Air Bubbles in T500 Lines After Bleeding, Cleaning, Etc.

[BlackBearT500]

Hi all,

My 1971 T500, that I just got running, is giving me trouble with constant air in the lines. The lines are the rebuildable type from a 1970 T500 - I bought the set off of eBay because my 71's originals were complete toast.

Regarding the Oil Pump Setup:
I have replaced all banjo seals with M6 Stat-O-Seal washers.
I have superglued around the 1-into-2 branches for both sets of lines in order to be sure they are not leaking.
I have removed and cleaned the balls, springs and banjo seats, being careful not to damage them.
I have successfully bled the pump and had the bike running for about 30 minutes of riding with no air bubbles evident in the lines.

My problem is the 2 lines furthest from the pump have many air bubbles in them now - after that initial 30 minute ride time. The line leading into the branch for the two lines has no air in it, neither do any of the other lines. Also, the bubbles are small and very evenly spaced within the two lines, showing a very consistent pattern.

Since the air bubbles are only local to the two furthest lines from the pump (after the branch), is it safe to say the issue is most likely within one of the two check valves?

Thanks in Advance!
Trenton

[GTandcbr]

Because of the location of the bubbles there has to be either faulty check valves or a leak at the junction . A small split in these oil pipes is very hard to spot. The check valves work in two ways. They prevent the oil tank draining into the crankcase when the engine is off and they prevent crankcase pressure pushing oil back up the pipe towards the pump when the engine is running. One way to test the pipes is to charge them with 2t oil and hang them up banjo's downward overnight. If oil escapes and bubbles appear the valves aren't doing the job. You can use a syringe to fill the lines.
My guess is it is the valves.

[BlackBearT500]

Okay, makes sense!

I did notice that a couple of valves were having a hard time with the ball sealing in its seat... As a bench test, I blew into the banjos (very gently) and noticed sometimes the balls were not sealing the lines in response to backpressure. This was after cleaning the banjos and their internals. I eventually got the banjos to where they WERE sealing in response to backpressure, not letting any air past the ball. I suppose it's a possibility the balls are not sealing properly yet again.

With that said, could the problem be associated with the info stated above, with the balls not seating? Because, I'm thinking the springs are likely doing their job - they seemed uniform and they were not sticking in the valves.

If so, what is the best way to get the balls to where they will seat properly in response to backpressure? I have already cleaned them thoroughly, but is there something else I should do?

Thanks Again!
Trenton

[GTandcbr]

Hi
I have read somewhere that you can use a rubbing paste with the ball and the valve seat but that to me is hit and miss unless you know what you are doing! Remember that if the valve is allowing crankcase pressure to push the oil towards the pump then no oil is going to the engine. If it was me i would go this way(not expensive) I know these are for GT750 but he does other models. Worth an email. Then you could be sure.https://hard-to-find-parts.de/epages/af ... 031/set%22" onclick="window.open(this.href);return false;

[BlackBearT500]

Okay,

Thanks for the suggestions. I may try the rubbing paste in the seats and purchase new balls and springs - I think I may have found a seller of repro internals for the check valves.

Thanks!
Trenton