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Old 03-26-2013, 08:42 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, 09:08 PM   #2
AtomicXRer
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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, 10:11 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, 10:27 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 03-27-2013, 01:25 AM   #5
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Quote:
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, 02:42 AM   #6
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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 03-26-2013, 10:36 PM   #7
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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 03-27-2013, 01:13 AM   #8
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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 $$ rebuilding his CR250. He took it out and trashed it running a 50:1 mix. He took some bad advice from someone as gospel - "all you need is a 50:1 mix with this monster-power synthetic oil, and your bike will make HUGE horsepower". When I heard about it, I instantly new that 50:1 was way to "thin" for a race bike, especially the way my nephew rides. I can understand that my factory manual spec of 20:1 is for all out racing for which the bike was designed. But that would have me puking oil out the end of my silencer.
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Old 03-27-2013, 12:58 AM   #9
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In a simplified explanation, the lower the rpm, the less oil is required in the premix. The higher the average rpm range run, the shorter is the contact period for the oil to be deposited and the need for more oil to be present in the mix.
Thanks, CharlieT, good information. I am a recreational rider, not a racer (just like to pretend). I will NOT be riding high rpm, all out MX. Most of my time is easy to moderate desert trail riding - no enduro racing. Looks like I have some room for experimentation with ratios, likely don't need to start with 20:1. I certainly have need for further education. I used to have a good 2-stroke tuning book - will look online, etc. for more info.
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Old 03-27-2013, 01:19 AM   #10
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20:1 is way too much...I'd have spooge and smoke all over the place.
That's what I'm thinking. The price of synth 2-T oil is not cheap, either. A 20:1 mix would be some high $$$ 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, 09:01 PM   #11
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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.
Quote:
Originally Posted by craydds View Post
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.

I was down there (Hatch/TorC) just last month...thaw is over so time to ride the north.
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Old 03-27-2013, 09:18 PM   #12
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So do I use Blendzall Green in my IT490 at 20:1 like the manual says?

At $56 per gallon for oil and permium gas at $4.35 mixed 20:1 with Blendzall will be $7.15 per gallon.
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Old 03-28-2013, 05:28 AM   #13
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At $56 per gallon for oil and permium gas at $4.35 mixed 20:1 with Blendzall will be $7.15 per gallon.
That's what I'm sayin'. Makes riding my KLX with straight gas seem really cheap. If we could run 40:1 it would cut the cost of the oil by half. Guess it's going to cost big $$ for premix to get that big POWER RUSH from riding a big-bore 2-stroke. Speed costs... how fast do you want to go?
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Old 03-27-2013, 12:03 PM   #14
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As you ride an MX bike.

As a rule of thump 1:50 or 2% for MX bikes is OK with modern fuel and modern two stroke oil.
Using this for my KTM 500 two stroke, (set up for trails riding), works very good does not leave much of deposits doesn't clogg the pipe and exhaust.

Too much oil will be sputted out and the engine will smoke a lot, 1:20 is old fashioned when often nothing else then motor oil used for four strokes was pured in the tank of tweo strokes.

If the engine is already "older" and havn't been overhauled you might use more oil the 1:50, it depends very much how you ride the bike, more MX or more trail riding for example. In thight trails where you use more the low and mid rpm too much oil is unhealthy the engine will often not get so hot to burn up the oil so it will sputted out at the rear end of the exhaust.

Instead when going very fast at an MX race more oil can be used for good conscience and to aviod any seizure, the engine will be more used at mid and high rpm will get much heater and therefor burn up the oil much better.

In own experience.
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Old 03-27-2013, 01:12 PM   #15
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I've been running Motul between 32:1 - 36:1 in my smokers..........old and modern with no problems. BTW, the new fuels suck canal water.

Scootern29 screwed with this post 03-27-2013 at 01:13 PM Reason: I can
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