RM250 STILL loading up

[psustang89]

Well, the recap is I bought a 94 RM250, rebuilt the top end, and it started loading up...BAD. So, I stepped the main jet from a 182 down to a 175, change my mixture from 32:1 to 42:1 with Golden Spectro and 93 octane, and repacked my silencer (not that it matters). The clip is in the 2nd position and the air screw is 1 1/2 turns out.

So, I've been told that stock jetting for my bike is 175, 48, 2nd slot, and 1 1/2 turns....which means my next point of attack in the pilot jet, right? However, I was under the impression that the pilot affect the bottom end, and my bike is loading up in the mid-upper range. Also, I've been told that MX bikes run rich from the factory and going smaller than stock on the jetting helps.

Basically, I'm tired of pulling the carb, buying jets, installing the carb, hauling the bike to the woods, and then finding out that it still runs like crap and fouls plugs. Today I fouled 2 plugs in about 3 hours of woods riding. My buddy didn't foul a single one in his 01 CR250 (oh how I wish I could afford a newer bike!).

Any tips, experiences, pointers???

I'm also looking to buy a flywheel wieight.....

 

[-Mark-]

ive heard alot of problems like this with the rm 250's , 94's and 95's, and most of the time its been to the guys leaving the fuel valve on, which results in fuel getting into the crankcases resulting in your plug fouling when u start it, check your fuel tanks valve by turning it off , unplug the hose from the carb and route the hose to drain it into a bucket or something , leave it over night , then check to see if there is any fuel leakage, if theres fuel then u may need to replace the fuel valve..

 

[sick 96 250]

well if stock jetting is a 175 for your bike then you most likely still need to drop the main jet a few sizes. They are almost always real fat on jetting from factory specs. Try a 168 or so and see what happens. Especially since you say its loading up on the mid and high end of things that sounds like the main jets preoblem since it basically controls that.

 

[psustang89]

Mark
It's not the fuel valve.


I'm probably going to drop the main one more and drop the pilot down to stock. That's my game plan right now.

 

[sick 96 250]

what is your pilot at now? I would say go to a 42-45ish pilot and around a 168ish main and you should be able to clear it up some then you can tell if you need to drop or raise anymore but that should get you close

 

[psustang89]

No offense Sick, but you previously told me to go with a 175 main, now you're telling me a 168? Anyway, my pilot is currently a 52, and I'm going to drop it to a 48. I'm fearful of burning up my motor since I leaned my mixture out to 42:1.

I'm probably going to ride today, and since I can't get a jet on Sunday I just moved my clip to the top position and moved the air screw out to 1.75 turns. We'll see what happens with that.

 

[sick 96 250]

yeah well you told me what jetting to had in there before and you didnt know what stock jetting was so I based it off what you already had in there. But since you say stock jetting for your bike is 175, 48 almost always they are rich at stock settings. Your the one having all the problems with your jetting so i am trying to help, I have jetted many bikes so I have some clue of what is going on. Why start a whole nother thread on the same topic if we went over this before? Good luck on jetting it then, i wont chime in anymore!!!

Oh and a quick word of advise, since you went to a 42:1 mix it is giving you a richer mixture when its going through the carb, its not leaning it out.

Here is you other thread on the exact topic...
http://www.dirtrider.net/forums3/showthread.php?t=137477&page=3&pp=10

If you look I told you go to a 172 but try a 175 just to see what happens.......

 

[psustang89]

I guess people don't understand what "No Offense" means anymore...

 

[Dizzed_Nimrod]

Is there lots of oil on the plug if so you might check the crankcase seal att the gearbox side. Just a thought. Any input´s good right :whoa:.

 

[psustang89]

Yep, any input's good. My seals are good. The leaner jets I've already put in have greatly improved the situation. I think I'm on the right track messing with the jetting and the like. When I ride it, I can tell that it's almost there, just not quite. Looks as though I'm not going to make it out today, but hopefully Wednesday. Then I'll see what affect the clip movment and the air screw adjustment made and rejet for next weekend if necessary.

