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What oil in YX 140?

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I have a pit bike with a yx 140 engine and its done 1hr so im goin to do its first/run in oil change but not quite sure what oil i should put in it. Should i put mineral or synthetic or semi synthetic oil in it and what grade... 5w30, 15w40, 20w50 etc etc???. I have asked a few people i know who ride pit bikes and they all run anything and everything they can get their hands on:bonk:, not very helpful but none of them seem to have any issues with what they use. What do you guys run and recommend to use?

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Ok thats what i thought, i already bought some 15w 40 mineral oil so i will use that. Cheers.

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I use Belray Thumper in my YX140, any opinions on that?

Need more info on that oil

Petroleum base oils are fine

NO Synthetics or Synthetic Blends recommended PERIOD

Forget the brands , its about the content

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The idea that synthetic oil will not allow the rings to seat is an old shade tree mechanic's tale, simply wrong. There is nothing wrong with using synthetic in a brand new engine, in fact many engines come filled with synthetic right from the factory.

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Belray Thumper is a mineral-synth blend (group 3 synthetic I think), JASO-MA rated for motorcycle wet clutches, which is the main requirement one must ensure the oil passes before dumping some in your motor.

I was getting about 6-7 hours fairly hard riding between oil changes on the plain mineral Valvoline stuff my uncle was buying for his bike before I came along, then started using this and am only just thinking about changing the oil again now (19-20 hrs riding later, deep sand for about 10hrs of that)

I was recommended this oil by a "mechanic" (17 year old kid that works in a chinese bike store whos dad is a car mechanic) they apparently run it in every one of their race bikes, with YX150 / Daytona 150 engines. Was a tad skeptical at first, as I bought into the "NO SYNTHETICS!!!11!" line, but have had no problems with clutch slipping, apart from the other bike that needs a clutch rebuild, and gear changes are still smooth and fast after nearly 20 hours of abuse.

So I'd argue the "no synthetic" line is bullshit, as Atomik mention the reasoning behind it being to stop clutch slippage, when any JASO MA rated oil will not slip with a wet clutch..

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Its good to see peoples different points of view on what to use. As a mechanic myself i cant see why synthetic oils would not be good for a pit bike engine, after all they really are just a glorified post bike engine arent they, but that also makes me think mineral is the way to go since it was all that was available when these engines were originally designed. I was tempted to use some 15w40 synthetic oil that we have at work but more and more people advise against it and im yet to hear a good reason why, as mentioned already some say the clutch will slip or the rings wont seat properly but im with cloud2901 on this and thinking it might just be bull$hit especially since nobody i know who has used synthetic oils has had any problems with it.

Ive changed the oil since my first post to 15w40 mineral oil like i was advised by most of you guys here and put another three hrs on the bike and so far i couldnt be any happier with using it, the engine has loosened up a little and become much more responsive and noticably more powerful than it was with 1hr on it, im only relatively new to pit bikes and i must say im surprised just how good the quality of them yx 140's are so far.

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Its good to see peoples different points of view on what to use. As a mechanic myself i cant see why synthetic oils would not be good for a pit bike engine

Good observation

Our recommendation is inside industry advise gathered via years of dealing with these little motors.

After working on many and selling hundreds since 2004

and answering thousands of tech calls ect.

We have found that the rings DO seat better with Petroleum base.

AND the clutch basket cush drive rubber wears out FAST with synthetics.

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Good observation

Our recommendation is inside industry advise gathered via years of dealing with these little motors.

After working on many and selling hundreds since 2004

and answering thousands of tech calls ect.

We have found that the rings DO seat better with Petroleum base.

AND the clutch basket cush drive rubber wears out FAST with synthetics.

That right there is a heaps good enough reason to stick with the poor mans oil:thumbsup:, thanks for the info T Bolt USA man.

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