Throttle Bodies

Fitting throttle bodies (ITB's) to a Honda B Series.

Introduction

While there are plenty of throttle body kits to choose from for the Honda B series it will set you back a minimum of 1200 for a good setup including all the little bits & pieces (linkages, idle valve mounts, filter etc) that soon add up. To add insult to injury even an off the shelf kit still need some degree of fabrication, especially to have then on a daily driver for street use.

The main advantage in going the DIY route is the massive cost savings you can make. You can pick up a suitable, complete motorbike air box and bodies from as little as 100, in brand new condition! Obviously some fabrication is required to fit them, but even including that it should come in way below buying a set in, depending of course on your skill level and how much work you have to pay others to do. And what's to be learned in just buying something in ready made?

An increasing number of people have been fitting motorbike bodies & carbs to their engines, although you are restricted to some extent by bore sizes. There are also a number of cars that are fitted with ITB's from the factory, which can be a good source for parts if you can track them down.


Some research done, I thought I would have a go at making a few different sets for my 1.6 Honda DOHC VTEC B series motor.

This article assumes you have some degree of aptitude in fabrication skills, knowledge of engines, their management systems and calibration. If you don't then please click here. For some details on Honda specific setups, get over to Honda-Tech.com and use the search tool.

The main components you need are:

  • Set of suitable throttle bodies.
  • Stock intake manifold to chop up, or fabricate your own.
  • Suitable engine management system (ECU) that is capable of running an engine with throttle bodies - quite different to using a plenum (manifold).
  • Use of a machine shop, to fabricate the parts.
  • Some aluminium and steel stock, to make the odd brackets etc from. 

 

Which Bodies?

I picked up three different sets of bodies to start this project with, not knowing much about the world of motorbikes this was a little more complicated than anticipated. It turns out that most motorbike manufacturers change their designs every 2 years and in-between continually make changes to models. This means when sourcing your bodies you have to be very specific, giving the exact model number and year of the bodies you want.

Thankfully, all the motorbike breakers I spoke were very helpful in advising me me which bikes shared similar sets of bodies. Even the local Honda bike dealer was very helpful, considering I didn't even own a bike! There seems to be a better spirit of people helping each other out when you deal with bikes, as opposed to cars. That said DON'T start calling bike breakers and asking for some bodies to fit a Caterham with a Ford Pinto - do your homework first and show that you've made some effort!