fine in my case (in fact it's a case of "my cup runneth over" with loads of oil splashing about up there!).

When you ran the engine, did the big end knock at all? If not then it looks like the oil is getting there at least...always a bonus!

Best of luck, hope you sort it - maybe someone else will chip in too.

Al

Chazzyb · Post by **Chazzyb** » Mon Dec 13, 2010 8:21 am

Assuming the oil take-off for the head is similar to the heavyweight singles, check that the gasket for the pump front end-cap has got a hole in it that lines up properly...

cbranni · Post by **cbranni** » Mon Dec 13, 2010 9:43 am

Thanks Al and Charles for the replies, I replaced both o rings on the pump, I bought a Paynes original gasket set on ebay these were included.
The pump revolves and moves back and fore The engine started ok with no knocks or rumbles and I ran it for at least 30 mins at a fast tickover with the odd blip of throttle, so if no oil was getting to bottom end I think I would have heard a few nasty noises. Dont think the oil pumps are same as heavyweights Charles, there are no gaskets just o rings.
Its just engine and frame at the moment, petrol tank is fairy liquid bottle, 6 volt from battery charger, but engine runs,I want to sort this issue before I continue the rebuild.
Right ........plan of attack, put the heating on in shed, do the ironing while it warms up, then......airline down oil way if oil tank bubbles, oil way clear, so must be pump, strip it all down again.....oh dear
Colin

cbranni · Post by **cbranni** » Mon Dec 13, 2010 6:00 pm

Hi all .........just an update........... I now have oil flow to the head, the plan worked, I'm very happy, many thanks
Colin

BigAl350 · Post by **BigAl350** » Mon Dec 13, 2010 6:06 pm

Hi Colin, that's great news! It would be useful to know what you did exactly - do you mean that blowing air down the oilway may have dislodged something (so the oilway was not clear?).

Look forward to hearing it's on the road soon!

Cheers,

Al