Rebuild for daughters first bike - Help Needed

[shannon1530]

I bought a couple of bikes, a '96 and a '00 to put together and make a good bike for my daughters first. After getting this completed, the problem is that bike will not idle, but the wierd thing is that when the engines dies, it will not restart until after sitting for at least a few hours.
Some details.....
1. Tank was nasty. I had it cleaned and the inside coated. I cleaned the petcock. The screens inside the tank look good. When I apply the vac hose, fuel flows nice. When vac is removed, no flow. I assume this is working correctly.
2. Carbs were dirty. Took them apart, to include drill out and removal of air/fuel mixture screws/washer/oring. Soaked in cleaner. Cleaned all needles/jets using guitar string, air, and solvent. Everything looks really clean. Choke works well. All orings good, all gaskets good. Boots are soft with no rips/tears. I assume these are working as well.
3. New battery. Good 14+v when running. Good 12 v when not running.
4. New NGK plugs, gapped to spec
5. New air filter/fuel filter. New fuel line.

Scenario....I start the bike using choke, bike starts right away. After idleing high for a few seconds, it settles down to around 1300. After a about 15 seconds, the idle drops and the bike wants to die. I can throtle up to above 3k rpms, and the bike will run. When I release the throtle, the bike wants to die. I then use the idle screw to set the idle higher. I can set it to 3k...the bike will idle there for about 15 seconds, and then the idle will drop and the bike will want to die. I can bring the idle back up using the throtle to 3k where it will idle for another 15 seconds and then start to die again.

If I let the bike die, it will not restart. The engine turns over like it is out of gas...it will not start. When this has happened, I have checked to make sure there is gas in the bowls, and there is. I have checked both plugs for spark, and there is spark. I have attempted to spray some ether in the cards while trying to restart, no change. If I let the bike sit for a few hours and do nothing else, it will start.

I am running out of ideas. My daughter has been to the MSF class and received her license...now she just wants to ride. Hopefully someone will be able to provide me with a solution so I can get this bike running.

Thanks in advance for reading my long post and offering some ideas.

[alex.s]

what are the mix screws set to? set the idle mix screws to baseline 2 turns out from all the way in.

if it does the same thing with set idle mix screws it sounds like your carbs are flooding... inspect the float valves and maybe the float height. maybe the float valve is getting stuck open and flooding the carb out

valve clearance adjustment is probably a good idea since you rebuilt the whole thing

[shannon1530]

I have adjusted the mix screws from 1.5 out to 3.5 out with little or no change.

I read on a forum (not sure where) that if you were to pull both plugs, disconnect the coils (no spark near by) and activate the starter and raw fuel came up from the cylinders that something was wrong with the needles in the float bowls.

It is my current understanding that the float bowl adjustment is to allow fuel from the incoming line from the tank to keep the bowls topped off, and that the bike runs off the fuel in the bowls. When adjusted wrong one way, the bowls get too empty and the bike runs out of gas. Adjusted the other way, and fuel come out the overflow.

In my testing, I did drain the bowls into a container after the bike dies and then compared that fuel level to the level in the same container if I filled the bowls manually and dumped that fuel into the container. It was nearly the same.

Will you please educate me as to how this would flood the carbs? I must have something wrong in my mind about how they work.....thanks

[alex.s]

there isn't much gas that can sit in the float bowls. the difference between "out of gas", running well, and "flooded" is really not much difference in gas level. maybe a few ccs

you say you start the bike with choke and it wont stay running without gassing it... what happens if you leave the choke off the entire time?

[shannon1530]

I can get the bike to start using the throtle. Without, it would not start.

If it would restart after I let it die from low idle, it would be easier to fix. I need to figure out why it will not restart? Once I can get it to restart, then I can prob adjust the mix screws to keep it running.

When I try and restart it right after it dies, the engine turns over but nothing else. I tried spraying some ether into the airbox (filter removed) to try and get it to start and got nothing. I then took the airbox boots off of the carbs and tried ether right into the carbs while cranking...still no fire.

Should the bike at least fire up with this ether? I was thinking I had a weak spark. When I check the plugs...I see spark...could it be weak....too weak to run/start the bike?

Also, I have a spare CDI that I tried...same problem.

[flynjay]

It sounds like you could be low on compresion. Have you done a compression test?

[shannon1530]

I have not performed the compression test only because I need the correct adpater for my guage to match this plug. I will be working on that this weekend.

Question: If the compression was incorrect, would that prevent the bike from restarting?

[Motofool]

Originally Posted by shannon1530

..........
Will you please educate me as to how this would flood the carbs? I must have something wrong in my mind about how they work.....thanks

Please check the links that I posted in this thread:

http://www.ninjette.org/forums/showthread.php?t=116053

The problem of your bike sounds like overheating due to lean mix.

If so, that would explain the need to wait for the engine to cool down to re-start and idle.

It could also be that some valve is staying partially open after the temperature rises, due to improper valve clearance or worn guides.

Another possibility is that the lubrication or refrigeration in the cylinders is not sufficient, making the pistons grow up with temperature and increase friction.