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Old 03-26-2013, 07:42 PM   #1
craydds OP
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Favorite Premix Oil and Ratio

I now have a soon to be running 1976 Yamaha YZ400. It fired right up when I bought it, but it is in pieces all over the house; will be re-assembled in the coming weeks. I have some questions about premix oil and ratios.
I bought a Yamaha YZ400C factory service manual. It calls for a 20:1 mix. That sure seems like a lot of oil! But I would rather mix a bit more oil than too little.
I would also like to use a full synthetic oil like the Bel-Ray MC-1, http://www.belray.com/bel-ray-mc-1-r...-2t-engine-oil , but it is sure expensive!
What favorite oils are you using? Full synthetic or... ? What is the premix ratio are you using, with which bike, and with which particular oil. Any good reference articles, websites, etc.?
Yes, let's start a PREMIX THREAD.
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Old 03-26-2013, 08:08 PM   #2
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Repsol 2T synthetic 40:1 KX and KDX

20:1 is way too much...I'd have spooge and smoke all over the place.
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Old 03-26-2013, 09:11 PM   #3
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You're going to get all kinds of answers, but few will be right for you and your bike if all you get is an I run X-oil at XX:1 ratio. there is no simple single answer.

Look at one factor, one of the most important, the engine rpm range in which will spend most of your riding time. THe reason for this is that the rpm determines the contact time the fuel/oil mixture will have with the moving parts it is trying to lubricate. In a simplified explanation, the lower the rpm, the less oil is required in the premix. The higher the average rpm range run, the shorter is the contact period for the oil to be deposited and the need for more oil to be present in the mix.

As an example. When I had a Beta Techno trials bike, I typically ran a premix ratio in the 80/100:1 range. Most of the time, it ran in a low rpm range. Now in our road race engines, we typically ran a premix in the 16/20:1 ratio as they typically ran a very high rpms.

So when you ask someone what ratio they run, you need to also ask what kind of bike, what type of riding, etc.
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Old 03-26-2013, 09:27 PM   #4
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BTW, google Gordon Jennings and two-stroke oil ratios or something similar.

Oh as for oil, in road racing, we ran a home brewed mix of synthetic and castor, generally in a 3:1 ratio.
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Old 03-26-2013, 09:36 PM   #5
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The manual may figure the bike was originally jetted from the factory to run Yamaluba at 20:1. I had numerous yz's in the late 70's and early 80s' and the manuals on my bikes all recommended Yamalube at 20:1. Of course I was running smaller motors back the and I never had problems with Yamalube(or similar oil) at 20:1. Back then my Dad thought more premix (more money)was still less than an engine rebuild from lack of lubrication. My older brothers routinely ran very little premix and always had to rebuild their motors.
When I went to bigger bikes, 500cc, I used to run 40:1 and never had problems. Like CharlieT noted, smaller engines run higher rpm's and need the extra lubrication while bigger engines run lower rpm's and need less lubrication.
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Old 03-26-2013, 11:58 PM   #6
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Quote:
Originally Posted by CharlieT View Post
In a simplified explanation, the lower the rpm, the less oil is required in the premix. The higher the average rpm range run, the shorter is the contact period for the oil to be deposited and the need for more oil to be present in the mix.
Thanks, CharlieT, good information. I am a recreational rider, not a racer (just like to pretend). I will NOT be riding high rpm, all out MX. Most of my time is easy to moderate desert trail riding - no enduro racing. Looks like I have some room for experimentation with ratios, likely don't need to start with 20:1. I certainly have need for further education. I used to have a good 2-stroke tuning book - will look online, etc. for more info.
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Old 03-27-2013, 12:13 AM   #7
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Originally Posted by daviethebiker View Post
Back then my Dad thought more premix (more money)was still less than an engine rebuild from lack of lubrication. My older brothers routinely ran very little premix and always had to rebuild their motors.
My nephew spent a lot of time and $$ rebuilding his CR250. He took it out and trashed it running a 50:1 mix. He took some bad advice from someone as gospel - "all you need is a 50:1 mix with this monster-power synthetic oil, and your bike will make HUGE horsepower". When I heard about it, I instantly new that 50:1 was way to "thin" for a race bike, especially the way my nephew rides. I can understand that my factory manual spec of 20:1 is for all out racing for which the bike was designed. But that would have me puking oil out the end of my silencer.
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Old 03-27-2013, 12:19 AM   #8
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Originally Posted by AtomicXRer View Post
20:1 is way too much...I'd have spooge and smoke all over the place.
That's what I'm thinking. The price of synth 2-T oil is not cheap, either. A 20:1 mix would be some high $$$ premix.
If you ever get tired of that gorgeous north country, come down and ride the hot desert. My main bike is a KLX300.
LET'S RIDE.
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Old 03-27-2013, 12:25 AM   #9
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Originally Posted by CharlieT View Post
BTW, google Gordon Jennings and two-stroke oil ratios or something similar.
Found this - http://www.bridgestonemotorcycle.com...oilpremix6.pdf . Found several others, too, like this - http://www.datafan.com/Horsepower_Bl...ners-handbook/ . Thanks for the tip!
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Old 03-27-2013, 01:42 AM   #10
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There is an awful lot of nonsense around the net concerning 2T pre-mix ratios, and little understanding of the fact that dual purpose oils (which can also be used in 2T oil injection systems) are far from ideal for use in pre-mix competition bikes!

