Can’t say I’ve ever had a problem with following the quantities/procedure in the handbook. I’ve also used Kev’s method of putting the 0.6/0.7L in through the crankcase breather first and then adding the 1.9L to the tank. Both work well and result in a level that shows about half way up the dip stick (after running the motor).

Assuming all the obvious stuff - the bike is level, you’re checking the oil on a warm engine after a short run and that you’re measuring the level with the dipstick pushed home (not screwed in), there shouldn’t really be an issue.

If you’re absolutely 100% sure you’ve got 2.6L in there and it’s still not reading on the dipstick following the correct checking procedure, then something isn’t right? Aside from physical oil leaks, clouds of blue smoke (or an airbox full of oil), which I’m sure you’d notice, there’s only one place the “lost” oil can be without any obvious visual clues – and that’s in the sump. Even though the XT is technically a dry-sump motor, it’s only semi- dry; there is a small sump to collect oil for scavenging and returning to the tank. This is why running the bike to scavenge the sump is essential to get an accurate reading on the dip stick.

The most common cause of “missing oil” (with no visual clues) in dry-sump motors, is that the pump isn’t scavenging the sump efficiently (the return isn’t keeping up with the flow) and there is a degree of “wet-sumping” going on (a build-up, or excess of oil in the sump). There only needs to be slightest drop-off in efficiency of the scavenge side of the pump to cause a small build-up/back-up of oil here.

However, I’ve never heard of this on an XT660 motor? I’m more than familiar with “wet-sumping” on dry-sump British bikes with worn oil pumps – it’s extremely common.

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