RM-250 keeps fouling plugs

[LesnarRKO]

Too Slow????

I have an 95' RM 250 and I thought that there was a problem with the carb. However my uncle seemd that the problem is that I'm riding too slow and that's why the plugs keep fouling out. And this is my first ever bike and I'm learning on it. I ride it in mostly 2nd and sometimes 3rd gear but i do get on straight aways and pin it in 5th gear. So if anyone could tell me if I'm riding too slow or if its the carb that would be awesome.

 

[tyesai]

It is in the jetting, you should be able to put around all day without fouling plugs.

 

[YZ165]

Indeed.

 

[LesnarRKO]

OK thats what I thought but is $80 to rejet a carb too much or would I be better off doing it myself?

 

[ellandoh]

even if you break even youll be further ahead, rejetting is easy, and when you go on a trip with elevation changes or temp changes you can handle it on your own. besides when your uncle feels the newfound low end ripp , midrange thrashing the bike will serve him, you can stand back and say................"ya, i did that :nod: "

try this :cool:
Spanky's jetting guide:

A correctly jetted carb makes a tremendous difference in the torque, midrange pull, top-end pull, and over-rev of your engine. If you have never jetted your bike correctly, you will almost certainly gain some performance at some point in the bike's powerband. A cleanly jetted pilot circuit can be the difference between having to clutch the bike out of a turn or not. The needle can make all the difference in the world for the power of the machine in most situations, as it controls the throttle range that most riders spend most of their time using. A correctly sized main jet could mean the difference between being able to rev out high enough to not have to shift one more time at the end of the straight, or the power falling flat on top and requiring you to make that extra shift.
Are you fouling plugs? Many people will tell you all sorts of band-aid fixes, from running less oil, to running a hotter plug. Both are incorrect fixes for plug fouling. It's all in the jetting.
The only way to know what jetting changes you will need is by trial-and-error. No one can give you jetting specs, because every bike is different, every rider has a different style, and jetting is totally weather dependent. Unless the person telling you what jets to use is riding an identical bike, on the exact same track, at the same time, his recommendations are meaningless.
Jetting is fairly simple, and is a useful skill to learn if you ride a two-stroke and want it to perform at it's best.
It's very important that you start with the pilot circuit. The reason is simple. The pilot circuit affects the entire throttle range. When you are at full throttle, the main jet is the primary fuel metering device, but the pilot is still delivering fuel as well, adding to the total amount of fuel that your engine is receiving.
Before you start to rejet your bike, you need a clean air filter, a fresh plug (actually you need several plugs to do plug-chop tests for the main jet), and fresh fuel. One important detail: Make sure the engine is in good mechanical condition. If your engine has a worn top-end, fix it first. Trying to jet a worn out engine is a waste of time. The same goes for reeds that don't seal properly, and a silencer that needs re-packing. Worn reeds will mimic rich jetting, and worn rings will mimic lean jetting.
Before you start the jet testing, install a fresh plug. Set the float level to the proper specs, an incorrect float height will affect your jetting all across the throttle range.
Warm the bike completely, and shut it off.
As already stated, start with the pilot circuit. Turn the airscrew all the way in, then turn it out 1.5 turns to start. Start the engine, and turn the idle screw in until you get a slightly fast idle, or hold the throttle just barely cracked, to keep the engine idleing. Turn the airscrew slowly in, and then out, until you find the point where the idle is fastest. Stop there. Do not open the screw any farther, or your throttle response will be flat and mushy, and the bike may even bog. This is only the starting point, we will still have to tune the airscrew for the best response.
Now is the time to determine if you have the correct pilot installed in your carb. The airscrew position determines this for you, making it very simple. If your airscrew is less than 1 turn from closed, you need a larger pilot jet. If it is more than 2.5 turns from closed, you need a smaller pilot jet.
Once you have determined (and installed it if it's necessary to change it) the correct pilot jet size, and tuned the airscrew for the fastest idle, it's time to tune the airscrew for the best throttle response. Again, make sure the bike is at full operating temperature. Set the idle back down (the bike should still idle, despite what you read in the Moto Tabloids), and ride the bike, using closed-to-1/4 throttle transitions. Turn the airscrew slightly in either direction until you find the point that gives you the best response when cracking the throttle open. Most bikes are sensitive to changes as small as 1/8 of a turn.
The airscrew is not a set-it-and-leave-it adjustment. You have to constantly re-adjust the airscrew to compensate for changing outdoor temps and humidity. An airscrew setting that is perfect in the cool morning air will likely be too rich in the heat of the mid-day.
Now, it's time to work on the needle. Mark the throttle grip at 1/4 and 3/4 openings. Ride the bike between these two marks. If the bike bogs for a second before responding to throttle, lower the clip (raising the needle) a notch at a time until the engine picks up smoothly. If the bike sputters or sounds rough when giving it throttle, raise the clip (lowering the needle) until it runs cleanly. There isn't really any way to test the needle other than by feel, but it's usually quite obvious when it's right or wrong.
Last is the main jet. The main jet affects from 1/2 to full throttle. The easiest way to test it is to do a throttle-chop test. With the bike fully warmed up, find a long straight, and install a fresh plug. Start the engine, and do a full-throttle run down the straight, through all gears. As soon as the bike tops out, pull the clutch in, and kill the engine, coasting to a stop. Remove the plug, and look deep down inside the threads, at the base of the insulator. If it is white or gray, the main is too lean. If it is dark brown or black, the main is too rich. The correct color is a medium-dark mocha brown or tan.
Once you have a little bit of experience with jetting changes, and you start to learn the difference in feel between "rich" and "lean", you'll begin to learn, just from the sound of the exhaust and the feel of the power, not only if the bike is running rich or lean, but even which one of the carb circuits is the culprit.
The slide is also a tuning variable for jetting, but slides are very expensive, and few bikes need different slides, so we won't go into that here.
Keep in mind, even though this article is intended primarily for two-strokes, four-strokes also need proper jetting to perform right, although they are not quite as fussy as their oil-burning cousins. The only real difference in the two is with the pilot circuit. Two-strokes have an air screw that you screw in to make the jetting richer, and screw out to make the jetting leaner. Four-strokes, on the other hand, have a fuel adjustment screw that you screw in to make the jetting leaner, and out to make it richer.

