NC29 grinds to a halt

[greggo]

Got an NC29 that runs for a bit then stops. Apparently it feels like fuel starvation.

First time it did a couple fo practice days and all but the last race of a race meeting, then just 'stopped'.

I stripped the carbs and found a couple of blocked jets etc. Cleaned it out and cleaned up the carbs. There was no debris in the float bowls or anywhere else. We changed the fuel filter too and tested the fuel pump and it seems to be working okay. Tested spark and all seemed okay there.

Cut to the next practice day, and 3 sessions into the day, same thing. Cleaned carbs, new filter, flushed tank, new fuel. Only this time still no worky.

Anyone had similar issues?

Random thoughts i've had are the CDI or coils getting too hot, a dodgy fuel pump relay, or a dodgy fuel pump. It 'seems' to be a fuelling issue but when I pull the carbs apart there is fuel in the floats. Could it be a couple of sticky float needles? (How do you clean those anyway?)

Next step is to try a different fuel pump and set of carbs.

[CMSMJ1]

how is the battery? Is it total loss?

[greggo]

Hmm it doesn't run total loss and still has its charging circuit. The battery as far as I'm aware is fine, but i'll add the charging circuit to the list of things to check. Might be a bit hard to check it's charging voltage while running tho...

When it stops it comes straight back to the pits and has plenty of juice for turning it over?

[tanuki]

not something as simple as a blocked tank breather is it?

[greggo]

It has an alloy fuel cap, this has a 1mm hole as the breather. That isnt blocked and i run the same set up on mine with no issues. Does it need to breathe anywhere else?

[Cammo]

It has an alloy fuel cap, this has a 1mm hole as the breather.

Silly question maybe, but is the 1mm hole in the right spot (i.e. right through to the tank chamber)?

I've seen a new alloy fuel cap that came with the hole drilled in the wrong spot (the hole would seal up when the cap was screwed on!).


Whenever I've had fuel supply issues it first shows up as cutting out at full throttle, when the throttle is reduced there's enough fuel flow and it will run for a bit, if you get the drift. Mine has never stopped abruptly, especially on track when lean angles etc also come into play and effect how much fuel can be supplied by the float bowls (not fun when it splutters at full lean!).

Is it possible to hook up a multimeter when the bike is on track to check that the fuel pump is working all the time?


Sounds like a shit of a problem because there could be so many causes, hope you get it fixed.