RM250 90 RM 250 Starting issue

OK So your at sea level (basically). According to my service manual and these jetting specs are for a stock set up bike no aftermarket exhaust etc. You should be running a 380 main jett, and a 45 pilot jett. However you do have the FMF pipe and silencer which will change your jetting requirments. Mostly for the main jett. So your current 360 size main jett should be pretty close. You may want to try a couple of smaller size main jetts. I would suggest getting a 350, 340, and a 330 they dont that much each. But you should stick with the 360 or 350 for now because it is winter time. As for your pilot jet a 55 is way to big. I would pick up a 50, 45, and a 42.5 (I know its an odd ball size). Again they dont cost that much. As for your air screw setting that 1 1/2 turns out is a rule of thumb, or a good starting point. The thing with you air screw is the further in (right hand turn) the richer it will run at Idle, the further out (left hand turn the leaner it will run at Idle. I run mine no more than 2 full turns and no less than 3/4 of a turn. And when you adjust it do it while the engine is running and at operating temperature, no more than 1/8 to 1/4 of a turn at a time. You did mention that your jett needle is set in the #3 position or in the middle of the 5 available clip position. That is a good factory setting for sea level, and should be the last carb adjustment you make.

I dont want to sound like Im talking down to Im just giving you information, and I dont really know what you do and do not know. So I have to explain this stuff like you dont know anything. It just works better this way so bear with me.

If it where my bike based off of the information that you have given me. I would start my putting new head pipe springs and a new pipe O-ring on it. This will prevent your (spooge) from leaking out of the head pipe and cylinder mating surface.

Then I would pull the carb, and reed cage off. Replace the reeds, pull the fuel bowl off, and replace the filter bowl gasket, and the gasket under top of the carb where the throttle cable goes in. Then I would take the floats off and the needle jet (not to be confused with the jet needle). The needle jet controls how much fuel enters the fuel bowl in conjunction with the floats. Inspect the needle jet, it will have two little wires that hold it on the float assembly. On the end of needle jet there is a tapered (pointed) tip that should be coated in rubber. There should be no groove around it where it sits in the hole. If there is any grooves or damage it needs to be replaced. Then I would double check the main jet size just to make sure it is a 360 main jet. Then I would remove the pilot jet and install a 45 size pilot jet. Reassemble carb. Double check your air screw take it our to 2 full turns from fully closed. Use fresh fuel and pre mix. Also install a new plug gapped to the correct gap spec. Before you actually try to kick start the engine turn your fuel on for about 5 min to fill the bowl. Choke it. Then do about 2-3 priming kicks (enough to just cycle the engine over). Then kick it for real. "It should start."

Once youve got it running you'll need to ride it to find where your running too lean or too rich. But we will cover that once youve gotten it running.
 
Here is the Jetting FMF recommends for that bike

http://www.fmfracing.com/RiderSupport/JettingCenter

"We developed these specs with a 32:1 fuel to oil mixing ratio of a 50/50 mix of race fuel and super unleaded, 0 - 1500 ft altitude at 70 degrees outside temperature."

Jetting Results
  • Main Jet
  • 360
  • Pilot Jet
  • 55
  • Needle
  • STOCK
  • Needle Position
  • 3RD
  • Power Jet
  • N/A
  • Air Screw
  • 1.5
    Well looks like smoke :ninja:'d me lol..
 
Thats more or less the same info I gave him. But with some extra options. I still think that the 55 pilot is way to rich. And with the info youve given him pretty much mirrors how the bike is currently set up. So if he does the things I (we) outlined and is able to get it started, and still has an overly rich condition after leaning it out a little more. He may have a larger more expensive problem other than a jetting issue:cry:. I hope for his sake that it doesnt come to that. But like you and I experienced sometimes it is what it is. Im just glad that I can help somebody else out the same way I was helped out.
 
My current main jet is a 360 that i just put in there..i throw a 45 pilot in there...seems like it should start on the current 55pilot tho and its not....but when i.get home tonight il check the carb and rejet it, put the new reeds in, put the different plug in and see what happends.

Whats the larger and more expensive issue i could have?
 
My current main jet is a 360 that i just put in there..i throw a 45 pilot in there...seems like it should start on the current 55pilot tho and its not....but when i.get home tonight il check the carb and rejet it, put the new reeds in, put the different plug in and see what happends.

Whats the larger and more expensive issue i could have?

Well I hesitate to tell you, but......... When I got my bike it ran just fine when I first got it. It was jetted pretty close for the time of the year also. Then summer time rolled around and I started to lean it out for the air temperature. Everything was fine till late summer. Then it developed a rich condition that wouldnt go away no matter how lean I jetted it. So I figured it was time for a new top end. So I replaced the top end and rejetted the carb for the elevation and temp and started my break in. Well it was a little to rich during the break in process so I started leaning the jetts out and no matter how lean I went on the jetts it was still way to rich, and it was a major pain in the ass to start. So I started asking questions just like youve done. Long story short I found out that the Nikasil coating that the cylinder is coated with was just plain old worn out. After all at the time it was like 16 years old. So I tore the engine down stripped all the steel parts off of it and sent it off get it replated. $500 dollars later I had a more or less new cylinder. Put a new top end in it again and its ran like a charm ever since.
 
