06 CR 250 Plug help.

[Joecr06]

Hi, I just recently purchased a 06 CR250. I have been fouling plugs like crazy.

My fuel mixture is 91octane @ 32:1 mixture. My riding style is usually riding high RPM. I just can't figure out why I am fouling so many plugs. I have used both BR8EG and BR9EG, the BR8 has seemed to last a few more hours then the BR9.

 

[rosscopeeko]

Congrats on your new bike purchase. You'll have to do a lot of reading on this forum but your question gets asked very frequently. It's a jetting issue. Maybe think about buying a jd jetting kit like me and then go from there. Also, if you can get higher octane fuel i would use that. The newer cr's will detonate quite easily and should be run on a high octane fuel. Where i live we can get 94 ocatane pump gas easily. Not sure what it's like where you live but i'd look around. Search for "spanky's jetting guide" in this forum to learn how to jet your bike.

 

[02'Cr Rider]

Here's spanky's jetting guide:

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.
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[02'Cr Rider]

This could be a good starting point.

http://www.procircuit.com/PCJETTING.htm

 

[jrm]

What's your altitude/air temperature? I have an '05 in which I'm running stock jetting at about 500 ft; I need to lean it a bit for summer, but in spring and fall it runs very clean. I'm using Bel Ray MC1 at about 45:1 and mixing 93 octane pump 50/50 with race fuel (VP C12) to take care of some mild detonation.

Have you checked your RC valve cables? There's a thread in this forum on how to adjust them. Proper adjustment makes a big difference in how the bike runs.

 

[crashogden]

i have a 06cr125 and it was doing the same thing and it quit after i put in some higher octane race gas

 

[Joecr06]

I appreciate all of your guy's help.

To answer JRM I live in Oklahoma, so the temperature changes ALOT, it was fouling in the 104 degree weather and also has been fouling in the current 50's weather. I am using PJ1 silverfire 32:1 @ 91octane.

It is hard to find 94 octane, but I do know where to get some.

 

[jason33]

have you checked the crank case oil level lately? you might have a bad oil seal-allowing the crank oil to burn in the cyl
whats the plug look like? wet /or black and oily?

 

[jrm]

By the way, make sure you're using the right plug. Honda specifies a fairly obscure NGK plug (not the standard BR9EG) for that bike. The specified plug has a stronger electrode, I think, to compensate for "increased combustion chamber turbulence" or something to that effect.

 

[chevyss_98]

Im Runnin 94 octane with Amsoil synthetic, at 40:1, i have had no issues what soever since i got the bike, and im runnin a BR8EG plug, im in an area where the temperature changes on a dime, same with the pressure and have had no issues, i would recommend 94 with a synthetic oil at around 40:1 to be safe, let us know how it works out

and i doubt it would be a crank seal because that causes these bikes to have crappy flow and pressure inside the engine, and this is a new bike were talkin bout

fuel and oil can make or break the ride man, git'r done and tell us whats up

 

[flattie]

my 05 was a plug foulin sucker aslo.....i live in in arkansas so were pretty close same climate.....i run one size lower pilot 37.5.....air screw 21/2 turns......one size lower main 410..... and two sizes leaner needle -67 with in factory clip location (2nd clip i think)...... also running br8eg..... mine still has the tendsy to load up on the way to the starting gate, but the br8eg resits fouling..... if i go any leaner on pilot or air screw it tends to cut out, i ride on a pretty sandy track..... other mods i've done is had eric gorr mod head for pump gas....and retarded timing by flipping timing tap, this setup has worked well all year and many diff temps....

 

[Joecr06]

Very nice, I think I am going to do some Jet work. Run the same stuff I am running now, BR8EG and 32:1 91 octane. I will just see what happens after some jet work.

I got a few other tune up questions.

When should I change the coolant?

When should I re-pack my silencer?

Besides Coolant,Cleaning Filter,Oil,Plug is there anything else I should be changing before a race?

Also, Do you guy's know how to make the frame look chrome? I have seen a couple bike with it done and was wondering how because it looks nice!

 

[jason33]

mothers alluminum polish,and "elbow grease" -
-a rag and buff it to a shine
if there are scratches you can buff them out with sand paper-1000 gri and soapy water---they the polish
try in a small un seen spot first

 

[motometal]

coolant doesn't really "wear out", if the right coolant is in there then it should be good to go, I wouldn't mess with that.

If your bike is anything like CRs a few years ago, the stock pilot jet is horribly rich. That's bad because every time you let off the throttle it is loading up, plus if the needle and/or main are on the rich side it never has a chance to clean out

Probably not the issue, but if you continue to have problems you may consider switching oils. Some types tend to foul plugs more than others.

 

[BSWIFT]

Where in OK? It sound rich to me. My 05YZ250 did the same thing. I had to lean down the pilot AND the main to clean it up. Motometal has lots more experience on the CR's and he's roosted some Oklahoma red dirt to boot!:) He doesn't like elbows though.;)

 

[ellandoh]

here in MI summers on an 03 i run 30pilot which is 1 leaner than stock, 6bhy38-74needle 2nd clip also 1 leaner than stock, the -73 is stock and finally 1 step leaner on the main 410


FWIW :cool:

 

[Joecr06]

Midwest City, Oklahoma. :ride:

 

[motometal]

here in MI summers on an 03 i run 30pilot which is 1 leaner than stock, 6bhy38-74needle 2nd clip also 1 leaner than stock, the -73 is stock and finally 1 step leaner on the main 410


FWIW :cool:

with my '03, i'm running a 30 pilot too, but it's really too rich still...air screw 2.5 or 3.0 turns out. Main 380 summer 390 spring and fall. Stock needle and needle jet, can 't remember clip position. I might try that needle...

BSwift has really sharp, pointy elbows :laugh: