Wet sumping while running

[clive]

I do not understand your measurements vertical and horizontal I am afraid so won't comment on your maths. However I had a problem with wet sumping whilst riding on a twin, it filled the primary chaincase and started pouring out. Only a few miles from home so returned and emptied the sump with the engine still hot, out came a a piece of piston ring. Bike was new to me with a fully reassembled engine (which later needed a full rebuild), but at the time the ring flushed out cured the wet sumping problem so it must have been restricting the return flow of the oil. Could this be a possibility on your engine?

[56G80S]

"The problem turned out to be the cap on the return end of the oil pump housing. A previous owner had put it on with slotted head screws which meant that I couldn't check them with the engine in the frame as there was no way to get a screwdriver onto them. With the engine out, I found that one was tight, two were loose and one was stripped. Air was being drawn into the pump rather than oil from the crankcase. A Helicoil insert, four correct screws and a new gasket cured the problem.
John"

Joining in again on this thread. I had considerable bore wear in the timing side bush. That was, I believe, my main problem at the Hampshire Jampot. However, for many, many, years the rear flat plate has been fasten with one bolt having a weak thread, I won't go into it again. While dismantled I have fitted a new stud instead, using the additional thread that is usually unused deeper in the crankcase. Glued in with the powerful Loctite (number forgotten). This means I will still be able to spanner it and hope this will remove any possible air leak.

The cases and rebuilt crankshaft are going off to Ken de Groome in the near future for line boring the bush and linishing the drive side axle. The oil pump plunger is going as well for inspection (plus a spare that I had). IKBA, he does know.

Johnny B

[cfaber]

Thanks for the suggestion John. In my case the screws fixing both plates (front being the slotted, non-tapered screws) and the rear the bolts, and when I removed the plates this time around to verify the dimensions they were all tight and cracked loose when removed. Also, there was no oil leaking around either plate until I cracked the screws loose.

[cfaber]

I do not understand your measurements vertical and horizontal I am afraid so won't comment on your maths. However I had a problem with wet sumping whilst riding on a twin, it filled the primary chaincase and started pouring out. Only a few miles from home so returned and emptied the sump with the engine still hot, out came a a piece of piston ring. Bike was new to me with a fully reassembled engine (which later needed a full rebuild), but at the time the ring flushed out cured the wet sumping problem so it must have been restricting the return flow of the oil. Could this be a possibility on your engine?

In this case, let's assume the bore is horizontal, multiple measurements were taken in a vertical position down the bore (from the top of the bore to the bottom of the bore) and then horizontal position down the bore (from right side to left side) with a 12-19mm telescoping gauge at the positions in the image to best represent the possible wear. I'd like to have gotten more measurements on the diagonal however all the drillings prevent that. (Does this make sense?)

AJSUntitled Diagram.jpg

[cfaber]

Joining in again on this thread. I had considerable bore wear in the timing side bush. That was, I believe, my main problem at the Hampshire Jampot. However, for many, many, years the rear flat plate has been fasten with one bolt having a weak thread, I won't go into it again. While dismantled I have fitted a new stud instead, using the additional thread that is usually unused deeper in the crankcase. Glued in with the powerful Loctite (number forgotten). This means I will still be able to spanner it and hope this will remove any possible air leak.

The cases and rebuilt crankshaft are going off to Ken de Groome in the near future for line boring the bush and linishing the drive side axle. The oil pump plunger is going as well for inspection (plus a spare that I had). IKBA, he does know.

Johnny B

Yeah, I suspect that may have been part of the excess wear on this bore as well, however the timing side bush on this thing measured out correctly when I had the engine apart and there was very very little slop (though I don't remember exactly, I know I wrote it down some place). Additionally from the first set of pictures on my build thread, you can see that the bush itself looks almost new, as if it was replaced at some point in the bikes life, which is possible given this bike was heavily used for trials racing here in the US.

[Joker_Bones]

The measurements are to seven decimal places of inches... A conversion from a metric reading?

[cfaber]

The measurements are to seven decimal places of inches... A conversion from a metric reading?

Yes, I didn't have a micrometer in bananas that could read the small bore size, so I had to use my metric one.

[cfaber]

Possible break through today. While I was reassembling it to check everything once again I noticed that the upper fixing bolt on the scavenge side pump plate nearest to the crank case wouldn't tighten down and was stripped, if this has been like this since everything was reassembled and I didn't notice, or it broke loose at some point. I'm wondering if the theory about leaking plate might be correct.
So now I just need to know what thread this is. To be, it seems to look like BSF 32, but am having trouble confirming this as the major diameter of the bolt is 4.05mm.

My 55 degree 32TPI gauge seems to fit, but I'd like to be sure. can anyone advise?

[clive]

Possible break through today. While I was reassembling it to check everything once again I noticed that the upper fixing bolt on the scavenge side pump plate nearest to the crank case wouldn't tighten down and was stripped, if this has been like this since everything was reassembled and I didn't notice, or it broke loose at some point. I'm wondering if the theory about leaking plate might be correct.
So now I just need to know what thread this is. To be, it seems to look like BSF 32, but am having trouble confirming this as the major diameter of the bolt is 4.05mm.

My 55 degree 32TPI gauge seems to fit, but I'd like to be sure. can anyone advise?

It can be relatively easy to find some of these things out by checking mid fifties parts lists which tend to have specifications included. In this case the 1955 singles parts list defines "000591 bolt fixing rear endcap oil pump 3/16 by 3BA ". (Subsequent edit looking this up on a phone is a mistake i thought 3/16 was too short and sure enough looking at the 56 parts list shows it as 5/16 long) All of these parts lists are available at http://www.archives.jampot.dk/. BA fixings crop up quite often on the bikes and it's worth getting taps and dies to suit. Other examples include the screws holding on the clutch inspection dome on the tin primary chaincase, the screws holding the filler cap on the AMC gearbox ...... 2BA
However I am unable to answer your question as to whether it is 55degree 32TPI and 4.05 mm but I expect you can find some engineering guides that will tell you what the thread form on 3BA is. Good luck with curing the wet sumping.

[cfaber]

Thanks Clive, I have the parts list and manual but just couldn't dig it out and forgot about the web representations.