Triumph Bonneville Carburetor Brace

Parts needed:
stainless steel tie-strap $2.00

Tools needed:
angle grinder
1/2" metal drill bit

Most of the airbox removal kits come with a brace to support the carburetors in the absence of the airbox's rubber boots. I made one myself for little cost out of a stainless steel tie-strap. First I cut the strap with the an angle grinder ($10.00 at harbor freight - gotta love those parking lot sales!).

The bar connecting the carburetors from the rear is just under 1/2" in diameter so I drilled a 1/2" hole close to the edge of the strap and used the angle grinder to open it up. I also reamed the the hole on the end of the strap to fit the bolt on the frame to which it will be mounted.

Allegra decided that the carb brace should be pink and so it would be.

Finally we mounted it to the frame.

Triumph Bonneville Mods for Airbox Removal

The Stock Airbox
Unfortunately the airbox can't be done away with completely because it holds the battery, acts as part of the rear fender and is a mounting point for various parts and systems. While the airbox removal kits offer a machined replacement to hold the battery and relocate mount points, we can do the same thing for much cheaper by chopping up the stock airbox. When cutting we have to carefully work around important features removing only as much as we need to fit the new air filters. I prefer not to destroy the stock parts on my bike so I ordered a spare airbox to tear up from a salvage parts dealer.

The battery box supplied by the kits provide a very minimalist replacement but as you're not using the space under the seat for anything else you may as well get creative with it. I decided to turn the air filter into a tool stash by tearing the pleats out with pliers. I clipped off the top and fitted some 1/4" vinyl tubing around the rim to keep it snug in its nook.

To make room for the new air filters, I had to cut from the front of the battery compartment, down and around the old-air-filter-turned-tool-kit. I used an angle grinder to cut most of the material off and then a hacksaw for the details. Both worked through the soft plastic like warm butter.

If you are planning to use the old air filter, make sure not to cut off the splines that hold it in place!

On the right side of the airbox are the rear brake reservoir and fuse box mounted on a metal bracket along with the carb heater relay press fit beneath the fuses. On the left side are two relay boxes and the starter solenoid. To make room for the new filters, the fuses, carb heater relay and starter solenoid all have to find new homes on the airbox. While deciding how best to go about doing this, my girlfriend hit upon the idea of using heavy duty velcro. This is great because it makes getting around the airbox for other maintenance much easier. Since the rubber mounts on my relays were toast, I decided to velcro those as well. The starter solenoid was relocated right next to the relays, while the fuses and carb heater relay moved to the front-facing side of the airbox.

A quick note about removing/installing the stock airbox: although I saw some posts online in which folks claimed to remove the stock airbox without removing the rear wheel, I was not able to do this. In the end I removed both springs, the rear fender, the left muffler (to access the axle bolt) and the rear tire. The extra space makes it much easier to fit the airbox and associated wires, hoses, etc. comfortably.

And that's all there is to it. Be sure to follow the manual closely when reassembling the rear of the bike. Don't forget to check the rear wheel alignment and tension the chain correctly before tightening the axle nut and make sure that everything is snug before calling it a day.

Triumph Bonneville Air Injection Removal

Secondary Air Injection System

Parts needed:
2 M12x1.25 bolts
2 crush washers

Total cost DIY:
$8.00
Cost at newbonneville/british-customs/bellacorse:
>$25.00

The SAIS is an emissions control system that pumps air into the exhaust to burn up any fumes that made it through combustion. Air travels through a hose from the airbox to a valve mounted on the frame above the engine and down two tubes that enter the cylinder next to the spark plugs. In order to aid combustion, a small amount of emulsified gas mixture is extracted from the left intake through a ribbed hose and also injected into the exhaust. Removing the SAIS is simply a matter of pulling it off the frame and plugging the holes where the hoses enter the cylinder.

Getting the SAIS out of the engine block is a little tricky if you don't want to mangle the metal tube because the hex is recessed and very close to the valve cover. Start by pulling the hose off of the reed valve.

Now turn the tubing around to expose the pinched hose clamp.

End-nipper pliers are good for opening these incredibly irritating hose clamps.

Now you can slowly ease the angle tubing leaving just the section that is screwed into the engine.

I slid an offset 13mm wrench down the tube to get at the hex. Be sure lay a shop towel down because you're probably going to smash the wrench into the cam cover when the threading breaks loose.

The hole left by the SAIS can be filled with a M12x1.25 bolt. This is a pretty uncommon size (at least in the US) but luckily it is the same spec as the drain plug for many Japanese car models. You can find one for a few bucks at your local auto parts store. Don't forget to buy M12 crush washers as well!

If the drain plug is too long or has a stub (like the one I got) you can cut it down to size with an angle grinder.

The crush washer is extremely important as this bolt has to seal the against the exhaust pressure. Aluminium and copper are both good choices. Remember that the space around the SAIS hole is very limited so the washers should be small. The two washers pictured below were too wide and I had to go out and buy new ones. Save yourself the extra trip!

Simply bolt the drain plugs into the engine and you're good to go!

Triumph Bonneville DIY Air injection and Airbox Removal

So I know that airbox removal has been pretty much beaten to death (at least by the Triumph community) but as I managed to save quite a bit of money doing this myself (not with a kit) I figured I'd document it. This modification replaces the stock airbox with individual air filters clamped onto each carburetor intake. The airbox snorkel and internal baffle restrict the flow of air into the carburetors; by removing the maze of plastic, we free the carburetors to draw in more air resulting in a modest performance increase. I'm going to skim through the steps that are explained elsewhere and focus on the parts that involve a little creativity and ingenuity.

For starters, airbox elimination consists of a few distinct parts. In no particular order (click the link for a detailed walkthrough):

the stock airbox has to be chopped to make room for the new air filters;
the carburetors have to be re-tuned to adjust for the increased airflow;
the secondary air injection system should be removed;
the carbs have to be braced against the frame;
the new filters need to be installed;
the crankcase breather hose must be re-routed and fitted with its own filter.

Finally, the carburetors need to be balanced and and adjusted until everything is running up to spec.

Instead of compiling one monolithic article, I've broken these down into a few self contained posts to keep things relevant.

Parts
Airbox mods:
2 K&N RC-1920 air filters (54mm I.D.)
1 stock airbox
heavy-duty velcro

AI removal:

2 M12x1.25 drain plugs
2 M12 crush washers

crankcase breather:
1 K&N 62-1015 crankcase breather filter

2 1/2" hose clamps

15/32" PCV hose

For carb tuning:
main jets, pilot jets, needle shims