012967 OIL PUMP PLUNGER 2-START, 1948-63 1956 G80S

[56G80S]

Hi All

This is part of my Hampshire Jampot recovery but I prefer to make separate entries by topic as it will facilitate finding by a "Search".

I had initially thought that the bore in crankcases was scored and that I might need to find a replacement timing side case. I spent quite a bit of time yesterday giving the cases a "second clean". The bore actual looked better than I thought. As did the plunger, the locating pin was perfect, no flat spot, no change of diameter in the working end.

I haven't measured the plunger yet but I did insert it the wrong way round into the bore i.e. the narrow end entered in from the take of point for the rocker box and vice versa at the other end. There was almost no rock at all, it was miniscule. I cleaned the blanking plate and the rocker box take off plate etc and refitted the whole into the case, filled the pump inlet point with WD40 put my finger through the timing side bush and turned the pump. It promptly spat the WD40 out through the return hole.

On the basis that WD40 is very thin, my finger very slow and there was less than adequate sealing with the old paper gaskets I think I may've got away with one. I will measure the plunger but haven't the tool (after watching the RideNut clip) to measure the bore although there was no difference when testing for rock in a variety of planes. I think I will splash out on a new plunger and timing pinion though.

There is a separate problem with the blanking plate but I'll post that in another thread.

Johnny B

[56G80S]

Update - not that there's a lot of interest - I've revisited this thread http://www.jampot.com/forum/viewtopic.p ... 8&start=50.

I've measured the plunger and it's in the "acceptable" range on those Army tech sheets. Smaller diameter 0.5615 and larger diameter 0.7165 (thanks to Mum's old "Perfecta" micrometer). There are some really very light striations on the part the Dixter identifies as where the main bore wear would occur. These are so light that, using all three lenses on my RuPer (thanks Dad) eyeglass they are about the width of the thread on the cotton bud I used to fish out a reasonable size piece of brass from inside the plunger. I'll do an edit and post a pic. I'll see if I can get a gizmo for measuring the bore.


In the meantime, I'll PM Dixter and ask where the Quad "O" ring would go as I know someone who would probably do the job if needed. The cases are a matching pair although there's another job to do as well I'm sure he won't charge me too much. Popping the blanking plate off and replacing the "O" ring not too much of a task until I can afford to get the bore sleeved if that needs doing. It will encourage prompt oil changes, I've a lot in stock.

Johnny B

[56G80S]

Now checked the bore in the crankcase more carefully using another legacy from Dad, a couple of dentist mirrors, one small enough to go through the cutout in the timing side bush. I can see very light scratches in the bore but nothing more than that. While I appreciate that the tolerances for this are very fine, it did "pump" WD40. I intend to re-assemble with what I have but be prepared to find that this doesn't work.

If it doesn't I will pop the plunger out, go down the "o" ring route as a stop-gap and keep my eyes out for a decent timing side crankcase half. I have realised I actually have more than one contact that would do this for me and one of these may be prepared to sleeve the pump bore as part of an exercise with apprentices. The other is a hydraulics engineer, so should know what it's about!

If it's the "O" ring route, well there's not likely to be rallies this year and if there are I'll go on the Yamaha, keeping the Matchless for local pottering about.

Johnny B

[Mick D]

Hi Johnny

I'm not sure of the history of this issue but from you description of the condition of the pump I wouldn't hesitate to put it back together - if it will pump WD40 it will pump engine oil.

Glad you're using your inherited tools - it's what they're for

Regards Mick

[56G80S]

Mick

Thanks a lot for the response. I've just sent a PM to Dixter so I he'll be able to send me what I need it it doesn't work properly and I go down the Quad ring route.

There's more to come on this saga, but I'll be posting it under " Drive side crankcase, bearings and witness marks"!

Cheers

Johnny B