Jetting and Premix Questions

[canyncarvr]

re: I don't understand the problem with...

I guess you could call it a trade off. The more oil run, the more power made...air/fuel jetting corrected. No argument..it's a fact. There was a white paper published some time back by McCullough in that regard. Up to the point the test engines wouldn't run due to oil fouling, the more oil in the premix...the more power they made.

Piston-to-cylinder sealing is important in a 2-smoke engine is the basic why of that.

While you may make more power with more oil...you also need a larger volume of that mix air/fuel wise. You gotta have the gas part, too! At some point you will want to do something other than: 1. Ride in a blue fog, and 2. Ride farther than ten miles before you have to go back to your rig to refuel.

Oil/lubrication requirements vary depending on the engine...and the oil. Super-M is indeed a blend. Maxima's req is 40:1 for a 200cc engine. Besides that, following is a quote that says Super-M is absolutely the best oil in the world:

Привет от Super-M ×. Хотите убрать эти приветствия? (з сюда писать ответ, только не забудьте об этикете) Некогда! Вырубай срочно! настроить...

..so don't argue with me about that either.

If you like SuperSyn at 452:1...I'm happy for you.

Anyway...as with most things the most important word is 'balance.' A balance between required lubrication, available power and miles-per-tank 'fer instance. It is possible (according to my bike, anyway) to have NO drips (spooge), very little smoke, plenty of power with smooth throttle response/transitions throughout and to run the same spark plug for over a year.

Stock needle clip position is #3.

If you're happy with an oem needle, a 160 main and don't want to mess with the pilot...you would be much happier if your bike was correctly jetted.

BTW....regarding 220s and smaller carbs. The two bikes (200/220) don't jet even close to the same.

From the original question I would infer that you haven't looked at the link noted in the 'Every kdx rider should read..' thread stickied to the top of this forum? CDave has excellent information to get you started in the right direction jetting-wise with various modifications.

 

[farmerj]

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CC, you are unbelievable! And entertaining!

And know what guys - I believe that he can actually read that!!

 

[OldTimer]

Okay, so here's the thing...
Suppose, for instance, that you've painstakingly rejetted all the way through and you're spot on at say, 5000 ft. Now you're gonna spend the week riding out behind your Grandma's house in Fla.
Instead of changing your primary, needle clip, and main, It sounds to me like you could just change the fuel/oil mixture and keep things running in perfect harmony. Right?
That sounds kinda crazy, but it seems to be in line with what I've read so far. See ?
I am missing the point eh?

 

[canyncarvr]

You can effect the air/fuel ratio by changing the premix ratio.

Perfect harmony? No.

You can find jetting information all over the place that has things like elevation charts and resultant jetting requirements (ex:CDave's site). I have never seen such a chart for premix ratio change.

The point of changing jetting to suit conditions is to tune the air/fuel ratio. It's a second-hand effect to change that air/fuel ratio by changing the amount of oil you put in the fuel.

I don't know how the volume numbers compare. Working with percentages is not going to get you a correct answer. For example: Changing from 32:1 to 40:1 increases the amount of fuel in a given volume by 25% (40-32=8 32 ./. 8=4 100 ./. 4=25). So....how does that relate to changing from a 152MJ to a 155MJ? If you think matching numbers works, you would have to put in a 190MJ if you wanted a 25% change in jet size (using the number of the jet) That don't work, 'eh?

That's a silly example to make an obvious point.

Are you going to mix up a dozen batches of different premix numbers...drain out each after testing..add another...etc to tune your bike at Grandma's house? Unlikely.

Get to know your bike and what it needs and it's matter of simply putting in the right hardware. Will take you ten minutes! (taking a beer break in the middle of the process!)

 

[Rhodester]

CC, I about died laughing at that!!! Even my wife got a kick out of it....it went beyond "motorcycle humor".

Old Timer, I ride from about 2800' to 6000' normally. I can get away with just main jet changes and air screw adjustments over that range and stay pretty crisp on my jetting. I wouldn't normally change my needle position or pilot jet (at least I haven't had to yet).

 

[OldTimer]

Okay guys,
First of all, I believe and agree with everything you're saying. I just used the altitude thingy to illustrate my confusion about the distinction between jetting and premix. I know you can't realistically trade one for the other any more than you can seperate one from the other.
But I'm still scratchin'.
Like, what's it mean when someone says, "Be careful when you change your premix as you may be running too lean afterward." ...So what, now I've got more lubrication, right???
I can see the bird poop on the windshield, I just can't figger out how it got there! Guess the 'ole coconut's hard to penetrate sometimes (knock knock...).

 

[canyncarvr]

I haven't gone back to re-read your other posts...just looking at the last one.

Being too lean air/fuel-wise has nothing to do with having more lubrication premix/oil-wise.

Say you change from 50:1 (jetted properly) to 32:1 (same jetting). You do that because you're headed for the dunes and think that 'more lubrication' is what you need for the mega-loading your bike will be dealing with in the sand with an 8-paddle tire!!

