Looks like monday will be fitting my new suspension from k-tech and my new pipes...now the question is, as I am going to have to mess about with the jetting I am thinking of modding the airbox so what would you do.
Don't just vote give me your reasons as well.
Cheers _________________ MC21SP - Roth-tax
CBR400 - track
MC21R - sold
MC21SP - sold
You've got to do something or it will remain forever limp wristed and be easily spanked by Rompy's '28.
I believe drilled (4x1" holes?) is dyno proven to give the best results. _________________ Please do not PM me technical questions, if you can't find it on the Forum start a thread
I have RS exhausts and my bike runs rich so I was about to remove the airbox lid and wire in the filter. If this is the case i'll get the 1" flat bit out....
I cut the back of the lid off. Just ran a hacksaw down the lip where the two tubes meet the box proper, then accross to the back. Makes for a nice huge hole. I also removed the web from the lid, though I don't know if that makes any difference.
I think it makes a great noise, and still keeps the intake roughly where Honda made it.
Bike made 62hp when it was properly setup... _________________ MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball
i did the same as dave but never took it back to dyno to see if made a gain or not,mine did make 62 with a daytona filter in the standard unmodded airbox _________________ ive seen more tarts than mr kipling
For the road, probably drilled or otherwise modded lid. But for the track, my bike has open carbs _________________ Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30
and rightly so, all other things being equal you want all the air thats available, that will definately give best peak power and is capable of giving best power in any situation (forced induction excluded).
If holding the airflow back increases power (and I agree it can do) then something is amiss and you'd find even more power if you sorted that out instead. Fitting an air box lid to increase power (whether it works or not) is treating the symptom, not the cause. _________________ Please do not PM me technical questions, if you can't find it on the Forum start a thread
Curious that nobody has chosen this option. My 21 had 128 mains. Was running lean, and I wanted to stagger the jetting (smaller in the rear cylinder), so ordered one jet each of 145 through 155. Wasn't really sure if that would be too much, or not, but needed a starting point regardless. Put the 148 in the front cylinder, and 145 in the rear. Kept the lid on the airbox (all of this is using stock-style filter). Wouldn't pull past 7k. Read some forums, popped off the airbox lid (no other changes), and ran it down the street again. WOW! What a screamer.
In my mind, I'm getting more airflow than drilling holes, still filtering the air, and a lottttt more noise.
Thoughts? Aftermarket pipes. Otherwise, who knows? This poor bike led a hard life before I got it....
i run open carbs on my race 300. Doing that has caused two flat spots in the low to mid range when accelerating on WOT through a given gear. I made up a protective panel out of thin sheet steel that sits in front of the shock absorber to stop pebbles or whatever flirting into the carbs off the rear wheel as a precaution - it maybe also acts as an airbox wall in a way? I've not run the bike without it to see if there's a difference yet. Seems that a lack of perfectly still air around the carbs upsets power at certain revs - but only a little, i'm not going to do anything about it because its not really a problem.
I had a similar issue with my MZ racer - which had no fairing and therefore even less still air around the carb. I found it seemed to run richer at higher speeds - so 4th or 5th gear speeds, possibly due to a slight vacuum forming around the mouth of the carb as air flowed passed it? It always ran fine if i dropped a few jet sizes.
As for sheer power - the 300 is definately fast but i dont know how much of that will be down to the influence of the open carbs. _________________ After years of moaning about immigrants now i am one...
Bouncing around in here, looking for more info on all of this. There was a posting that showed a graph of open carbs vs. lidless box with a wired-in filter, and the difference was tiny. This seems like a reasonable, inexpensive, safe way to go.
Surely you would want still air around the carb inlets if possibe but not at to restrict the airflow, hence the HRC airbox. Some bikes (particular unfaired ones) would suffer more at speeds with no airbox at all - although the generally dont go as quick anyway .
A through flow of air around the carbs would make it very unpredictable as to how much air it will be able to suck in.
My vote is HRC airbox if you want to MOD it.....otherwise leave it standard.
Don't have a graph of a standard air box lid but this graph shows the difference between the back cut off the airbox and two large trumpets moulded in [apparently air needs a 3d shape to cause high airflow!] and a copy of a JHA airbox lid which has two long trumpets but smaller diameter.
Run 5 [blue] is better mid range and a slight increase at the top end.
Not sure if picture is attached!!! _________________ MC21 300
Aprilia RS250 track bike
Thoughts? Aftermarket pipes. Otherwise, who knows? This poor bike led a hard life before I got it....
Yes, WAY to effing loud. _________________ MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball
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