in a 2000 r1 engine (linked with '98 electrics) at about 7500rpm, she starts to splutter and pulls really slowly, spitting the odd flame out the side...this continues until you get to 10000 ish rpm, where she takes off and pulls really well...
at first i thought there was too much air, so i made it much richer, but it still happens. ive got the dynajet kit on with k&n filters...any thoughts?
cheers!

Sticking carb piston or something like that? It'd be interesting to see what a wideband lambda up the exhaust does at that point!!

Have you checked all the HT leads, are all 4 plugs firing without breaking down?

My R1 motor had exactly the same fault as what you have described, it turned out to be a faulty HT lead breaking down. Diagnosed it by using a timing light on each plug lead in succession.

Also a bent carb needle can cause the similar symptons.

Regards,
Lee.

i checked them when i first got her running by taking them out, they all sparked as far as i remember...did you have to replace the leads?ill check that tomorrow...cheers!

Yes I replaced all four leads with copper core replacements once I discovered the faulty one.

The faulty lead did not break down at idle, only at above 7-8k rpm, but the timing light showed up the fault at idle speed.

Regards,
Lee

[Edited on 20/12/08 by maximill666]

is the timing light just like a continuity tester? do you just start the engine and take the lead out?

I used a timing light/strobe to indicate the ignition pulses at each lead, the one that was failing had eratic/irregular pulses.