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Having owned a 2 stroke for 3 days, can someone tell me what the consequences are to running fuel that is either too rich or too lean? A fellow 2 stroker topped me off as he was leaving and I learned after the fact that he was running 40:1 where I am running 32:1. I haven't burned much if any of the 40:1, but wasn't sure what the results of this could be. Think I need to drain it and stick with manufacturer specs..

Using the search function on mix ratio, you'll likely find that many are running 40:1. I ran 40:1 in the KDX (I believe RickD still runs 40:1 in it) and currently run 40:1 in the KX.

If you look Here, you'll also find CC's mind boggling discussion of the difference between the two mixes you describe.

As far as mixture goes...40:1 is a richer mixture than 32:1. If your jetting was spot on for 32:1, you may find that 40:1 will have your bike running richer than you were before (ie. more spoo and less crisp). Will it hurt your bike...NO!

There are many discussions on this forum regarding mixture and jetting. Do some searching and have fun learning!

No... not nessesarily. Most do not run 32:1 as the manufacturer suggests. Not that there is anything wrong with this ratio but rather the ease of mixing 40:1.
It will not hurt your bike one bit running 40:1 and that is what most run.

First off, the KDX is more of a woods grunting type bike and is not running 8K and above all the time like MX bikes that require a richer mix of oil.

Also, when the KDX was manufactured... there were not allot of synthetics out there to protect better IMHO.

32:1 is good, 40:1 is good, 50:1 and you start pushing the fold but I have run this without problems.

The number one thing you should do though.....

Pick a ratio and a oil and stick with it. Then you jet around this one solid factor.

Cool, thanks guys.

Yes. You need to drain it!!!

Well, first you need to move up here..then you need to drain it.

Well, FIRST move up here, THEN have your buddy fill your tank on a regular basis...THEN drain it!!!


...and give it to me!!


If you bothered following QC's link, or if you did the math you would know the difference air/fuel-wise is very small. If you were/are worried about running 40:1 and the hurtin' it will do to your bike...it won't so don't.

If you haven't rejetted, you're likely running too rich at 32:1..and 40:1 will make it MORE rich...but not by brazillions of points, numbers, figures, densities, volumes or whatever measuring stick you choose.

I believe RickD still runs 40:1 in it)

Yep, still do (with Maxima). I haven't found the reason to change it. Thought about going to 50:1 or so, but didn't go for it.

Rick

I like 40:1 because it is a no brainer, 16oz of oil to 5 gallons of gas

Most oil comes in a 16oz container ('cept now my Mobil1 comes in a quart ) Makes it really easy to mix

Does it take a brain to dump that pint into four gallons of gas?

This clears something up for me that I've had bass-ackwards for years. I thought 'rich' meant the oil % was greater than spec. It's actually refering to the gas part of the equation.

So from this standpoint, there shouldn't be any great harm in running a little lean either? Guess you will smoke a little more than normal and run the risk of poor performance due to lack of adequate gas in the chamber?

Steve Sims wrote:This clears something up for me that I've had bass-ackwards for years. I thought 'rich' meant the oil % was greater than spec. It's actually refering to the gas part of the equation.

So from this standpoint, there shouldn't be any great harm in running a little lean either? Guess you will smoke a little more than normal and run the risk of poor performance due to lack of adequate gas in the chamber?

Actually, unless there's other problems, there's a tendency for the 2ts to smoke more when they're running richer - running a bike leaner might smoke a little less . . .

Don't worry too much about the "rich" thing - seems to be a common point of confusion. The important thing is to be as descriptive as possible. Generally, it's easier to follow someone when rich = more gas, one way or another (premix ratios, jetting, etc).

canyncarvr wrote:Does it take a brain to dump that pint into four gallons of gas?

What kinda dummy would only get 4 gallons when the can holds 5?

Re: 'Actually, unless there's other problems, there's a tendency for the 2ts to smoke more when they're running richer - running a bike leaner might smoke a little less . . . '

An astute observation...and thank you for saying so.

You can have dripping spits out the back and be lean on the verge of blowing the thing up, thus, 'Don't jet by spooge!'