 

[Matt Fisher]

Does that bike have the Mikuni TMX or a Keihen? I had a bugger of a time getting my TMX equipped 92 RM250 jetted right for 2 reasons:

1) After doing a full rebuild, the rings did not seat. It would run, and being a 250 2-stroke, still made power, but it just wasn't right. Put a different set of rings in there, they seated fine, and most of the issues went away. Check your compression.

2) The needle was too rich, and getting a leaner one took 6 weeks from Suzuki.

I was chasing the eternal rich condition until both of these items were fixed. Then it ran great, and I sold it. Arrugh.

 

[j32]

what reeds do you have?
try a 170,and the stock pilot ,run it and check the plug
new reeds you jet down,not up,because you dont use the stock reed stops
use the stock pilot see how it does
if the carb isnt shutting the fuel off it need a new needle and seat,check the float height!!
im not sure whats wrong -i didnt work on it ,but mine doesnt foul plugs -40:1 klotz
is the power valve opening up right?/ that model is tricky -the left side adjuster-1.5 turns,well it sticks if it isnt just right!!!,it will put too much pressure on the shaft ,and bind it up
ill get that fly weight out to ya asap-mon or tues ok

 

[psustang89]

I moved the needle clip to the top position and turned the air screw out 1.75 turns. I rode yesterday for 3 hours of hard woods riding and didn't foul a plug, but the top end still wasn't right. It's not smoking, but just loads up under full throttle. It's running much better, almost to the point where I don't want to mess with it anymore.

I rings are seated and my compression is good. It makes plenty of 250cc power.

I have the Keihen carb.

I think the reeds are stock and I just flipped them. They're sealing fine. The power valve is also working properly. I really believe it's a carb issue. Changing the jets has had a giant affect on the problem. I haven't checked the float height though. That's on my to do list before next weekend, along with new rear wheel bearings and putting front brakes on my 954.

I hope to see that flywheel weight by next weekend too. It shouldn't take more than a couple days to get here. Thanks!

 

[Motocross26]

By leaning your fuel/oil mixture, you actually made your air/fuel mixture richer.

When you take oil out of your mixture, you have more gas in the mixture, making your bike run RICHER.

Go back to 32:1, see how it runs. You may need to lean your brass out a little more, but this will take you closer to optiumum jetting.

 

[kimoajaj]

Nice to know that there are several guys out there having problems to solve jetting issues:).

On my 2001 KX250 I first had a 50 pilot jet (if I remember correctly) , then I put in a 45 jet, checked plug several times, but I thought it was kind of ligte brown, and it didn`t run as good as it did before, so I put in a 48 jet, somehow (I don`t know if I`m crazy or something) but I think it got a much nicer engine sound, sounded somewhat more "crisp" and it also got better low end power.
Today it fouled a plug, I had been riding slow for 5 minutes or something, then I started to ride faster on a woods trail, and after 45 seconds or something it just stopped.. and my friend on an RM250 had to ride home and get a plug wrench and a plug.. .
I hate fouling !!!.

Jetting is a pain in the ass, also, the temperature plays a huge role I think.. .

Good luck with your jetting:)

 

[psustang89]

I understand the gas/oil mixture thing, but I don't think I'm going to go back to 32:1. I've met some semi-pro woods riders and they run 50:1. I figured at 40-42:1 I'm somewhere right in the middle. It's running much better too. I think I need to lean the pilot out and see what happens. Thanks for the input.

 

[j32]

the pilot isnt going to help the wide open throttle though
check the carb,when it is off to see how far open the slide opens!! mabe it is opening too much,i know it sound crazy but i have had bikes that did that
did you change the cable?-(after market one)-it wouldnt hurt to look you know?
i have had bikes that opened up too much and the needle came out of the jet hole!!!
so for you people that use the 3rd and 4th clip position check the slide wide open!!!!!!!
how about the timing??? is it running flat wide open because of that?
did you retard it at all??