Air in 2 stroke oil lines on 1970 T500

[Thumper69]

Hi All.
Just joined.
I have a 1970 t500 that has air bubbles in the oil line.
Pulled lines off and tried blowing thru them , not much luck.
Wash lines in petrol and placed the check valve spring with taper on spring to banjo , no problems blowing thru them.
Make a two stroke mix up and run bike to bleed all air out of all lines.
Fit lines to crank case and run again.
I got air bubbles from crankcase back to the right angle on plastic pipe were the junction is, this is were the two lines go in to one but no air bubbles past this junction to the oil pump.
Does any body have an idea.
Cheers with Beers.
Thumper69

[joolstacho]

Oooooohhh, brave lad, with a Combat!

[jabcb]

Seems fairly common for the junction block to develop an leak.
The leaks I’ve seen have been on the two-line side between the two lines.

If you prime the lines with a different colored oil than you have in the oil tank, then you can check to see how well they work.

[jabcb]

Oops, left off an important point.

Clean & seal the junction block.
I used a product called clear liquid electrical tape.

Another member might have a recommendation for what's available in Australia.

[Coyote]

Wash lines in petrol and placed the check valve spring with taper on spring to banjo , no problems blowing thru them.

No problems blowing through them in what direction? You said air entered back from the crankcase. If so, your check valve is shot. If you used compressed air, you can almost bank on it. Compressed air over compresses the tiny spring inside and the tension is lost. That makes the check ball free to float about.

[Vintageman]

Sounds like check valve bad or pump is leaking air, tighten things up even the big nut with O’ring on pump. You made need a pump seal kit.

Check valve test. You should be able to suck directly on the banjo check valve and just crack the valve open. It will take a little sucking for it opens at a little over about 3 psi. Once it cracked it kind of makes a fluttering sound usually. If you try to blow into it, you should not be able to. If you can that check valve isn’t checking. I don't think it’s the pipe junction. But you could test that by blowing into oil pump end and put a little liquid soap to find leaks.

Oh if you don’t feel like giving the banjos a BJ without oral protection adjust your compresser's output to just over 3 psi and it will open them. My compressor regulator can be adjusted this low and with good resolution. If yo above this flow will be too high and ruin check valve

[Thumper69]

Thanks for all the answers.
Out of desperation I pulled the lines off the other t500 I have and its all good, it seams that the leak is in the junction were one line breaks into two,
Can you still get these lines.
Thanks again'
Cheers with Beers

[Vintageman]

NA

Don't through them away. I have had same issue more than a few times and check valve or air leak at pump. Have not seen junction bad. But if it is you could use some JB Weld. You can change check valves... some on eBay out of UK but, I had poor luck with those. There are ones form Kawasaki that work fine for me.

But look like you are all set. Keep an eye on it.