Ok, here's the deal, I bought a R last week and it's great but I still have some trouble adjustting it...

Just for further reference, here are the thing that could affect my carburetor...

Airbox Lid removed
FMF Pipe
Uni Filter
50-60 degrees temp


Ok so here what happened today...


The quad runs extremely well on middle rpm but it lacks top end...It bogs on top end. Since needle is mainly 1/4 to 1/2 throttle, I figured out that the problem was the main jet since it really bogs. I told myself that I was a little on the rich end. I do a plug test and everything seems alright but maybe a little rich. The plug seems to be black on a half, and chocolate brown on the other (:confused[img]i/expressions/face-icon-small-wink.gif[/img]...I'm currently running on a 165 (Which others said was high)

So I go at the mechanic shop and to my displeasure, they don't have any 158-160 so I buy a 162 since it will be better than nothing. I change it and start the quad...I ride it and it'S even worst (Seems to bog from 3/4 instead of WOT)...Then something strange happened...I go WOT and the quad start to really bog like it wants to die, then it smokes A LOT...It die even if I'm WOT And I'm feeling bad a little since I just bought it and though I had blown it up...I check the plug and it's oil filled and fouled. I try to kick it again but it's over (It normally start with one kick)...I change the plug and it goes back to life. I go road test it again and the same thing happens !!!! It stalls again and foul the plug. I never fouled a plug before. Now I putted the 165 back in but didn't buy any others plugs yet. It start but the plug is fouled anyway....

I'd like to get help on what's going on and why it isn't running well on top end. It reallys bogs as if it would be hitting a rev limiter and it pisses me off. I tried to be as specific as possible, feel free to ask any others information [img]i/expressions/face-icon-small-smile.gif[/img]

My friend thinks it's mixed to rich (About 40-45 to 1) but I don't think it's the problem since I runs the machine hard and there isn't going to be any carbon deposits. I mix it strong since It's my first 2 stroke and I just want to be safe [img]i/expressions/face-icon-small-smile.gif[/img]...By the way, I mix with IPONE as of now but I will change ...


SMALL QUESTION BY THE WAY, I WILL LOOK STUPID TO SOME BUT I DON'T REALLY CARE SINCE I ADMIT I'M NOT A MECHANIC EXPERT....WHAT IS THE PURPOSE OF THE AIR SCREW ???

PS: Sorry if not everything is clear, english is not my primary language, thanks for your comprehension and help,

Pierre-Yves [img]i/expressions/face-icon-small-smile.gif[/img]

 

How old is the fuel? Did you mix the fuel, or has it been in there since the last owner? What ratio is it mixed at? Is the air filter clean?

If the filter is dirty, clean it. If you don't know about the fuel, get rid of it and start with fresh fuel, mixxed at 32:1 or 36:1, something like that. If tehre is too much oil in the gas, jetting won't help.

 

The fuel is brand new. Drained the gas tank when I bought in and refueled/remixed it...Filter cleaned after every ride...

EDIT: Just for information, I changed all the fluids (Transmission Oil, Coolant and Brake Oil)

 

I would recommend a smaller main jet, if 165 is fouling the plug. Try a 158 or 160.


Are you riding it in the same basic air(altitude and weather) as the previous owner?

 

That'S the problem...165 isn't fouling plug, 162 was...That's why I'm confused...

And yes I'm about at the same altitude/temp that the previous owner...

Thanks

 

Anybody can help, I need to fix that tomorrow as much as possible for my sunday ride [img]i/expressions/face-icon-small-sad.gif[/img]

 

in one of my post i wrote that if you mix the oil thicker it will lean out the fuel. what octane. go to a 155 main or 152. watch the plug and if wants to rev but no power it is lean . if it bogs it is to rich. my lt 250 was real tempamental like that

 

ok this is the post

the problems of jetting
this is great worth reading

Before changing jetting you should first check for any intake leaks. Carb cleaner works great but water will do.
Start your quad or bike . Hold throttle at stead idol spay the intake if there is a spike in the RPM's, you will then need to fix the leak. Don't over torque the intake bolts it will warp, making the leak worse.

make one change at a time .
You think you did everything right. Bought the most expensive pipe. Paid extra for that jet kit. Followed all the instructions to the letter. If you were lucky, the machine just might actually perform better—except, of course, for that pesky off-idle stumble or the giant flat spot in the midrange, or how about the severe top end miss (must be the darn rev limiter!).