Well, by the time you get to the coast (where the dunes are around these parts) you've dropped 1500' in elevation. Put that together with sand riding and having considerably leaned your air/fuel ratio...you're going to stick your bike!

'But.... but....I had more lubrication!' you protest.

So? What you HAD is a more lean air/fuel mix. It's the gasoline that burns with the supplied amount of air. The temperature of your coast burn is going to be considerably hotter than your 'home' burn. Might even be some detonation happening...the onslaught of the 'grey ash of death.' You know...pretty much vaporized aluminum from 'stuff' (probably the piston) getting literally blown away?

Most of the above based on,

So what, now I've got more lubrication, right???

Exactly! So what, indeed!

 

[OldTimer]

Ahhh,
Okay, here we go...
So leaner fuel/air burns hotter or rather has a lower ignition point and no amount of oil is gonna quench the Burning Hell Fire you've created with an over lean fuel/air mixture. BINGO! right?
I guess sometimes the answer is so obvious that the question is hard to conceive!
So, who played Lumpy in Leave It To Beaver then, tough guy?

 

[kingsxjt]

Frank Bank! Anyway, CC, How do you "settle" on a premix ratio then? I mean we are recommended by Kawasaki to go 32:1. I know our bikes are pretty much jetted too rich from the factory and everybody around here rejets and changes to 40:1 or higher. You can be jetted correctly for the coast with your 8 paddle tire running 263.5:1 and seize too. I just wonder then how everyone "settles" on their mixture? I fully see the point you made about running 32:1 with incorrect jetting. How to decide on premix ratio...??? What was the midgets name on Fantasy Island?....things that make you go hmmm?

 

[2wheeler]

The Plane!!!!!!!! The Plane!!!!!!!!! Tattoo

 

[G. Gearloose]

"Smiles everyone....smiles!" :)

You can be jetted correctly for the coast with your 8 paddle tire running 263.5:1 and seize too.

I'd bet the bank on that one.

 

[OldTimer]

How do you "settle" on a premix ratio then
?

Here's what I think I've learned from this discussion.....
If you're running just a touch on the rich side with 40:1 premix then try using 32:1 and vice/versa, if you're spot on, then go :ride: ride!

 

[kingsxjt]

I would really like to understand how you do settle on a premix ratio. CC, are you out there? I wasn't at all trying to be "snappy" (although Gearloose put it that way) about my response to the 8 paddle tire. How do you decide on a ratio?

 

[canyncarvr]

I decided on what to use based on a few things: 1. What the oil manufacturer says (Maxima says 40:1 for my application), 2. What is commonly used by other bikers with more experience than I have, 3. What's easy!

40:1 is easy. One pint to five gallons. It works. It fits. It's recommended. It's fine with me.

It's generally considered that Kawi recs 32:1 (as other bike mfgs recs) as a CYA (CTA?) measure. Yamahama wants 24:1 in their 2-stroke twin (Banshee)! Good grief!!

At some point there is a realization that what suits them isn't what's best for the rider.

 

[kingsxjt]

Thanks CC! I'm settling on 36:1. The amsoil I'm using doesn't come in pints so I have to pull out the Ratio Rite anyway. I just switched from Super M to Amsoil Interceptor because I wanted to use full synthetic and I buy Amsoil Gearbox lube and fork oil from an Internet distributor who's cheap. The Interceptor boasts low smoke and keepin' the powervalve clean too. I was smoking pretty bad with the Super M and decided to give the Amsoil a try. Emptied the tank and mixed up a fresh batch at 36:1. Funny thing is the bike is spooging much more than it did before. It spooged quite a bit before, but after I put the fresh tank of Interceptor in and put just a couple of miles on it rippin' around in the yard it was blowing out spooge (very wet). I mean that if I just twist the throttle W/O one good time it will spray my hand pretty good and will drip off the silencer when sitting still.I pulled the cleanout plug out of the stock silencer for the first time and spooge just poured out! I didn't have this problem before and I'm just wondering if the Interceptor is cleaning out the system. I am really considering rejetting also to see if it will help. I haven't been on any rides yet to see if it cleans out yet either. Any thoughts?

 

[kingsxjt]

Bump!

 

[Powerlock25]

my vote is for 40:1

Just cause Tollhouse says to put 2cups of Chocolate Chips in the cookie batter doesnt mean that 1.5 cup isn't plenty to make darn good chocolate chip cookies. Its a plot to send you back to the store to buy more Chocolate Chips!!! :)

I vote 40:1 for the reason of ease. Good lubrication. More gallons per mix.

Let's say you have a 5 gallon gas can. If you want to run 32:1, you can only put 4 gallons in it and mix a pint of premix.

By running 40:1 you fill that can with 5 gallons and your pint of premix.

You get a gallon more mixed gas. More playtime!!! Less $$$ spent on gas and premix. Less time at the pump!! less time mixing. More cookies, etc, etc....

 

[sigurd]

Good discussion. Nice quick and dirty on the 40:1. I liked the technical post on this subject for a better explanation.

For those who don't have a five gallon gas can there is a nifty fuel/oil ratio calculator that I found at at-speed(dot)com/air/oil_gas_calc/html.