Carburettion (??) issues - NC29 racers

[matt69]

Today at the track I was having some issues, that seem fueling related to me.

At wide open throttle the revs would rise to just under 13.5 then drop to 12k before rising again to 14.5k or so.

The bike has a standard engine,but a HRC CDI, full exhaust, ram air box, quick action throttle, 160 main jets, standard needles with 2 washers under them and a hi flow filter mod. It had been dynoed and carbureted well until this.

The plug colour looks good.

Any hints? Should I try bigger mains? The HRC manual has 165 as an option.

Matt

[ChowderV4]

clutch slip?

i had a similar thing with my zxr and it was clutch slip

[matt69]

clutch slip?

i had a similar thing with my zxr and it was clutch slip

That is a thought as well, but I thought clutch slip would make the revs rise?

It is also popping when I roll off the throttle.

Matt

[leopard_pagan]

Clutch slip revs rise, bike doesn't speed up as the revs go up, as the clutch gets bite again the revs drop a little. My bike is suffering this at the mo, changing clutch friction plates as soon as my clutch gasket arrives.
Popping on roll off is common & is fuel related. Someone with better knowledge on this can explain better.

[ChowderV4]

Clutch slip revs rise, bike doesn't speed up as the revs go up, as the clutch gets bite again the revs drop a little. My bike is suffering this at the mo, changing clutch friction plates as soon as my clutch gasket arrives.
Popping on roll off is common & is fuel related. Someone with better knowledge on this can explain better.

Leopard i right about the clutch, so that is a possible cause of your problem, and the popping will jut be un burnt fuel in the exhaust system igniting when you roll off, could mean its running a bit rich

[ChowderV4]

Clutch slip revs rise, bike doesn't speed up as the revs go up, as the clutch gets bite again the revs drop a little. My bike is suffering this at the mo, changing clutch friction plates as soon as my clutch gasket arrives.
Popping on roll off is common & is fuel related. Someone with better knowledge on this can explain better.

Leopard i right about the clutch, so that is a possible cause of your problem, and the popping will jut be un burnt fuel in the exhaust system igniting when you roll off, could mean its running a bit rich

[leopard_pagan]

Clutch slip is defiantly one of my bikes problems..... Been doing it for over a year & DONT buy cheap clutch plates! I did & they were under spec & didn't work. Sent em back & company said they have had several complaints about them!!! Then why still sell them!
Bike has been sat for last 6 months with another issue which is now sorted, so clutch with right plates is my next job. Chain 2nd & then save up for new diaphragms for the carbs & get them redone.

[matt69]

I think it was simply fuel starvation. When I checked the fuel in the tank, I've got a 10L alloy tank and fibreglass cover, there was only about 500mL left in the tank. I think that when I braked for the corners the fuel sloshed forward, allowing air to be sucked in by the fuel pump. As I accelerated this air caused the fuel starvation until the fuel was sucked back into the carbs.

Thanks for the replies.

Matt