850 w/Mikunis running problem

When changing, I drained all of the oil out of the tank and crankcase before pouring new oil into the tank.

I like the plugged breather idea. Which hose is the breather? I've got one enormous one that goes down to the engine and another (forward of that on the tank) that is routed through a long hose and lashed to the back of the right swingarm.

nomadwarmachine said:

Which hose is the breather? I've got one enormous one that goes down to the engine and another (forward of that on the tank) that is routed through a long hose and lashed to the back of the right swingarm.

Click to expand...

The engine breather should be the one running from the rear of the timing cover to a spigot in the oil tank filler neck?

The tank breather is the forward spigot that you apparently have lashed to the swingarm, which is not where it would have been originally.

I never touched the breather hose (or any other hose) while changing the oil. I just drained the tank, removed the banjo bolt per the Clymer's instructions, and replaced both before pouring in oil.

Is it possible that I cracked the tank while pushing it slightly out of the frame in order to remove the banjo bolt? If so, I would expect it to leak even with the engine off (it does not).

nomadwarmachine said:

Is it possible that I cracked the tank while pushing it slightly out of the frame in order to remove the banjo bolt? If so, I would expect it to leak even with the engine off (it does not).

Click to expand...

Difficult to say, but there would be oil returning to the tank, plus some oil mist and a bit of pressure from the engine breather with the engine running so would leak mor readily if there was a crack?

And you haven't said how long the dipstick is? If it's the short type, then you would be over-filling the tank even to the mid way point.

The dipstick should be 3-5/8" long, with the high mark 2-1/2" from the underside of the cap?

I made the mistake of overfilling my oil tank when I was still new to the bike. I thought anything below the top fill mark was OK. It turns out my bike prefers to have its oil level at just below the halfway mark on the dipstick.

2 things to consider -

1) Is the oil level you filled to the same as before you changed your oil?

2) Is it possible you could have kinked the vent hose that runs out your swingarm?

It sounds to me like it was a combination of just a little too much oil in the tank and a loose filler cap. The filler neck has a tab stop for the cap, like a radiator cap. You have to push down and turn to put the cap on and off, and fully on is almost a half turn past that.

I would lower the oil level to the bottom mark on the dipstick, clean the excess oil off, make sure the cap is tight, and go for another ride.

Once you're sure everything's good, raise the oil level a little at a time until you find your bike's maximum fill level.

I find its best to check the oil shortly after the engine has run. If you wait a few days, you'll likely get a 'low' reading due to wet sumping.

BillT, I like this idea. Tonight I will measure the dipstick length (to make sure I have the right length) and then have a go with this approach.

The length of the dipstick in my bike is just over 3 1/2" and the "H" mark is 2 1/8" from the base of the cap. I checked my buddy's '71 750 and the measurements are the same.

A fair amound of the oil has drained back into the case due to wet sumping and I could not get a good measurement of the level.

No apparent cracks anywhere on the tank and no leaking from the tank while parked.

I'm going to give the tank a good thorough cleaning this week, then run it, fit the cap as snug as possible, and then see where I am.

Thanks again!

I know this may sound stupid but your seat base isn't pushing on the filler cap is it, the cap should fit into the dished recess on the base.

That's a great idea! I don't know and will check. Thanks!