Had the cars out for another run and it is missing at 4.5 - 5K in 4th at about 75-80 coughs and splutters

Replaced all the plugs but they were nice and tan/grey. I think I need to advance or retard the ignition but what way do I go is it advance at higher revs or retard?

Engine - 1.8Zetec
Carbs - GSXR750
Ignition- Megajolt
Fuel Press about 4psi
Car - MK Indy

[Edited on 25/505/09 by mad4x4]

don't you have to adjust the ignition map on you megajolt by connecting up your laptop, then increase the advance on the ignition table. then go out for a blat and see if its any better

If you get a misfire around 4k, check that the mount for the VR sensor is REALLY rigid - it's a recognised issue with MJ.

Not that it's MJ's fault, just that a lot of builders have reported misfires between 3.5K and 4.5K, usually solved by re-mounting the VR sensor.

4PSI fuel pressure sounds a bit high to me; I thought bike carbs ran on low pressure?

Are you using the matching bike fuel pump, or an adjustable fpr?

I can't talk as have yet to get my car on the road, but have had it running, bit that's what my research has led me to!

I running zx9r carbs on my car and the fuel pressure is around 1.5 - 2psi as they dont need huge psi

quote:

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Originally posted by Charlie_Zetec
4PSI fuel pressure sounds a bit high to me; I thought bike carbs ran on low pressure?

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More like 1 - 2 psi... but at a high volume/sec.

Just what a bike fuel pump delivers...

Whats the VR sensor is that the one the vacum goes onto? I don;t use the TPS sensor.

4psi is too high, as said. What pump are you using? If its not the bike pump it needs to be the same type whereby it stops pumping when the floats are full...

VR should be OK as its mounted to the block reading the back of the flywheel.

Worth connecting the TPS on the carbs to the megajolt if they have one.