1984 Honda Aero NB50m

[alvin]

Hello,

I have an 84 Aero 50 nb50m that is blowing fuel from the exhaust!

Can anyone help me pinpoint my problem? I've cleaned the carb

really really well and did it again. I know she'll start. I've checked

and visually inspected the fuel screen. I have blown and sucked

on my petcock as well. (sorry) I Any help would be appreciated.

Thanks,

Al

[Wheelman-111]

Greetings:

You didn't specify how it was running, but
Random thoughts in no particular order:

1. Carb Float Needle Valve sticking open. Even though my original needle looked fine, even under magnification, iand seemed to work on open-bowl inspection, it wasn't moving freely in actual operation.

That would absolutely flood the intake, cases ports and combustion chambers with more liquid fuel than the engine could burn. The evidence of excess would be found in the exhaust.

Polish up the float needle bore with a partly-stripped Q-Tip and some polishing compound - I used Colgate - and get a Gin-You-Whine Honda-san spankin' new float needle and see if this doesn't correct the issue. It solved my leak problem where nothing else did.

2. A bad assembly job on the carb, missing jet or bystarter bushing, anything that could cause excessive fuel invasion - and a bad plug preventing ignition. (Again, I don't know if/how well it runs at all...) You need to be sure the needle is correctly engaged in the float's "legs".

3. A chronic leak situation with fuel (see above) and/or oil pooled in the crankcases - should blow out with the first start, but may prevent that start. In the case of the oil pump, replacement is the preferred remedy. Honda-san's Service Manual specifically recommends against dismantling the pump to check for oil-tightness. Even by Trained Professionals. Several people have done it. I'm not one of them. Used pumps show up all the time on eBay; Search SA50, NB50M in MrCycles/OEM sites to get assembly part numbers for compatibility. (Bike Bandit uses useless BB part numbers.)

You mention several steps you've taken to rule out fuel supply blockage, such as filter inspection, and petcock flow demonstration. However you would seem to have the opposite problem - too MUCH fuel, going uncombusted out the pipe. Does the petcock STOP the fuel flow as it is supposed to? After initial drip, NO flow - not even a drop a minute - is acceptable. If both the petcock and float needle are leaking, this would explain your scooter symptoms.

[alvin]

Thanks for the reply so fast........ the aero started and ran but idle was way up there. All set screws were closed. I opened up the air mix to
1 1/2 turns and adjusted the idle. Then it died and started right up and
thats when I noticed the fuel out of the exhuast.

Anyhow got my new float needle today and installed and once again made
sure that everything was fine. Reinstalled the carb and still fuel poored
out of the carb.

Fuel was dripping excessively from the petcock and so I ordered a new
one. Once again thank you for your help.

Al

[maddog]

dude, you said fuel was comming out your exhaust now its the petcock & carb, which is it.

[alvin]

Just removed my muffler and it is full of fuel.......trying to drain it all
out at this moment. Seems to have a hard time draining. Would be
ok to put oven cleaner in it? Or just be patient and let gravity do its
thing?

al