2006 cr250r????

[Pierce]

What spark plug's are you running? Mine seems to be fouling up way too easily. Fresh top end as of this afternoon, took it for a blast and after 4 laps of riding I pulled into the pits for a quick rest started it up again and she just didn't wanna keep running.

Current plus NGK B8EV looking pretty dirty and was brand new.

[mattwood]

hey, not much help but was that u at kimmys? borrowed my dads screw drivers?

[CaMo]

what oil you running and what ratio man?

[Pierce]

hey, not much help but was that u at kimmys? borrowed my dads screw drivers?

Haha yeah bro that was us aye. Took it out to have my first blast on it but wasn't out there long at all

Cam I'm running Motul 800 fully synthetic 32:1

SAid in the owners manual to use BR9EG-N-8

[mxracer_nz]

was it fouling b4 new top end? did you install top end? ive seen guys poor way to much oil over barrel piston etc when putting new top end in and if you just putting round 4 4laps it wont clear the excess oil out

[crazyxr250rider]

PLEASE read this before you change your plug/oil :fuel ratio (this a copy paste job from similar thread)


you dont go to a hotter plug or adjust the mix you adjust brass.
heres what i read on thumper talk.
Motu would love reading this stuff











Any of you that believe that spooge is caused by too much oil in the mix are flat out wrong. If you know how to jet, you can run any amount of oil you choose, and have absolutely zero spooge.

Looks like it's time for a little pre-mix 101. I don't usually get into ratio discussions, because mix ratios are like religions to most people, and they tend to be closed-minded and hard-headed on the subject, but I'll put in my $.02 here anyway.

There is a prevailing myth that less oil is better, and that the oil in the fuel is what lubricates the engine. And there is also a very common belief that spooge is caused by too much oil in the fuel mix. Both are wrong. The engine is lubricated by the residual oil that builds up in the crankcase. All the oil in the fuel does is replenish this oil. And spooge is caused by rich jetting.

When an engine is jetted too rich, the excess fuel leeches heat from the combustion process, causing the combustion chamber temperatures to be too low to effectively burn the oil, or even completely burn all of the fuel. The result is spooge and deposits. The spooge is nothing more than unburned fuel and oil passing out the exhaust.

If you have a spooge problem, you have a jetting problem. You don't get rid of the spooge by reducing the oil, you get rid of it by fixing the jetting. Correct jetting will produce an air/fuel ratio of about 14:1, which will produce combustion temperatures in the 1200 degree range. This will provide sufficient heat to consume the premix oil.

You don't choose a mix ratio based on "spooge", you choose the ratio based on the amount of oil your engine needs to provide sufficient protection and adequate ring seal. The common misconception is that mix ratios are "one-size-fits-all", when in fact nothing could be frther from the truth.The amount of oil that is correct for one rider on his bike may not be enough oil for another rider/bike, or it may be too much oil. It all depends on engine displacement, riding style, and how hard you push the engine.

The best way to determine if you are running enough oil is to check the level of the residual oil in the crankcase. If the ratio you run leaves enough residual oil in the crankcase to cover about 1/8" of the bottom of the crank wheels, then you are fine. If you don't have that much residual oil in your crankcase when you pull the top-end off, you aren't running enough oil for your riding style and conditions.

With that said, to have that amount of residual oil in the crankcase at 50:1 (a ratio made popular by magazines and oil bottles), you can't be riding very hard, or your bike is jetted richer than necessary simply to deliver enough oil. I arrived at 26:1 for my bike with my riding style because that is the amount that gives me the proper amount of residual build-up. Small-bore engines require greater oil concentrations than larger engines to achieve the proper amount of residual build-up, because they rev higher and have higher intake velocities. Along the same lines, someone that pushes the engine harder, and keeps the revs higher, also needs to use higher oil concentrations to achieve the proper residual build-up.

To understand why the residual oil is so important, you have to understand what happens to the oil in your fuel when it goes into the engine. While the oil is still suspended in the liquid gasoline, it can not lubricate anything. It has about as much lubricity at that point as straight gasoline. When the gasoline enters the engine, it evaporates, dropping the oil out of suspension. Now that the oil is free, it can lubricate the engine, but it must get to the parts to lubricate them. The way it gets to the bearings and onto the cylinder is by being thrown around by the spinning crankshaft, and being distributed through the engine by the air currents moving through the crankcase. The main bearings are lubed by some of this oil dripping down through tiny "drip passages" in the cases above the bearing pockets.

People believe that the oil just rushes right through a two-stroke along with the fuel, but that just isn't so. It can take 90 minutes or more for the oil migration through a two-stroke to result in a complete oil exchange.

The oil eventually makes it into the combustion chamber, where it is either burned, or passes out the exhaust. If the combustion chamber temps are too low, such as in an engine that is jetted too rich, the oil doesn't burn completely. Instead, some of it hardens into deposits in the combustion chamber, on the piston, and on the power valve assembly. The rest becomes the dreaded "spooge". The key to all of this working in harmony is to jet the bike lean enough to achieve a high enough combustion chamber temperature to burn the oil, but also still be able to supply enough oil to protect the engine. If you use enough oil, you can jet the bike at it's optimum without starving the engine of oil, and have excellent power, with minimal deposits and spooge. At 50:1, you simply can't jet very lean without risking a seized engine due to oil starvation.

