GT550 oil pump

[joewillybob]

Having trouble with air in 1 oil line on my GT550. I've taken the pump off, cleaned everything so that I can see any oil leaks,reprimed the lines and reassembled everything.Run the bike for a short time and the same line has air in it again. I see no oil or evidence of leaks anywhere.Possibly a bad pump? Are the pumps the same for all years GT550? You can see the line where it comes out from base plate and there is very little oil coming out of the pump.Thanks.

[Coyote]

These pumps don't move a lot of oil. Are you remembering to purge the air out with the bleed screw near the top of the pump? Even if you do, you will get a few bubbles of air in the lines from trapped air in the pump.This clears up in about 20 minutes of running.
Are air bubbles slowly moving along as the engine runs? When you prime the problem line, does the oil move freely through it? If not, you have a blocked check valve. Also check the banjo bolt for clogging.

[Cliff]

Sounds like a leaking or stuck check valve at the end of the line at the banjo bolt. Is this one of the lines that feed the main bearings?

[joewillybob]

Yes. it is the line that feeds the center main bearing. Re-bled the pump yesterday. No air came out. As stated earlier, you can see oil pumping through all the other lines. The one thats getting air in it is the easiest one to see,and, virtually no oil is visible coming out of the bottom plate of the spider.

[Cliff]

Yes. it is the line that feeds the center main bearing. Re-bled the pump yesterday. No air came out. As stated earlier, you can see oil pumping through all the other lines. The one thats getting air in it is the easiest one to see,and, virtually no oil is visible coming out of the bottom plate of the spider.

It's quite possible that crankcase compression pressure is being allowed up the line because the check valve is stuck open. Be very careful when servicing those lines!

[Coyote]

Be very careful when servicing those lines!

And Never EVER use compressed air!

Remove the pump and the manifold beneath the pump. Remove all 6 banjo bolts. Put one of those bolts in your pocket and head for the hardware store. Buy a nut that fits the banjo bolt. Now assemble the banjo bolt (with a sealing washer on both sides) in the check valve end. Put on the nut and tighten. All that is left exposed is the hole in the banjo bolt the goes into the motor.
With a syringe, oil can or other, try to force a little fluid in the open end of the bolt.. If fluid flows (I use alcohol). the check valve is definitely stuck open.No fluid should pass in that direction.
I have had some luck freeing up the valve by passing lots of alcohol through from the manifold end. Rap the valve against something hard to try to dislodge the ball. Continue with the alcohol. If that doesn't work, you need a new manifold. Naturally these are no longer available. I have been known to splice on another line with a known good check valve. As these lines are formed, you need the same line from a donor manifold.

[joewillybob]

Thanks, I'll try flushing with alcohol.

[tz375]

Last time I tried that, the alcohol was not mixing with the oil at all well, so I reverted to using degreaser first to emulsify the oil and residue. I flushed that out with WD40 and flushed that out with two stroke oil. I use a simple old hand held oil can to push liquids through the lines.

In one case I had to repeat that several times, but as Coyote mentioned, do not use compressed air. The air pressure pushes the ball up into the spring and it cannot seal after that. This is from a check valve I opened up that would not hold pressure and leaked.