Bonneville America Forums Forums Technical Forums Performance Mods totally original thread re: airbox removal! (lie)

Okay okay, i've read through previous threads and have managed to confuse myself more than make things simpler..

Basically, the guy who's fixing my bike's 'breathing' problem is going to take apart the carbs and suggested that whilst he was at it i should look at the Stage 1 Dynojet kit (about £100 over here) and he could sort that at the same time.

now personally i've fancied removing the airbox, sticking some filters on and relocating the battery.

question is:

Will that basically do the same thing (in terms of improving performance) as a Stage 1 Dynojet kit?

I'm assuming cost wise it's a pair of K&N's, crank case breather, carb brace and somethign like the carb super jet kit from Jenks Bolt (i can deal with the battery relocation a bit later).

the guy is an engineer and he's happy to do the job. I'm just looking to see if the cost and faff difference is particularly great between the two.

Any advice as always gratefully received!

Ant

Have you upgraded the exhaust? That way-too-expensive Dynojet kit is useless without upgrading the exhaust and then fitting a better air flow.

Assuming you have an aftermarket exhaust on the bike, you really want to do both - increase the airflow by either 1) pulling the snorkle out and putting in a single Uni or K&N filter (easiest & cheapest option) or 2) cut up the airbox and put pod filters on (this will flow more air but more work is involved).

Once you figure out the intake setup, you can either get the dynojet kit which contains larger jets, needles, etc, or just keep reading this forum and order the parts individually which will cost less.

If you have a pipe and go with a single Uni filter and pull the snorkle, you might try a 125 main (130 if its a really free flowing pipe) and a TBS neeedle. The cost would be about $25 for the Uni filter, $7 for the main jet and $15 or so for the needles.

If you go with pod filters, consider a larger main jet and a 45 pilot jet. If you go with the 45 pilot, you may not need the TBS needles.

There are a lot of great resources on this site which will provide you with the technical details of our carbs. Someone will post some links.

My experience, mostly acquired from my service dealer, is that if you open up the stock airbox (remove snorkel, UNI or K&N filter, maybe bellmouth) and get the best needle/jet arrangement - there is no need to remove the airbox.

From the dyno results I've gotten, I don't see any gain from removing the airbox. There are a lot of "freaked" bikes whose dyno results can't touch mine. Plus, I like the airbox and battery where they are.

Pipes - Yep, i've got Short TORS on the bike (i suspect thats a lot less free flowing than normal after market pipes but i prefer the 'quiet')

For reference, K%N Pods are what i've been seeing on most bikes with battery relocated yeah? I've seen a few ebay 'Triumph America' K&N filters and they're totally round rather than tapered (like i assume the pods are).

Apart from losing the cheesegraters (which i'm happy to do) are there any negatives to losing the airbox vs opening it up?

The jet kits that Jenks does seems to be good value - though i've only seen Thruxton needles rather than TBS ones (from reading other threads it looks like the difference between the two is a debate in itself).

The guy doing it is an engineer anyway so he should be up on what he's doing - its just worth me making sure by buying one thing i wasn't giving myself more expense later on (i.e. by getting the pods, seperate bits etc i wasn't missing something vital from the Dynojet).

in fairness, the only real performance thing i'm concerned about is fixing the current underlying problem - any improvement in performance or look (mines fairly stripped down) is just an added advantage.

I have a 2007 BA with short (tapered)TORs too. I just recently cut up my airbox and put in pod Uni filters. I did this in a way to allow the cheese graters to stay in place but without spenfing the $300 for the freak kit. I am also changing the exhaust. I have not finalized my jetting for the pod filters and new exhaust yet because its winter and its too darn cold to test ride right now.

However, If you want to take the easiest route which will cost the least and give you the biggest bang for your buck, I'd pull the snorkle, put in a 125 main and a TBs needle. I rode with this setup for quite a while and it works very well. If you do anything else on the intake (like drill the bottom) you may need to go up to a 45 pilot jet and in that case lose the tbs needle and put a shim under the stock needle. If you keep the stock pilot you want to turn out the mixture screw a few turns. If you go with the 45 pilot you don't need to turn it out as much.

First Bit: The newb questions

I noticed the Jenks Bolts guide to tuning seems to be a little updated (got 2007 results rather than 2006).

Do you reckon i'm safe to go off the Thruxton results (w/ no airbox) as a basis for tuning?

It recommends that with Off Road Pipes, Thruxton Needle, No Airbox, Decent Filters and what i'm assuming is UK Altitude :

Main Jet: 140
Pilot Jet: 40
Shims: 1
Pilot Screw: 2.5 Turns
Air Hole(?): 3mm

Pats Calculator seems to suggest 146 Main jet but then it doesn't have an option for 40 pilot jet or airbox removed (unless thats what the 'all removed' section is on snorkle though!

Thanks for your patience all!

Second Bit bit: Not related to Performance Directly
As a side (and i'll post this second bit in a more relevent forum) has anyone considered putting info like this and stuff thats in the tech vault into a wiki (like wikipedia) with some kind of big table that anyone can update with their performance mods etc.

I'm aware some dyno stuff has been saved and that there's a wealth of information to be had by clicking 'search' but it certainly might be a neat feature and a nice way of collating all that data.

Ant

40 seems a very small pilot most run a 45 and I wouldn't go less than a 42 with your set up, but that all depends on where you live. Never just set your mixture screws, you need to adjust them the right way. That is also a good way to tell if you have the right size pilot jet in there. Then you have to consider that your pilot size will effect your main size and then the needle will play into that as well. You need to find someone that lives at a similar altitude that has done the work to set up their bike the right way, then you could use that as a starting point or Pats calculator will also give you a good starting point. Once you think you are close the only way to do it right is a Dyno run then adjust...repeat until jetted right.

Yeah, what Ian said.

I believe our bikes had a 42 pilot jet stock, so either leave it alone (and maybe try a TBS or Thux Needle) and go up on the main jet (135 - 140?? with the pods and TORs) and test ride - full throttle blast to redline. If the main jet is too big the engine will probably cut out at WOT as the mixture will be too rich and you will essentially "flood" the engine. If it pulls strongest at 7/8 throttle versus full throttle, that's another sign the main jet is too big and you need to go down. To be safe, start with a large main jet (probably 140 for your setup) and go down in size until it runs best at WOT. After doing that you can swap the needles and or change the pilot jet to fix any issues at partial throttle settings.

There can be a fair amount of trial and error involved in the jetting process if you don't have access to a dyno. However, with time and patience, you can get very close just using the Butt dyno.



You'll be able to tell if it's too rich (it will feel doggy) way off in terms of being too rich or lean. If it pulls to redline cleanly