The 250r Jetting Answer

[Ndog]

I have figured it out. I know why almost everyone with a 250r has had jetting problems (mostly with boggy rich running). I could not figure out why with a clean system and clean carb, jetting would have to be dropped from factory. BUT HERE IT IS--

20:1 IS THE KEY! You see back when this trike was engineered the mixtures were ran 20:1 because the oil was not as advanced as the oil we have today. When we all use new oil and synthetics and run 32,40 even 50:1 (with redline and other synthetics) we drastically alter the fuel to oil ratio. When there is less oil in the gas per given volume there is more gas! LESS OIL IN YOUR PREMIX MAKES A BIKE RUN RICHER!!! Most people dont understand this concept. They think more oil means richer NO!!! The mixture is air to fuel not air to oil. It is the same reason things run rich in humid weather. The water in the air takes up the volume and makes less air. ANYWAY.... the point is that because we dont run 20:1 these days, the jetting needs to be slightly dropped (mostly the pilot). That is why these things run sloppy down low with stock setups. YOU ARE ALL WELCOME.

[crackshot]

Yep, 20:1 is the best. I jetted to altitude per Honda, ran 20:1 HONDA REGULAR GOOD QUALITY 2 stroke oil (endorsed and recommended by Honda Racing) and runs killer, idles perfect.
No smoke when warmed up.
I will never run synthetic again, the stuff is crap. I should have learned the first time when it fouled out 4 out of 6 plugs in my boat.

[TimSr]

Ive heard this theory before, but there are a few things wrong with it. Rich/Lean refers to fuel to air ratio, not gas to air ratio. Fuel= gas/oil mix. While mixing at 20:1 may give you less gas, it gives you more oil, and the same amount of "fuel" is sucked into your cylinder to be burned, its just that a higher percentege of that fuel is oil. Now, look at how fast gas burns, and how fast oil burns, and you can see what happens to the burn rate of your fuel with more oil in it. When fuel burns slower, with other conditions remaining the same, it will result in a richer condition, not a leaner one. Rich means incomplete burn.
If your theory held true and more oil meant leaner, a 50:50 gas oil mix would result in melted pistons, but fouled plugs area lot more likely.
Im not sure what "jetting problem" you are referring to, as proper tuning and setup is required of any factory machine, and Ive never seen it as a problem, but factory jetting on any bike or ATV tends to be on the rich side so as to error on the side of least destruction. Most stock machines new from the factory could stand to be leaned up a bit in most areas they will be ridden.
As for synthetics being inferior to 1980's oils and their current equivilants, I think youll be hard pressed to find people who would argue that the advances that have been made in oils over the last 20 years are anything short of phenominal. There is nothing wrong with running general purpose two cycle oil at 20:1, but it should be considered minimum, and a very long ways from optimium.

[Ndog]

Ive heard this theory before, but there are a few things wrong with it. Rich/Lean refers to fuel to air ratio, not gas to air ratio. Fuel= gas/oil mix. While mixing at 20:1 may give you less gas, it gives you more oil, and the same amount of "fuel" is sucked into your cylinder to be burned, its just that a higher percentege of that fuel is oil. Now, look at how fast gas burns, and how fast oil burns, and you can see what happens to the burn rate of your fuel with more oil in it. When fuel burns slower, with other conditions remaining the same, it will result in a richer condition, not a leaner one. Rich means incomplete burn.
If your theory held true and more oil meant leaner, a 50:50 gas oil mix would result in melted pistons, but fouled plugs area lot more likely.
Im not sure what "jetting problem" you are referring to, as proper tuning and setup is required of any factory machine, and Ive never seen it as a problem, but factory jetting on any bike or ATV tends to be on the rich side so as to error on the side of least destruction. Most stock machines new from the factory could stand to be leaned up a bit in most areas they will be ridden.
As for synthetics being inferior to 1980's oils and their current equivilants, I think youll be hard pressed to find people who would argue that the advances that have been made in oils over the last 20 years are anything short of phenominal. There is nothing wrong with running general purpose two cycle oil at 20:1, but it should be considered minimum, and a very long ways from optimium.

I wasnt saying anything about newer synthetics being inferior. They are far better thats why we all run them at 40:1 +. I was simplly commenting on a big difference in the 1985 recommended ratio vs. what most of us mix today and how that might cause some richness down low in our bikes. I have tried my theory and it didnt really help. I either have to drop my PE pilot down to mid 40's (from 52) or just put the money up for a modern keihin or something. thanks for the input