Suzuki 2 Strokes

I'm working on a 76 750 that I have a problem with.

I picked this bike last year as a parts bike and then ended up peicing it back together, I rode it a hand full of short rides last summer. Now when working on the bike I removed the oild pump cover and noticed that there was air bubbles in the oil line on the far right side (kick start side). I pulled the pump thinking something was plugged in it, after a good inspection and cleaning I didn't see anything wrong. After reinstalling it I started the bike and let it idle while holding the pump in the full throttle position to fill the lines and prime it. It all looked ok, I went for a short ride (maybe 2 minutes). Now the same line (right side) has a bunch of air again.

What do you guys think is causing this? I have an idea but I don't want the sway anyones thoughts.

And without having all the covers off and being able to see. Where does this line go?

I would try opening the pump arm all the way open a couple more times while the bike is idling. Before you start the bike. Crack the bleeder screw at the head of the pump until oil starts to drop out. This also helps to escape air. After you close the screw, start the bike holding the control arm wide open. Pump it back and fourth several times. If that does not work. I would guess hardened or missing o rings on the octopus. Perhaps the pump itself is not tight enough to the octopus. Or you have a crack or hole of some kind in that line. The line you are referring to goes to the right cylinder. It's pictured furthest to the right. Its best to remove the pump and starter cover to inspect. Otherwise, you will only see half of one line. The one you are referring to. A little air will not hurt, if by running the bike it works its way out very soon. Just keep a close eye on it. If it does not go away. Then I would make sure I resolved the problem quickly. If you see the bubbles moving forward, the air should disappear by running the bike. If the bubbles stay in one spot, then you need to address it.

Thanks for that.

I pretty done everything you said already, and I had a solid flow to start with but after only a couple minutes of actual riding I had air again.

As of now I don't see any leaks, which would indicate a bad seal at the base of the octopus, you would think a bad seal there would allow the pump to bleed down and show up as a leak. Same goes for a cracked line.

My thought as that the relief valve is stuck open not let the oil line hold and build pressure, and if this line goes into the intake maybe the intake vacuum is pulling on it.

The line in question (one to right of the pump). Does this feed the intake or bearing?

Old School wrote:Thanks for that.

I pretty done everything you said already, and I had a solid flow to start with but after only a couple minutes of actual riding I had air again.

As of now I don't see any leaks, which would indicate a bad seal at the base of the octopus, you would think a bad seal there would allow the pump to bleed down and show up as a leak. Same goes for a cracked line.

My thought as that the relief valve is stuck open not let the oil line hold and build pressure, and if this line goes into the intake maybe the intake vacuum is pulling on it.

The line in question (one to right of the pump). Does this feed the intake or bearing?

A bad check valve may also cause air into the lines. Remove the octopus and do a leak test on it. The main seal you are referring to will not cause air in the lines. It will only cause a leak under and around the pump. You could also have a cracked line without leaks. Remove, clean and inspect it. Also check to make sure your inlet hose is routed correctly. That could cause air into the lines if the oil is not flowing freely to the pump. I would replace o rings that are inserted into the ports of the octopus. There are six, one to each line. Harbor freight sells a huge metric assortment kit for $10 dollars and the correct size is in that kit. Start there. When I bought my 750 it did the same exact thing on the same exact line. Opening the bleed screw and opening the control arm back and forth fixed my issue. Intake has nothing to do with the lines. The lines feed lubrication to the crank bearings and pistons. Until you sort it out. I would suggest mixing fuel. But do not go without using oil in the pump also. As the lines feed oil to the crank bearings. Mixing fuel will not help the crank bearings. Im not sure it that right line feeds bearings or piston.

I don't think that any of the lines are cracked, I have very LIGHTLY applied both pressure and vacuum to each of them and none have shown any signs of leaking down. All appear as though the check valves are working and holding a slight pressure in each line.

The line in question (the very right one out of the pump and goes into the intake), that said. My thought as of this point is that the o-ring might not have a 100% seal, not enough to leak oil because the pump is low pressure, but when the carbs are slammed shut during riding causing a high vacuum in the intake the o-ring is allowing air to be sucked in.

Someone else posted the same problem on another forum recently and it turned out to be a slight weep on one of the pipe clamps at the pump end. Cured by painting the clamp with something like clear nail varnish or superglue - can't remember. I'll see if I can find it and post a link.

HERE IT IS (clicky linky) half way down page 4.
Sealed with superglue - I expect most blokes don't tend to have much use for clear nail varnish on here, I certainly don't, but could do with some red/orange glitter nail varnish for the tank and side panel badges!!!

That's a cool read. You could also brush on a quality automotive clear coat.

Alan H wrote:HERE IT IS (clicky linky) half way down page 4.

There have been a few long threads on oil line repair options there and also here on this board. Take a look at this one also on the KC board. The sealing option can work for a while in some cases.

Thanks again.

I cannot detect a leak at the line, But I did use Honda bond around it yesterday. I have not tested it just yet, I wanted it to setup good over night.

I still feel the o-ring is to blame. Not having a new one on hand, I used an old trick of mine on it. I took and put the o-rings in a little brake cleaner for about a minute and then into oil. The cleaner makes them feel like new and slightly expands them again. The trick is just dont leave them in too long are they will really swell up.

Old School wrote:The cleaner makes them feel like new and slightly expands them again. The trick is just dont leave them in too long are they will really swell up.

I might try that as it sounds like a good idea. I guess if I drink it it will go straight to the parts I need to expand.
I'll let you know what the wife says later. Any brake fluid or Dot 5 only so there's less water retention?

Well so far so good, I got the chance to take a short ride. It looks like I may have gotten it sealed, there wasn't air in any of the lines.

Old School wrote:Thanks again.

I cannot detect a leak at the line, But I did use Honda bond around it yesterday. I have not tested it just yet, I wanted it to setup good over night.

I still feel the o-ring is to blame. Not having a new one on hand, I used an old trick of mine on it. I took and put the o-rings in a little brake cleaner for about a minute and then into oil. The cleaner makes them feel like new and slightly expands them again. The trick is just dont leave them in too long are they will really swell up.

That does work, temporarily. Soaking them in oil. Problem is, not too long after you soak rubber in oil. It will go back to where it started, hard. It only helps doing this to rubber parts if you have a problem fitting it to another part. If that rubber part acts as a seal. It will be destined to fail again. For a couple of bucks, just buy new. Then you eliminate that one possibility. Let us know your finds. How and what you did to eliminate the air.

I will say I have o-rings in wheel cylinders that I "treated" back in the early 90's that are still sealing good.

I believe in this case it was the o-ring allowing the air to be drawn in during hard deacceleration.

Also putting them in oil only helps to neutralize them after the quick bath in Brake cleaner or carb cleaner, they are what actually softens the rubber part up.

Years ago I worked in a transmission shop, I seen guys put old transmission seals in carb acid and leave them in too long. The parts would come out 5 times the original size.

Old School wrote:I will say I have o-rings in wheel cylinders that I "treated" back in the early 90's that are still sealing good.

I believe in this case it was the o-ring allowing the air to be drawn in during hard deacceleration.

Also putting them in oil only helps to neutralize them after the quick bath in Brake cleaner or carb cleaner, they are what actually softens the rubber part up.

Years ago I worked in a transmission shop, I seen guys put old transmission seals in carb acid and leave them in too long. The parts would come out 5 times the original size.

I'd bet, that your old shop charged the customer for new parts. For the seals that did work after soaking them.

The stories I could tell about the things I seen during my 20 years in the transmission business, not just my shop but many others including local dealers.