'02 YZ250 bogging & dying!

[Dazza5]

Hi all, i have just purchased a 02 YZ250, the bike has just had a full rebuild, rebuilt crank new rod new brgs piston & rings etc, the bike starts great first kick no choke etc, but as it gets warmer it starts to die and then rev again and if it dies completely it will start back up again straight away, i have put in a new plug, cleaned carb, swapped mufflers, timing 'appears' to line up with the marks correctly and ive also checked the fuel petcock and it runs fine, This is really starting to bother me because i just want to ride the thing! If it were timing wouldnt it do it all the time? It has great compression also as it should with a new top end, i dont have alot of money left to spend after purchasing the bike and then the appropriate safety gear to ride with. Any help would be greatly appreciated.

Also the pilot jet was pretty clogged when i cleaned the carb, then this morning when i started the bike it started to bog alot sooner than it did before i cleaned it.

I hope this info helps, i am no mechanic but i will try my best to explain.

Thanks

[Akzle]

worn jets/needles.

Does it run less-shit at wot?

Followed by coils/ignition.

[Dazza5]

worn jets/needles.

Does it run less-shit at wot?

Followed by coils/ignition.

Hi wot u mean with out throttle? It seems to run ok idling. Just checked timing its spot on and reed valves ok, im just trying to eliminate things

[husaberg]

Breather blocked on fuel tank.....left field check fuel flow at tap.......
but if it is genuinely bogging unlikely

[Dazza5]

Breather blocked on fuel tank.....left field check fuel flow at tap.......
but if it is genuinely bogging unlikely

Yep checked breather ok, and drained 1l constantly out of fuel tap into jug.

[pete376403]

WOT = wide open throttle. Also known as WFO.

[Rhys]

running to rich would be my guess, if it starts from cold with out choke and the plugs are black ?

[Reckless]

Assuming you have checked for a good fat spark when you put the plug in and that side of things (plug, lead and earthing is all good :)
Whats the plug like wet?? or dry.
If its lean check your Carb to engine boot for cracks

If its wet it'd have to be wet not just black for this condition imho?
Check the Choke Circuit is shutting off.
Check the breather tubes out the carbs we had something similar when we didnt let enough air into our dump bottles (holes to tight) carb is pressuring.
Had the same on a CR250 I bought it as a bike that was having trouble. They'd run it through the mud and the dump tubes were caked with mud up inside blocking them. Cheap Bike that was :)
Secondly make sure the float valve is seating and not letting to much fuel in.
Rudimentary test is: Turn the carb upside down and gently blow through the inlet the weight of the floats should seal the needle valve.
Check the float levels.
Then its jetting.
Check for spec's on needle etc but it should rev to 1/2 throttle ish without even a main jet installed.
Dont just give it a fistful you have to check the progression
Ie Pilot jet just cracked, Mid+Needle and emulsion tube there to 1/2 and from there main on up to full throttle.
Remember the Pilot lets fuel in off throttle as well is it bogging after the second or third twist?

Main rule you cant blow a 2 stroke by going rich, you can by going lean.
My guess if its truly fuel bogging its your float level, Needle valve or reeds are not sealing?
Research Std specs for, Pilot needles etc Std specs are a damn good pace to start on a bike that could have been fucked with since 2002.


My 2c all care no responsibility LMAO :P

[roogazza]

or the other way ,main jet blocked ,idles ok but won't take throttle ?

or rich and floods, can go either way.

shouldn't be that hard to fix anyway.

[trapster66]

Heya, definitely carburettor problem, take it off and take it to a good bike shop mate, if you don't really know how it works you run the risk of blowing up your new bike :-(
it shouldn't cost much to get them to clean and check/reset for you(much cheaper than a new engine)