Hi,
I don't have personal experience of running a 160 but I have checked the 160 handbook as well as the manual and the 2.1 litres is what is specified but if you look on page 20 as attached you will note that the book actually states that using the oil filler neck and dipstick will allow oil level measurement. So that begs the question why they didn't fit one in the first place as it clearly shows that there isn't one fitted in the parts book!
My suggestion is that you get hold of a filler neck and dipstick as this will make life a heck of a lot easier. If you then fill the engine up to the top mark on the dipstick (As the handbook states, that is with just the dipstick held against the edge rather than screwed in) I expect you will get a lot more oil in. Generally speaking I check the oil on level ground with both wheels on the ground as with the bike on the stand all sorts of things like tyre sizes etc can cause the bike to be leaning more forward, reducing the ability to get oil in. Usual thing is to rest the bike on a stand on the right hand footpeg leaning away from you and just pull the bike towards you to upright when checking the level. Personally I think 2.1 litres is going to be a lot of oil as we only run 1.875 litres in our 250/350 narrowcase race bikes. So if you have 1.8 litres or more in there I would not be too concerned. 1 litre is not enough and is incorrect. One other thing that is laughable in the book is that it describes the oil capacity as "about 2.1 litres!"
The other thing is to remember once you start the engine an element of oil will become trapped in the cylinder head and you may have to top up the oil slightly to reach the correct position on the dipstick after first start up. Personally again, I tend not to bother with the dipstick itself and judge the oil level by looking down the hole of the neck and observing the oil level relative to the step in the neck. For our race bikes with 1.875 litres, this is just below the step.
I would be interested to know how much oil you manage to get in with the neck and the bike on level ground relative to the step or dipstick.
Nigel
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