Airbox questions.

D

Deano

Two Stroke
I have installed a K&N filter, dropped the snorkel and made the adjustments to the carby based on that.
If I now want to pull the restrictor plate and open out the other side of the box, will this mean the mains will need changing again and I do more tuning?

The Thunderbike mechanic told me that by doing all these changes to our airboxes we loose some economy. He said that a certain amount of vapour is caught in the box and then reused. By removing the box or opening it up, he believes it will effect fuel usage noticably. So, to those of you that have done this full modification, has it affected the economy much?
I imagine most of us are not too worried about a slightly more expensive run, if the power is there to use in a real way.
 
PieMan

PieMan

Two Stroke
I'm using no more fuel now with pods than I was with an airbox. Your right hand has more to do with economy than anything else.
 
W

wiseanhyzer

Two Stroke
I've done just that, open the other end of the airbox and pulled the restictor plate. I get 43mpg/69kmpg (us gallon) in town. I get slightly better if I'm out on longer rides. That's the same fuel rate I was getting before I opened both ends of the airbox.

And yes, you'll need to re-jet and adjust the mixture screw a little. I'm using Thruxton needles, 2.5 turns, 135 main jets and stock idle jets. Runs great! Go for it.
 
D

Deano

Two Stroke
wiseanhyzer said:
I've done just that, open the other end of the airbox and pulled the restictor plate. I get 43mpg/69kmpg (us gallon) in town. I get slightly better if I'm out on longer rides. That's the same fuel rate I was getting before I opened both ends of the airbox.

And yes, you'll need to re-jet and adjust the mixture screw a little. I'm using Thruxton needles, 2.5 turns, 135 main jets and stock idle jets. Runs great! Go for it.
Click to expand...

Thanks. I want to remove the plate and open the end as you have suggested. When I first removed the snorkel and installed the K&N we set it up as 118 mains and 1 washer needle and adjusted the carb's. Been going good, with a dyno of 51.52 at the back wheel.
Here's the thing, I live quite remote and to have any work done, it is organising a trip away and stay over to do it. I am scheduled to go there again in a few months, but I am wondering what will happen if I do the work suggested now and try to run it up there on the settings I have so far. Is the bike likely to run badly, can I do it damage by running it too lean or rich for the ride.
 
W

wiseanhyzer

Two Stroke
I would think the bike would run badly. I would not run the bike after pulling the restrictor plate and cutting the other side open without changing jets and adjusting the mixture screw. It would be too lean to be any good.

Changing the jets and adjusting the mixture is not too difficult, but you do need the right tools. It can be done at home if you're willing to do the work yourself.
 
FoothillRyder

FoothillRyder

Two Stroke
wiseanhyzer said:
I would think the bike would run badly. I would not run the bike after pulling the restrictor plate and cutting the other side open without changing jets and adjusting the mixture screw. It would be too lean to be any good.

Changing the jets and adjusting the mixture is not too difficult, but you do need the right tools. It can be done at home if you're willing to do the work yourself.
Click to expand...

I agree with the comment about how the bike would run without a jetting change; but now I'm gonna ask (because I can)...

Does one have to remove the exhaust system to get to that right side carb (for jetting work)? It looks like it might be possible; but I would hate to get into and find that I did - after all - have to remove it. For me it isn't a major thing, since I'll be replacing much of the exhaust system anyway, and doing the jetting work (at least the first iteration) at the same time; but the question is still valid.

Anyone?
 
D

Deano

Two Stroke
Cheers guy's, I guess I will do airbox mod's once up there (if I can arrange it) or do them here and trailer the bike up. I was sent some awesome pic's of the airbox mod and how to do it, but
I was wondering if I will do the mod's or buy a removal kit (as aussie Dave has suggested to me)
 
W

wiseanhyzer

Two Stroke
FoothillRyder said:
Does one have to remove the exhaust system to get to that right side carb (for jetting work)?
Click to expand...


I don't remove the exhaust to change the jets. But I do remove the carbs from the rubbers and swing the bottom of the carbs to the left side of the bike so you're looking at the bottom of the carbs. Tie/zip tie the carbs up to the frame so you can easily get to the float bowls and use both hands. Change jets and adjust mixture screw and then put them back in place. It might be possible (if you have help with small hands) to get to the float bowls without swinging the carbs out to the left, but I've never been able to get in there easily. Not with the Scrambler high pipes on the right side.

Sorry I don't have a good picture handy. Also, this is just my 2 cents. Someone else may say otherwise.
 