Experience tells me that almost every hop-up anybody has ever done to an ATV has produced at least one point in the rev range that carburetion is considerably worse than stock. Why? Because all you have is a piece of paper that gives you recommended jetting settings. And unless you happen to be lucky enough to ride in those same conditions, there will be some point in the rev range where you will be too rich or too lean.

WHAT IS JETTING
Jetting is providing the engine with a combustible mixture. The ideal combustible mixture ratio is 14.7 parts of air to one part of fuel, with the most power being produced around 12-13:1. While a motor can (and will) operate on a mixture that is considerably richer or leaner, power output falls off. If you happen to go leaner and ride it hard, you may end up with an over-heated motor, or worse, a seizure.
Also be aware that carburetion is measured at throttle position settings. It has nothing to do with engine rpm or transmission gears. So telling the pipe manufacturer or Boss that it skips in third. but not fifth gear is totally useless information.

Did you know that your fuel pre-mix ratio (two-strokes only!) affects your jetting? A carburetor jet flows X amount of fuel and air at a given time. In that fuel is, say, 32 parts of fuel and 1 part of oil (32:1). If you change your pre-mix ratio to 20 to 1 because you are afraid of burning up your motor, all of a sudden the amount of fuel has been decreased by 37.5 percent. And since it is the fuel and NOT the oil that keeps your ring-ding cool, you run even leaner and hotter! Same theory applies to four-strokes as well; the more fuel entering the engine, the cooler the piston will be. The oil and water cooling systems are not designed to cool the piston; only the little bit of fuel that is mixed with the incoming air charge prevents your motor from seizing. ONLY after the heat has been transferred through the piston to the rings and then to the cylinder, will the cooling system get the chance to do its job.

WHY DO I HAVE TO REJET?
In a stock engine, the factory has spent a considerable amount of time and money trying various jets and needles to come up with jetting that not only passes the EPA (Environmental Protection Agency) regs, but allows the machine to be operated at roughly factory rated output without overheating and blowing up. When you, as an owner, change anything to do with the intake that would remove factory built-in restrictions to air flow into the engine or, exhaust changes that would do the same for air flow out of the engine, then you will need to rejet. Why?

A carburetor is designed with fixed size main and slow (pilot) jets. The jet needle attached to the bottom of the slide is fixed at a certain height. Only the idle mixture screw is adjustable. If you have increased air flow as outlined above, the increased volume will still be mixed with the same amount of fuel as before, resulting in a lean mixture. If you replace the main jet with a larger numbered jet, the jet’s internal hole will be larger, thus flowing a greater quantity of fuel at 3/4-full throttle. If you raise the position of the slide’s jet needle by lowering the jet needle clip, you are allowing more fuel to rise out of the needle jet at a given part throttle position which is generally 1/4-3/4 open. If you replace the low speed (pilot) jet with a larger numbered jet, the internal hole will be larger, thus flowing more fuel at very small openings of 1/16-1/4 throttle.

I STILL FEEL I CAN JET BETTER THAN THE FACTORY CAN
Even if you popped for the extra expense of a jetting kit, don’t expect your jetting to be "spot on" unless you are willing to experiment and try different jets. Why? Say you install the main jet the jet kit recommends and it seems to run OK. Is it truly the best for your machine in your riding conditions? It may not be, unless you experiment by going up a jet size at a time until your machine exhibits a stumble at full throttle, indicating a too rich mixture. Then by dropping back one size you can be confident that now you have the correct jet for your machine in your riding conditions.
The same thing should also be done with the other fixed jets of your carburetor (jet needle and slow speed pilot jet.).

WORKING WITH INDIVIDUAL CARBURETOR CIRCUITS
So, how do you start? At the bottom. Then you jump to the top and work your way down.

IDLE MIXTURE SCREW:
The idle mixture screw is the only externally adjustable carburetor jet available and controls up to 1/8 throttle only. There are two types of idle mixture screws. One type is called a fuel screw because it regulates the flow of fuel into the idle circuit. This type of screw is located ahead of the carb’s slide tower (motor side) and is most often found under the carb’s bore and upside-down directly ahead of the carb’s float bowl. By turning the screw out you increase the amount of fuel that is allowed to slip around the tapered needle and into the carb’s bore where it is mixed with air that has snuck under the carb’s slide.

If the idle mixture adjustment screw is located behind the carb’s slide tower (airbox side) then the adjusting needle regulates air flow into a fixed flow of fuel intended for idle. By turning this screw inward you are reducing the air flow, thus richening the idle mixture.
When the motor is up to operating temperature, set your idle speed screw to a stable idle. Then use either your idle fuel or air screw to obtain a stable idle. Reset the idle speed screw as necessary after obtaining the correct idle mixture.

