No start: Have spark, have fuel, have air

[isaac]

Hey guys, new to here but have had my 1999 GZ250 for nearly 8 years now. It ran great that whole time aside from eating its starter clutch at 2,000 miles (never heard of this ever happening) and its most recent no start. It has 12,000 miles now.

It ran fine before it was parked a few months ago. It's been parked before, gummed up carb, cleaned it out and all was fine. This is not that problem.

It has fuel, air and spark. It has compression (it didn't just disappear while the bike was parked). The intake and exhaust are sealing as well as they ever did. It ran before just fine with the exact same configuration it has now.

Why I'm completely stumped: It has seemingly everything necessary to run, yet it doesn't even kick. Cranks over just fine, but no firing. It will on rare occasion backfire through the intake or exhaust. It seemingly refuses to fire inside the actual cylinder.

Fuel: I've tried spraying starting fluid, spraying gasoline, putting oil in the bore to rule out a gas washed cylinder. Of course I've already cleaned the carb. It seems to flow fuel just fine. I also had changed out all the fuel from the tank, and replaced the air and fuel filters. I

Spark: Changed the plug 4 times to rule out fuel or oil fouling. Changed the ignition coil (which seemingly helped nothing). Cleaned all grounds. Cleaned ignition switch contacts. It has throughout all this had a nice blue spark, regardless of gap, which I have also changed repeatedly. It seemingly fires in regular intervals while cranking.

Air: I've sealed it all off, replaced the intake manifold and seals. Tried different filters. Tried just having my hand over the intake and varying it. Varied throttle and idle stop all over the place. Varied the mixture screw all over the range. I've adjusted the valves and they're well within range. It compresses just fine.

So what else could it be? Does the CDI ever "half break"? Does the ignition pickup in the side case of the engine ever send a signal that's completely off timing? Those seem about all that could possibly be left assuming it's not just cursed.

Ideas? Thanks!

[blaine]

Welcome to the forum.It sounds like the CDI unit may be faulty.It is possible for the pickups to send a faulty signal,if the flywheel got damaged or moved,by the key breaking in the flywheel,crank groove.But my first guess would be the CDI unit.
:) :cool:

[Water Warrior 2]

Just a wild a$$ suggestion here. Can you feel exhaust pulses with your hand at the end of the muffler when trying to start the bike? Maybe a small furry critter found a home in there and blocked of the pipe while nesting.

[isaac]

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 .

[blaine]

I think your main problem is a the flywheel.If you don't have the proper key in the keyway,the flywheel will move when the bike is running causing the erratic behavior you describe.How did you remove the flywheel? Did you have the proper puller,so the flywheel didn't get twisted.What the problem with the starter drive that keeps popping up? If the grove in the flywheel is wore,or the flywheel is not seating on the crank properly, that will alter the timing enough to cause your problem.
:??: :)

[isaac]

Eh? I just wrote that I welded on my own alignment pin in the same place as the original one and put it all together and it runs fine, spark wise. The flywheel is aligned and isn't going anywhere. The starter clutch explosions have come from the three bolts that hold it all in place backing out and hitting the side of the engine and ripping apart. I fixed this by grinding down my own grade 8 bolts and using locktite.

Now it's just visibly running rich and lean. This is made obvious by the bike's response to starting fluid while running. When it's running rich (and gas is flowing out of the front of the carb while this happens) the bike will die if I spray starting fluid. When it's running lean, it gets noticeably better when I spray starting fluid. When I'm riding the bike for the 30 seconds at a time that it's running right, it has full power through the entire powerband. Then it either floods or runs out of fuel. Then depending on how the bike is feeling I either need to start on full choke, no choke at all, or no choke + twisting the throttle. Then it acts normal again.

I'm sure I could fix the fueling issue by just buying another carb but that'd suck considering all the time I've invested on troubleshooting this damn thing.

[isaac]

One more thing: When it's running seemingly rich (or at least the fuel is coming out of the vent on the mouth of the carb) if I turn on the choke, the fuel stops flowing out and recedes back into the hole. This is all at idle. It's almost as if the engine isn't inhaling all the fuel that's making it into the float bowl, so it spills out, then when I turn on the choke the carb has a new place to route the fuel into the engine so it stops spilling out.

[JWR]

Sound like trash in the carb needle jet???

[PimpS]

Hello guys!

Yesterday i noticed that first, but the problem went away soon so i thought it's a newbie thing... Today hapenned to me three times:
I insert the key, put it on, the light for neutral was on, battery was on, press the button to start a bike... and nothing... tried it many times, removing the key, put it back, and nothing... then i pressed the button to start a bike, and bike started... I drove for 5 km without problem, parked the bike, turn it off and after a few seconds wanted to start again... nadfa, nothing...
What do you think? CDI unit, what is that, what cost...? geez, i want to go for a longer ride after work, is it safe?

Thank you for your replies!