W

wiseanhyzer

Two Stroke
Deano said:
Cheers guy's, I guess I will do airbox mod's once up there (if I can arrange it) or do them here and trailer the bike up. I was sent some awesome pic's of the airbox mod and how to do it, but
I was wondering if I will do the mod's or buy a removal kit (as aussie Dave has suggested to me)
Click to expand...

Yeah, think about doing that. I love the double opening air box mod but I'm going to ditch the box altogether and install pods now. Go all the way. :rock:
 
FoothillRyder

FoothillRyder

Two Stroke
wiseanhyzer said:
I don't remove the exhaust to change the jets. But I do remove the carbs from the rubbers and swing the bottom of the carbs to the left side of the bike so you're looking at the bottom of the carbs. Tie/zip tie the carbs up to the frame so you can easily get to the float bowls and use both hands. Change jets and adjust mixture screw and then put them back in place. It might be possible (if you have help with small hands) to get to the float bowls without swinging the carbs out to the left, but I've never been able to get in there easily. Not with the Scrambler high pipes on the right side.

Sorry I don't have a good picture handy. Also, this is just my 2 cents. Someone else may say otherwise.
Click to expand...

Excellent tip, and it does make sense. Trying to do anything properly when you cannot see what you're doing just invites a large mess (and rework). Thanks.
 
FoothillRyder

FoothillRyder

Two Stroke
wiseanhyzer said:
Yeah, think about doing that. I love the double opening air box mod but I'm going to ditch the box altogether and install pods now. Go all the way. :rock:
Click to expand...

I've considered that as well; but I'm not convinced the gains are worth the effort (yet). The airbox may offer intake 'resonance' benefits - perhaps related to fuel mileage (perhaps not) - that the pods don't provide.

Of course that might just be complete BS; but.... :D
 
sportyone

sportyone

Street Tracker
FoothillRyder said:
I've considered that as well; but I'm not convinced the gains are worth the effort (yet). The airbox may offer intake 'resonance' benefits - perhaps related to fuel mileage (perhaps not) - that the pods don't provide.

Of course that might just be complete BS; but.... :D
Click to expand...

well I've heard, if you remove the air box or chop it around, there is a big possibility that you will upset the vacuum produced within the box and the carb slides will not rise as quickly or smoothly as they should ? so why chop the box, if it's meant to be there ?
the box has designed with performance ratios by a computer & is there for a very good reason, as well as suppressing some noise too ! I've heard to that when tested on a dyno, many twins work better with free flowing pipes & a high flow filter, even with the snorkle left in ! :shh:
 
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FoothillRyder

FoothillRyder

Two Stroke
sportyone said:
well I've heard, if you remove the air box or chop it around, there is a big possibility that you will upset the vacuum produced within the box and the carb slides will not rise as quickly or smoothly as they should ? so why chop the box, if it's meant to be there ?
the box has designed with performance ratios by a computer & is there for a very good reason, as well as suppressing some noise too ! I've heard to that when tested on a dyno, many twins work better with free flowing pipes & a high flow filter, even with the snorkle left in ! :shh:
Click to expand...

I can be convinced to believe just about anything, as there is so much 'speculation' about what 'might' be true and otherwise. I'm going to take things one step at a time and try to do my own testing - without the benefit of a formal dyno, just my tired old butt.

I will say that my Thruxton with TORS and a K&N - with no rejetting - put out more than 62 rwhp. Fattened the mixture a bit based on some A/F measurements and it went up to more than 67. Just for reference, it was 53 and change to begin with.

I'm going to be creative with the exhaust, do my own thing, change the jetting as I 'feel' will be appropriate, and see what my butt says. :)

Oh... and I'll keep you guys posted with info and pics, maybe even a vid.
 
FoothillRyder

FoothillRyder

Two Stroke
ivar said:
The airbox on these bikes are not designed with performance in mind.

Lots of good info on the subject over at triumphrat.net , with dyno and a/f graphs for various configurations..:
http://www.triumphrat.net/twins-tec...ning-modifications-and-so-on.html#post1132928
Click to expand...

Kindly allow me to make a small correction - the airbox on these bikes is not designed with horsepower in mind. 'Performance' is too broad a category IMHO. I'd already been through most of the great info at the Rat forum, so nothing new there; but there are plenty of good arguments in favor of keeping the airbox. My conclusion based on what I read was that careful modification of the airbox resulted in power that was essentially equal to that produced without an airbox. Are there differences? Sure.

Like I said, I'm gonna make my choices and test with the ol' butt dyno - and keep you wankers posted. :D
 
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