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Make: Yamaha
Model:YZF-R125
Year: 2009
Engine type: Liquid cooled 4 Stroke 124cc
Performance modifications: None
Riding style: Aggressive Road
What recommendation are you looking for? Engine, Gearbox, fork oil etc. - Every oil, fully servicing it over the next few weeks.
 

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643 Posts
Make: Yamaha
Model:YZF-R125
Year: 2009
Engine type: Liquid cooled 4 Stroke 124cc
Performance modifications: None
Riding style: Aggressive Road
What recommendation are you looking for? Engine, Gearbox, fork oil etc. - Every oil, fully servicing it over the next few weeks.

Gearbox oil is the same as engine oil on our bikes m8.
Engine oil - any motul, 5100 till 300V. I use 300V myself
 

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Discussion Starter · #92 ·
Make: Yamaha
Model:YZF-R125
Year: 2009
Engine type: Liquid cooled 4 Stroke 124cc
Performance modifications: None
Riding style: Aggressive Road
What recommendation are you looking for? Engine, Gearbox, fork oil etc. - Every oil, fully servicing it over the next few weeks.


Hi

A 10w-40 is ideal for the engine/gearbox.

http://www.opieoils.co.uk/c-782-10w-40.aspx

The best oils there are the Silkolene Pro 4 and Comp 4, Motul 300v, Redline, Amsoil, Shell Advance Ultra 4 and Castrol Power 1 Racing. The Motul 5100, Castrol Power 1, Shell Advance VSX and Silkolene Super 4 are good cheaper alternatives.

For some reason, we don't have the fork oil listed on our databases.

Cheers

Tim
 

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Make: Mazda
Model: mx5
Year: 1997
Engine type: 1.8i
Performance modifications: Aftermarket exhaust, probably going to have an aftermarket air filter at some point too.
Driving style: use on road and occasional track days, so it's going to be driven hard.

I'll start with just the general engine oil :p
 

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Discussion Starter · #95 ·
Hi

I would use a 5w-40 synthetic.

http://www.opieoils.co.uk/c-656-5w-40.aspx

Out of those, the best ones are the Fuchs/Silkolene Pro S, Millers CFS/CFS NT, Motul 300V, Red Line and Gulf Competition. The Motul 8100 X-Cess, Millers XF Longlife, Fuchs GT1 XTL/Supersyn, Gulf Formula G, Shell Helix and Mobil Super 3000 are good, cheaper alternatives.

Cheers

Tim
 

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I know Yamaha recommends 10W-40 viscosity for the YZF R125 2021 model. With the short change intervals of only 3000km, I´m thinking to use a 5W-40 (e.g. MOTUL 7100 5W-40 4T - Motul ) in the winter season und a 10W-50 (e.g. MOTUL 7100 10W-50 4T - Motul ) in the summer time.
What do you think.
 

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2008 YZF-R125 (180cc)
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707 Posts
for the last 2 years the clutch has dragged on my dirt bike, meaning i effectively was not able to switch to neutral when the engine is running, and also I had to start the bike against a wall every time it had been standing for a week or so i.e. so, start the bike with front wheel against the house, rev it, drop it into gear and just grind the back tyre till the clutch breaks loose....fun/exciting process! 😬 .

it turns out I had put the wrong weight of oil in the gearbox... it had 10w 40 rather than 5w 30... I replaced the oil recently once I became aware of my mistake and now the clutch doesn't drag and i can select neutral as intended.

Why is this relelvant? well the new oil is not really all that different from the old (the same change you're suggesting but the other direction) but those 5w made a HUGE difference to the usability/functionality of the bike, because it had been designed to use 5w 30 not 10w 40.

so IMHO if yamaha says use 10w 40 semi-synthetic, use 10w 40 semi-synthetic. You don't know what things depend on that specific viscosity or what knock-on issues you might be causing by having thinner or thicker oil.

I hope that helps.
 

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2008 YZF-R125 (180cc)
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your answer got me thinking to double check what I thought I knew re oil so I got digging in the manual.

I dunno if this is useful but i found this in the owners manual (for gen1), not the service manual. Is there perhaps a similar pdf/manual thing for the 2021? Seems to have a variety of oils it can use, depending on temperature range.

Interestingly no 5w in there, even for very cold temps, and having just had the experience with my dirt bike and seen just how differently that worked on 5w30 vs 10w~, i don't think I'd do that to my shiny new '21.

but yeah they don't really specify mineral/semi/fully synth.

I always used to run fully synth on my cars but they were all dry clutch. Some people (on here) seemed to have issues with fully synth. When I looked into it ages ago there seemed to be a general leaning (on here) towards 'silkolene 4' 10w40 semi-synth which is what i've been using for the last 4+ years and have not had any issues, but it migh tbe worth asking yamaha cos it might be different on the newer bikes..

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