Beegreenstrings Posted March 3, 2011 Report Share Posted March 3, 2011 I have a 1984 Hond Nighthawk 650. CB650SC.It was my dad's only new bike he ever purchased. He rode that thing all the time. I think it was his only get away from working his ass off most of his life to be sure I and my brother and sisters got what they needed.He gave it to me a few years back, wanted to take it to Cycles-R-Us in Medina and drop it off, and I would not let him! It's been in my garage for a few years now and I have tinkered with it from time to time. But, I have no knowledge of this thing!He stopped riding it when it died on him at my uncles house. Would not refire. I put the jumper cables to it and it fired right up. However, it will not stay running and has a miss.I have replaced the rectifier and the stator (with the new upgraded design) supposed to be a better one for that bike)and a coil pack. Still same issues .DOES anyone have knowledge of these issues with these bikes? I would love to make it streetable again. Truthfully I would love to return it to him so he could ride it again... Any help would be much appreciated. Quote Link to comment Share on other sites More sharing options...
ReconRat Posted March 3, 2011 Report Share Posted March 3, 2011 Well, I have one of those in pieces scattered all over...Sounds like the battery is shot.Determine if all plugs are firing properly. If not, find and fix.My first guess is the carburetors. They have to need cleaning by now.Replacing the stator was ok, they were known to die just from old age. Quote Link to comment Share on other sites More sharing options...
whaler Posted March 3, 2011 Report Share Posted March 3, 2011 Are you close to Medina, as I would be more than willing to take a look with you and see if we can get it road worthy.PM me if you would like to discuss this further. Quote Link to comment Share on other sites More sharing options...
Casper Posted March 3, 2011 Report Share Posted March 3, 2011 If I were a betting man, I'd say carbs.Run some Seafoam through it and see if that makes a difference. Quote Link to comment Share on other sites More sharing options...
Meanie Posted March 3, 2011 Report Share Posted March 3, 2011 If I were a betting man, I'd say carbs.Run some Seafoam through it and see if that makes a difference.I second that. I had an '85 nighthawk, when I bought it it ran fine. Then it started shutting off at random times. I had the stator replaced, and the carbs cleaned and balanced and it ran like new. They are actually really fun bikes to mess around on. I miss mine at times...although I looked like a Shriner riding it. Quote Link to comment Share on other sites More sharing options...
Beegreenstrings Posted March 3, 2011 Author Report Share Posted March 3, 2011 Run some Seafoam through it and see if that makes a difference.Done this already...I miss mine at times...although I looked like a Shriner riding it.I know what you mean... Quote Link to comment Share on other sites More sharing options...
buildit Posted March 3, 2011 Report Share Posted March 3, 2011 Sounds like the battery is shot.+1 Quote Link to comment Share on other sites More sharing options...
wht_scorpion Posted March 3, 2011 Report Share Posted March 3, 2011 these guys are right I had a my first bike was a 83 nighthawk 550 and the first bike I crashed DWI hit mebattery and drain the carb bowls reset the floats the little screw at the bottom Quote Link to comment Share on other sites More sharing options...
mgbgt89 Posted March 3, 2011 Report Share Posted March 3, 2011 If its been sitting for any amount of time with fuel in the carbs, They need to be pulled apart and cleaned. Every jet needs to come out and be cleaned. The emulsion tubes (the part that the needle jet goes through), has tiny little holes that block very easily. The idle jets also have tiny passages that will clog. Simply spraying carb cleaner down the throats wont do. Get yourself a shop manual, a can of berrymans carb cleaner and have at it! Another thing to verify is that you have a steady, strong spark. The early electronic ignitions honda used were garbage. I actually prefer breaker points to them. 1-4 fire at the same time, and 2-3 fire at once. It's a wasted spark system, so it fires on the power and exhaust stroke. The CDI boxes fail regularly on those. If you don't have spark on two of the cylinders, you can swap the cdi boxes and see if it changes where it is missing. The battery must be fully charged in order for the units to work well. I usually take out the bikes battery and wire it to a car battery while i'm trouble shooting. PM me if you need anymore guidance. I've brought back 6 old hondas from the dead so far. Quote Link to comment Share on other sites More sharing options...
mgbgt89 Posted March 3, 2011 Report Share Posted March 3, 2011 (edited) Usually if it runs on choke, but wont run without it, It needs the carbs cleaned.Another thing to verify is that the vacuum operated fuel shutoff is working. On my 82 nighthawk, and my friends 81 CB900F there was a small diaphragm on top of the carbs with 3 hoses going to it. Fuel in, Fuel out, and a vacuum line. It has to be pulling a vacuum on that line for fuel to flow. A cracked vacuum line would stop all fuel flow. Its also a common place for fuel to varnish as well, which would block fuel flow to the carbs. If you find that is bad, You can cap the vacuum line and run a fuel line straight to the carbs from the tank. We did that on the 900F, which also allowed enough room to install an inline fuel filter. Bypassing the shut off you run the risk of your whole tank draining onto the ground or into your engine if you leave the petcock on, but if your floats and needles are working properly you don't need to worry. That CB900F's shutoff was NLA, so that was the main reason for the bypass. You'll also find that it starts faster without it, since you don't have to be cranking the engine to start the fuel flow. Edited March 3, 2011 by mgbgt89 Quote Link to comment Share on other sites More sharing options...
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