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2 Stroke Engine Oil Contest

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I don’t tell mx racers what oil or ratio run based on trail riding so why do they feel it necessary to tell me how to operate my cycle for race conditions? I’ve never had a motor go boom even tho I don’t use 32:1. It may have something to do with anticipated load.

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31 minutes ago, shrubitup said:

I don’t tell mx racers what oil or ratio run based on trail riding so why do they feel it necessary to tell me how to operate my cycle for race conditions? I’ve never had a motor go boom even tho I don’t use 32:1. It may have something to do with anticipated load.

Run whatever floats your boat doesn't matter to me or anyone else's long as works for you. Try Rotella at 60:1 😂😂

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SS - It is Motul that recommends their 800 Off Road oil at 50:1 for motocross. Motul 800 is one of the high quality full synthetic oils that can be used at high ratios because of the oils high viscosity and viscosity index. Here is the page showing Motul recommending 50:1 http://motul.speclube.com/wp-content/uploads/products/specifications/800_2TFactoryLine_OffRoad_8371_(GB).pdf

Other really high viscosity oils are Honda HP2, Motul Kart, ELF HTX 976+, Bel-Ray MC-1, Repsol Moto Racing, RedLine Allsport.

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I ride an air cooled bike and these type engines have more piston/cylinder clearance and make less piston noise with more oil (lower fuel/oil ratio). So I advise for air cooled engines that people use a semi-synthetic that is a blend of synthetic and mineral oil. It is less viscous and so more of it should be used to get the same final mixed viscosity. They are typically used at 35:1 instead of the 50:1 typical of the high viscosity fully synthetic oils. 

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Posted (edited)

There are two ways to determine fuel/oil ratio:

1) for race engines that you want the best power from them you just use a lot of oil, close to 32:1 (of any type oil with a viscosity of at least 2 @ 200*C). You also want this ratio for air cooled cylinders to prevent piston noise.

2) for water cooled engines and you are not concerned with absolute best power and are on a budget and just want adequate protection, then you can use my oil ratio calculator to know how high you can go on fuel/oil ratio and still be protected.

From 65cc to 250cc Honda recommends 32;1 of their full synthetic HP2 oil, and Yamaha recommends 30:1 of their mineral non-synthetic Yamalube 2R oil.

My calculator says Yamalube at 30:1 is good for the tiddlers up to 125cc (reving to 12K RPM) and 34:1 is good for the 250cc reving to 9500. So Yamaha is doing both- recommending lots of oil for good ring sealing (good power) and recommending according to the oils viscosity.

Honda is in over-kill with a high viscosity (3.2 @200C) full synthetic at 32:1 and they could just as well recommend using about 4 other oils that according to their viscosity would better match that ratio. But the HP2 oil is cheaper than they are so the temptation is to stick with it. But consider this- when you use more than what is needed of a high viscosity oil for decent protection then at low and mid range RPM you have more power loss due to viscous friction.

So for owners of water cooled engines the question presents itself if we want to spend more money for best power or use just enough oil for decent protection if we aren't racing.

Edited by jaguar57
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Hi wondering if you can help me with the correct ratio for my 1995 watercooled Suzuki rmx250 using  putoline mx5 2 stroke oil . Bike is used on the road and trail riding so will experience wide open throttle also would like to keep the spooge levels low without risking engine damage 

cheers in advance 

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For further help on ratios please go to www.dragonfly75.com/moto/oil2.html

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On 10/8/2018 at 7:11 AM, Romney1 said:

Hi wondering if you can help me with the correct ratio for my 1995 watercooled Suzuki rmx250 using  putoline mx5 2 stroke oil . Bike is used on the road and trail riding so will experience wide open throttle also would like to keep the spooge levels low without risking engine damage 

cheers in advance 

How long and how often is it WOT

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There would be the odd time of wide open throttle on open roads but mostly just normal riding 

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One thing you didn't mention is that when you change oil ratio, you need to check jetting.  If you reduce the amount of oil, you have increased the amount of fuel entering the combustion chamber.  The bike runs rich and people think they have too much oil.  Even worse, if you increase the amount of oil, you effectively lean the bike out which can cause it to ping and do damage.  It is much better to pick a ratio, and maybe your method is a starting point, and stick with it.  Then, jet the bike for the atmosphere and altitude that you are riding.

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