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RM 250 still bogging, help!

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Posted by: 1998RM250---------------------

Hey guys I picked up an 07' RM 250. I got it from a kid who knew nothing about bikes, but the guy who owned it before was a pro ama rider and modded it. I've been running 93 with motul 808 premix 40:1 and the bike it stil bogging after cleaning the carb. It wont even really hit powerband before 3rd gear, bogs and fouls out plugs. When the powervalve opens it still doesnt seem to be running right either. The kid said he thinks the bike is bored out and the guy might have ran 110 ocatane. I also noticed the silencer packing is soaked in oil and it seems to be running rich... would race fuel make a difference, or my air fuel screw out of adjustment be causing these problems?


Posted by: 1998RM250---------------------

I just took a look at the mixture screw, it was turned all the way in very tight! I set it 2.5 turns out and it felt better, but still bogs a bit down low. Which way leans the bike out, I believe its still running a tad rich and my clutch might even be slipping... It seems like the bike should be pulling harder the way it revs, hmmm I'm not sure though.


Posted by: 1998RM250---------------------

Well I guess not too many people are familair with tuning these bikes huh? I believe the bike has a 162 main jet, but all I know is it sucks down all 2.4 gallons in a little over an hour! turning the airscrew out should lean it out correct? Also the bike has a hinson racing clutch, and i was wondering if the plates or something could need alignment? My buddy was saying something about how that could cause it to stick...
I just want to get this thing right because today I ran a 450 and it pulled me pretty good! With all the mods this bike has and stuff, when its running right it should be the other way around?


Posted by: julien_d---------------------

Yes, turning the idle screw out will lean it, but only the idle circuit. Try raising the clip one notch up on the needle (dropping the needle further down in the bore), to lean it out over the midrange. If this improves it, try another notch up and test again.

The jetting stickies here have great guides to getting your jetting right. The principles there are going to be the same regardless of what bike it is.

Assuming everything is in good repair and sound, and the bike had good compression and proper carb function, jetting is where need to start. Fouling plugs would certainly indicate a rich condition, provided it's not sucking in tranny oil or anything.


Posted by: whenfoxforks-ruled---------------------

When/if you get it running better, replace the silencer packing. You should be telling us what the plug looks like. Especially if it needs race gas. You could be melting the piston.


Posted by: 1998RM250---------------------

Okay thanks, there arent many 2 stroke guys left around here to give me advice that I know of. I will take a look at the jetting guide, and pull the carb apart tomorrow most likely. The bike seems to have good compression and its not sucking any tranny oil, I will have to really find my compression tester though. Hopefully I'm not melting the piston!


Posted by: Rich Rohrich---------------------

Quote:
Originally Posted by 1998RM250
Okay thanks, there arent many 2 stroke guys left around here to give me advice ...


... or maybe they are just tired of dealing with you.


Posted by: 1998RM250---------------------

nope lol almost everyone has 4 strokes here, I'm trying to learn on my own though!


Posted by: Matt90GT---------------------

http://www.motocrossactionmag.com/M...F6F09FC20E9F64C

MXA usually does really good on their jetting. Seems like stock, drop the main and needle down is where they ran the bike.

PRetty simple 2 seconds of searching on yahoo to find jetting specs for the bike. Gosh, need someone to hold your hand while jetting the bike??? Also at 40:1 if the bike is jetted 32:1, you are running rich. So either run the 32:1 or fix the jetting.

What pilot jet is in the bike? what needle and clip? Get a new plug, run it with a plug chop and post the color. I would start by repacking the muffler though.


Posted by: 1998RM250---------------------

no need for anyone to hold my hand, I'm just not used to carbs so much... looks like the 38mm pwk needs a special tool to remove the screws on the tps sensor? I found out my old filter was falling apart as well, so i pulled the carb off and the bowl had some crap in there... I just want to get this thing running right, it used to be a pro ama bike the guy raced with ricky carmichael!


Posted by: 2strokerfun---------------------

A pro racer probably ran the bike near wide open all the time, which means it might be jetted rich for the average Joe Rider. But I also have to say there weren't many 250 2 strokes racing against Carmichael in 2007. As stated above, the air screw will help at idle, but have little or no effect above 1/4 throttle. As others have stated you really need to get a new spark plug and do a throttle chop. Try lowering needle a notch (raising the clip). Do these things then report back with your findings.


Posted by: whenfoxforks-ruled---------------------

Mouse bedding air filter? That would cause some issues!


Posted by: 1998RM250---------------------

thanks guys I will be working on it and report back... It pretty much just bogs unless your on it wide open all the time, and ive never seen a bike suck so much fuel ever!
Main jet is a 160, but I cant find markings on the others?


Posted by: 1998RM250---------------------

before i mess with the needle, i heard running race fuel leans out the mixture a bit... Is it safe to run AV fuel from the local airport? I believe its 100 octane leaded for $3.69 a gal?
Sunoco wants $7.25 for 110, does that sound fair, I'm trying to figure out the best fuel for the dollar.


Posted by: whenfoxforks-ruled---------------------

The av is a no no, and fix the carb. After you fix the too much fuel issue, read the plug, it will tell you what else needs to be done. The jetting stickies, the other posts on seemingly the same subject, and the technical archives. Check them out, there is a few on av gas.



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