Idles but wont rev up

[BC GZ]

I've been playing with this thing for a couple of days now, it's an 05 with only 560 miles on it and it wasn't running. I've replaced the fuel, replaced the spark plug and taken the carb off and disassembled it and cleaned it 4 times now and it will now fire up and idle but as soon as you touch the throttle it bogs down and dies. Even if you try turning it ever so slightly it just dies. I've tried adjusting the mixture screw and that doesn't do anything, I've worked on lot's of bike and never had any be so stubborn... what am I missing?

[5th_bike]

The manual only mentions 1) clogged main jet 2) clogged needle jet 3) improperly working throttle valve and 4) clogged fuel filter.

Since it idles fine, you could rule out air leaks before the carburetor.
However, when mine is still stone cold, it also has trouble revving up. It needs to be warm to run better and hot to run fine. Did you try starting it (full choke) and wait say half a minute before opening the throttle ?

I'm somewhat at a loss too :??: so please wait until someone else chimes in.

Oh and by the way: Welcome to the GZ250 forum ! :rawk:

[blaine]

Welcome to the forum.Make sure that the carberauter vent tube is not blocked or pinched off.Is the plug in the bottom of the drain tube on the air box?
:) :cool:

[BC GZ]

I let it sit there and warm up, took the choke off and it idles great but no luck one the throttle is turned. I will go out and check the vent tube now

[BC GZ]

I just pulled the cap off the drain tube for the air box and a bunch of liquid came out, kinda smells like paint thinner so I'm guessing old gas?

[blaine]

I just pulled the cap off the drain tube for the air box and a bunch of liquid came out, kinda smells like paint thinner so I'm guessing old gas?

Yes,old gas,and blow-by from the crankcase. :) :cool:

[BC GZ]

Any other ideas out there? I think the filter is fine, i emptied the tank through the petcock. I have soaked and blown air through all the jets and all of the passageways in the carb, I guess it may be possible for a blockage but seems doubtful to me

[blaine]

Any other ideas out there? I think the filter is fine, i emptied the tank through the petcock. I have soaked and blown air through all the jets and all of the passageways in the carb, I guess it may be possible for a blockage but seems doubtful to me
The filter must be checked from the inside.It can look clean from the outside and be plugged.It draws air from the inside.Always blow air from the outside in to clean.If you blow air from the inside of the filter it will be ruined.
:) :2tup:

[BC GZ]

Check that one off the list :??:

[5th_bike]

I let it sit there and warm up, took the choke off and it idles great but no luck one the throttle is turned. [...]
And what if you leave the choke on ? (the same, I presume) :sad:

It still sounds like most likely a clogged jet.

[alantf]

The filter must be checked from the inside.It can look clean from the outside and be plugged.s

Just one question. How do you see inside the filter? mine has a sort of cover at the intake end, & a solid plate at the other. In the 4 years I've had the bike, I've only been able to check it by blowing through, & checking that it "seems" to be clear. Surely there's a way to look inside, or am I missing something? :??:

[blaine]

Just one question. How do you see inside the filter? mine has a sort of cover at the intake end, & a solid plate at the other. In the 4 years I've had the bike, I've only been able to check it by blowing through, & checking that it "seems" to be clear. Surely there's a way to look inside, or am I missing something? :??:
I forgot about that cover as I used a after market filter.With the OEM filter,the cover will pop off.Than you can hold the filter up to the light.If no light shines through,the filter is plugged.
:) :cool:

[alantf]

With the OEM filter,the cover will pop off.

Is that the cover at the intake end, or the flat cover. They both seem pretty solid, so I don't want to damage the filter, trying to get the cover off. :??:

[blaine]

Is that the cover at the intake end, or the flat cover. They both seem pretty solid, so I don't want to damage the filter, trying to get the cover off. :??:
The air diverter at the intake end.
:cool: :)

[BC GZ]

Ya it does the same with the choke on, I guess I'll have to take it all apart again

[geezer]

dude you need to take it all apart again, good thing it only takes an hour to disassmble this bikes fuel system, if i were you id pull the tank drain it pull out the strainer and clean all the gunk off the strainer 05 with 600 miles? you know its jacked all up, go through the carb again, and clean the shit outa it everything nees to come off and be cleanedand and make sure your float is set up right and that the screen is clean of junk when you go back together with it makes sure you dont havee any air leaks, i would spray down the intake manifold and intake track with some carb cleaner and see it its not leaking in ainy air, good idle then dies with throttle sounds like airleak to me bra

[alanmcorcoran]

It still sounds like most likely a clogged jet.

