rm 125 won't start, Any ideas??

Hi guys,

My 2003 Suzuki rm 125 that i just bought won't start. I took apart the carb and cleaned it up and found that the bike was jetted terribly- 25 pilot jet (stock is 40) and a 440 main jet (440 is stock) The bike has the full bills pipe exhaust system on it so i re jetted the bike to a 35 pilot jet and a 460 main jet. I also checked the spark plug which didn't look to bad and made sure that the gap was in spec along with checking the compression which seemed to be about 150(that is, if i checked the compression correctly) Once i got the bike back together i gave it some kicks and no such luck, the bike still wouldn't start. Do you guys have any ideas on what could be stopping it from starting??

thanks for the help,


I feel for you dude, bikes that wont start are the worst. Remember, as a wise man once said an engine with fuel, compression and a spark at the right time HAS to start!

You say it is a bike you have just bought, how long have you had it? Have you had it running up until now and it just suddenly stopped or was it bought in this state? You say it has compression and you obviously know what jetting to use as you already have another RM so check that the bike is sparking correctly, thats usually my first stop.

Good luck

I bought the bike in late October around the 28-ish in the same state, CT. I ran the bike 2 times. Then about two weeks later went to kick it over and it wouldn't start. So i checked and replaced the pilot jet, etc. I already checked the spark plug for a spark and it did have one. Thanks for the idea! Do you have any other thoughts?

oh yeah, and the bike did, for the most part, just suddenly stopped starting.

my wifes blaster did the same thing a few years ago, check the reeds. she had a cracked one, it had compression, but would push the exhaust out the intake when you kicked it.

just an idea. hers with the seat off you could see it coming out the carb with the filter off.

The plug looks ok and you cleaned it up. Bah. Put a NEW one in. It may look "ok" and produce some spark, but still might be the culprit. Fresh gas and a new plug. Easiest stuff first.

Also, did it run since you changed the jetting? Where's the air screw set? I'd go to stock jetting and go from there unless you have very specific information that the pilot comes rich and the main comes lean from the factory (based on your jet sizes that you chose to install).

Tell us what you find. It drives me crazy when a problem is brought to the board and we never hear the end result. It might help someone else (me, maybe) with a similar problem in the future. Thanks!

I always start with the plug

thanks for the responses, i will definitely check the reeds and look into getting a new spark plug, along with changing the air screw around a little bit. The bike hasn't run with the new jets but did run with the old ones. I changed the jetting because it stopped running to see if that was the culprit.

I was wondering if by any chance it could need a new air filter, because i know its getting gas (you can smell it when i kick it over), it has good compression and a spark, could it just need to take in more air?

My nephews cr125 had same problem and I had the same problem with my sons yz80. It had a bad spark plug in both instances. I also found in my rm250 if you gap the plug like .002 over manufacter reckomended you don't fowl as easy. I would bet it was a bad spark plug. Also if you smell gas you probably fludded it so if you can get someone to pull start your bike it will probably start and once it does you need to haul ass on it to blow all the gas out of the motor but do not try to sit and rev it once it starts you have to either get the bike moving or hold it at a fast idle sitting still. Unless you filter is dirty or over oiled it wouldn't be the problem.

Thanks for the response, i will definately have to try setting my next plug .002 over and i will check my air filter and try to get some of the oil off it, might have stuck a bit too much on, thanks for the response!

How exactly would i pull start it? is that like bump starting it?

thanks again!

Good news guys, I got it running today. I took the air filter out and the seat and side panels off gave it some kicks with no throttle and it started up, seems like it was kind of flooded with gas and needed more air.after revving it a bit (some spooge and a bit of smoke was coming out of the pipe) it cleared up, i put the filter, panels, etc. back on and took it for a little test run, ran great!

Thanks for all of the help!

yes it is like bump start but you have someone pull you with another vehicle like a car or quad. by the way if you had stuff coming out the pipe I would repack the silencer. It's probably soked with oil and not keeping bike as quite as it should be.

yeah, that's probably a good idea. I will probably either repack it or wait a couple moths until i get the pro circuit nature friendly silencer.

Thanks for all the help :busted:

thats how mine was when it got cold out. couldn't get it to fire, but when it was warm outside it ran fine. then i just didnt touch the throttle when i kicked it and it started fine. just make sure it's jetted right for the colder air.

for next time when it floods turn the choke off and hold the throttle wide open and kick it a few times it will blow all the gas out the carb

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