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Proper Gas/Oil ratio?

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Posted by: Doclar---------------------

This 2000 KDX200 is my first 2-cycle ever. What do you recommend for proper gas/oil ratio and is there any oil favored over another? Someone told me 44:1 !?!


Posted by: Dazza---------------------

I use 40:1 ratio.The oil is synthetic castrol tts.Never had a problem.
Personally I wouldn't go any higher but others do and seem not to have problems but I'll stick to 40:1.
Do a search on ratios and look at the results 25:1,32:1,50:1etc etc etc
Make your own mind up on it.


Posted by: ninjaman---------------------

I run 100:1 Amsoil.
No fouled plugs, no oil residue, runs a lot cleaner, very little carbon and cost less per gallon of fuel.


Posted by: R. Phillips---------------------

Depends on how you ride. If you do woods, and only torque it up a little on straits, 40 something:1 is fine.

You will hear hundreds of variations on this subject. 32:1 up to 100:1
To each his own. I personnally don't have the cash laying around to do premature top ends. OEM says 32:1 and I just try to stay close to that.

Common sense tells you that the harder you run it, the more lube you need in the jug.

I went to 40:1 to fine tune my jetting. It runs clean with less smoke.


Posted by: paull---------------------

i run 40:1 silkolene ester synthetic with no hassles at all my mate has a 89 model kdx and he runs 50:1 motul 800 and rides very hard with no problems at all


Posted by: RJ-KDX---------------------

Amsoil 2000 @ 40:1. Less smoke, less money per gal, and it's synthetic.




Posted by: canyncarvr---------------------

Keep in mind that a change from 32:1 to 40:1 effectively makes your air/fuel mixture richer. If you're too rich to start with and running 32:1, going to 40 will make things worse A/F-wise.

A point of view other than 'It works for me!!!':

Service Ratios: Normal use ratios are 32:1 to 50:1. Racing requires greater oil content. Ratios no higher than 40:1 should be used. Small displacement, high-RPM racing engines should use rations no higher than 32:1.

..from:
http://www.maximausa.com/technical/oilratio.html

From the same site:

Recommended Premix Ratios
50-80cc (24-32:1) 125cc (24-40:1) 250cc (24-40:1)
500cc and up (32-60:1)


Posted by: IRISHCOFFEE---------------------

Do not want to upset anyones boat but NO test devised to date sibstantiates the claim of a measurable difference in flow between ratios typically used. The idea that 20 to 1 is leaner than 50 to 1 CANNOT be demonstrated. The flow differences just cannot be proven to effect jetting. The theory has merit, reality is another thing.


Posted by: canyncarvr---------------------

Huh?

What does difference in flow have to do with it? It's merely a matter of amount of fuel : amount of oil.

You're saying no one can 'substantiate' that 20:1 is leaner than 50:1?

You're kidding, right?


From the tech tips on the maxima page:
Jetting: Increasing oil (per gallon of gas) may require increasing jet sizes. Decreasing oil (per gallon of gas) may require reducing jet sizes.

MY boat's on an even keel!


Posted by: Lew---------------------

My backyard mechanical understanding of jetting is the relation of air to fuel. In our 2 strokes spooge and smoke are just a product of poor jetting (by virtue of oil being mixed with the fuel), not wrong oil ratio. This is why we don't change oil ratio to correct jetting. rich jetting = more fuel. So it would only make sense that if you changed from say - 32:1 to 40:1 you would in effect be delivering an addition 8 parts fuel to air. Thereby creating a more rich jetting situation.
Lew


Posted by: canyncarvr---------------------

Your 'demonstration' please..............yanno...substantiate that!!

Just razzing to no particular good end, folks . I get a good bit of it, so I'm just sharing the wealth!!

Where lew is wrong I have absolutely NO clue!

'cuz he's not.

Actually, I'm sure there IS some difference relative to 'flow' just due to the viscosity change of the mix when A/F ratios are changed. I think that was what IRISH was talking about.

Putting the idea of flow rate change due to oil amount differences and lean/rich effect due to ratio changes is an odd juxtaposition.

Still...the idea of 'flow' as he first stated probably does matter....some. Probably not enough to make any difference.

....doesn't have anything to do with ratio changes......


Posted by: John Harris---------------------

Looks like most use SYNTHETIC not blends or mineral for clean running. If you use synthetic, 40 to 44 to 1 will work fine to lube your machine and run clean--with the proper jetting. I was one of the last ones on the planet to switch (to synthetic) but I am glad I did.


Posted by: XRDadKDXBeni---------------------

Get a 4 stroke and forget about the mixing ratio! XRDad


Posted by: canyncarvr---------------------

Off topic...but re: 4-strokes...400 in particular.

I remember (last weekend!) watching a mature gentleman on what he surely thought was going to be a nice ride. The 'nice ride' ended up being fraught with a BUNCH of 'go-rounds' due to fallen trees and such. He dumped his xr400 on one such tree crossing.

While I bounced over the obstacle with a grin..bounced back over it to go fetch my sportrak-90 riding 9yr old daughter..came back with her...got her over the trees..

and he was STILL kicking that thing!!!!

Got to the top of the trail. Sat around for awhile. Never DID see him.

(yes, I did ask if I could help him with anything. He declined)


Posted by: KdxChode---------------------

He probably decided to call it a day. He needed to go home and tear his top end apart, the XR was overdue for a valve adjustment anyways.

Ratio? what's that?

I just run 40:1 cause thats how much oil comes in the bottle. One bottle of oil, five gallons of gas...Done


Posted by: XRDadKDXBeni---------------------

Just playing guys. We also have a KDX220 and run it at about 32:1 - I believe you can run just about any premix ratio and if you are an average rider, you won't be able to tell much difference. Top end ware may be accelerated, but its probably a difference of only a few hours longevitity over several hundred (or maybe thousands) of hours of operation. If you're a pro/expert, then I believe the jetting aspect will come into play - jet for performance based on the mix you use and you will be rewarded with more power in a better tuned engine. As for me, its 4 strokes in a 250 cc package, they're easier to start, canyncarvr, especially for a mature gentleman like me. heh, heh, heh.


Posted by: Lew---------------------

Quote:
Originally posted by XRDadKDXBeni
Get a 4 stroke and forget about the mixing ratio! XRDad


These to need to be jetted correctly


Posted by: HOTRODKY428---------------------

I WOULD RATHER CHANGE A PLUG OVER AN ENGINE REBUILD ANY DAY


Posted by: BRush---------------------

Quote:
Originally posted by IRISHCOFFEE
Do not want to upset anyones boat but NO test devised to date sibstantiates the claim of a measurable difference in flow between ratios typically used. The idea that 20 to 1 is leaner than 50 to 1 CANNOT be demonstrated. The flow differences just cannot be proven to effect jetting. The theory has merit, reality is another thing.


You lost me there. Sure 20:1 is leaner than 50:1.

"Lean" or "Rich" from a combustion standpoint concerns only the gasoline to air ratio. Premix oil is not fuel.
When the piston is squeezing the fuel charge just instants before the spark plug fires, you have three things in the combustion chamber:

Air
Gasoline (fuel)
2 Stroke Oil (lubrication)

The more 2 stroke oil is in the fuel charge, the less room there is for gasoline. That means that a 20:1 gas/oil mix has less gas for the given volume of air then a 50:1 gas/oil mix.



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