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91 Posts
Discussion Starter #1
Disclaimer: The following is provided as a GUIDE ONLY, and neither myself nor take any responsibility for the outcomes of someone else doing the following. You follow these steps at your own risk!

Aim: Make your carby more enjoyable! (quicker!)
10mm socket
Phillips head screwdriver/cordless
2 cone foam filters
Wire cutters

Please note this is done on a D15B4 twin carb motor in a EG GL Civic.

Remove your twin carby lid which is held on by 4 clips.

Remove any hoses that are attached to your intake arm to make sure there is nothing stopping you from removing the whole airbox system off.

After that undo the bolts that hold the intake box in place, and then go ahead and remove the bolts that are holding the mesh/spacer to the carby throat.

After you have removed it all, you should be left with the following:

Just give if a clean with carby cleaner since you have removed everything.

Now, you will need a foam cone filter (or anything that you prefer thats open end) to put onto the spacer which will go back onto your carb throat.

The diameter you will need for the filter inlet is 54mm but you will need something that fits snug on it so take the spacer with you to the shop you that you are going to get your filter from:

After you have mounted the filter onto the spacer, screw it back on with the 2x10mm bolts for each carby throat.

(please note that I haven't done this yet, but I will upate with photos once I have)

91 Posts
Discussion Starter #2
Next we will be doing the Keihin CV carb modification.

To do this you will need a phillips head screwdriver and a wire cutter, it's fairly simple to do and I did it while the intake box was off to give me some space to work with.

You want to remove the 2 lids that are right behind the carby:

They are held on by 2 phillips head screws.

After doing that you will see a little black stopper (little plastic) in the middle of where the spring sits inside, just remove that.

After that you want to take out the spring which is sitting inside:

And cut 2-3 coils off it (I cut off 3 1/2) so I was left with this:

After that just put the spring back in with the uncut side at the bottom:

And put the lids back on and just screw it back on and your done!

The springs control the rate at which the diaphragm piston valve rises when you push the accelerator. After the mod the valve rises much quicker, due to lessened spring density. This vastly improves throttle response. The plastic stoppers prevent the diaphragm valves from raising above a certain point, to keep fuel consumption lower. The higher the diaphragm raises, the bigger the needles open, the more fuel you get into your engine. The increased air from the cone filters and the fuel from the quicker lifting and higher lifting diaphragm means a cool 10-15HP increase (if you have a decently built engine already, otherwise, expect less)...

I will update the thread once I have put the EG back together and go around for a test spin, but results are promising :D

Please note that this has been done on a D15B4 Twin Carb motor on a Australian Delivered Civic EG4 Hatchback.

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