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GT750 Oil Pump Output. How much oil should be going through

Posted: Mon Sep 18, 2017 10:30 pm
by garbal
I've seen a lot of coverage on this topic but nothing that really answers my question.

I've got smoke from Left and Centre cylinders but nothing notable from Right Cylinder.

I'm worried I'm not getting oil there. I loosened the banjo fittings that are still accessable on the right and there is very little oil travelling through

them. How much oil should be going through this fitting?

Thanks for your help guys!

Re: GT750 Oil Pump Output. How much oil should be going thro

Posted: Tue Sep 19, 2017 1:40 am
by GTandcbr
First of all the oil flow to the cylinders is less than the amount fed to the crank. Dont forget also that the SRIS is feeding waste oil around the cylinders too. The smoking can be caused by several things. What 2t oil are you using? Modern fully synthetic oil hardly smokes at all whereas mineral oil can smoke a lot. Irregular smoking of different cylinders can be caused by stuck open or stuck shut SRIS valves.
Its surprising how little oil is fed to the motor, what is the 2t consumption like?
If you haven't read this it may help
http://www.pinkpossum.com/GT750/Oilpump.htm" onclick="window.open(this.href);return false;

Re: GT750 Oil Pump Output. How much oil should be going thro

Posted: Tue Sep 19, 2017 10:20 am
by Alan H
My gt750 does about 1000 miles to a litre of semi synth 2t oil for reference. Smokes for the first half mile or so, then only on acceleration.

Re: GT750 Oil Pump Output. How much oil should be going thro

Posted: Tue Sep 19, 2017 2:10 pm
by Suzsmokeyallan
You really need to remove the oil pump and set it up in a test rig to check its output across the six outlets.

Re: GT750 Oil Pump Output. How much oil should be going thro

Posted: Tue Sep 19, 2017 6:36 pm
by garbal
Pulled the pump off and apart, the drill rig idea followed and there is a little oil coming out of each port, Primed the lines and put it back together, bled the pump and the lines all filled up with oil. I could see it pushing the bubbles along the lines. (Not many as I used a syringe to fill the lines).
Seems to be working well. I guess I was worried for nothing.
Thank you guys for your responses!

I've got a whole 80 miles on the total rebuild, I'm running pre-mix to be safe and have the pump turned right up.

I'll ride it a bit and see how much oil it uses.

Very helpful site!

All the best!

Re: GT750 Oil Pump Output. How much oil should be going thro

Posted: Thu Sep 21, 2017 2:16 pm
by rngdng
Be careful not to run too much oil. Too much oil actually leans out your mixture and makes it EASIER to seize a piston.



Lane

Re: GT750 Oil Pump Output. How much oil should be going thro

Posted: Tue Oct 03, 2017 4:50 pm
by Suzsmokeyallan
You do realize using premix will not help the big ends on a crank with the oil guides installed.

Re: GT750 Oil Pump Output. How much oil should be going thro

Posted: Wed Oct 04, 2017 8:21 am
by tz375
Actually that's not really true. The oil slinger plates are there to feed oil from the pump into the big end pins so that oil gets to the big ends. That oil then comes out of the huge spaces either side of the con rod.

When a bike is run on pre-mix the oil mist fills the bottom end and the big ends do get oiled - just not as well as with a pump.

The main bearings though will not get much lubrication at all though... :?

Adding oil to fuel obviously displaces some fuel as it passes through the jets, but as long as it's not more than say 50:1 it won't make a noticeable difference. At say 32:1, 3% of the fuel has been replaced with oil which does not burn quite the same way or with the same energy density and is probably not an issue but if you were jetted lean to begin with, it could become marginal. 3% is the equivalent of half a jet size and since oil still burns the effect is probably closer to half of a half of a jet size. Lane's point is still valid though. We need to be aware of the consequences of our changes.