GZ 250 Forums - View Single Post - No start: Have spark, have fuel, have air

isaac · 03-10-2012, 03:25 PM

Well I finally got the bike running, and it was a weird problem that Blaine suggested.

As I mentioned before the starter clutch went out at 2,000 miles. Since then I've had to fix that 2-3 times. Well it appears as if the most recent time came back to haunt me. The flywheel had sheared off most of the locating pin (maybe a woodruff key, but it was disintegrated) and had misaligned. As a result, the strip of metal on the flywheel that passes by the ignition's impulse sensor to tell it when to trigger the ignition wasn't lined up with the right part of the engine's stroke. The ignition was firing regularly, but at the wrong time, so it never lit up.

I couldn't figure out a way to get the remains of the locating pin out of the crank, so i welded some steel over the top of it and filed it into the shape of a locating pin. I bolted the flywheel back up, and the bike runs now.

It also runs like total crap, and I can't figure out why.

Intermittently it will perform flawlessly. This is a rarity though. Most of the time it's vacillating wildly between too much fuel and not enough, in all conditions.

Regardless of if I run it with the petcock on On, Reserve or Prime, regardless of if I take the pod filter off or leave it on (this bike was properly set up for this filter and ran fine a year and a half ago), it will run like crap in one of two ways: either it's rich or lean.

When it's rich (no changes necessary for it to do this) fuel will literally be flowing out of the vent hole of the carburetor (the bottom right hole on the mouth of the carb) while it's running. While it's doing this, if I spray any starting fluid into the carb, it will die immediately, regardless of throttle position. Idle is very stable while it's doing this. If I cover the air jet (bottom left hole of the mouth of the carb) the idle will increase.

When it's lean (no changes necessary for it to suddenly do this), it needs the choke to start, but will idle without the choke when it's warmed up. The idle is extremely unstable with lots of hiccups. It won't rev at all unless I'm spraying starting fluid into the carb, and it idles better when I spray starting fluid into the carb.

When it's running rich, if I take it for a ride up and down the block, invariably at some point it will suddenly shut down. Needless to say I don't take it farther than my own street because of this.

Seemingly all of this happens at random.

The carb manifold and seal are nearly new (replaced last year), the carb has been soaked in B12 chemtool, every jet and passageway blown out, every seal replaced, rubber diaphragm on the slide is excellent, the float valve and seat are clean and in good condition and seal completely tightly, the float is seemingly at the correct height, all passages are seemingly clear, the choke opens and closes completely, the mixture screw has been at 2 1/2 or 3 turns and that seemingly does nothing.

Ideas? Thanks .

03-10-2012, 03:25 PM	#4
isaac Member Join Date: Dec 2011 Location: Orlando Posts: 39	Re: No start: Have spark, have fuel, have air Well I finally got the bike running, and it was a weird problem that Blaine suggested. As I mentioned before the starter clutch went out at 2,000 miles. Since then I've had to fix that 2-3 times. Well it appears as if the most recent time came back to haunt me. The flywheel had sheared off most of the locating pin (maybe a woodruff key, but it was disintegrated) and had misaligned. As a result, the strip of metal on the flywheel that passes by the ignition's impulse sensor to tell it when to trigger the ignition wasn't lined up with the right part of the engine's stroke. The ignition was firing regularly, but at the wrong time, so it never lit up. I couldn't figure out a way to get the remains of the locating pin out of the crank, so i welded some steel over the top of it and filed it into the shape of a locating pin. I bolted the flywheel back up, and the bike runs now. It also runs like total crap, and I can't figure out why. Intermittently it will perform flawlessly. This is a rarity though. Most of the time it's vacillating wildly between too much fuel and not enough, in all conditions. Regardless of if I run it with the petcock on On, Reserve or Prime, regardless of if I take the pod filter off or leave it on (this bike was properly set up for this filter and ran fine a year and a half ago), it will run like crap in one of two ways: either it's rich or lean. When it's rich (no changes necessary for it to do this) fuel will literally be flowing out of the vent hole of the carburetor (the bottom right hole on the mouth of the carb) while it's running. While it's doing this, if I spray any starting fluid into the carb, it will die immediately, regardless of throttle position. Idle is very stable while it's doing this. If I cover the air jet (bottom left hole of the mouth of the carb) the idle will increase. When it's lean (no changes necessary for it to suddenly do this), it needs the choke to start, but will idle without the choke when it's warmed up. The idle is extremely unstable with lots of hiccups. It won't rev at all unless I'm spraying starting fluid into the carb, and it idles better when I spray starting fluid into the carb. When it's running rich, if I take it for a ride up and down the block, invariably at some point it will suddenly shut down. Needless to say I don't take it farther than my own street because of this. Seemingly all of this happens at random. The carb manifold and seal are nearly new (replaced last year), the carb has been soaked in B12 chemtool, every jet and passageway blown out, every seal replaced, rubber diaphragm on the slide is excellent, the float valve and seat are clean and in good condition and seal completely tightly, the float is seemingly at the correct height, all passages are seemingly clear, the choke opens and closes completely, the mixture screw has been at 2 1/2 or 3 turns and that seemingly does nothing. Ideas? Thanks .
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