 

[LesnarRKO]

Where would I buy new jets?

 

[ellandoh]

Where would I buy new jets?

suzuki dealer will probably have them, any other shop can get them . approx 4- 6 dollars a piece

open up your carb check whats in there. it will be stamped somewhere on each jet in TINY numbers.

if you lean your pilot jet and it gets hard to start you leaned too much

right at the moment if you are fouling plugs try just lowering the needle, thats free and may cure it

 

[LesnarRKO]

Ok I'll do that, but I cant ride that long I live in a bitchy neighbor hood how can I check the plug to see if I fixed the problem without riding till it fouls out? And I need to know if lean would be a smaller one or bigger? And should I rich it or lean it out?

 

[ellandoh]

smaller number on pilot and main jet =leaner
smaller number on needle=richer

warm the bike up in the garage to cut down on the bichy.
plug should be dry and tan

 

[LesnarRKO]

If lowering the needle just once didnt do it should I do it again and if so how many times should I adjust the needle before i re-jet? And when I do re-jet what jets should I re-jet and should I make it leaner or richer?

 

[ellandoh]

fouling plugs while riding slow lean out the pilot
i would lower it til the clip is in the 2nd position

lowering/leaning out the needle jet is considered rejetting :) youre on your way

 

[LesnarRKO]

How would I know if when the needle is in the 2nd position? And to lean out the pilot do i buy a new one or adjust it with a screwdriver?

 

[Tyler3386]

Try the needle first. It controls the fuel flow when you are 1/4 to 3/4 throttle which is probably where you ride mostly. If you are fouling plugs that usually means you are too rich, you are burning too much gas for the air flow you have. You should make sure your filter is clean before rejetting because a bike with a dirty filter will run richer. That may be your problem right there if your filter is dirty, it wont flow as much air.

Needle clip position refers to the number of slots from the top or bottom(depending, most people say from the top or bottom). Your needle will have like 5 or 6 slots. To lean out your ratio. you want to drop the needle which means raising the clip. You want to go 1 slot at a time and see if your mid range performance gets better. Its kinda confusing but makes sense when you think about it.

 

[LesnarRKO]

If I went to buy jets to replace which ones should I get and what sizes?

 

[LesnarRKO]

Ok here's the situation. My 1995 RM-250 keeps fouling plugs and I know its in the jetting. I need to know how to adjust the throttle needle. And which jets should I change? And should I lean them out? And when I do that can I still keep my mixture at 40:1? I'm planning on leaning out all the jets by one size and lowering the throttle needle to the second adjustment, would this be ok? And when I adjust the throttle needle to stop flooding should I raise the clip and lower the needle and will I here clicks? And when I adjust the pilot air screw do I replace this or adjust it by tightening or losening? And I also have a FMF Fatty Pipe and dont know what to do for that? Somebody pleeeeeeeeeeeeeeeeeeeeeez help. :bang:

 

[rodH]

40:1 should be fine, do you have a manual for your jetting settings???

 

[LesnarRKO]

No i dont

 

[LesnarRKO]

my bike hasno idle and this is my first bike and have no idea what the power should feel like

 

[LesnarRKO]

Needle Position

How would I adjust my throttle needle and know that it's in the second position? And is the second position measured from the bottom to top or vice-versa?

 

[LesnarRKO]

I need help

I have a 1995 RM-250 with a FMF Fatty and the main jet is set at 175 and on FMF's site it says that the stock settings for the main jet is 172 would this make a big difference and could this be why my engine is constantly fouling out plugs?

 

[nickyd]

not likely you'd foul plugs constantly - tell us more....do they foul after a washing, every time you start it?

 

[rm_racer]

If your bikes like mine ('94 RM125) Take off the carb cap (what holds in your slide). Then, slide the spring up and remove the throttle cable. Then take the needle assembly out. Take a (8mm?) ratchet and take out the bolt that holds down the needle. Then slide out the needle and pop off the e-clip. (becareful, some times they go flying). Now move it up or down, which ever way you need to, then reverse the process and put it back togeather.

BTW, I dunno if it measured from the top or bottom, I go from the top normally, i.e. 3 positions from the top.

Hope this helps.

 

[LesnarRKO]

No they foul out and I usually ride around 2nd to 3rd gear and I fouled out two plugs that where already worn but still it seems like somethings wrong with it.

 

[LesnarRKO]

How do you tell from one position to the next?

 

[rm_racer]

Theres grooves that the e-cilp slips in to. I think theres 6 or 7 of them.