2 stroke oil constantly seeping into carburetors

[mikes bikes]

Motor, hard start after fresh rebuild, would only run with choke on, while troubleshooting I found 2 stroke oil seeping out the bottom of the reed block, seperated the carbs from the reed blocks and the area was full of 2 stroke oil, cleaned everything nice, placed white paper towels inside the carbs, let it all sit overnight, next morning paper towels are soaked with blue oil.

Seems like the oil just sitting in the tank is causing enough pressure to push oil through the oil pump and out to the carbs.

Saw a post mention the oil pump check valve, relief valve or pop-off valve. But I had no luck finding more info.

The Yamaha parts diagram of the oil pump shows a spring/ball setup for each outgoing oil line, is that the “valve”?

Any advice much appreciated? Thank you.

[tacky1]

You need to remove the oil pump and remove the check valves and clean them. The oil line feeds out of the pump have check valves behind them. Take a pic of the pump. Twist out the oil line feeds. They are a press fit. Clean them and them push them back in. Line them up to the original position in your pic. Then I give them a light tap of a small hammer to to make sure they are tight. Done.

[silverstrom]

You can see the checkvalve parts in this photo of mine after disassembly. The checkvalve body, spring, and ball. The springs tend to collect crud over the years, often what looks like white fuzz. That could be from the oil tank production process. Can't figure out what else it could be. Anyway, it's a very common problem and a very easy fix.

[mikes bikes]

Very good, I'll give it a shot. Thanks for the quick replies!

[jrodenhiser]

Get replacement springs or stretch them to put some tension back in them

[mikes bikes]

I removed the body, spring and ball, cleaned things well, put it all back, seems to have done the trick. The ball and spring were not too dirty, but I did find tiny little pieces of black something, not sure what it was or where the material came from, but they are now clean and not leaking anymore.

[tacky1]

Nice one, Thanks for letting us know.. :)

[Arrow]

Get replacement springs or stretch them to put some tension back in them

Take GREAT care with that latter procedure. The springs have a VERY long life, unless they have been previously damaged.
Stretching the springs increases the pressure needed to push the balls of their seats. If there is any scoring in the main 10mm bore, or wear, the pump could/would not pump properly, particularly at low revs/throttle.

[Arrow]

Yamaha changed the spec. of the springs in the last generation of these pumps, to short and very soft, along with increased bore/camshaft clearance. Both not needed. Along with another modification - that was needed.

Built around 4000 so the knowledge is pretty strong and therefore the help.

[silverstrom]

Get replacement springs or stretch them to put some tension back in them

Take GREAT care with that latter procedure.

I think most members here knew that was a terrible idea when they read it, which is why no one said anything earlier.

[Arrow]

Hi Silverstrom. Just trying to keep people safe. Unfortunately, it's very hard work these days. Sorting out all the problems/logistics takes a lot of my time. If no one said anything earlier, they may have assumed it was a good idea.
The wait for our pump builds at the moment is very long due to this;
Sorting out all the problems, instead of building.