Arrgh!! Stumped again!!

[razor]

I thought I had my RM250 figured out, but it is till loading up on me 1st gear through 3rd. I am currently running the mikuni carb with.....
45 pilot jet
air screw 1 1/2 turns out
20 to 1 ration using premium gas and redline oil
stock needle on second notch from the top
360 main

When I bought the bike it was hard to start and loading up. I found the wires from the stator melted and fused to the pipe. Now it starts on the first or second kick. I am wondering if I should change back to 40 to 1 and rejet for that mix. That is what the guy was running before me. I am afraid the jetting I have now might be to lean? When I ride it out on the gravel road, it runs great from 4th to 5th. No hesitation whatsoever. The pulls really hard!! When i head back home to our driveway after a fast run, I will blip the throttle and the front tire easily comes off the ground. Then I think the plug gets loaded up and she bogs down on me. Sorry its so long.

 

[fatboyslim]

What do you mean by "loading up"?

 

[whenfoxforks-ruled]

Put the oil ratio that the bike was designed to run. Check the plug if it has issues. The plug will tell you if it is rich or lean.

 

[spark250]

20:1 seems way fat!!! Manufacturers usually call for 32:1 and that is a little fat in my opinion. Try the stock jetting and 40:1 as you mentioned.

 

[snb73]

20:1 seems way fat!!! Manufacturers usually call for 32:1 and that is a little fat in my opinion. Try the stock jetting and 40:1 as you mentioned.

Agree, 40:1, start with stock jetting and rejet.

Post your bike year in your profile. That makes a big difference. My 2003 RM 265 runs well with a 168 main.

 

[razor]

Sorry for the late response.

fatboyslim.. It runs like crap until I run past half throttle to wot. When I turn around to do the run again, she is snappy. Front wheel comes off the ground when I blip the throttle, then it seems that she is getting to much and the spark is not keeping up until I get on it on 3rd gear again.

whenfoxforks-ruled.... I have the Clymer book and it states to run 20:1 ratio on it. When I pull the plug, it is wet and a little oily.

snb73
spark250......
Will do. Thanks for the help. I will go to the stock jetting, and 40:1 and start all over with the jetting. I will update the profile. Thanks for the help.

 

[razor]

I forgot to mention the guy I got it from was running 40:1 on it, but it was loading up then too. So my question is, Will my bike be ok if I run the 40:1 and leave the main and the jets the way it is, or will my jets be to lean?

 

[razor]

I just found this on the web and I'll be damned if it is not exactly what my bike is doing. To the T!!!

http://www.youtube.com/watch?v=Sp77ehjpVr0

 

[whenfoxforks-ruled]

First thing is to replace the float valve and seat if applicable. Does the manual say 20:1 for break in and then 32:1? I find it hard to believe an 89 is supposed to run 20:1 all the time. I like starting at the bottom of the throttle. Get it to its highest idle, how many turns out is the air screw? Less than 1, you need a bigger pilot. More than 2 1/2, you need a smaller pilot. Next would be the clip. That one needs to be rode, 1/8 to 1/4. Erratic surges means lean and a blubbering bog rich. The main you can feel also, or cut the plug off. Screwing with the oil ratio is foolish, an ignorant answer to jetting problems. What the manufacture recommends for that model is what you should run, simple? If jetting changes do not seem to work, then you have some other mechanical issue going on. Reeds, silencer packing and air filter, and not to mention a good motor! Any decent 2 stroke oil and premium gas. And run what plug that they recomend. Get a plug and check the shiny spot on the electrode tip. The plug will tell you if the timing is close and if the heat range of the plug is correct. No one can give you their jetting or plug choice and be good for you. Way to many variables. You can seemingly have all these ying yangs with the ratio and plug advise, and be sitting on an engine with main crank seal issues or a dirty clogged air filter. Learn how to do a plug chop, and read your sparkplug!

 

[Shaw520]

Razor,.. if you read this far and still havnt found your answer,....... then you should re-read the previous post,... it all in there.

 

[razor]

That is what Clymer said to run. I am hoping the three wires that were fused onto the pipe from the stator were robbing the spark. I will try 32:1 and go from there. if I cannot get it to run right, my fathers day present will be to get it fixed at the local dealer. the air screw is just over 2 turns for the idle to increase.The main feels ok. the needle is at the second clip from the top. Did you by chance watch the video link? That is almost exactly what my bike is doing. Everybody is saying or most everybody is saying it is too rich. the guy at the dealer told me this also. What confuses me is what is rich? I thought rich was more gas and less oil, and lean was more oil and less gas. Am I correct here? If I am correct, then 20:1 is leaner than 40:1 right? So if I am running way rich, how is that possible if I have a lean mix. I appreciate all the info and help everyone has put in. Forgive my ignorance, but I like to tinker and try to fix it myself before I have to take it to the dealer.

