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7 Posts
Discussion Starter · #1 ·
I bought a CB300F about a week ago. I've noticed that when I hold the bike level and check the oil, the sight glass is totally or almost totally full. If I move the bike a couple degrees off level, I can see a small air bubble through the sight glass.

Is this too full? As I said, the bike is new and I'm assuming the dealer would have checked the oil level but I just wanted to double check.

I tried searching for a thread on this but couldn't find it. If I missed one, please point me in the right direction


1,260 Posts
it does make a difference even a degree out of vertical
to how oil level appears in the sight window..

owners manual [p 55 - 58] requires 'a firm level surface
and motorcycle in an upright position' when checking..

on levels it states 'between upper and lower levels'..

p56 'adding engine oil'; 'if the engine oil is below or near
the lower level mark, add the recommended engine oil.'

'... until it reaches the upper level mark'..

'do not overfill above the upper level mark'..

plus; 'NOTICE overfilling with oil or operating with
insufficient oil can cause damage to your engine.'

when the bloke at the dealers i took delivery of my cbr300r
went over the bike with me, oil level seemed too low to me,
but he said that 'as long as its visible, its ok' and seemed
sure of himself..
after riding home and cooling i checked level
carefully, which was too low for my liking, so checked
the owners manual in particular p56 'adding engine oil'
on adding oil 'until it reaches the upper level mark'..

added about 30 - 40ml of oil, close to the upper level..

took her for a ride, when cool checked [level surface]
and it was still near and below the upper level mark..
where it stayed until changing oil/filter at 250km..

our sump only takes [p58];
[changing oil & filter] 1.5 litres (1.6 us qt, 1.3 imp qt)
[changing oil only] 1.4 litres (1.5 us qt, 1.2 imp qt'

so you can be precise if you like in changing oil
by measuring out the recommended amount
into a separate bottle or jug etc, before pouring..

honda gn4 1 litre oil kit bottles have see thru
lines up the side with graduation marks,
so you can pour one out into a jug etc
then refill it to exactly the right amount
using the graduated bottle itself,
plus the other 1 litre of oil..

given our small oil sump capacity
and small filter, i reckon you can give
her an ok change whenever you like,
especially during crucial first phase
of wearing in..

the best way to find out how much oil is in there
is to empty it out [after warming her up]
and measure it directly..
then of course refill accurately..

Premium Member
5,459 Posts
I often get a buddy to 'sight me' when I'm checking my oil. Sitting in the crouch position beside the bike with one hand on the handle bar I then push the bike away from me until he tells me its level, then I check the oil level.

I keep mine half way between lower and upper but I live in a cool climate. Would suggest using upper level for warmer climates.

188 Posts
I stand astride the bike with a bubble spirit level on the tank (4cm) and use a shaving mirror in my right hand to see the sight glass.
I also keep mine in the middle of the two level lines.

Premium Member
3,009 Posts
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1,260 Posts
just on sighting method, aside from excellent use of
levels or mirrors etc, i like to position her against
or close to a wall, go down on one knee holding
throttle with right hand, left hand over seat,
thus able to move her to and fro gently
without fear of losing her/falling away..

if i did lose her away to gravity it would only
be a couple of inches til left bar touched wall..
down on left knee allows for quickly rising,
and also for ok close sighting..

going for verticality, the oil bubble itself
is and can be used as your level..

moving her to and fro an inch or so
will result in whatever oil is in there
moving up and down in the sight window..
between the up and the down points
must be her vertical position..

225 Posts
Has anyone fitted a drain valve to replace the drain plug? Like a fumuto or E-Z valve?
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