Oil pipes

[nickst4]

I've only recently got the '76 GT550 back together again after a bottom end rebuild by Pete Odell, and replating of the bores plus new pistons, all this to restore crankcase compression which was marginal.

I've started the motor twice so far, but am worried about the oil flow from the pump. The first time I fired the motor, having primed both the pump and delivery tubes, all the tubes filled with bubbles so I cut the motor PDQ. I took the pump off again, checked it's drive peg was in position and that the shaft from the gearbox was turning. I drained and cleaned the oil tank and fitted new hosing from there to the pump. Reassembling with priming of pump and pipes, I fired the motor again, this time on premix for safety. Now, all the oil delivery pipes are full of oil except that one to the far left of the motor. If I stop the motor for a couple of minutes, that pipe collects a couple of droplets of oil from somewhere. Spinning the motor on the starter has those droplets positively shoot into the engine, as if the pipe has an air leak, but there's no sign at all of any oil escaping as you might expect if the pipe was holed.

So; is it right that all the oil pipes should always be full of oil, or is there something different with the far-left feed? I bought a complete set of new banjo ends with integral check-valves for the pipes, but didn't fit them because the old valves tested OK and I couldn't see an easy way of replacing the ends. Ought I to have gone ahead with this?

I'm thinking I'll have to take the pump off again and check the oil-pipe harness closely, but if someone has any ideas as to what is happening, please let me know! I should add that the oiling system on this motor was OK before I took it off the road because I did enough miles on straight petrol for it to have seized-up otherwise.

Thanks,

Nick

[barney01]

If the oil pipe has an 'air leak' there would be oil leaking out onto the crankcase. Lift the pump off the spider and invert it. Wipe the base. Put a small screwdrive through where the pin locates and flip it around a few times. Oil should appear at every hole if not that hole is blocked. Try taking the cap off the oil tank as the vent can block preventing flow. The most common cause of air in the pipes is faulty o rings in the spider or its badly seated.

[nickst4]

Thanks Barney. I think you are on the right track with suspecting the seating of the pump and O-rings. I replaced the three little cross-head screws that hold the pump down with stainless socket-heads of, I'm pretty sure, the same length, but I know one at least is going tight in the thread as I finish winding it in. I reckon that side of the pump is just not quite seated on the O-ring, hence the very rapid sucking-in of the few droplets in that pipe. Whether the thread-form of the new screws is slightly fatter than the old ones I don't know, but a mm or two off the length of those screws should see the pump go down square. Fingers crossed!

Nick

[nickst4]

A follow-up on my query: a test-firing today had all the little oil pipes start and finish full up! As Barney suggested, the problem lay with the seating of the pump block on the spider with all the O-rings. I made sure the holding screws were running right down smoothly and then carefully tightened them bit by bit so the pump went down squarely. Obvious really!

Most gratifying is that the motor now fires almost before I hit the starter button, because previously there was more blow-back than suck from the carbs and the starter sprag had been ruined. The next step will be a cautious spin round my local lanes, keeping well clear of everyone else of course. I'm looking forward to re-acquainting myself with Suzuki tripledom!

Nick

[barney01]

Great news! Enjoy your ride

[canaletto5]

Fit some spannies, that'll make sure everyone keeps socially distanced from you (Or become a grumpy old Yorkie dwarf, it has the same effect)

Have fun and post pics!

[nickst4]

Hi Guys, (and Girls, if there are any!)

I asked before about the filling of the oil pipes on my '75/76 GT 550. I improved the fixing-down of the oil pump, and made sure it was tightened evenly. No difference: the extreme LH end of the set of pipes remains more-or-less empty. Now I've have just replaced the sealing O-rings with some viton 7mmODx3mmIDx2mmthick O-rings and was pretty sure that would cure it. Again, no difference.

Now I suspect the pump itself is at fault. Do they deteriorate? Are they serviceable or do I look for a replacement? So far, I've loved riding the bike again but only for frustratingly-short trips.

Please advise!

Nick, in Norfolk

[canaletto5]

I've got a spare pump you can borrow to test it Nick, PM me your address

Kev

[barney01]

It is extremely rare for these pumps to fail. They are very robust. However there are two little pistons inside, one supplies the crank and the other supplies the cylinders. They slide up and down on springs and it has been known for a piston to stick in the bore.

[nickst4]

Thank-you Chaps! I see there's a new old stock pump on offer on a certain auction site, the only catch being the hefty price. D'you think I should jump in and buy it or rely on getting my old one working again?

Nick