RM250 1996 severe wet fouling

[navinbhat]

Hello all,
I own a RM250 1996 model (bought second hand 6 months ago). It has been exhibiting severe wet fouling since then and the first plug of the day lasts about 10 mins and then it chews up a plug per minute or worse. So far I have :
1. Checked quality of spark, stator and ignition coil by the bike shop and they tell me its fine.
2. Replaced reed valves to Boyesen
3. Changed to lean jetting
4. Replaced air filter
5. Replaced piston/rings
6. Replaced crank case seals
7. Replaced spark plug cap
I did notice some smoke coming out of the exhaust valve drain pipe (strange) and the exhaust pipe leaks a lot of oil from the rear end.
I am running 40:1 ratio using Motul 800 synthetic and drain the fuel
tank after every ride to prevent any oil sedimentation.
What started as enthusiasm is now ending in pure frustration.. but not
yet ready to give up.
Hopefully you can point me in the right direction.
- regards
Navin

[EastCoastMotion]

Try lowering the ration level to 32:1, 40:1 is what they say to run in the book but i was told by a technician at a suzuki shop that its better to run it @ 32:1 so you avoid fouling the plug. In your case im not sure because you have an EXTREME amount of fouling going on. Try lowering the ratio it and see what happens. Best of luck.

[Dave2122]

Not to demean what has been posted but I run Motul myself with no problems at 50:1 in my RM250... A quick lesson on ratios.....40:1 would be 40 parts of fuel to 1 part oil,which is lean compared to 30:1 or 20:1.... With that formula you do not want to change from 40:1 down to 32:1 as that increases the gas oil mix to 32 parts fuel to 1 part of oil which is to rich


Now on to your problem which I am sure is related to the carburator.

You will need to check your float height as per the factory manual. Set it to the recommended height.
Next check your needle valve which is attached to the float assy. If it is worn or grooved it will not seal correctly and cause fuel to overfill the bowl

Next check your float assembly and make sure it does not have a pinhole in it which would cause it not to "float"

If you do not have a manual I suggest you buy one as a 2 stroke needs to be set up propper to run correctly and that goes for any 2 stroke not just a Suzuki.

Hope I have helped you understand your bikes issues.....

Let me know how you make out.

[navinbhat]

Thanks for your reply Dave.
Now, I do have a Clymer manual and pretty much go by the book. I have checke d the float height and it is correct. I will however follow your suggestion on checking the needle valve and float assembly for holes.
Question : why don't you doubt the CDI ?
What surprises me is that the 2 stroke is the simplest of all engines and yet the most temperamental.
I agree with your assessment on fuel:oil ratios though there are many conflicting theories about more oil is leaner.. but lets not go there.

[92 RM 125]

i dont think ur problem is electrical (im pretty sure on this). uv got it down to either jetting (thats where im putting my money) or reeds. check your reeds for proper clearance and what shape they are in. then jet the bike following this guide. ill be really surprised if this doesnt fix it.
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 air screw 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 air screw for the best response.

Now is the time to determine if you have the correct pilot installed in your carb. The air screw position determines this for you, making it very simple. If your air screw 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 neccessary to change it) the correct pilot jet size, and tuned the air screw for the fastest idle, it's time to tune the air screw 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 air screw 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 air screw is not a set-it-and-leave-it adjustment. You have to constantly re-adjust the air screw to compensate for changing outdoor temps and humidity. An air screw 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 begine 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, ansd 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.

[EastCoastMotion]

<-----Dumbass

i thought more oil=less fuel = leaner

[Dave2122]

No harm done...we all make mistakes.......