Honda NU50 Troubleshooting

Jay Williams /

I have an 82 Honda urban express that I have been trying to work on and have been running into some problems. When I first got it I cleaned the carburetor/petcock and replaced float valve, new carburetor gaskets and new spark plug. I bypassed the oil injection and auto choke by using vacuum caps. Running 50:1 premix. Started but didn’t run well. Replaced reeds and burned out muffler hoping that it would increase performance of the bike but no luck. Sprayed the motor down while running to see if any performance changes, but nothing. It starts and idles fine, the muffler spits out a lot of white/gray smoke. The bike doesn’t go over 10 mph and it seems as if it is getting too much gas and not revving out. I don’t have an air box but when I block some of the air getting into the carb with my hand it just gets worse. I even down jetted the carb to see if that would make a difference but no. Bike has no battery, but I don’t think that will affect performance.

I’ve been doing searches here but not sure where to go now. Any suggestions?

Re: Honda NU50 Troubleshooting

I would still suspect the carb. Did you get the float level right? I've had similar performance issues that weren't solved until the 3rd time cleaning the carb.

Re: Honda NU50 Troubleshooting

john cervini /

I've done 3 Urban's in the past month. I've found the stock airbox must be in place with an oiled filter to be able to tune the carb at all. Also clean the autochoke. Inside the carb next to the main jet on the bottom there is a tube that's pressed in. Using vice grips that needs to be removed and cleaned as well. After all that is done start with the air mixture screw one and a half turns out. Once it's at operating temp you can fine tune the mixture. Also isn't a bad idea to blow out or replace the vacuum lines.

Re: Honda NU50 Troubleshooting

Jay Williams /

I've taken off and cleaned the carb a number of times now. Is the float adjustable with these carbs? I understand that I need an airbox but even with an airbox on could this really cause significant performance decrease? Wouldn't that make the bike run richer?

And I plan on pulling that brass tube out but, previous owner looks like they tried to as there are piler marks on there and it is pinched a bit. Carb cleaner runs through the tube so it doesn't seem to be clogged. Still a problem?

Re: Honda NU50 Troubleshooting

Still sounds like your pipe is clogged up. Try unbolting it and running it briefly to see if response improves.

Re: Honda NU50 Troubleshooting

Jay Williams /

I tried with the pipe off and no difference unfortunately. I'm starting to think that the carb is done, I feel like I've exhausted my options

Re: Honda NU50 Troubleshooting

Gruff "(OFMC)" - /

pull the sidecovers and look behind your flywheel to see if there is any oil in there/ should be dry, same for the drive side look for oil it should be dry . If there is signs of oil then that would mean your crank seals neeed to be replaced also check for....... white and grey smoke is a sign of blowby get a compression gauge and checkk it if its lower than 95 its gonna run bad should be 140+ check topend for damaged rings cly./ piston out of specs.

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