250 watercooled running out of fuel and dying?

[QuadZ250]

Is the stock petcock big enough or am I running out of fuel flow? It runs great at idle and just cruzing around but as soon as you really get on it it dies just after? I'm thinking the petcock does not have enough flow to feed the motor?

Tri-Z 250 Water cooled
34MM Mikuni VM
470 main jet
45 pilot jet
Ported Polished
Rechambered head
Reed spacer
Pipe and silencer

Thanks, Chris

 

[toytech]

possible, take it off the tank, take out the screen tube take it apart and drill it out a little bigger and drill out the outlet tube and try that, thats what I did to my banshee

 

[Awk08]

i'd check the petcock for clogs and the float adjustments, but i switched to a banshee petcock just beacause the 5/16th fuel line was the same as the inlet on my 34mm pj
i say if the inlet is that big, it requires a petcock and fuel line that size to feed it

 

[Boostfed]

Are you sure its a fuel issue?

just asking because when i got my 250r.. it would do the same deal..would idle fine.. then once it got warmed up.. it would sputter in the high revs and die..

i went and got a new stator.. works and runs great now..

is it only happening once the bike is warm or all the time?

 

[QuadZ250]

It happens all the time warm or cold It runs around great until you throttle it too long then its like a switch turns off and it dies? i can restart it but not by kicking i have to pull start it! I just got it running I'm still tuning it! I've pulled the petcock and cleaned the screen its better but still does it? I'm ready to sell it and go back to a stock or near stock
Blaster! Maybe the jet isn't big enough and its running out of fuel on top end? 470 is stock on a stock Tri-Z Mine is nowhere near stock!

 

[schmidty]

check the ohms on the stator and see if its good my blaster did the same thing kinda and i check every thing but not the stator and the sator was it a bigger jet would make it run richer or it could be engine seals to.

 

[QuadZ250]

seals and bearings are all new! it idles fine and runs great most of the time! I can pull start it easy but have failed to ever kick it!

 

[Awk08]

I can pull start it easy but have failed to ever kick it!

/\/\ thats sounds like a pilot jet issue to me, wheres your airscrew set at ????
and needle clip position ????
has it passed a leakdown test ???

 

[QuadZ250]

Pilot is a stock 45, needle is on the third clip and leakdown is good! airscrew is 1 turn out

 

[Awk08]

that all sounds ok, one more fuel move that might work......
possibly, when it dies out, hurry and shutoff the petcock, drain the bowl into sumthin and see how much is in there, compare that to how much it holds when just sitting

i'd then move on to checking electrical, electrical troubles do like to only show themselves under power, and i have seen sumthin as simple as a bad plug cap, cause a weekend of havoc, and stumped 5 or 6 of the best blaster guys i know
start simple, plug wire boot, ground wires connected good, then onto stator ohms, and cdi as a last resort

only one other thing strange like this i've seen....vf3's inner cage moving backwards into a reed spacer under power

 

[YZ Otis]

Try it with the gas cap loose. A plugged cap vent or crimped vent tube will cause a vacuum in the tank. Thoroughly clean the carb. I've had bad YZ cdi/stators where they went flat & wouldn't rev but it wouldn't kill the engine. Sounds more like fuel.

 

[QuadZ250]

I'm fairly sure it is a fuel problem, i have checked the vent in the cap and it is good and unclogged! I'd like to ditch this carb completely and change to my 35mm TMX but the cable is much different and i have to find the correct cable for the twist throttle plus it is missing the air screw and it has to be ordered! Ughhhhhhh what a pain in the butt!!

 

[YZ Otis]

Here's a long shot. I once left a little wad of paper towel in the exhaust port to keep dust out. Forgot to take it out when I put the pipe on. The wad would stay down in the pipe at low rpm but with more flow would get pushed up into the stinger & choak the motor till the rpm's went down and sucked it back into the expansion chamber. Embarrassing but true ... LOL

 

[Awk08]

Here's a long shot. I once left a little wad of paper towel in the exhaust port to keep dust out. Forgot to take it out when I put the pipe on. The wad would stay down in the pipe at low rpm but with more flow would get pushed up into the stinger & choak the motor till the rpm's went down and sucked it back into the expansion chamber. Embarrassing but true ... LOL

i had that happen on a stock pipe, cased a big double and broke that cast iron thingy loose in there, it did that exact same thing, die out under heavy power, i chased jetting problems for over a month, till i pulled the pipe to install my f7, and i heard clunkity clunk as it bounced around inside there.
worth a look, i'd assume sumthin in the silencer, loose packing chunk ????
could cause the same thing ????