MAIN JET
The main jet controls 3/4-full throttle only. Ideally you should start very rich (large numbered jet) and test at full throttle. It should skip. If not then you are not rich enough! Once you have your rich stumble, back off one size at a time until full throttle operation results in normal operation. (Note: If your ATV runs faster at 3/4 throttle than full throttle you are definitely lean on the main!)

JET NEEDLE
The slide’s jet needle controls 1/4-3/4 throttle. It does this by passing upward through the needle jet. The needle jet is a long brass tube that contains many small holes in its sides that air passes through. Fuel from the float bowl enters this air stream from the main jet and into the center of the needle jet where it mixes with the air to create an emulsion. This mixture of fuel and air is then metered by the height, taper and diameter of the jet needle as the emulsion passes upward around the jet needle into the carb’s bore where it mixes with still more air to (hopefully) arrive in the motor in a combustible fuel-to-air ratio.

If you have a soft hesitation, without a hard stumble, anywhere between 1/4 and 3/4 throttle, chances are your needle is lean, so raise the needle by lowering the clip. Conversely, if you have a hard stumble, chances are the needle position is rich, so lower the needle by raising the clip.
If you get very unlucky you might have to start playing with jet needle taper which controls how fast the mixture increases as the jet needle is raised. This would come into play if you were lean at 1/4 throttle, yet rich at 3/4 throttle. The length of the needle comes into play here too. The diameter of the needle controls how much fuel escapes around the needle while still inside the needle jet. The larger the diameter of the straight section or "L" length, the leaner the mixture. Or finally, the "L" length, which controls how much the slide rises before the tapered part of the needle starts.

SLIDE CUT-A-WAY
The slide cut-a-way controls the amount of air allowed to pass under the slide at 1/8-1/4 throttle. It controls the transition from the low speed (pilot) jet to the main jet-fed needle jet/jet needle. Replacing the slide with one that has a smaller number (less cut-a-way) will decrease the amount of airflow under the slide at 1/8-1/4 throttle openings, thus creating a richer mixture at that throttle opening. If you have a rich condition at 1/8-1/4 throttle and you can’t go any leaner, try a smaller cut-a way.
But thankfully, jet needle taper, diameter, "L" length and slide cut-a-way are usually not affected by most simple pipe/air filter modifications.

LOW SPEED (PILOT) JET
The low speed (pilot) jet controls fuel flow at 1/8-1/4 throttle. The low speed (pilot) jet is usually not affected by most simple pipe/air filter modifications. However, a slightly lean low speed (pilot) jet can raise havoc in the winter where its fuel is added to the total mixture strength required to start. You may find going one level up will help a winter cold start situation.
Finally your idle mixture is revisited if you have a deceleration backfire situation. When you chop the throttle and use the motor to decelerate, if you get a stream of backfires, try increasing your idle mixture strength 1/4 turn at a time until the backfire goes away. Note: If you reach a point where your idle mixture is 4 turns out (for fuel type screws, NOT air type screws), try going up one size on the slow speed (pilot) jet and reset your idle mixture screw to 1-1/2 turns out and repeat the process.

One final note; reading about how to jet will not make you "good" at jetting. And asking someone a thousand miles away why your machine skips in third gear won’t get you the answers you seek. Even Boss can’t help you when you write him asking "I just bought an XYZ pipe. What jet do I need?"
Only hands-on, trial and error experience can solve your jetting problem. So go purchase a handful of jets and get your hands dirty! You are out five big ones for that pipe and jet kit, and now have a hobbling pile. fast or last

remember one at a time
git her done!
402 270 1768

 

Thanks...I searched and the general consensus would be that I should go with a 155-158 jet. By the way, that post of yours about jetting is really informational...Thanks [img]i/expressions/face-icon-small-smile.gif[/img]

The only thing i'm not understanding is why it's running better with a 165 than with a 162 even if it's on the rich side. Don't understand why I fouled plug with a 162 either [img]i/expressions/face-icon-small-confused.gif[/img]

 

AND BY THE WAY, WHEN HE FOULED PLUG WITH THE 162, THE PLUG WERE COMPLETELY OIL FOULED :S.....I JUST HOPE THE RINGS AREN'T WORNS OUT :S

I wonder what's going to happens with the 165 and a new plug in...