 

[whenfoxforks-ruled]

Run the proper ratio, and quit thinking about rich and lean as in the ratio. It is the air and fuel ratio from your carb. For some reason it is falling on its face, randomly. The float valve should be changed yearly. If it has a seat, it also. A defective valve can be not shutting off the fuel when it is supposed to, it may even look okay. It is cheap and easy to change. Then try dropping the clip and see how it runs, that will richen it. Worse, go the other way. When I gazed over a parts fiche, the stock needle and the next 2 were discontinued. Usually that is for a good reason. Buy one. By not reading the plug correctly, you could be rich on top and lean on the needle. A leak down test would be nice to rule out bad seals or leaks elsewhere. If someone has meddled with the porting it could run like that also.

 

[razor]

I will try lowering the needle first. Thank you for your help and advice. I appreciate it.

 

[whenfoxforks-ruled]

Lower the clip, raise the needle. See what happens.

 

[razor]

I have not had a chance to raise the needle yet. Freethrow contest and Timberwolves game this weekend. On top of that we are getting 6 to 8 inches of snow by tomorrow night. I will raise the needle tomorrow hopefully, run it in our shop and see how it runs. I will keep you posted whenfoxforks-ruled.

 

[razor]

Ok I decided to try the 40:1 ratio after talking to a really nice guy at the farm supply store. They sell Suzuki and Artic Cat there as well as service them. Here is what I am running....

40:1 premium and redline oil
45 pilot jet instead of the stock 55
360 main jet instead of the stock 370
air screw is out 2 turns
stock needle 6AEJ01-62 on the second clip from the top
NGK B8EGV plug gapped at .024

Outcome... the bike is running just about as it should, I need to tinker around with the air screw. That is where I am at with it. There is no more blubbering on the bottom, the throttle is nice and crisp. I have a video of the bike running and me twisting the throttle if anyone wants me to send it to them, so that you can hear it and possibly let me know how to get it just right. Also I am wondering if it is just right the way it is for the cooler weather. It was about 36 degrees when I shot the video with my phone. Also my spark plug had ust a small spec of oil on the top outside of the ground electrode. Everything else was clean on the plug. The small spec of oil was the size of a pin head. Thanks for the help guys. I am anxious for the warmer drier weather to come!!!

 

[whenfoxforks-ruled]

Strikes me as a little odd, you are overall, leaner than stock at 37 degrees. 55 to a 45 is the oddest. As long as the plug does not show running lean, erratic rpm, lean surge. Dialing it in with the air screw will tell you if you are okay on the pilot. Watch that leaner jet on the top also. If everything is good, when it gets hot you will have to lean it out more.

 

[razor]

My bad. She is loading up again. I am taking it in for a leakdown test. I feel it is the right crank seal.

 

[whenfoxforks-ruled]

http://www.bikebandit.com/assets/product_images/05MotionProLeakDownTesterLG.gif, just like that. I would venture to say that an ingenious sort could make one out of plumbing expandable plugs, schrader valve and psi gauge, for under 50 bucks. More important, double check for play on the crank ends!

 

[razor]

Thanks for the link. I leaned it out as much as I could on the pilot. However the Clymer book shows that is should be a 55 pilot jet for stock and I swear the guy said the stock one for an 89 was 50. I am going to put the 370 main back in it, and if indeed it supposed to be a 50 pilot jet for a 89 RM250 I am thinking about going down to a 40. What do you think? I also have the clip on the top for the needle.

 

[whenfoxforks-ruled]

If you are on top of the needle, you need a leaner needle, or the one you have has issues! Worn, not stock or bent? 40 pilot is pretty lean, as long as the plug, or how it runs dictates!

 

[razor]

I put the 370 main back on and put the 40 pilot jet on. It seems like I am on the right track there. The throttle has never felt crisper. I still have to fine tune it with the air screw. I had it out 2 turns. I had a dentist appointment so I could not mess with it as long as I wanted to. Now in first and second it starts to pull like it should, but still loads up just a little bit. When I whack the throttle it sounds a lot crispier, except past 1/4 throttle where it sounds like it got the wind knocked out of it. You know what I mean? Like when someone is talking and they get punched in the stomach and they try to continue talking. Sounds kind of like that. Sorry for the weird description, but that is what it sounds like to me. Then it is only for a second then it clears until I whack the throttle again. I actually have a video of the dirt bike sounding like this. I cannot upload it. If you send me a e-mail address I will send it to you so you can hear it. Thanks for all of your help. I am going to order a leaner needle.

 

[whenfoxforks-ruled]

Change things one at a time. I do not know about your version of the powerband, kinda sounds lean. That goes back to the pilot, maybe the needle. One or the other need to be fatter. it just sounds like you changed more than one thing at a time. Try the bigger pilot. If no desirable change, then put it back and move on to the needle. If you jumped sizes you may have jumped over?

 

[razor]

I am back to where to square one. Only difference is I am running the 40:1, needle clip is at the highest clip, and the pilot jet is a 40.

So as it stands,
40:1 with Red Line and Premium
Stock Needle at the leanest clip
40 pilot jet
NGK-B8EGV gapped at 0.024
370 Main Jet
Air Screw 2 turns out

I am with you. I think I need a fatter needle.

 

[whenfoxforks-ruled]

Wonder if JD could hook you up?