IMAG0898.jpg
good reeds :shocked:
 
Ok the problem I had with my bike this spring was just a simple seal in the carb. It took me two top ends to figure it out. Look at the least expensive parts first, hoping it's nothing major. It sounds like a seal problem to me though but if I were you I would be asking for "Big Dan's" opinion :D
 
hey guys sorry its been so long... i'm in the military and i was gone on some training for the past few weeks out of state....

so i put a new plug gapped to .024, put new boysen power reeds in, rejetted to a .360 main and .45 pilot and 1.5 turns out on the adj screw, and checked the carb seals and there both still good and still nothing it wont start...

when i put the top end in it was sleeved so i just got it bored out and put the new piston in never got it recoated but i don't see how that would matter....
 
hey guys sorry its been so long... i'm in the military and i was gone on some training for the past few weeks out of state....

so i put a new plug gapped to .024, put new boysen power reeds in, rejetted to a .360 main and .45 pilot and 1.5 turns out on the adj screw, and checked the carb seals and there both still good and still nothing it wont start...

when i put the top end in it was sleeved so i just got it bored out and put the new piston in never got it recoated but i don't see how that would matter....
You matched the new piston to the bore size, right? It should at least fire. It has compression,air,fuel and spark right? And you still got nil? Spark plug is sparking?
 
No doubt in my mind its getting enough air. Fuel?????? It should be getting fuel even if its only getting a little bit of fuel it should still start and idle. Or atleast try to start. So no spark could be the culprit.

Try this. Choke it, Hold the throttle wide open, and then try to start it. You may want to try this with both the choke on and off. With the throttle wide open its gonna get fuel. If this doesnt work, pull the spark plug, and check to see if its wet with fuel. If its wet we know your getting fuel. If its not wet well maybe just maybe you havent turned your fuel on??? I know I know what kinda dummy do I think you are. But as I mentioned before I HAVE to assume that you really dont know much, if anything, so bear with me. But Im gonna assume that your smart enough to remember to turn your fuel on. However sometimes I forget to do this simple but manditory function.
Also, did you ensure that when you installed your new spark plug that the boot was seated all the way? Im guilty of this also but on a grander scale not even connecting it.

OK so for the sake of saying it, lets just say that your getting fuel to the carb because obviously your plug is wet with fuel. And that your spark plug boot seated all the way on the plug. It could be your coil, your CDI Box, or even your stator. But it could also be something as simple as your plug boot and plug wire are just worn out or broken. So take the seat off, take the tank off, so you can get to those items and look at them. If you have a multi meter (fluke) use that to check for resistance and continuity (bad connections). Your manual (remember I said youd need one) will tell you how to check those items. So once youve gone through and performed all these checks Ive given to you, let us know what happend.
 
the bike is acutally a 90' not a 91'... have no idea why i stated 91' i just noticed that sorry...

http://www.ebay.com/itm/1990-Suzuki...74084499&pt=Motors_Manuals_Literature&vxp=mtr
^^ is that the manual i want to buy?

yes piston was matched to bore size...

i took the spark plug out and tested it against the jug and its getting a decent spark comming off of it so i doubt its spark... i did hold throttle open and kick it and check the plug and it just dosen't seem like there is enough fuel on the spark plug. seems liek there should be alot more since i'm holding the throttle wide open. so maybe its a fuel issue but i can't see where it would be comming from since the carb is jetted and clean???... how much fuel should be on the plug if i'm holding the throttle wide open and kicking it 10-15 times with no start?

should i spray some gas into an open carb and see if it hits on that? and then wed for sure know if its a fuel issue... but it is getting spark.
 
Yes that is a genuine factory service manual. That is exactly what you want and need.

Well when you pull the plug is should be visibly wet. Enough that if you wipe it with you finger it should show wet on your finger. So what you need to do now is get that manual! What Im thinking based off of what you just posted you could have a couple of things wrong. Your fuel line or the pick up in the gas tank could have some crap in it, not allowing enough fuel to enter the carb bowl. Or....... your floats are fuel soaked so they ride correctly OR........ your float assmebly didnt get reassembled correctly. OR....... your floats are out of adjustment. You will need your manual to tell you and show you where to measure to and from. Im pretty sure that the setting is 15mm +/- 1mm. But you need the pictures to help show you where to measure it at.

So get that manual, its your best friend when it comes to working on your bike. It is truely worth its weight in gold.

Oh and the jetting that I told you came out of my 92 service manual based off of a bone stock bike but modified by what Ive learned with my bike. The 91 and 92 bikes are nearly identical. But your 90 might could be a little different in the jetting procedures. So get that manual to make sure that your set up correctly. Plus use the info that FMF sent you for jetting procedures the recommend for the pipe you have on your 1990 RM
 
alright so i took it outside and had my buddy tow me to a decent speed and bumped it and it starts but it wants to go almost full throttle without me giving it any throttle. it just goes like wide open... bike runs great tho...

could my idle screw be too far out?
 
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