380 oiling problem

[karl pa]

My 380B chewed up the crank pin and bearing on the center and right cylinders last year. I got the crank back from the shop and the old crank pins are wore bad from what looks like a lack of oil, the left cylinder is fine. I checked the passages in the engine and all clear, I hooked an oil line to the pump and ran the pump with a drill and all pipes flow oil.
I mounted engine and started on premix, held the pump lever open, left and right cylinders smoke but not center.
My next step is to drain oil tank and fill with different color oil to see if all lines are flowing.
My question is, the main bearing gets oil from the one oil line the cylinder gets oil from the other oil line, where does the connecting rod bearings get oiled from? The oil coming from the main bearing or a combination of both oil lines?

[Alan H]

On my 550s after an engine rebuild, I tend to inject a small air bubble in each oil pipes (pump off) the refit the pumps and spin the engine with the electric start with plugs out to see that all 6 bubbles move down the oil lines. I realise that you can't do that with the 380, but if you take the pump off and inject a small air bubble into each pipe on your 380, then refit the pump and with plugs out put the bike in 1st gear and spin the back wheel so the engine turns over quickly and the bubbles should move down all the pipes. That will show that all the pump pistons work and all oil lines are clear. The bottom 3 pipes on the crankcases feed the main bearings, and the top 3 feed the inlets which 'splash' the little ends. The bearing on the right end of the crank is lubed by the oil in the clutch casing. Note that the oil doesn't flow at the same speed in all the pipes, but I can't remember if the 3 upper ones flow faster than the lowers or the other way round. (Ancient brain fade.)
Full description of the oil pumps here - https://www.oldjapanesebikes.com/mraxl_ ... s/page-A57 but unfortunately Ian never did 'a field guide to the 380', but the pumps on all the triples work similarly.

[karl pa]

Thanks for the info Alan. At this point it is much easier to change oil color, to remove oil pump I must remove the air box, and I don't want to reinstall the air boot again unless I need to. My issue seems to be big end bearing oil starvation.
After the oil flows out of the main bearing does it oil the big end bearings, or does it mix with cylinder oil and then oil the big end bearings.
Looking at parts diagram, do the oil guide plates direct the oil into the big end? and if so do they need to be in a certain position?

[Alan H]

The oil guide plates clear the oil away from the big ends (which is why the triple engines can't 'just' run premix) & cause it to mix with the cylinder oil to lube the small ends as well as the cylinders. I'm sure the main bearing oil lubes the big ends as well.

[markush]

The oil is guided from the guide plates into the hollow crank pin and via a cross hole in it to the connecting rod bearings.
The guide plates have a small flange that is inserted into the crank pin, so actually they cannot be installed incorrectly.

I always change the oil color once at the beginning of the season to see whether it is pumped correctly in all lines.

[karl pa]

Thanks Markush

[karl pa]

I drained the blue oil out of the tank and added red oil, 4 of the 6 lines turned red but 2 stayed blue. I opened the pump but can't see anything wrong, pistons move freely, but I can't make sense of how the oil pumps through passages in the housing and the rotor. and I don't understand why it worked when I tested with a drill turning the pump. Time to try another pump.

[markush]

Have you checked the relevant lines and check valves to see whether they are clogged etc.?
For example, you could squeeze oil through with a syringe.

[karl pa]

Thanks for the advice, I will check that next.

[markush]

btw:
There is a fairly detailed description of how these pumps work in the GT750 engine manual.

https://www.oldjapanesebikes.com/mraxl_ ... /index.php

[Alan H]

Lots of knowledge on that site plus here - https://www.kettleclinic.co.uk/kcforum/ & here - http://www.pinkpossum.com/
There are several references to pumps etc. and I posted one from the GT550 field guide earlier on this thread!
(There's several on the OJB website.)

[karl pa]

Pushed oil through all 6 oil lines, looks like the problem is the pump.
I understand how the pump works, I am just not sure how the oil transfers through the holes inside the rotor and into the pump body and out the discharge, the position of the holes in the rotor and pump housing, even Ian said the workings is confusing and never went into detail how it functions.
He says most time failure occurs it is from sticky Pistons, mine are not, they move freely.
According to pink possum one piston does 3 lines and the other piston does the other 3 lines, if only 2 lines are not flowing it is do to plugged line or check valve, but I can push oil through all 6 lines using an oil squirt can.
On mine the 2 lines not pumping are 180 degrees from each other and there are no other holes in the pump body at that level.

[Alan H]

Check pm's. I had a similar dodgy pump some time ago, and after a lot of time spent and much swearing, it was donated to the local scrapman at high speed.

[karl pa]

Tried pump again, bench test it works fine but mounted on bike, will not flow in 2 lines. Time to try another pump,

[karl pa]

Tried a 550 pump, same results, 2 lines not flowing.
Using squirt oil can I can flow oil easily through all lines, could it be something with the o rings? possibly swelled and blocking pump hole?
Or something with check valves?