The ratio used is largely dependent on the heat being generated by the motor. An example of this would be a trials bike being run on 100:1, and a road racer on 30:1. Obviously the road race motor is running far higher rpm, and gets much hotter than the trials bike.

One of the main reasons for using more oil in high heat applications is due to more oil helping with heat dissipation. In some cases road racers will increase the amount of oil for courses with long straights, where motors are held flat out for longer, and reduce oil on tight twisty courses with less high rpm running.

In all cases though less oil will mean cleaner running, better pickup from low rpm and more power. However less oil is not a good idea if its a high heat application such as road race or MX. Using more oil for trials and recreational riding, will mean reduced power, less responsive motors and exhausts which become badly clogged very quickly.

Best possible oil to use for any pre-mix competition bike is a product specifically designed for this purpose, and not one of very thin dual purpose injector oils, whose use on comp bikes which may be used infrequently is far from ideal, purely due to the very thin injector type oil not being very good in terms of providing good corrosion protection when bikes are not being used.

Using full synthetic pre mix only oil, for air cooled trials 70:1, for water-cooled trials 100:1, for recreational off roading 60:1, for serious MX racing 40:1 will work fine. If you choose to use dual purpose injector type oils, increase amount of oil by 20%, as these oils are generally thinned by the addition of kerosene, so are a lot less oily than proper competition lubricants.
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Old 03-27-2013, 04:43 AM   #11
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Originally Posted by Twin-shocker View Post
Using full synthetic pre mix only oil, for air cooled trials 70:1, for water-cooled trials 100:1, for recreational off roading 60:1, for serious MX racing 40:1 will work fine. If you choose to use dual purpose injector type oils, increase amount of oil by 20%, as these oils are generally thinned by the addition of kerosene, so are a lot less oily than proper competition lubricants.
The different types of 2-T oils was confusing. Some might be premix-and/or-injection and some are premix-only, like the Bel-Ray MC-1. Thanks for the excellent information and clarification, Twin-shocker. Based on your information I will use the PREMIX only type and not the "dual-purpose" type.
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Old 03-27-2013, 05:13 AM   #12
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heavy (synthetic) oil load+leaded race fuel=more power+longer engine life

I run 32:1 with fuel containing 6% oxygen and 5 grams of lead per gallon. Results in a very fast long living air cooled big bore.
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Old 03-27-2013, 05:39 AM   #13
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heavy (synthetic) oil load+leaded race fuel=more power+longer engine life
I run 32:1 with fuel containing 6% oxygen and 5 grams of lead per gallon. Results in a very fast long living air cooled big bore.
I like the idea of a full-synth oil. The claim is no smoke and no carbon build-up, along with better lubrication, etc. All sounds good, if it is really true. Experiences anyone? Reality check?
Caveat: In my 4-stroke motors I see NO reason to run synthetic oil, despite any claims by the synth-oil company. I use mineral oil ONLY in the motors and drive-trains. In my old BMW's I believe (as do many others) that synthetics are HARMFUL.
Now, back to 2-strokes.
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Old 03-27-2013, 10:04 AM   #14
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Most 2/'s will produce max power at a ratio around 18/20:1, contrary to the "conventional wisdom" that less oil produces more power. As for spooge, until you get below 16:1 the spooge is a result of improper (too rich) jetting. Even when we ran a 16:1 mix, we had no problems with spooge. However it was not unusual to change jets 2-3x's a day. Your typical recreational rider rarely ever changes the jets and consequently can be too lean at times but more often than not too rich.

I think it is Maxima that had some decent web pages that showed oil deposition and gave some good recommendations as to premix ratios needed to provide adequate lubrication.

With straight synthetic, the top end looked great, no problems with gumming up and sticking a ring. However on engine teardown, there was minimal residual oil coating on bearing surfaces, etc. With straight castor, it would have a tendency to gum up the rings and leave more residues on the crown. However in engine teardown, the lower end looked much better and had more residual oil film present. That's why we blended a full synthetic with a castor. Trial and error showed a ratio of 3:1 worked best using the oils we did in our engines.

BTW, if you read that Gordon Jennings paper on 2/'s, you will have a better understanding of a 2/ motor than 90% of the people that ride them.
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Old 03-27-2013, 10:39 AM   #15
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I did not go through all and read them, but I know this get offroad fuel or marine grade gasoline, because the ethinol garbage out there will give you headaches JMHO
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