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Airbox baffle removal - thoughts

4K views 4 replies 4 participants last post by  lrutt 
#1 ·
So after much consideration, and mostly out of curiosity, I thought I'd give it a go. having already pulled the snorkel and carved the filter cover, I was impressed with the difference these changes had already made. I started from this:

790cc Bonneville
AI gone
Snorkel gone, filter cover carved
42s 1 turn, 120 mains
NBZT needles, 1 shim
TORs

I wrestled the baffle out, went back to stock needles, 1 shim, put 138 mains in (all I had), left the 42s at 1 turn.

Initially, I was disappointed. I didn't get the "wow" I had got from the snorkel and filter cover mods. low-end acceleration and mid-range seemed a bit boring. I went back to the NBZT needles and this seemed to improve things a lot. However, WOT still doesn’t pull that hard, any more than it did before, actually pulls better at 3/4 throttle than WOT, both before and after baffle, probably a sign the mains aren't right, and I should probably get some 130s or 135s to see if that improves things. I also have a suspicion that low end grunt - pulling in 5th at 40mph - is sightly worse than before, but again could be imagination.

So the bike is definitely way better than when I bought it, but I think mostly because of the snorkel and filter carve, rather than from the baffle removal, the gains from which are probably only detectable with a dyno. That said I’ll run with it. Wasn’t too hard so if I ever want to put it back I could, but again I don’t think it makes that much difference. even looking at the TTP site, their dyno results show the biggest gain with the breathe, the baffle removal only giving slightly better results again. I do think I am approaching the realm of race tuning rather than optimizing for every day use. Also the TORs must be a limiting factor to some degree. They are straight-through, but I believe a bit more constricting than other more open pipes.

Still, all good fun - interesting to play with these things and see what happens! :) I know my valves are out of spec, and due for 12,000 adjustment in about 1k, which knowing me is about 2 weeks away lol. That may also have an effect.

Anyone thinking about doing any of this, I can't recommend pulling the snorkel and opening up the filter cover enough. Baffle removal remains to be seen if it was really worth it.

Just my 2cents / pence, depending on your atlantic orientation.... :)

Nick
 
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#2 ·
maybe when you get accustomed to the 138's you could switch to 130. should make a bigger diff that you could feel rather than a small change. after that you may want to try 140's with 40 pilot, no shim. all of this should provide hours of fun. when i make changes i like to run 2 or 3 tanks of fuel, check the millage and keep a record so i don't do the same thing over.
 
#3 ·
Good advice, thanks. Definitely worth persevering and trying different combo's.

N
 
#5 · (Edited)
I have almost the same setup, I don't think I went near that high on the mains. I'm thinking 125's but don't recall as it's been a while.

and I just shimmed the stock needles. I can say it pulls like a rocket to redline though so the mains are spot on. Starts easy and midrange is crisp, very little to no backfiring on decel.

oh, and I bought those NB air screws, that have the thumb wheel for adjust. so so so much easier to tweak.

I have the 42's and about 1 turn. I also removed the carb heaters.
 
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