Diagnosing why a dirt bike (2-stroke) won't start.

22 replies to this topic
  • xisabel

Posted December 26, 2008 - 06:22 PM


I have an RM. I have this same problem after it sits for like a month. I put the gas on, the choke, and kick, about 3 million times, 10,000 curse words - you get the idea. It never just starts.

It has about 5 hours on this thing - that's it. What's the first thing I should be looking at? Any links or otherwise would be great. I'm not a mechanic yet and have yet to even read the manual. Should I just take it to a shop and let them charge me - I"m assuming it's a minor issue. I don't know what a reed is, a float so I'm really at a loss. Got a lot of learning to do but haven't even got an experience riding partner to bounce things off yet.

  • biker boy

Posted December 26, 2008 - 06:47 PM


cheep gas maybe?

  • urlosin

Posted December 26, 2008 - 06:52 PM


Make sure you are draining old gas out of carb before turning on gas and trying to start.

  • aakmetz

Posted December 26, 2008 - 06:53 PM


try this, turn gas on, wait about 3- 5 min, ( i usually put my gear on at this time) then use about 5 slow gentle kicks w/ choke on. then kick hard, the slow gentle kicks will draw fuel into the cyl, turning gas on and waiting will allow carb bowl to fill, make sure your plug is dry and clean also.

  • xisabel

Posted December 26, 2008 - 07:07 PM


Cheap gas, not a chance. I'll try the 5 minute wait and see what happens

  • redrider606

Posted December 26, 2008 - 07:23 PM


you need more curse words it works for me:thumbsup: :busted:

if nothing works the carb may need to be cleened from just sitting but sometimes when mine dont start they need new rings but i dont think thats your problem in this case

  • mihylo33

Posted December 27, 2008 - 04:02 AM


read up on the service manual then clean the carb. Be sure to drain the gas in the carb after every ride or varnish builds up in the bowl and jets causing a no start situation. I have this problem on a pw50 we own. Once I clean the carb it starts 1st kick.

  • drumurr

Posted December 27, 2008 - 08:23 AM


bad gas, use some fuel stabilizer in your gas if its going to sit that long
gas can be old when you buy it

  • lastchancebev

Posted December 27, 2008 - 03:21 PM


You want to try bump starting the bike - I relied on that growing up. Almost all dodgy running bikes will start this way I find.

Poor quality gas or not the bike has probably gummed itself up in the carb. After the first half dozen or so kicks taking the pluig out and kicking it through - this can help to clean out a flooded engine.

  • jeremy01

Posted December 27, 2008 - 03:37 PM


turn the gas off and lean the bike on its side and let the exsess gass leak out the turn the gas back on.then put it in gear and rock it back and forth.after you do all that kick it with good hard kicks(do slower ones not real short fast ones) if that don't work just push start it

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Posted December 27, 2008 - 03:51 PM


So in the past when you have got it running did it run good?
Did you ride it hard? Sounds like you are just starting out and the 2 strokes, especially the 125's, need to be ridden hard or at least revved high or can easily foul plugs. How does the plug look?
Don't take it to the shop. Even if you know nothing it is easier to clean the carb than to take it to the shop. But if you are rich and lazy.....
First make sure you are getting a spark. If not change plug. If you do have a spark then make sure you are getting fuel. Dont be worried about the carb just take it off and look inside. Remove a couple jets and poke small wire through them. If anything goes wrong come back here and you will be helped. But if you are rich and lazy....

  • 04_edge

Posted December 27, 2008 - 03:51 PM


my bike tends to do that if i let it sit for over a week or so. i find that if ive started it a day or two before, when i go to ride it will start on the first or second kick usually...i figure it just has something to do with the gas sitting in the carb...

  • RhinofromWA

Posted December 27, 2008 - 03:53 PM


You need a few things for a 2 stroke to fire.




If you are missing any of those it is going to be hard to start. even low compression will start if you bump start it. It will spin the piston faster than the preasure can blead off and it will fire.

Check that you have spark from your plug. take the plug out and hold the threadded part against a cylinder nut or something. kick (or use your had if you are by yourself and see if a spark is present on the plug.

then see if you have gas. Is the plug wet from all the kicking?

Compression barring any failure will probably be OK. I don't know the age of the bike or how many hours are really on the bike.

Even with those three item present it may not run well but you should be able to have it fire and run poorly. :busted:

Old gas can be an issue...but them you wouldn't be getting gas as the jet would be clogged with gass goo or a varish residual from the old gas.

Generally for me, if I have a cold bike, sitting a while. I have my gas on, lean the bike over almost to the ground until gas just begins to spill out the vent tube (1-2 seconds) and choke on, and kick.

  • hotrodrm

Posted December 27, 2008 - 08:06 PM


try a new spark plug

  • rooster78910

Posted December 28, 2008 - 02:06 PM


you didnt put fuel stabilizer in the fuel i assume, and then the gas sitting in your carb went bad. so you will probably just need to drain the gas and put new gas in, you might need to clean the carb. that would be my guess.

  • matthew trachsler

Posted December 28, 2008 - 02:13 PM


check ur plug! 80% of the time its the spark plug on my yz 125 the spark plug went after about 4 hrs of riding u should replace the plug right after break in. if the plug isnt the problem try to clean out the carb but if ur not quite the mechanic yet i dont recomend u do that yourself. and if that doesnt work very rarly it could be ur running to rich of a gas mix do u have oil dripping out the back of ur exhaust pipe my buddy had a problem were he ran to rich and his bike wouldnt run it took him about a week to figure out that his pipe was crammed full with oil so his exhaust couldnt get out!

  • zig06

Posted December 28, 2008 - 06:08 PM


Just wondering, but exactly what year and model is this bike? If it only has 5 hours on it, then that "should" eliminate anything that could be worn out.

Also, its wintertime in the Northern Hemisphere, so what are the current temps like in Yugoslavia? The reason that I ask is because your jetting could be totally off if you are trying to start in extremely cold temperatures.

  • anthony250

Posted December 29, 2008 - 12:04 PM


my rm250 was hard to start same like you problem curse and yell until i put in a new spark plug and a gapped the spark plug now starts 1 kick all the time. maybe wrong spark plug wrong gap ''you never know"

  • calatis

Posted December 23, 2012 - 03:15 PM


how many kicks on a 2 stroke before you end up flooding it? my kick strat sometimes doesnt grab and end up smashing my leg is that normal or is there a clip loose or worn somewhere?

  • nathanvg

Posted December 05, 2013 - 10:56 PM


Having a hard time to start my yamaha I can't start it by kick starting it and push starting it will turn on the bog down after 3seconds


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