I have a 2003 honda 300ex all stock and was riding it and it started losing power and i dont know what happened but it will not start.Ive tore it apart and checked the timing chain and made sure it didnt jump time and every thing was right.Its getting good fire plug is firing bright blue.So i took the carb off and cleaned it and even sprayed ether in carb and it will still not start.I checked the valves and it seemed to be workin fine and valves were workin fine.If anyone could help it would be greatly appreciated thank you.

 

Is the cross hatch gone on the cylinder walls?

 

As in cross hatch what are u referring to not too familiar with 4 strokes have done some engine work on them but not much.

 

zoooom is referring to the marks that are left on the cylinder walls from when the factory honed them. If they are smooth and have vertical gouges in them you may have and ring issue. Do you have a compression checker? That would rule it out pretty quick. I compression check can tell you alot about your rings, piston and valves.

Did the bike lose power over time (weeks, or hours or were you just driving along and all of a sudden it lost power and died)

 

The bike belongs to my brother but i was with him while we was riding and it ran good al day and start losing power and all of a sudden quit and hasnt started since.I checked the comprsession and it was great but the rockers had a little wear but i left the tops off where u could see the rockers workin and adjusted the valves by the way they were supposed to be set but i was told possibly could have a valve stuck and might be the reason its not running.

 

try poping the clutch to crank it, as in some one pull you off if it manual , if this dont crank it, u need new rings , all engines need is air , fuel, and a tight motor, if its getting gas and fire, the motor isnt tight, ...... i would think..... my 75 cents.

 

i had same problem do u have a tether cord killswitch check the rubber piece and make sure its on if u do

 

do a leak down it will tell you a lot. Did you just pull the valve covers or did you pull the cam cover.

What was the comprsession????