After fitting a set of LitetekBlair's excellent Viton o-rings in the carbs, my NC30 won't start. I have the HRC fuel tap mod, and I am wondering how the carbs should be primed if there is no vacuum to draw the fuel into the float bowls? Or am I barking up the wrong tree?

For the record, I have changed the plugs and charged the battery.

Your barking up the wrong tree :) All the HRC mod does is remove the need for vacume from the engine to open the fuel tap, ie as soon as you turn the tap to ON your carbs will fill with fuel.

That was quick, thanks!

The plugs were dry when I pulled them, despite sporadic attempts at starting (I leave 5-10 mins between crankings to let the battery recover). I just wonder if the fuel is getting through.

I haven't tested the spark yet, but the fuses are all good. It's night-time here, so it'll have to wait until morning.

Have you rebuilt the tap right? pull the pipe off the carbs and turn the tap on to see if fuel flows, if correct the carbs will be getting plenty of fuel. As for the cranking, i find the best way is to crank it for a few seconds, rest for a few secs then repeat, no need to wait 5 mins.

The tap has been working with the HRC mod for the past year. No problems (with a note on the top yoke to remind me to turn off the fuel!).

To insert the o-rings I split the carbs minimally, so I could get just enough room to extract the fuel line joints, replace the o-rings, and re-assemble. I guess I'm concerned I made a mistake with the carbs since the bike was firing without any problems beforehand, and I can't smell any fuel.

Crack open the drain screws on the float bowls and see if theres any fuel in them, if all you've done is work on the carbs then unless you missing something silly id say you havent put them back together right.

Get the carbs out again and redo the procedures to check it all again whilst out/in your hands.
Any screws for air/pilot blocked or closed?

Maybe:
Enough fuel in the fuel tank?
Killswitch on ON?
Anything blocked the inlet / air like cloths/tissues?
Carbs fitted correct in their carb rubbers and all air tight?
Leads to plugs measured and checked it does fit correct on the plugs/bobines?
Floatchambers level checked and working?

Just a few things I can think off rightnow.

Drunkn Munky wrote:Crack open the drain screws on the float bowls and see if theres any fuel in them, if all you've done is work on the carbs then unless you missing something silly id say you havent put them back together right.

this sounds like a good place to start before remoinv everyhting..

a long screwdriver will get in there, see if you get fuel draining out of all 4 float bowls.

if not tap the float bowls with the handle end of a screwdriver.. sometimes the floats can get wedged stuck or open..

After finding fuel in the float bowls, I turned my attention to the spark. Very weak, even with the battery at 14.2v. Removed and measured the coils:

Rear Coil:
Primary resistance: 3.6 ohms (Haynes range 2.5-3.5 ohms)
Secondary resistance without plug cap: 15.0 K ohms (Haynes range 11.0 - 14.0 K ohms)

Front Coil:
Primary resistance: 3.9 ohms (Haynes range 2.5-3.5 ohms)
Secondary resistance without plug cap: 15.05 K ohms (Haynes range 11.0 - 14.0 K ohms)

The HT leads are pretty knackered, so I will replace them in the morning.

The measurements indicate that the front coil is well past it's sell-by date, and the rear coil is going the same way. Does anyone know if these coils are generic, adn readily available from automotive or bike suppliers, or are they something special for the NC30?

tanto wrote:After finding fuel in the float bowls, I turned my attention to the spark. Very weak, even with the battery at 14.2v. Removed and measured the coils:

Rear Coil:
Primary resistance: 3.6 ohms (Haynes range 2.5-3.5 ohms)
Secondary resistance without plug cap: 15.0 K ohms (Haynes range 11.0 - 14.0 K ohms)

Front Coil:
Primary resistance: 3.9 ohms (Haynes range 2.5-3.5 ohms)
Secondary resistance without plug cap: 15.05 K ohms (Haynes range 11.0 - 14.0 K ohms)

The HT leads are pretty knackered, so I will replace them in the morning.

The measurements indicate that the front coil is well past it's sell-by date, and the rear coil is going the same way. Does anyone know if these coils are generic, adn readily available from automotive or bike suppliers, or are they something special for the NC30?

Don't believe these leads are that special made for the NC30 or NC35. The real differences in leads should be in the materials used for the inner core and their thickness. Copper cored should offer a higher capacity outtage and stronger power for the sparks. Ask member Rick O. on here as he can provide you new and all ready-to-fit HT leads to replace the old ones.