Throttle kills engine

[giganticflying]

Hey everyone, I thought I had an electrically issue, which you can follow the progress of here:

http://www.thegsresources.com/_foru...(seemingly)-no-spark-or-starter-functionality

...but it turns out I just need to learn a few things about the starter system and the ignition. Now it appears I have a fuel issue. After tearing apart and cleaning/dipping the carbs, changing the motor/gear oil, replacing the spark plugs and cleaning the tank, I can get the bike to start up for the first time in four years. But! When I apply any throttle, it kills the engine. Is this a fuel/air screw adjustment situation? It idles at around 1500 to 2000 without choke. Going back into the garage tomorrow, hopefully with some good knowledge. Thanks in advance.

 

[Guest]

Hey everyone, I thought I had an electrically issue, which you can follow the progress of here:

http://www.thegsresources.com/_foru...(seemingly)-no-spark-or-starter-functionality

...but it turns out I just need to learn a few things about the starter system and the ignition. Now it appears I have a fuel issue. After tearing apart and cleaning/dipping the carbs, changing the motor/gear oil, replacing the spark plugs and cleaning the tank, I can get the bike to start up for the first time in four years. But! When I apply any throttle, it kills the engine. Is this a fuel/air screw adjustment situation? It idles at around 1500 to 2000 without choke. Going back into the garage tomorrow, hopefully with some good knowledge. Thanks in advance.

Do you have the air box and all that installed and buttoned up?

 

[giganticflying]

Going to do that tomorrow as well. The airbox is newly sealed and cleaned, I just figured that if the airbox is off and the slightest throttle is still killing it then there is still something wrong.

 

[Nessism]

http://www.thegsresources.com/_forum/showthread.php?t=171846

 

[giganticflying]

Whoops. I'll throw it on tomorrow. The other thing I forgot to note though is that the plugs look black when I pull them after idling for a while, which according to the manual indicates its rich rather than lean. I'll post updates tomorrow. Thanks everyone.

 

[giganticflying]

So I put the airbox back on. It starts up just fine (with choke. I even got it to kick start!), but only stays on for about 6-7 second before it stops again. It's not an abrupt stop, it just gradually dies over the last 3-4 seconds. Some have suggested to clean the carbs but I gave them an incredibly thorough cleaning a few weeks ago. Before I go back in there, does anyone have any other suggestions?

 

[giganticflying]

Also, the boots are nice and squishy with no cracks. I got new o-rings for the engine side. With my lack of knowledge in motorcycles, I can't really tell if this a lean issue or a flooding issue.

 

[Missile99]

Is your petcock in the on position when trying this? How much gas did you put in? If not much, turn to reserve. Otherwise, once started, put in prime to test fuel delivery. Don't leave it there if you turn it off though.

 

[giganticflying]

I've been trying to start it in prime and turning it to ON when I'm not working on it. I also have a new fuel line.

I started backing out the air screws on the outside of the carb and it seems to idle a little longer but still does the same thing. I'm at about 3.5 turns out with seems way too far.

 

[Katarat]

The filters on the factory petcocks can get plugged up over time too. Another thing to check if you don't get good gas flow in the prime position

 

[giganticflying]

The fuel hose I installed is clear and appears to be full all of the entire time. Sometimes there are small air bubbles so I imagine there is some kind of flow. Right before I left I got it to start up and idle without choke until I tried throttling after turning out the the pilot screws on the outside of the carbs.


How many turns should the idle screw be turned against the plate?

 

[Steve]

Some have suggested to clean the carbs but I gave them an incredibly thorough cleaning a few weeks ago.

Please describe your "incredibly thorough cleaning". :-k

Was it anything like this?
http://members.dslextreme.com/users/bikecliff/images/vm_carb_rebuild.pdf

If not, I think you know what is next on your agenda.

Every shortcut you take is just one more opportunity to do it right.

.

 

[giganticflying]

It was exactly that, except for the manometer portion, since I don't have one.

 

[Missile99]

Okay. Your carbs are fully cleaned, the air box is sealed and you have no air leaks. The mixture screws at 3.5 turns out should have caused a really lean idle mixture. Idling without choke is always good. I'd like to stick with simple questions before you tear your carbs open again. Is this fresh gas or stuff that's been sitting in a gas can for mowing lawns? It doesn't take long for this newer gas to go sour. What is the primary voltage to your coils? Is your spark decent looking? I looked at your other thread. The way I check is to lay all the plugs stuck in the boot on the head. Check in a darker area. Turn the key on and turn the engine by hand.

 

[Guest]

I haven't heard any mention of pilot fuel screw adjustment, just air, could it be that you missed those when you cleaned the carburetors. If so, they are due for another tear down and 24 hr. soak in carburetor dip with the pilot fuel screws removed. Did you bother to adjust the floats?

 

[giganticflying]

The gas is brand new. I de-rusted my gas tank with apple cider vinegar and screws, rinsed with water and baking soda, then rinsed with fresh gas, drained, and filled with fresh gas.

I don't know the voltage to my coils. I'll buy a volt or multimeter on Monday when I go to Harbor Freight. There is visible spark with all the coils, but I'll try it tomorrow in with the garage light off to see if any are weaker than the others.

The fuel screws I set to about 5/8 of a turn since I kept reading either 3/4 or a full turn. I did remove the fuel screws (and all other parts) before dipping the carb bodies.

Now that you mention it, though, I did forget to adjust the float height.

 

[Guest]

I think that is your next step, you have something going on that doesn't make any sense if the carburetors were rebuilt properly. Check your manual, but I believe they are set at 24mm then check them with a sight tube as the bowls fill and then running. The level should be in the middle of the float bowl edge where they screw to the carburetor, that should keep the level just below the gasket. When you adjust the tab on the float it is helpful to find a miniature set of channel lock style pliers to hold the tab while you bend it ever so slightly, measure height again and repeat until they are dead on the measurement. The baby channel locks will keep you from twisting the tab.

 

[giganticflying]

I'll give that a shot, but is there anything else it could be? I mentioned before that the plugs are ash black. Any thoughts on that?

 

[Guest]

Could be too much fuel, also float related. Lightly seat your pilot fuel screws and tell me if the tips stick up into the carburetor throats. If they do, the screws have expanded the seats by being screwed in too tight. This changes the adjustment game because you have to compensate for the damage done previously to emulate proper settings. I would set the pilot fuel screws at about 3/4 out to begin and the air screws to 1 1/2 out. It won't be right but it should start with choke if everything is clean, bench synced properly and the float heights where they should be. Then the tuning fun begins.

 

[KEITH KRAUSE]

For basic starting purposes, adjust the side air screws to 1 3/4 turns out from lightly seated and adjust the pilot fuel screws to 3/4 turn from lightly seated. For what I assume is a bike with stock intake/exhaust, those adjustments are close enough that any stalling issues cannot be attributed to them. Your model should idle well at 1,000 to 1,100 rpm's. Turning the idle up higher causes it's own problems.
If you didn't clean the pilot circuit 100% then you'll have hard starting and stall easily. If you dis-assembled the slide/jet needle assemblies, then you must carefully bench synch the slides or starting will be difficult regardless of what else is checked. Did you bench synch? Did you re-assemble the jet needle assemblies correctly, including the positioning of the nylon jet needle e-clip spacers? Float heights should be set right in the middle of the factory range (.95"). Float bowl vent lines routed under the seat and no kinks.
NGK B8ES plugs, properly gapped? Do you see all solid bluish sparks when you turn the engine? Could be lots of things.