1949 G80 Rocker Oil feed crankcase flange

Samuel · Post by **Samuel** » Sun Mar 11, 2007 3:05 pm

I discovered my exhaust valve was not getting any oil supply after replacing pushrods, valve and valve guide.

On the crankcase outlet, there are four screws holes and two extra holes, one between the top screws seems to provide the oil supply, the other between the inner screw holes appears not to have a function. The aluminium flange which feeds the pipe to the rocker box only has one hole for oil and this is on the side when fitted with its outlet pointing up - this means there is NO oil flow !

Are there dffferent designs of flange with different oil flow hole positions and which one should I have for an 1949 Iron Head G80?

itma · Post by **itma** » Sun Mar 11, 2007 3:13 pm

Only flange only as far as I know.
how is the regulator screw for the oil feed in the head set? 1/8th out is enough
favourite way to stop oil to the guide getting through is that the hole in the guide is not lined up wih the feed in the head, or even a guide with no hole fitted.
to check oil flow simply disconnect feed pipe at head and run engine, you`ll see soon enough if it gets there; you have`nt obscured the feed putting the gasket on wrong? and don`t over do the sealent here, grease is enough.

Samuel · Post by **Samuel** » Sun Mar 11, 2007 3:34 pm

Bit of a misunderstanding going on here. The oil is not leaving the crankcase as the flange for the pipe to the rockerbox is not matching up to the oil hole in the crankcase - the oil appears from the hole between the top two screw holes. The other hole mates up to outlet hole in the flange.

It does not make sense to me unless the outlet is meant to be horizontal rather then vertical - but the pipe to the rockerbox is in a vertical direction ? Its certainly not a problem with gaskets or goo - its a fundamental issue of the design of the oil outlet and flange orientation. I have looked through my manuals and the AJS & M Archives but not found anything on this detail yet.

john · Post by **john** » Sun Mar 11, 2007 5:46 pm

Samuel,

Yes it can get very confusing,

But this is what I understand, if you look at the flange as you call it (AMC call it a oil pump end cap 000773) the oil output pipe is at 12 o’clock, the oil feed to the cap is at 3 o’clock. Thus the cap should have an opening to accept this feed, does it?

If it does not, there is an explanation from a manual I have read saying that at the end cap from a pre-war V twin will fit and looks the same but has the oil feed opening is in a deferent place.

In a 1931 part manual I have looked up shows part 656 (v-twin end cap) with the oil feed at the 12 o’clock point and the 1946 single I own has the feed at the 3 o’clock point.

I hope this helps

John T

Samuel · Post by **Samuel** » Sun Mar 11, 2007 10:30 pm

Agreed it is an oil pump end cap part 773, I just found it in the BMS Spares List for '49 Matchless.

The end cap has oil outlet to Rocker box at 12o/c and an inlet from crankcase at 3o/c - but the crankcase has holes at 12 and 3o/c and the oil seems to come out at 12 not 3 as far as I can tell !

Further investigations are required....

Don Madden · Post by **Don Madden** » Mon Mar 12, 2007 1:31 am

The pump plunger rotates as it strokes. For the first half or so of forward motion, the relief on the side of the plunger aligns with the port which feeds the rocker box via the hole at the 3 o'clock position. The port feeding this is visible in the pump bore.

The final half or so, the relief aligns with a port which feeds the big end, via the drillway at the 12 o'clock position. This hole is acually a drillway to the T/S bush intersecting another from the forward blanking plug which is the timed port.

No oil acually flows from the front surface at the front cap, (when it is fitted), as this part of the drillway is bypassed. It must be covered by the gasket to prevent external oil loss.

If all this seems confusing, try tracing the oil flow of the return pump.

Cheers, Don.

Samuel · Post by **Samuel** » Mon Mar 12, 2007 11:18 am

So something has happened to the pump - it supplies big end as evidenced by output from 12 o'c position but all output from the 3 o'c oilway seems to have ceased. I replaced the pump and pin when I rebuilt the engine last year all was fine then. The most recent incident was an exhaust valve sluggish due to over oiling on new years day following which I replaced the exhaust valve and valve guide and re-assembled.

itma · Post by **itma** » Mon Mar 12, 2007 11:39 am

have you the pump to match the pin?
its easy to fit a late pump with wide groove in an engine that has a thin guide pin

Don Madden · Post by **Don Madden** » Mon Mar 12, 2007 6:53 pm

Remove the pump plunger & clean out the passage. It is best to use air pressure from the front but first stuff some rag into the pump bore to catch anything dislodged.

You can probe the passage by using a small length of dowel angled from the outer edge of the pump bore into the port on the inner side of the bore. Another similar dowel can be insterted through the front of the case. by twirling one of the dowels you should feel it with the other.

Cheers, Don.

Samuel · Post by **Samuel** » Mon Mar 19, 2007 1:30 am

Removed plunger and pump this weekend. Pump was fine, plunger was stiff in the bolt and only had a tenueous location in the pump slot which was evident by the slight machining effect on the end. New plunger and locating bolt from Russels, front pump end cap, paper gaskets and new pipe to rocker box from Jampot Spares scheme (old pipe seized in front cap) Flushed and refilled with straight 40 for now. Oil flow restored to rockers. Relief as bike performed on Saturday at last. Thanks for all the helpfull comments.