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Carbs, vac leak, or something else??
My honda 99 nightwing idles at 1000rpm when I start it up and at 3000rpm after 10 min of riding. When it is first turned on, it stalls if i lay on any throttle in neutral. In first gear, i can let out the clutch but it dies if i put on more than a few seconds of gradual throttle. To get it moving i must use 75 % throttle. It starts rolling as I let out the clutch, the rpms drop from 1000 to 0, and then rocket up to 4000-5000 with delayed acceleration.


Other symptoms are throttle lag, especially in the lower gears. And when I hold constant throttle it feels as if I am tapping on the brake, but it is really the engine loosing a bit of power, and then regaining it. This is more common when i just got the bike started, and in the lower 3 gears.


Someone thinks I just need the carbs synched, but I don’t know that could be the only thing for all of this.


Any ideas?
 

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Carbs, vac leak, or something else??
Yes. :mrgreen:

Certainly check for vacuum leaks.

It does have a stock air filter on it, right ??

Then I suggest a double dose of Berrymans B12 Chemtool carb cleaner in the gas.....and doing warm up runs with the engine over a couple of days.

Sounds a LOT like the carb(s) need a good cleaning and the B12 sometimes does amazing things without taking anything apart.

It does run better with the choke operated a bit, right ??
 

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For the carb syncronisation being far enough out to cause these problems would need them being fitted to different bikes IMO lol! You may find the float level is set too low, the fuel supply is compromised....bad filter/s or stuck float needles.

It may even be a severe tank vacuum caused by the vent being inoperative...this doesnt explain the sudden increase of rpms though. As Ken says a good dose of cleaner wont go amiss...maybe even two or three...and a simple spray of starter fluid around the inlet boots will show any leak with an increase of revs.

One point is the clamps on the boots being too tight can lead to leaks.

I suspect the carbs are bunged up somewhere along the line....probably in the idle circuits which explains the lack of a smooth rev increase from idle to where the main jets and needles take over.

good luck
 
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