With the high oil concentrations that I use, I tend to get far more life from my cranks and rings than most of my friends that run leaner oil ratios. The high oil content also produces better ring sealing, so more of the combustion pressure is retained.

One small point. No one ever broke an engine by using too much oil.

Now we come to the issue of ring seal. Simply put, the rings alone can not effectively seal the cylinder. They also need oil to provide a complete seal against the bore surface. And up to a point, more oil will provide a better seal.

I have run Dyno tests on this subject, as a school project in Tech School. We used a Dynojet dynamometer, and used a fresh, broken in top-end for each test. We used specially calibrated jets to ensure the fuel flow was identical with each different ratio, and warmed the engine at 3000 rpm for 3 minutes before each run. Our tests were performed in the rpm range of 2500 to 9000 rpm, with the power peak of our test bike (an '86 YZ 250) occuring at 8750 rpm. We tested at 76 degrees F, at 65% relative humidity. We started at 10:1, and went to 100:1. Our results showed that a two-stroke engine makes its best power at 18:1. Any more oil than that, and the engine ran poorly, because we didn't have any jets rich enough to compensate for that much oil in the fuel. The power loss from 18:1 to 32:1 was approximately 2 percent. The loss from 18:1 to 50:1 was nearly 9 percent. On a modern 250, that can be as much as 4 horsepower. The loss from 18:1 to 100:1 was nearly 18 percent. The reason for the difference in output is simple. More oil provides a better seal between the ring and the cylinder wall.

Now, I realize that 18:1 is impractical unless you ride your engine all-out, keeping it pinned at all times. But running reasonable ratios no less than 32:1 will produce more power, and give your engine better protection, thus making it perform better for longer.

[CaMo]

nice info dude!

As said above it can all be changed with the jetting. I had a similar problem running 32:1 with yamalube 2r racing oil. I changed to motul and problem solved so no need to mess with jetting however I do now get a bit of leakage out the exhaust and breather pipe which I presume could be sorted with better jetting.

I'm sure many 250's run 40:1 as they are probably not getting thrashed as much as a 125 but depends on the rider.

I hear people talking about adjusting the air screw a little as well.

[Danger]

Honda never sorted out the jetting on the 05-07 CR250, they lost interest in the two stroke. These bikes have been a major problem trying to jet right. They always seem to be running rich somewhere, yet also display symptoms or running lean. My friends 05 CR250 has been a major pain to get running right and I'm still not 100% happy with it. If I owned it and monitored it from ride to ride so I could try changes perhaps I would be happier with it.
As to the oil ratio debate, you have to bare in mind the kind of riding that you do. I tried running my RM250 at 32:1 so that I could run the same fuel as my KTM200. It was too much oil, even with the jetting being good. If I was doing flat out runs all the time it might be ok. But in the off road world a lot of your time is at 1/4 throttle or less. The pipe just does not get hot enough to burn off the excess oil. I went to 40:1 and made changes to the jetting because when you reduce the oil, your bike runs richer because the fuel flows through the jets easier. I also increased my 200 to 40:1, used leaner jetting again, less smoke and less spooge.
Motul recomends using their Motul 800 at 50:1 and I have changed to this in the last month on the 250, again with a jetting change. This has been an improvement in the amount of smoke and spooge produced. I certainly have not noticed any drop in power, although I dyno probably would indicate that I have lost some power due to the lesser ring seal. But if I can't notice it I'm not missing it. But my bikes are running cleaner.
Jetting is really a moving target, depending on the kind of riding you are doing most of and temperature and it helps to keep a diary of settings for each ride along with temp, humidity, altitude if you travel to central north island or higher regions of the south island and soon you have a history of what has worked in what conditions and gives you a starting point for future reference. After a while and with experimentation you also develop a feel for a bikes performance and what rich and lean feels like.
The air screw should be used to make minor adjustments to suit the days conditions, eg during the day as it heats up you might go a little leaner as opposed to a cold morning. Also some times a little richer air screw can provide a little more torque in the low mid range for tight off road riding.

[Pierce]

Lots good info there folks. I've changed my spark plug to a slightly hotter plug NGK BR9EG which is what is recommended and will also check the carb settings tonight after work.

So you guys think I may be running to much oil in it (32:1)???

[crazyxr250rider]

Just stick with it and sort the air/fuel out.
Im sure that on NGK that the lower the No. the hotter the plug and the the higher the No. the cooler.

[Danger]

We went the other way and changed the 9 series plug for an 8 series.

[Pierce]

We went the other way and changed the 9 series plug for an 8 series.

Oh ok. I've got a pair of both so I can check them both I guess.

[Danger]

We settled on the following, although I still think it could be improved on. It might give you a starting point. This is for summer in Auckland, sea level high humidity.

Main 410
Clip #3
Pilot 40
Airscrew 1 3/4-2 turns out
NGK BR8EG
Oil ratio 40:1 (don't listen to that 4 stroke rider lol) and considering 50:1 with a jetting change.
I remember considering a different needle, but can't remember the specifics now.

[B0000M]

i have an 06 cr250r, my jetting seems spot on- the previous owner set it up. its running a fmf fatty pipe and shorty muffler. if you like you can copy my jetting, i just have to pull it to bits, cheese is planning to copy it too i think

[Danger]

I don't know if the 06 jetting will work in the 04 as I think the 05 on had a different engine or managment system? But would be interesting to see. But you have been running the same jetting in winter and summer Sam? If thats the case it is not optimal.