Honda Spree and Elite 50 Forums

So i bought a 1986 Honda Aero 50 that had been sitting for many years and after cleaning the carb, putting a new air filter in and cleaning up everything else, it seems to work well except for how it idles. When I first start it up, the engine starts to rev, coughs, and keeps doing this until it maintains what would probably be an engine speed at 20 mph. When I adjust the idle speed down it drops to a normal idle, and then as it warms up it slowly drops until it dies. What could be causing this?

Don't quote me on this. But I've read a couple of posts that talk of extremely high revs on start up and the cause of it was a carb slide put in backwards. Check to see if you put the carb slide in correctly.

Update- I cleaned the carb again and didn't see any obvious issues. I made sure the air box was seated well but didn't really formally check for vacuum leaks. I put it back together and had the same situation. It revs pretty high when it first starts but after about a minute it settles down to normal. Is this just the bystarter giving it extra fuel and I've just been paying too much attention to it?

yes my scooter dose 2500 rpm when i starte it cold and after it worm up it drop down to around 2000 rpm ..
swimmingfree

Don't set your keel screw until the engine is is at operating temp.

I had gotten it running for a while, but had electrical problems that looked like a mouse chewing on the wires. I fixed up all of the exposed wires, but had issues starting it again. I cleaned the carburetor again, but now I can't get it to hold an idle again. The only time I can get it to steady out is with both the idle mixture and speed screws all the way in and the bystarter unplugged. If any of these change, it slowly dies out and can only be kept up with the throttle. I feel like I've cleaned out the carb quite well but this is sounding a lot like a clogged jet. What should I do from here?

clean the tank and petcock filter .Replace the fuel lines with new ones

Greetings:

Does a successful bystarter electromechanical test guarantee the circuit in the Carb will close when it heats up? Not if the socket is full of resin. Just a thought.

I checked the bystarter like you said and it seems to be working. I cleaned the carb again and this time took out the idle speed and mixture screws and cleaned them as well. I put it back together and it ran better, but if I let it idle for a minute or two it would slowly start to die again and needed the throttle to keep the revs up. Changing the idle speed and mixture screws didn't seem to affect it much. Any more thoughts?

Would it be worth it to just buy a $30 knockoff carb on ebay? I've cleaned this carburetor at least 4 times and it seems like nothing is really curing the issue...

low compression could cause your issue

It's definitely your pilot circuit on the carb. It's the skinny brass tube that's within the carb when you remove the lower bowl. When you remove the lower bowl, at the center of the carb is the main jet circuit, and mounted parallel to the main jet tube is the brass pilot circuit. Soak the carb over night or even longer (of course removing the float valve, all rubber o-rings, and screws first) in a carb cleaner and then blow compressed air through it thereafter. You might even need to run a thin-guage piano wire through the brass pilot too (which will test your nerves).

As Pauly said, check your fuel tank & petcock valve (silver valve that screws into the lower porting on the fuel tank) for contamination. Clean the fuel tank thoroughly and blow out the petcock valve (unfortunately by mouth) and replace both the vacuum line and fuel lines leading from the petock valve to both the silver intake pipe & carb. There's a fuel filter up in the tank that you should pull out & clean when you remove the petcock valve (be careful not to lose the little 0-ring that's on the fuel filter).

Hope this helps....

My Chineese Knockoff kehin does this since day one. I tune it where is does not want to take off on warm-up and stalls when warm, tune it for warm running then while warmup it wants to jump off the stand. My soloution is going to be to use my old Dellorto from another build Manual choke and all.

Despite Perfect plug chops IT's a lot easier to tune when the weather is warmer. which makes me think I'm still jetted rich so some 50:1 premix and a little more needle seems to have broadened my tuning window, while I wait for my manifold to come in from Racing planet.