shut off at high speeds
 

I am having a issue and I would love to call on yalls wisdom.

my gz250 is stalling at high speeds(70mph ish) engine cuts off as i roll off the throttle then the bike dies . After a few minutes it starts right back up again . I bought the bike two weeks ago and I have cleaned the needles in the carburetor , changed the oil and filter.

one issue that might be related , is that when i am accelerating ill be in the power band and then loose it , then get it again .

the bike came with what I guess might be a ebay pipe that back fires and might not have a baffle.

Re: shut off at high speeds
 

ok so electronics are still working when it stalls .

and when I looked under the search someone suggested draining the air box it did have a little oily fluid but not much. and its still stalling after i let off the the gas around 70mph . also im running the bike hard when im testing it which is revealing for problems in the power-band .

Re: shut off at high speeds
 

Will it run if you don't go that fast??

Re: shut off at high speeds
 

If it has an Ebay pipe that is already backfiring, then your mixture is bad and chugging and choking at high speed could also be a symptom of that.

You may beef to up the gas flow a little with a rejet. It's really not hard at all and you can do most of the adjustments without pulling the carb or the gas tank.

Simply drilling holes in the back of your stock muffler will lean the bike out and something as simple as an unplugged breather hose can make it almost unrideable. It's a delicate balance that has to be kept and the PO slapping a universal muffler on there is most likely the cause of the problem.

EDIT: Since this only happens at high speed, close to WOT, it means your main jet is where you need to focus. I'll bank that the PO adjusted the idle mixture screw and the needle, which would take care of low speed and midrange but he probably didn't adjust the main jet.

Re: shut off at high speeds
 

thanks guys .I dont think the previous owner adjusted anything and i have problems all over the power band but mostly when im running at wide open.
i am looking into a hi-flo air filter and shimming the carb . would these be benefit or is the main jet my best bet.

JWR the bike ill run all day lond as long as i dont run at top speed WOT

Re: shut off at high speeds
 

When jetting on your own, you really need to set the main jet first. The main is what gives you the best outcome at full throttle but also has a little effect everywhere else. So, first thing to do is set the main and then adjust idle and midrange after that.

There are several posts you should look at before diving in head first.

http://faq.ninja250.org/wiki/Can_I_impr ... jet_kit%3F
(Use this resource... it's awesome. But be sure to check back here for part compatability.) The Ninja and the GZ are very different beasts.

viewtopic.php?f=8&t=15&hilit=rejetting

viewtopic.php?f=9&t=1058&hilit=jetting

viewtopic.php?f=9&t=513&hilit=jetting

viewtopic.php?f=8&t=617

Re: shut off at high speeds
 

If it acts like it is running out of gas, it could be the float bowl level??
You had the carb off...

Just a wag????

The reason I say that...after it sits a while it will go again...time for the bowl to refill???
Usually with jets or air wrong, it will run, but like crap.

Re: shut off at high speeds
 

ya i think your on to something with the running out of gas . the tank has some redneck engineering on the hoses from the tank to the carb ill take some pics

Re: shut off at high speeds
 

Pics always help.

And it's important to mention all the crazy weird stuff that POs do before asking for help. Shortens response time and lets us zero in on possible source.

http://blog.makezine.com/wood_bike.jpg

Re: shut off at high speeds
 

The hose from the tank to the carb must be straight with no bends or kinks as it is gravity fed.Any abnormal kinks or bends will cause the condition you describe.I know from having a fuel line that was too long with a bend in it.Also if you have a after market muffler you are running really lean.As stated you need to rejet.I ended up using a 132, after intake and exhaust mods.
:cool: :roll: