Ok ... The car was missing badly so as I had spare jets of different sizes I thought I would experiment by increasing the jet sizes.
After going from 155 to 160 to165 to 175 it now pulls like a train....with the dB killer baffles in. Take them out and it still misses at high revs. My feelings are that increasing the sizes again should cure this. However I have made an aluminium plenum that is being welded up. So am going to hang fire until this is complete as this will be be coupled to a K&N induction kit that will be sited in the air intake behind the driver.

Any thoughts and I presume it has a rev limiter as I cannot see it mentioned in the workshop manual I downloaded. Max power is at 9800 I had it up to 11500 with no cut out. oo eer.

TBH you are playing Russian Roulette by swapping jets and simply opening the throttle to the redline!

The only real way to figure out what jets are needed is to either fit a wideband lambda sensor or go for a dyno session. The cost of either will be about the same so at least with a WB setup you can continually monitor your AFR after any tweaks made to the induction or exhaust.

[Edited on 2-8-10 by RazMan]

Whist I appreciate your comments. I did not simply change the jets and reline it, give me some credit. I drove around for some time noting its response changing the jets and monitoring again. It was only with the larger jets that it pulled well and that was the only time it revved to the red line. I want to get the carbs roughly right before the rolling road to save the time that I am paying for. It takes a while to get the carbs off remove the float chambers and change the jets and reassemble.

I didn't mean to insult your intelligence and was just giving my point of view which is based on experience

I recently changed my cams and throttle body, and continued to drive the car after a global fuel increase of 5% as a safeguard. The car was pulling well but I weighed up the cost of getting a wideband setup or a session on the dyno. I decided to get the WB for the reasons stated above ..... and was glad I did! The map needed to be changed quite a bit and I was running so weak in the powerband that I ran the real risk of holing a piston (remember I said it pulling well?)
With a lot of tweaking the engine is now producing much more power and running far safer. The driveability has also vastly improved.

After that experience I will now never take the risk of making any changes in the fuel without paying close attention to the AFR gauge - money well spent.

Good point.....and very well made

I have been looking at the wideband lambda gauges and sensors such as this

Is this the sort of thing you used?

I haven't used that particular model but it certainly looks ok - cheap too. I used the excellent Innovate LC-1 which is probably the most popular one, although a bit more costly. Stay away from Jaw or DIY types as they do not have very good reviews.

Looks like my Birthday pressy. As you said its got to be worth it.
As i'm on carbs. what aftermarket ECU would you suggest, powercommander??

[Edited on 4/8/10 by Lightning]

Certainly can confirm something like an LC-1 is *invaluable* when tuning a car. I got mine (without display, for feeding into the megasquirt) for £136.

I have the old ZZR1100 on carbs and fiddled around with the jets quite a bit. I bought a dynojet kit, fitted the needles and the largest jets in the kit 155. Went better, but still missed at the top end in top.

Spoke to a lad who ran a championship winning Jedi with the same engine, and he was using 200 mains! (2.0mm) and had given up going any larger as that was the size of the hole in the casting in the carb.... So I just copied him!

Runs a bit (OK a lot) rich at low revs, but goes like a rocket when you open the taps!

Mike (player of Russian roulette with his engines!)

i fitted the aluminium plenum and the induction kit over the weekend and the difference is staggering. No change of jets just replaced the TTS sausage air filter.
Reduced induction noise is the first thing and the resposivness is the next.
The best description I can come up with is that the engine now sings.

When I put my last car on the Rolling Road with a Fireblade engine. We tried the foam filters against an airbox that I made and there was at least 5% increase in power.