I agree on the dipstick ! Stand bike upright then look into window. Remove oil fill cap and smell oil in engine if it smells like gasoline your oil is contaminated with fuel. Petcock has failed , replace with a Yamaha Raptor petcock and plug vacuum hose to carb then replace oil & filter. Make sure to install oil filter correctly ! Oil takes years to dry out , so I doubt the oil went anywhere. Unless you have 2 qts of oil under the bike. Don’t run bike until you figure it out !

How much oil came out when you drained it?

How much oil are you putting back in there?

It says 1800ml next to the sight window.  I always get about 2 quarts out and put 2 quarts back in with a new oil filter.  That puts it right in the middle of the window.

If the bike wasn’t warmed up and it’s super cold outside, I suspect the oil is just “frozen” on the left side of the motor from leaning on the side stand.  That doesn’t seem to be your situation.

There really isn’t anywhere for the oil to hide especially if you are filling at the fill hole.  If you were filling from the top with the head cover removed (maybe after removing the head), it would overflow if there was a clog between the upper and lower motor.

If you cheat and lean the bike to the right when checking, hopefully you can see some oil then???  Yes/No?

How’s your eyesight?  

Weird…

Hmmm.  Strange.  Makes no sense…. The oil fills straight into the crankcase.  It should all be sitting down there.  If you lean the bike super far right, you should see oil in the window.

Since the bike starts and doesn’t blow a cloud of black smoke, the oil isn’t somehow magically rising up over the piston rings and filling the cylinder.

I’d try leaning it way over to the right and look for oil.

I’d have to get the manual out, but I think the motor gets 2.4L of oil after a complete engine overhaul.  My thinking here is that other 0.4L that usually stays in the motor after an oil change has drained down and been removed when you drained the old oil.

How thoroughly did you drain the oil?  If you rocked the bike back and forth and side to side and tried to get every drop of dirty oil out, you may have removed more than “normal”. It might take an extra 0.2-0.4L to refill yo where you can see it.  I’ve done that before.

You could try adding 0.4L and see.  If it’s too much, drain some off.

ThumperPaul wrote on 03/01/25 at 06:48:47:


The oil disappeared from the window before I changed the oil, without any leaks, and before the engine was started.
It did it all by it's self at the same time on two separate Suzuki motorcycles.

 I will lean the bike over as far as I dare.

Are you checking the oil level with the motor warm?