RM 250 fouling plugs!

[1998RM250]

Hey guys I finally got to run the RM 250 this weekend, and i noticed if im not always on the throttle it seems to bog down a bit in the lower rpms. Pulled the plug and it was messy, replaced it and ran great until i was crusing around on some trails... same problem! Is a jet in the carb clogged or somethin, the previous owner said he didn't ride much? I was thinking maybe it was the way the bike is jetted as well because it rips for top end, but it just doesn't like being babied.

 

[GarbatyA4]

Hey guys I finally got to run the RM 250 this weekend, and i noticed if im not always on the throttle it seems to bog down a bit in the lower rpms. Pulled the plug and it was messy, replaced it and ran great until i was crusing around on some trails... same problem! Is a jet in the carb clogged or somethin, the previous owner said he didn't ride much? I was thinking maybe it was the way the bike is jetted as well because it rips for top end, but it just doesn't like being babied.

I'd clean the carburetor, both jets, needle, check the float level. Clean filter, fresh gas. Give it a tune up and see how it performs. Also set your slow circuit. Previous owner could have tinkered with the fuel screw.

good luck.

 

[1998RM250]

I'll clean the jets later, and put a new plug in... I noticed theres some sort or electrical wire going to the carb, its a keihin carb and never seen anything like that before.

 

[rmc_olderthandirt]

It doesn't sound like a clogged jet issue as that would tend to make the bike run lean and yours sounds like it is rich.

Going through the jetting exercise would be your best bet. Do a search in this forum and you will find lots of information. Don't assume that it was ever correct, even from the factory.

You may also want to change to a hotter plug. This may be necessary to properly jet the bike anyway as you can't "read" a wet plug.

Rod

 

[dirt bike dave]

I noticed theres some sort or electrical wire going to the carb, its a keihin carb and never seen anything like that before.

Not sure if it came on your RM, but the '97 and '98 Honda CR250 had a 'powerjet' carb. Basically, there is a solenoid that flips at high rpm to lean the carb out for more power.

I agree with the previous posts that your bike's symptoms seem like your jetting is too rich, and you might want to try one step hotter plug.

 

[1998RM250]

Oh btw guys its an 07' RM 250... I'm sure the bike is jetted, as im told it was bored out. Like i said it really rips, just does not like to cruise through the trails at lower rpms. Oh man does she ever suck fuel too, that 2 gallon tank barely lasts two hours of trail riding! The previous owner was running a br8XXX type iridium... I put in a BR8ES, what should I try next? Maybe I am mixing the oil too thick 32:1 as well? I just want to be cautious, but i did also notice my silencer packing has alot of oil in it.

 

[russdaddy]

ive got a 1990 RM250 that i just got back from being completely re-built,and when i got it back the shop had put a Br8eg in it instead of the br8es,before they switched the plug for me it wouldnt idle for more than a couple seconds without dying,now i can easily let it sit for atleast a minute before it requires any throttle to keep from trying,ive yet to foula plug,with the br8es they fouled pretty frequently.

 

[dirt bike dave]

Oh btw guys its an 07' RM 250... I'm sure the bike is jetted, as im told it was bored out. Like i said it really rips, just does not like to cruise through the trails at lower rpms. Oh man does she ever suck fuel too, that 2 gallon tank barely lasts two hours of trail riding! The previous owner was running a br8XXX type iridium... I put in a BR8ES, what should I try next? Maybe I am mixing the oil too thick 32:1 as well? I just want to be cautious, but i did also notice my silencer packing has alot of oil in it.

FWIW, over bored bikes often require leaner than stock jetting. Even then, they can be quite thirsty.

Your symptoms sound exactly like what I would expect if your jetting was too rich. If you want to keep the safety of a fat main jet, you should at least try turning out your air screw and getting a leaner pilot jet to clean up the low speed running.

 

[1998RM250]

thanks for the great info, i will still remove the carb and clean it because the filter was disgusting when i got it. I think maybe I will try the br8ev which is the platinum tip plug, the last iridium plug's electrode was fried!

 

[_JOE_]

Follow this --- http://www.dirtrider.net/forums3/showthread.php?p=1340315#post1340315 --- and you'll never have to worry about your jetting. I would have leak down test done before hand just to make sure you're not compensating for a bad crank seal.

 

[GarbatyA4]

I've been running a the same BRxEG plug for 2 seasons now. EG is the race version, finer electrode.

 

[rmc_olderthandirt]

I think maybe I will try the br8ev which is the platinum tip plug, the last iridium plug's electrode was fried!

In my experience, fouled plugs and fried plugs do not go together, they are at opposite ends of the spectrum.

A "fried" plug has gotten so hot that the ceramic blisters, the electrodes melt, or other bad things happen.

A "fouled" plug didn't get hot enough to burn off the combustion byproducts and any unburnt gas/oil.

If your plugs are both fried and fouled then you must be operating between the two extremes. This would suggest to me that your main jet is too lean and your needle jet is way too rich.

Be very careful when you start the jetting process as an attempt to lean out the mid range (needle jet) could cause such a lean condition at wide open throttle that you could damage the engine.

Rod

 

[1998RM250]

hmm thanks, maybe the iridium tip plug wasnt fried... I can't remember if the electrode is smaller or not or them. Always somethin with these bikes, even the new ones I guess!