I agree. It is possible, in some cases, to nurse it past this condition just by letting gas go through it (idling), but if the bike sat for a while, you'll probably have to take more direct measures.

[Dickey]

To preface my two cents, I'm a newbie to this engine and my wrenching experience is mostly limited to automobiles; but is there any chance that the ignition is not behaving as it should? My three wheeler is a one lunger and it had an issue like that ages ago that turned out to be a hoky coil wire that was grounding out as soon as the rpm increased. I had rebuilt the carburetor twice before realizing that the engine wasn't ever trying to catch again after letting off the throttle and going back to the idle circuit.

[mrlmd1]

There are many reasons your bike is doing this, but an almost new (560 miles) bike should have no problems like that unless a rat ate your wires, It's most likely related to the carb or a vacuum leak and not something in the ignition system. If you feel concerned about that then give everything a careful going over and look at it. You may also have some gummy deposits or dirt in the little screen over the fuel intake tube in the gas tank from sitting for years unused.
Do you have a free flow of fuel from the petcock if you set it to prime and disconnect it from the carb, or open the drain screw on the bottom of the carb with the petcock in prime? Maybe your fuel flow is restricted.
Also try and run it with the gas cap off just to make sure you don't have a gas cap vent problem causing a vacuum in the tank.
Both of those ideas may be far-fetched but are real easy to rule out a fuel delivery problem.

[jonathan180iq]

Might want to make sure that the vacuum tubes that run under the tank haven't cracked. The petcock flows gas based on engine vacuum. Without Vacuum, you will get no gas. I think you have a weak vacuum which gives you just enough to ilde but once you need to open it up the mixture can't compensate.

Take off the gas tank, replace all vacuum hoses (If for nothing else, simply because it's an '05 that sat for so long and it won't cost you $5. I would do this even if it's not the problem) and flush the tank with a good, strong cleaner.

The good thing about being a single cylinder is that there are only so many things you can check. You'll eventually get this nailed down. And for the benefit of other who read this in the future, please update us with your results.

[jonathan180iq]

....thinking more, given the bike's age and low mileage, you really need to do this kind of catch up maintenance everywhere you get a chance. Think of it like restoring an old car. Even though it's an '05, it never even got past it's initial break-in period and then sat for 6 years.. That's a harsh life. Sitting for so long, and if the carb was dry, then some of the inner seals and things might have dried out as well, also leading to some of these symptoms.

I know it's kind of a different beast, but I once had all kinds of trouble out of an old '92 Murray push mower. I worked on everything, cleaning the carb, replacing the plug, check the seal around the muffler, changing oil... I even replaced the kill cable before realizing that there is a gasket and a rubber diaphragm under the carb which seals the area between the gas tank and carb. That diaphragm wasn't punctured or anything, but it was thin enough that when it stetched under the engine vacuum load it would allow too much pressure to build up in the system and kill the engine instantly. A $4 diaphragm resurrected a long-dead lawn mower.

Like I said earlier. Just hang with it. You'll get this.

[Jrod]

Had the same problem with the bike I just bought. Threw some chemtool in and let it idle for about 10 minutes to get it into the carb and let it sit overnight. Came back the next day and drained the remaining gas out of the tank (which the previous owner said had been sitting for over a month) and drained the float bowl as well. A sizable piece of gunk appeared in the float bowl after drained, along with old nasty fuel. Filled up the tank with new gas and a little more chemtool and it fired up just fine. Idled a bit rough for about 10 minutes but after that it ran like a dream.

[Water Warrior 2]

While you are messing around by the carb you might as well install an inline gasline filter. They are cheap and do a good job of catching the remainder of the gunk in the tank. Any auto parts, dealer or small engine repair shop will have them.

[Rococo]

Had the same problem last year. Check your petcock valve, the diaphragram inside some times goes damaged when is not in use. (Quote my mechanic!). I replace the valve and problem solved. Expensive solution but worked for me.