No Start, Not Sure What Else it Could Be!
 

Hi, I recently bought a beat up Hawk 250. Not ridden very hard, just poorly modded. The battery it had was too small, so I had to kick start it to turn it on, but once on it would stay on. There was sputtering when I went full throttle at low RPMs, but otherwise, it was fine.

I was able to ride it 40 minutes to car wash, then, after a hard start, about 15 minutes back home. The next morning, I was able to start it and run it with a very high idle until it was warm enough to change the oil.

Once I changed the oil, all bets were off. Could not start it. There seemed to be no spark, so I bought this kit.

I ended up removing the wiring harness from the bike, and installing this kit except for the key and killswitch. I now have (weak, but consistent) spark.

The bike came with a Nibbi carb and an aftermarket exhaust. The carb has a 105 jet and the needle is set to the 4th notch down. The air/fuel screw is 2.5 turns out. I have fuel flow to the carb; the bowl fills up. I'm unsure if I have fuel leaving the carb, but when I use starter fluid, nothing happens. Altitude is 925ft.

I adjusted both valves to .06mm, spark plug gap to .032", and I've checked all the connections. The ignition coil has 1 ohm resistance.

One thing of note is that the old CDI was 6 pin, rounded connectors, and the new one is 5 pin, square connectors. Could this be a timing issue?

When I try to start the bike, I put it in neutral, turn off(on?) the kill switch, and press the starter. All it does is turn over. I've tried spraying starter fluid directly into the carb, to no avail.

This is my first Chinese bike, first carbureted bike, and first time I've taken over somebody else's project.

If you have any ideas for troubleshooting/tuning the Nibbi carb, I'd love to hear them because as of now, I'm at a stand still.
:thanks:

Make sure you have an AC CDI and Not DC.

Would AC vs DC create a no start situation? Do they make AC CDI's in the 3+2 square connector config or do I need to rewire for the 4+2 round connecters? Is there a specific CDI you could point me towards that you know works for the Hawk? Thanks!

This is a direct replacement. https://amzn.to/4d2meLo

Which nibbi carb is it? 28 or 30mm? Sounds to me like the pilot jet is the wrong size, so you are having a double whammy of poor fueling and ignition issues.

Don't forget to check the ground for the primary side of the coil. Also test the coil as it could just be bad/weak. (assuming it isn't the CDI you bought)

What happens when you spray starter fluid in it ?does it fire for a second or two or nothing at all ?

Nothing at all. No sign of life.

I'm at 6000'+ elevation and I'm using a 108 main jet, about to go 110, so I'd say definitely up that main jet...120 or 125. What pilot? I'd go 40 on the pilot just to be sure there's fuel, but you might need a 38. Put the needle back to middle and set the air mixture screw to 1.5 turns out. With the air mixture screw at 1.5 turns out, you have half a turn (roughly) of adjustment in either direction. Choke on?


Also, since it was running with the old wiring harness, I'd go through it checking continuity and if good, I'd go back to it...maybe put new waterproof connectors on it.

Rough Density Altitude adjustment for jets is 1 point per 1000ft. So if you are running a 110 at 6000ft and you came down to 1000ft, you would want to up to a 115.

You have no spark .

Good call, Megadan. I read that at one point but my mind is like a sieve. Retention at all time low!

It's the 30mm carb. Do I just need to play around with different sizes or is there a way to tell whether I need to go up or down?

The coil is directly grounded and has 1ohm resistance. Are there better ways to test than checking resistance?

Cool, I'll try 115/40 and see how that does.

Yep, choke on. Going to try 115/40 and turn the screw to 1.5 out. Also installing the new AC CDI tomorrow so hopefully that combination does something for me.

I only changed out the harness because it wasn't starting with the old one.

I can visually confirm that I have spark. It's a weak looking spark, but it's there. Going to try out the new AC CDI and see if that gives me a stronger spark.

Are you using the plug that can in the kit? If it's one of those cheap Torch plugs, That could be the problem. Get a good NGK plug. Also check the plug wire cap to see if it has a resistor in it.

Get rid of the 30mm nibbi. That will solve all your problems. It's way too much carb for an otherwise stock cg250. I have a fully modded engine, cam, big bore, ported head, and I run a vm26 clone, which is basically the stock carb, but with Mikuni jets. Example: https://www.amazon.com/Hessenboom-Mo...%2C166&sr=8-31

If you absolutely must keep it, your pilot is too big. Use a 35. At most a 38. If you are stock a 115 main should do the trick, but with the PE30 having reduced velocity it often requires much bigger jetting than would be normal, so maybe have a 120 on hand as well.

Did everything here, and after cranking it until the battery died, then kicking it a bunch, it started up! I let it run for a few minutes at a really high idle just to let it warm up, then started bringing down the idle screw. Throttle response was perfect and idle was a bit high so I brought it lower. The bike died. Now it won't fire back up. Going to recharge the battery, but any ideas for what might be going on? Spark plug was pretty black so I turned the air/fuel screw in half a turn and cleaned the plug.

I was also getting serious kickback before I started it, but not anymore.

Re reading post # 1, are you positive that there’s no water in the fuel? Just my thought…

You said "the battery it had was too small". I didn't read anywhere that you replaced it. Likely cause of weak spark and hard starting...

What RPM was it idling at when it was running? And what RPM did it die at?

Water in the carb is definitely a possibility, especially since it was running before the car wash. But it was running after the carwash too! So...

A motor can actually run with a discharged battery, no problem, as long as the battery isn't shorted inside, grounding out the system (doesn't sound like it here). Spark actually comes from the Coil with power and trigger from the stator through the CDI.

It would be good to get a reading on the charging system if it decides to start again. You may need an extra pair of hands, but get a voltmeter on that battery when it is running... 13V, 14V??? This would help rule out the reg/rec/stator.

If that checks out, did you install the new coil?

I did have a bad stator in a Suzuki GS850 that still sent a good trigger signal but wasn't generating power. So the CDI was run on the battery until the battery discharged. Then it stopped.

You also said something about kickback, which could be the CDI going wacko. But you said you were testing a new CDI before.

If you did, I guess the CDI didn't fix it. I'd recommend assessing that charging system. The only thing that didn't come in your kit is a new stator/pickup coil. A bad stator could be the problem. You've replaced everything else, right?

https://www.chinariders.net/showthread.php?t=34080

Any luck?