1982 Nighthawk CB650sc Starting troubles

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Bater55
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Joined: Wed Aug 16, 2017 10:19 pm

1982 Nighthawk CB650sc Starting troubles

Postby Bater55 » Thu Aug 24, 2017 9:54 pm

Hello all,
I have been working on this bike for the whole summer now. I bought it 3 years ago, rode it often then moved off to college and it sat. I went through the carbs, cleaned them and put them back together. I rebuilt the starter clutch, the springs were shot and the torx bolts holding it in were all loose. Bought a new battery and now it is finally ready to get on the road and I can't get it to start. It turns over but it just doesn't want to fire. The carbs are getting fuel but when I checked the spark plugs they did not seem to have a lot of gas on them. I am getting spark from all four but it won't fire up. Is this an electrical or timing issue? I am pretty new to doing this but I have spent a lot of time in the manual and with this bike but I am stuck and looking for some help. It sat for a year so I figured it would start up with a new battery and a carb cleaning but that has not been the case. Any help/direction would be great,

Thanks!

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GeorgeSweety
Posts: 41
Joined: Tue Aug 08, 2017 11:47 am
Location: UK.

Re: 1982 Nighthawk CB650sc Starting troubles

Postby GeorgeSweety » Fri Aug 25, 2017 5:13 am

Hi Bater, I'm having a similar kind of problem but mine is starting on 1,2 and 3 but number 4's plug is dry. Fuel is getting to the carb but it doesn't seem to be getting to the cylinder. It will run on 3 cylinders but peters out after a very short time, I'm suspecting that the fuel tap may be blocked at the moment. Have you undone your carb drain screws to check for fuel in your float bowls?
Last edited by GeorgeSweety on Fri Aug 25, 2017 5:43 am, edited 1 time in total.

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Folsoml
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Location: North Florida

Re: 1982 Nighthawk CB650sc Starting troubles

Postby Folsoml » Fri Aug 25, 2017 5:19 am

I always have to ask about the actual process you went through when you cleaned your carbs. I knew a guy who said he "cleaned his carbs" over and over again, but still had trouble. I eventually learned the cleaning consisted of soaking the whole still-assembled bank in pinesol and water.
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GeorgeSweety
Posts: 41
Joined: Tue Aug 08, 2017 11:47 am
Location: UK.

Re: 1982 Nighthawk CB650sc Starting troubles

Postby GeorgeSweety » Fri Aug 25, 2017 5:51 am

Hi Folsoml, I don't know what Bater has done to his carbs but I stripped mine down, all jets out, ultrasonic cleaned all parts, soaked jets in white vinegar to dissolve crusty deposits, cleared jet holes with very fine wire and carb cleaner then chucked them in the cleaner. All diaphragms appeared ok, no holes, O rings replaced. De-rusted the tank with Deoxit, rinsed tank out with hosepipe, rinsed tank with petrol, added inline filter just in case :roll: The one thing I didn't do was clean the tap or tap filter, was working fine befor but now nothing comes out when I switch to reserve.

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GeorgeSweety
Posts: 41
Joined: Tue Aug 08, 2017 11:47 am
Location: UK.

Re: 1982 Nighthawk CB650sc Starting troubles

Postby GeorgeSweety » Fri Aug 25, 2017 7:02 am

Hi Bater, my problem was solved by putting a different tank on my bike with a known to be working fuel tap. Took a few start attempts to get the fuel through all four carbs but now she is ticking over at 1100 +/- Keep us updated with any results or progress you may have.

Hamman
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Joined: Fri Jul 21, 2017 10:49 am

Re: 1982 Nighthawk CB650sc Starting troubles

Postby Hamman » Fri Aug 25, 2017 11:06 am

I'd pop off the tap and take it apart if possible and blow some compressed air through it. If anything, switch over to the manual style.

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GeorgeSweety
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Joined: Tue Aug 08, 2017 11:47 am
Location: UK.

Re: 1982 Nighthawk CB650sc Starting troubles

Postby GeorgeSweety » Fri Aug 25, 2017 1:14 pm

Hi Hamman, my tap is the manual type. The rubber seal had split and collapsed inside the tap and there is a small rubber sheath that sits inside the filter body that the internal plastic fuel pipe slides into. This rubber sheath had worked its way down to the bottom of the internal filter (probs when I pulled the tap out) and looked like it (and the collapsed seal) was blocking the reserve from working. I had only put a gallon of gas in the tank, so trying to start it on reserve, the fuel would just trickle past the rubber debris and fill the bowls but as #4 float bowl was the furthest away from the tap it got any fuel last and was the first to starve.
I dug the old rubber seal out of the tap lock nut and found an O-ring, I.D 14mm x 2.5mm that fit nice and snug in the nut but figured from the remains of the old seal that the bottom of the tanks filter also sat on top of the now dead seal. This was fixed by inserting a smaller O-ring inside the nut O-ring. I pushed the rubber sheath back inside the filter using the plastic pipe on the tap, a slight bit at a time so as not to damage the mesh, it should sit about 15mm from the top of the filter. I pushed the plastic pipe into the filter so that the bottom of the filter sat inside the lock nut O-ring and on top of the slightly smaller O-ring that I had inserted inside the 14mm I.D. O-ring.
I also sprayed Carb Cleaner on the filter and through the tap then gave it a blow with compressed air before I assembled it. I refitted it to the tank and it works like new in both ON and Reserve and the bike fired up with its own tank, on all four cylinders :D
Hopefully Bater may have something just as easy to fix, but working out what the problem is, is the hard part.


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