Hi there,
Anybody know if this is normal for RT3 360, back pressure from engine creates air bubbles in the oil feed. Hard to film when moving, I can see the bubbles move when turning over the engine. I see DT400 has oil feed relocated to carb side therefore not effected by back pressure. Is it a problem that was modified by Yamaha or not to worry about 
Thanks
youtube.com/shorts/O-Q2STHNd3I?feature=share

I have no personal experience on RT3, but I suppose it depends on how far down the line do the bubbles travel. A couple of mm should not be too much of a problem.

Half an inch or so may mean your outlet check valve in the pump is stuck open.  Edit.  Having found your vid, I would say dirt in your outlet valve.  The bubble should move towards engine only.

Run premix if you must.  But do not run the engine as is.

Thanks for the reply, I’ll strip down the pump and have a look at the check valve.

I would not worry about it...  bubble is "bouncing", not moving towards pump. 

I believe there are reasons Yamaha used very small ID hose that is not transparent.  One is that oil might move around that bubble and give the illusion no oil is pumping.  (Very common illusion that also happens with clear fuel line...  many people have spent countless hours trying to "fix" a fuel flow issue because the clear line does not fill with fuel when petcock is turned on).  And a smaller ID oil line is less likely to trap bubbles.

What happens to bubble when engine is actually running?  Are you getting normal smoke? 

Fix is to use original hose. 

 

My experience with clear oil line produces no bubbles. The oil line was installed without completely bleeding “the tank to pump line.” Or perhaps’ the oil pump was not bled at all.

Remove the screw. Bleed. You’re done.

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Pump is definitely bled, I can manually move the oil and bubble until pipe is full of oil. I do suspect there’s a non return valve issue but the pump I have is unlike the one in my manual. I’ll try posting a video, see if anybody knows where the check valve is located on this pump.

youtube.com/shorts/W-dwE8V-1II?feature=share

Replace the clear hose with genuine Yamaha black (still available), bleed and then forget about it. 

Check valve ball and spring are under the small brass spigot. It is a very tight push fit, not screwed in.

 I had to grip mine tightly  in a soft jawed vice this morning, twisting and pulling at the same time.

I wish I could be so carefree, got a fair bit of time and energy into this little bike and they’re not exactly two a penny anymore and definitely not here in the UK. I like to be able to see what the oil is doing & it definitely looks weird right now but then again as you say black pipe was originally fitted so who knew what was going on.