The Blackbird engine uses 4 carbs, one for each cylinder. They are set up for use with the standard bike airbox and exhaust and when used in a car installation with a freer-flowing filter and exhaust the jets need changing on the carbs. I got a kit from TTS including a filter and the rejetting kit. I'm not using the filter at the moment as it would require a hole in the bonnet. I'm going to wait to do some tests to see how much extra power would be liberated before taking jigsaw to GRP. If you don't use the bike airbox (i.e. socks or sausage filter) and don't rejet it then it won't rev properly. And what would be the point of that.....

The TTS kit is actually pretty easy to fit although the instructions aren't that good. I eventually decided to do the job after getting some advice from someone who'd done it before (cheers Ed). And this is how to do it......

The carbs in all their glory

The float bowls: these needs to be taken off using the silver cross head screws - one at a time. Also visible are the mixture screw (the brass crosshead pointing towards the camera) and the float bowl drain screw (pointing to the left, contained in the bit with a pink dot on it). Make sure you screw the drain screws in when you try to start the engine - I didn't and fuel spewed out!

This is what it looks like with the float bowl off.

That's the main jet which needs to be changed.

This is with the main jet taken out - you can see the threaded bit it goes into.

Next step is to change the needles - take off the plastic cover using the 3 black cross head screws. The needle holder is the black plastic bit with the arrow pointing to it. Thread one of the cross head screws into this and use it to pull out the needle holder. Mine were quite stiff, so some force may be required. Hold the black square bit surrounding the needle holder in place: this doesn't need to come out.

This is what should come out: the needle holder, the needle and the washer. A long spring will also come out. Replace the needle, putting the e-clip at the proper height (2nd position) and reassemble using the replacement spring.

These are the trumpet holders which need to be taken off by removing the black cross head screws.

This is the air jet you need to drill and cap. Drill down about 2/3mm.

I put tape over the carb mouth to stop the swarf falling into it.

Then put the little brass plug in the resulting hole, glued in place.

Usual disclaimers apply - only trying to help!

This document maintained by Dan Bromilow webmaster@danstuff.info.
Material Copyright © 1998 Dan Bromilow