PimpS

[alantf]

You'll probably find it's something as simple as a bad contact in the red kill switch. This is a "regular" problem with the GZ. Rocking the switch on/off a few times usually cures it temporarily. If you find that this is the problem you'll need to take the switch apart and clean it. :2tup:

[PimpS]

OK Alan! I called my mechanic, he assured me that it has to be something with the contacts in one of the switches (whether red, clutch, sidestand...). Other friend didn't know that i have to pull the clutch before starting, so he was more specific and told to look the clutch. In the few minutes time i have between the classes i went down and checked. Yup, the small switch (like a straw comes out, when clutch is pulled and mine came out 2 mm short). When i started the bike, he didn't, when i gave a straw a little touch, to come out, bike started with no problem... Now i know...
Is it ok to try to spray it with a WD-40?

Thank you Alan for speedy reply and help, next time i might need to clean the red switch, i'm starting to know my bike and his health quickly... ;)
Can't wait to finish today's job, yihaaa!

PimpS

ps: to you guys and many my friends i'm like a kid, enthusiastic and overworried when something goes wrong, but overecstatic when the bike is being parked, just wanting to sit on it and go!!!! but then again, i am what i am, most mf's don't give a damn, said anthony kiedis (RHCP)...

[alantf]

Is it ok to try to spray it with a WD-40?

YES! :2tup:

[PimpS]

Just came back from my 130 km ride... Great! A lot of fellow bikers on the road, saluting to each other... It's great!!! ;)

[isaac]

Just to finally put this to bed: A couple months ago I bought another carb and swapped slides. Both had good diaphragms, good needles. The slide on the old carb had a bit of signs of melting on the front of the absolute bottom of it. The new one did not.

Fired right up and ran fine. After all the crap I went through. I'm definitely a pro at cleaning out a carb by now though.

[Water Warrior 2]

Good to hear you got it running right. Another bit of info to share. Thanks a bunch for the update.

[jonathan180iq]

Definitely thank you for the update... No one ever updates stuff a year later. What were you doing with the bike in the meantime? Did this issue persist the whole time?

[isaac]

The bike was just sitting on my back patio, occasionally ridden when I could get it to stay lit for a lap around the block. I wouldn't dare take it farther. Yeah the bike was extremely erratic on fueling the entire time, to the point where it would vacillate wildly between over/under fueling at random. Sometimes spraying starting fluid in while it was running would speed up the engine, and sometimes it would kill it instantly. Sometimes the engine needed full choke to run at all, and others you pull the choke and it'd die instantly. Sometimes it'd have full power, other times it was barely running. Very intermittent, and very frustrating. All solved with a new slide.

Of course now I'm dealing with the more recent issue after riding the bike regularly for six months and a noise in the top end gradually getting louder until I was compelled to disassemble the head and found an exhaust valve seat falling out.

[Goose51683]

Isaac,

I know this is an old post but do you have any pics of the locating pin you are referring to. You issue sounds an awful lot like the issue I'm having. I have a CDI on order (which is taking forever) but I'm not all that confident that is the root problem.

[isaac]

I don't have a picture of it but it's really easy to locate, after you get the nut off. When you take the left side cover off and undo the nut on the crankshaft, you'll see a hole where the flywheel meets the crankshaft. That hole is a keyway. The key slots between the flywheel and crankshaft to line it all up.

This is something I've said many times, and this is out of very, very extensive experience with removing the flywheel: GET AN IMPACT WRENCH. You will commit suicide attempting this without that tool. It's a godsend. I'm talking the difference between you spending hours on just removing that one part, cursing and throwing tools, to it coming off in seconds. Get an impact. It can be an air impact or an electric. I've done it with both. I've attempted it the other way in a pinch many times. It's a nightmare.

The impact is already helpful for getting off the crank nut, because you won't have to very awkwardly (and unless you're very strong, with great difficulty) hold the other end of the crank still. With the impact, you just pull the trigger, or worse case scenario put some vise grips on the flywheel to hold it a little. Just get the impact and use it. Be sure to check if the nut is reverse threaded. I forget if it is. You can tell by looking at the direction the end of the thread engages the nut. After the nut is off, you'll need a 3 jaw puller that you'll have to grind away parts of the insides of the arms (with an angle grinder or bench grinder) to get it to fit around the back of the flywheel to press it off. Get and modify this puller. Again, this is a tool that's the difference between this being a nightmare job and this being very easy. Just get the tool.

Be aware many parts of the starter clutch will attempt to fly away when the flywheel (starter clutch attached to the back) very violently comes off after the impact wrench has tightened the 3-jaw puller very very substantially. I'm not kidding: It is very damn violent when it releases. Spray PBlaster in there to help, so that the force is less to remove. Have rags and whatnot ready and around the area to catch flying parts. There are three of each pin, roller, and spring in the clutch.

Pull all that off and you'll see the locating key immediately. It'll probably still be pressed into the crank. That's if it's still there of course. If it shot off into the distance when the flywheel exploded off, then you'll have to find it. If it actually was eaten off of there like on mine, then it gets way more complicated and you'll have to literally weld a new pin onto the crank out of steel like I did. It works fine though.