new to this..hope i didnt screw it up...

F

ftw2012

Member
Feb 1, 2009
10
0
so i just bought my first dirtbike a few months ago its a 03 cr250r and it seems like a pretty nice bike...today after i got it started it seemed like it was runnin kinda crappy and i remembered that id been told if you dont ride it hard that it will foul up since its a 2 stroke...so i took it down the road and opened it up for a mile or so...finally it seemed to be running alright and respond well when i cracked open the throttle. when i slowed down to an idle to turn around the bike quit on me...after a long push home i see that it does have spark and that it seems to backfire or almost sneeze back at me when i try to get it started. i dont really think i over rev'd it or anything...still had plenty of powerband....hoping i can be lucky enough that im describing something that someone with experience will know whats wrong or have a good guess..thanks for any input!
 
Last edited:
J

jdager

Member
Apr 26, 2008
77
0
step one, put in a new spark plug, and it probably wouldnt hurt to clean the carb. if that doesnt do it, you may be looking at a top end rebuild (not that bad). were you mixing oil in your gas? if so, at what ratio?
 
F

ftw2012

Member
Feb 1, 2009
10
0
yes i am mixing gas and oil...should be 32 to 1....i will admit that the last time i filled up i used 50 to 1 mix but then i added about 3 oz of oil to the 2 gallons...which im pretty sure makes it a 32 to 1 mixture, or at least close to that or a little bit extra oil...i know that i unscrewed the plug and then reconnected to plug wire and pushed the kick start with my hand and i had spark....i hope your right about the plug.....wont get a chance to check on that for a few days....thanks for the quick reply
 

IndyMX

Crash Test Dummy
~SPONSOR~
Jul 18, 2006
5,548
2
Amo, IN
If you just poured the 3 oz of extra oil into the tank, you probably seized up your engine.

Premix should always be mixed in a can prior to pouring in the bike, so you can make sure it's mixed in well. Just shaking the bike a bit probably didn't mix it well enough.

How handy are you with tools?

I'd suggest that if it doesn't fire right away with a new plug, you should pull the cylinder and inspect.
 
F

ftw2012

Member
Feb 1, 2009
10
0
maybe i should say that, not the last time i rode, but, a few times ago when it quit, i pulled the plug and there was a little BB type thing that was stuck in the plug that was preventing the plug from having to make an arc across the plug to complete the circuit...if that makes any sense...and someone told me that you ruin a 2 stroke if you drive it in the winter....it was about 34 degrees F today when i was roddin on it if temp makes that much of a diff without rejetting...i dont know just thought id throw it out there...
 
F

ftw2012

Member
Feb 1, 2009
10
0
the oil and gas had been mixed in the tank for a long time...i added the 3 oz before i poured in the 50 to 1 mix...but if they could separate thats possible...i wouldnt have any problem pulling the engine and checking it out if thats what needs to be done....thats what i was afraid i would have to maybe do.....i was thinking maybe it was in the carb since it was running good wide open and at half throttle but since it quit when it slowed to idle maybe it was the idle circuit in the carb......just trying to remember back to my schooling to be a mechanic... isthat fairly easy if i have a half way decent back ground in mechanics? im just use to working on cars with all there sensors and stuff so im not sure were to start...i guess ill start with a plug and then maybe a carb cleaning...hope i dont have to go as far as a top end rebuild...is there much involved in that in a 2 stroke? thanks again for your help and quick responces!
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
The oil and your mixing habits had nothing to do with it, completely different issue, get a ratio rite and gas can. That bb could have been detonation, that wfo run down the road was not good! Engines run leaner the colder it gets outside. That means your engine will run lean. Get a manual and some tools. You will probably be able to see the damage, by pulling the pipe off and looking at the piston.
 
A

aaronnaland

Member
Jan 19, 2009
104
0

pull off the pipe, the spark plug, and the carb so that it lets in light from the other 2 holes then it will be easy to see damage. look for any black on top of the piston. there can be some and it would be fine but its a good idea to pull the cylinder off if there is alot and look at the rings at least.
 
U

ulmanb

Member
Jun 12, 2003
50
0
Once you get the piston/rings checked out, I would highly suggest you either spend some time jetting and checking plugs or get yourself a JD jet kit which will eliminate a lot of the guesswork for you.

Running at that cold temp without re-jetting could definitely cause some issues.

The method of your oil mixing shouldnt be the issue. I often have to mix my gas in the tank on long rides when we stop at gas stations, I just make sure to take it easy for a few minutes letting the gas and oil bounce around and mix together.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
Opposite end of the light spectrum. Lean or detonating is silver the last I looked. The exhaust edge is supposed to be a nice machined edge. And a trouble light, or a safer method, flashlight should have been a given?
 
F

ftw2012

Member
Feb 1, 2009
10
0
whats up? just got my bike halled home lastnight and pulled it apart...i need a new piston and rings for sure....and maybe a new cylinder too...my question is can i take this Cylinder down to my local engine machining shop and get it bored out to 10 ,20 or 30 thousants over just like you can with a car motor and then buy the approprate sized piston? does anyone have any suggestions? id like to get a piston that will last a long time....im not too concerned about having top performance, id rather have something that will last longer then something that will go faster....ive read that forged pistons will probably last longer then cast and different stuff like that. hope i get some suggestions before i have to go buy something...thanks a bunch!
 

IndyMX

Crash Test Dummy
~SPONSOR~
Jul 18, 2006
5,548
2
Amo, IN


No, you can't just have the cylinder bored out. It will also need to be replated.

Best bet is to send it to someone like Eric Gorr and have it done the right way.
 
You must log in or register to reply here.

Similar Topics

No idle 50% throttle
Replies
1
Views
141
muxus
K
Help KTM125 SX 2003 cooling down unusually.
Replies
2
Views
315
KTMkid
K
1
Powerband not "hitting right".
Replies
1
Views
915
_JOE_
J
Help 2011 KX250F Bump start only! Please Help!
Replies
0
Views
169
Rid'nRip
R
how to know if i need a new top end
Replies
18
Views
8K
whenfoxforks-ruled
Cookies are required to use this site. You must accept them to continue using the site. Learn more…