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