BC AIRBOX REMOVAL-really!

OK, so I have the TORS with a correct re-jet for them, other than that no performance mods, well i do have AI removal, but thats just for less pipe's bluing I think. I mentioned doing the airbox removal to my dealer when the bike was new, and he said that there would be a lot more intake noise (which I don't know if thats a positive or a negative) and that since there's a perfectly functional air filter and box on there now, why hack it up?. He also mentioned that with NYC being a city, with a little more soot, etc, in the air, and the generally more heavy duty kind of riding (stop and go traffic etc) that the stock air filter would do a better job of filtering the air entering the motor. So my question is, do these K&N filters allow better air flow to the motor at some expense of letting in foreign particles that the stock filter would otherwise have caught, and what kind of and how much extra noise is there with this mod. I like to cruise on my bike at pretty low rpm and really dont rev over 4k rpm's very often, so I think this mod isn't for me, but I am curious, I mean I was considering doing it at first.

I'll try my best to answer some of your recent questions:

GleaminTwin,
You have a Scrambler which is an 865cc 270 degree twin. The airbox mod for the other 270 degree twins (and I assume for the Scrambler) from Newbonneville.com is called the FREAK. I know little about 270 degree twin's response to airbox removal; however, I would suspect it would be similar to the 865cc 360 degree twins which to my understanding is not quite as beneficial as for the 790cc 360 degree twins.

For slow speed riding, you would be wasting your money and time doing this mod, IMHO. The hp increase on my 790 is mostly above 6000 rpm which is well above 80 mph in 5th. For the individual cone filters to let more air into the engine, they would have to do less filtering than the stock filter, IMO. The greatest restriction to the stock air intake setup is not the stock air filter, IMO--it's the restrictor plate in the airbox that restricts how much air can get through the airbox--again I'm not sure if the restrictor plate is removable for the 270 degree twins. The restrictor plate can be removed from the 360 degree twin airboxes by removing the right side of the airbox and simply pulling it out, and then resealing and replacing the right side of the airbox--there have been past threads on this with very good pics...Ridge's pics come to my mind first.

Intake noise: Ever hear a V8 auto engine with a 4-barrel carb without an airfilter? That's about what it sounds like--just not as loud--but it seems as loud because it's right between your legs. :-D Some do not like the sound--others like it...I'm one of the latter. The sound begins around 5K rpm when the throttle is wide open. The sound is often described as a "honk" sound. It is loud enough to mute my music on my Starcom 1 motorcycle communications system--which means the microphone inside my helmet is picking up a pretty loud volume of sound. :-D You would never hear this intake sound under "normal" (whatever that is) riding conditions, IMO. In other words, if you shift below 5K rpm and cruise under 90 mph, you will never hear the intake "honk". It "honks" when the throttle is wide open with the rpms above 5K. I cruise a lot at 5500 rpm and I never hear the intake because the throttle is far from wide open.

Larry

[ This message was edited by: RedBird on 2006-11-06 19:59 ]

Despite some of the comments on this thread, airbox removal, K&N filters, rejetting and head work DO work, and worked very well on my bike. This work was completed by a highly respected tuner and represents an overall power and torque increase in excess of 30%. Stock Thruxton's on his dyno make 52 to 53 bhp before modifications.

Here are the dyno results from the tuner's alleged conservative rolling road. He indicated that other dynos give higher figures than his one. This guy prepares race tuned engines for club racers, so knows what he is doing. The figures shown below are measured at the rear wheel, not crank.

The most important point here is not the actual figures, as dynos all read different, but the improvements achieved with the modifications, all measured on the same dyno, carried out by the same operator.

1st dyno chart shows bike fitted with TORS (60.1 bhp), and afterwards with airbox removed, K&N's fitted and regetted to suite (65.1 bhp).


2nd chart shows airbox mod (65.1 bhp) and afterwards with head gas flowed and skimmed (now 10.4 to 1) now 70.6 bhp


3rd chart shows the torque figures for the 3 stages starting at 48.6 ft Lbs, ending with 61.3 ft Lbs

Okay, I'm convinced.

Though an air box removal & pods sound cool, I'm going to
come clean about being lazy..... even though the bike is
currently apart and air box easily accessable. 'Sides, I've spent too much money on this project as it is. So I'm keeping the air box in.

That said, may I ask for help removing the divider plate????

I've got the little 790 Black, and I've read differing stories about the removal. I've read that it requires breaking tabs, and I've read it can be done without any trauma to yer parts is parts.

Does somebody have a link to instructions for removing the divider/restrictor plate on the little 790?