Triumphrat

markbvt · 04-24-2007

I had read through Keef's airbox mod post and decided to gut my airbox as well and save the cost of a removal kit.

I figured I'd start with the carb rejet, since I didn't want to risk making the bike unrideable by cutting into the airbox and then not being able to get the carb bowls off due to stripped screw heads or something. But to my surprise, the butter-soft screws came out without issue.

Carbs with bowls removed, prior to rejet:

Turned out that while the infamous carb screws came out easily, the pilot jets did not. I had to make two trips to the hardware store to find a screwdriver that was just the right size to get those bastards loose.

But eventually I got them out and proceeded with the airbox mods. I started by removing the left side panel. (I stuffed a clean shop rag in the carb mouth to prevent debris from getting in.)

Next I removed the right side panel and restrictor plate. I used a Dremel with a reinforced cutting wheel to cut away the parts of the airbox that were in the way. The K&N pod filter slipped onto the carb easily.

Next I cut down the side panel to clear the filter, while leaving mounting points for the brake master cylinder and electrics intact. This also preserves the slot for the allen wrench that comes with the bike.

I cut an inch and a half or so off the end of the crankcase breather hose and attached the breather filter. I was able to push it up between the carbs in an upright position.

Left side filter installation worked the same as on the right side. Again, mounting points for electrics remain intact, for the most part. I'm going to put together a toolkit to stow in the old filter location (thanks for the idea, Keef!). With airbox side panels reinstalled, here's what everything looks like.

And here's the pile of discarded airbox pieces.

Went for a test ride after I finished -- wow! The intake roar at WOT is pretty astonishing. Throttle response was good through the entire rev range, and the bike pulls hard throughout. Only issue I noticed was a slight bog right off idle when the engine's hot -- I'll turn the mixture screws in half a turn and see if it goes away. Jetting is 135 mains, 42 pilots, Thruxton needles with one shim, 3 turns out (currently; will decrease), pipes are old TORs that have gotten packed out and flow better than new ones.

Next up: stainless steel braided brake lines. I expect those to take a lot less time.

I should also fabricate a sturdier carb brace -- or at least, a second one. The left carb is vibrating quite a bit.

--mark

pabonne · 04-24-2007

Nice work Mark. :upthumb: Great pics of the process. This is a mod I've been mulling over for months and with each new post it just gets clearer and less intimidating. I'd be curious to see performance gains of pod type filters vs high-flow stock-type unit with snorkel and restrictor plate removed. For sure the pods look bad-ass though.

Panthermark · 04-24-2007

Very nice, what did you make the carb brace out of?

markbvt · 04-24-2007

Quote:

On 2007-04-24 07:18, Panthermark wrote:
Very nice, what did you make the carb brace out of?

It's a cut-down piece of light-gauge angle iron I had lying around. I had already cut it in half for some other project, so I cut it to length, cleaned it up a bit, and notched the end to slip over the carb connecting rod. I think I'm going to need to make a second one -- this one held the right carb pretty well, but the left still vibrates a fair amount.

--mark

Rusk · 04-24-2007

I would say that this post pretty much removed any and all remaining intimidation I had, with ripping my airbox out. Absolutely great photographs! :upthumb:

markbvt · 04-24-2007

Glad my post helps!

A few tips on performing the airbox surgery:
• Give yourself plenty of time. Some parts of the procedure may take much longer than it seems like they should. The pilot jets, for example, took me a couple hours to remove, including two trips to the hardware store. Save yourself some time by making sure you have the right size screwdriver before you begin. Take your replacement pilot jet to the hardware store and find a screwdriver that fits it perfectly and that preferably doesn't get any wider (if it does, you'll need to file it down) and is no more than 4" or so long. Also, an inspection mirror on a stick (like dentists use) is extremely helpful. Work slowly, deliberately, and carefully in order to avoid making a mistake that will cause you a much bigger pain in the a$$.
• Start with the carbs. This way if you can't get the screws or pilot jets out, the bike is still rideable. When you're tightening the stainless steel replacement screws, be careful -- the carb body is made of soft metal, and it's easy to strip the threads. Yes, I discovered this the hard way. I'm hoping I'm not ever going to need to remove the left-side carb bowl again.
• If you're replacing your needles with Thruxton ones or shimming the stock ones, remove the caps and springs from the tops of the carbs and be careful not to disturb the rubber diaphragms. Use needlenose pliers or a hemostat to pull the little plastic widget and the needle out of the slide without raising it. I've heard the diaphragms are a real pain to get seated properly if they've been removed. I had already dealt with enough other annoyances, so I did not want to find out for myself.
• There's no need to remove the airbox from the bike, or even to put the bike up on a lift. Side panels can be removed with the airbox in place. There are three screws on each side that are hard to get to because they're obscured by the frame. Grab onto the heads with vice grips or needlenose pliers and turn them a little bit at a time -- eventually you'll get them out. (FWIW -- I've removed the rear fender from my bike. If you haven't, you may need to remove it to get to all the screws -- or you may not. I don't know.)
• Be careful not to get any plastic chips/dust into the carb mouths.
• Cut away airbox side panel pieces a little bit at a time to get the covers to clear the filters while leaving as many of the stock electric/etc mounting locations intact as possible.
• Side covers fit back on the bike without modification, and the appearance of the bike once fully reassembled is like stock, unless you walk up close and look for the pod filters.

One word of caution -- if you don't want a hellacious intake bellow at WOT, don't do this mod. I was surprised at how loud it was. However, at partial throttle it remains fairly polite.

--mark

sweatmachine · 04-24-2007

Quote:

On 2007-04-24 13:35, markbvt wrote:
One word of caution -- if you don't want a hellacious intake bellow at WOT, don't do this mod. I was surprised at how loud it was. However, at partial throttle it remains fairly polite.

--mark

but it sounds so cool!

markbvt · 04-24-2007

Quote:

On 2007-04-24 14:19, sweatmachine wrote:
but it sounds so cool!

Yes, it does! :-D

--mark

cw · 04-24-2007

Depending on which screw stripped, you could put a nut on the backside, buy a longer bolt and screw it all the way through.

I'm guessing the reason why the stock screws are so soft is to protect the threads of the carb body. Stripping the head of the screw is a lot better than stripping the threads of the carb body. The soft screws prevent you from overtightening them at the expense of the screw itself...

Quote:

On 2007-04-24 13:35, markbvt wrote:

• Start with the carbs. This way if you can't get the screws or pilot jets out, the bike is still rideable. When you're tightening the stainless steel replacement screws, be careful -- the carb body is made of soft metal, and it's easy to strip the threads. Yes, I discovered this the hard way. I'm hoping I'm not ever going to need to remove the left-side carb bowl again.

--mark

keef · 04-24-2007

Good work, Mark.

Needle and thread next then