Restoring Airbox

[gareth]

Currently running ZRX1100 carbs with Mikes Oval pods. I was curious what would happen if I put the airbox back on. So, since I gutted the original airbox to fit the pods, I picked one up on Ebay for 99c. I fitted a new K&N, and spent ages trying to install the carbs/ box. The spacing on the ZRX carbs is slightly different from stock and the airbox boots were a bit stiff so I got very frustrated. Eventually, I attached the airbox to the carbs OFF the bike and then folded the entire assembly, snorkel and all, back into the bike and onto the intake boots. I had to remove the battery and top airbox bracket, but it was WAY easier this way. The carbs are a little shorter front to back than stock carbs and the side covers show a gap between the chrome trim and the edge of the covers; might have to do something about that at some point if this Revert-to-Stock Mod is a keeper.
Predictably, the bike behaved more smootly off idle and low rpm. Choked off at 4.5k with a big stutter as it seemed to go way rich. The carbs were jetted large for much more intake air with the pods... Plugs sootier on the metal ring, porcelain OK.
SO, at some point in the next couple of days, I will drill the airbox out and see if that helps.
I really just wanted to see if the big velocity stacks on the original airbox would have any effect. With the pods, the power came on "all of a sudden" with big lurches at about 5k or so. But this was unpredictable, and I thought that it might have something to do with the carb slides not acting "together" at once. But I dunno, really. Anyone got opinions on what the velocity stacks are actually supposed to accomplish and what I might expect in restoring them..?

[cywelchjr]

Currently running ZRX1100 carbs with Mikes Oval pods. I was curious what would happen if I put the airbox back on. So, since I gutted the original airbox to fit the pods, I picked one up on Ebay for 99c. I fitted a new K&N, and spent ages trying to install the carbs/ box. The spacing on the ZRX carbs is slightly different from stock and the airbox boots were a bit stiff so I got very frustrated. Eventually, I attached the airbox to the carbs OFF the bike and then folded the entire assembly, snorkel and all, back into the bike and onto the intake boots. I had to remove the battery and top airbox bracket, but it was WAY easier this way. The carbs are a little shorter front to back than stock carbs and the side covers show a gap between the chrome trim and the edge of the covers; might have to do something about that at some point if this Revert-to-Stock Mod is a keeper.
Predictably, the bike behaved more smootly off idle and low rpm. Choked off at 4.5k with a big stutter as it seemed to go way rich. The carbs were jetted large for much more intake air with the pods... Plugs sootier on the metal ring, porcelain OK.
SO, at some point in the next couple of days, I will drill the airbox out and see if that helps.
I really just wanted to see if the big velocity stacks on the original airbox would have any effect. With the pods, the power came on "all of a sudden" with big lurches at about 5k or so. But this was unpredictable, and I thought that it might have something to do with the carb slides not acting "together" at once. But I dunno, really. Anyone got opinions on what the velocity stacks are actually supposed to accomplish and what I might expect in restoring them..?

My understanding is that they smooth the airflow before it hits the carbs. With pods you tend to have more turbulence when the air hits the slides, so just pods with velocity stacks may help as well. The other thing the airbox SEEMS to do is provide a SLIGHT scavenging affect on the crankcase. As to whether this is significant, I cannot say, but just looking at the design, at least at higher flow rates. It also on the older carbs gives a place for the vent lines for the carbs to hook to that is to filtered air (not something I think is really significant other than it keeps a LITTLE of the vapors from getting into the air (yeah right)).

[petejw]

Hi Gareth,
I was running the zrx carbs with pods,
they do run much better with an air box,
due to the vent tubes in the top of the carbs,
from memory the main jets were 130 or 140,
and the needle was raised by a thin washer,
i cant remember what the pilots were off hand.

what jets are u running atm?

[gareth]

What I'm most curious about is just how much I have to cut into the airbox to flow the same amount as four pods, but including whatever advantage the stacks might allow... I have a jardine 4-2 spaghetti system with supertrapp mufflers..I can adjust the exhaust back-pressure by messing with the disc sytem.
I think the next step might be a data-logging O2 wide band set-up.
This would at least give more data. If not more info...the SF has an 1100cc motor, 200cc bigger than my first car, and I can't understand why everytime I twist the throttle, it doesn't practically launch me into orbit, power-weight wise.. I had a Fiat 850 coupe car, with a 903cc motor, that could do 75mph with six college students crammed into it. WTF.
I'm getting pretty tired of subjective butt-dyno nonsense, especially when an alternative has been available since Bosch came up with the wideband O2 sensor... I can guess that the system is running rich/lean but really that's as far as it goes/
It might be time to splurge...
As the datalogging technology becomes cheaper and more widespread, maybe we can finally find some way of posting realtime mod results in lambda terms that don't require high-cost dyno time. Eventually, maybe, there might be a way that the forum can post actual graphs from stock exhausts, alternative carbs and muffler systems, and finally get close to what this 1100cc engine is truly capable of.
Then one can hope that the rider has the skill to make the best use of the info..

[natemoen]

What I'm most curious about is just how much I have to cut into the airbox to flow the same amount as four pods, but including whatever advantage the stacks might allow... I have a jardine 4-2 spaghetti system with supertrapp mufflers..I can adjust the exhaust back-pressure by messing with the disc sytem.
I think the next step might be a data-logging O2 wide band set-up.
This would at least give more data. If not more info...the SF has an 1100cc motor, 200cc bigger than my first car, and I can't understand why everytime I twist the throttle, it doesn't practically launch me into orbit, power-weight wise.. I had a Fiat 850 coupe car, with a 903cc motor, that could do 75mph with six college students crammed into it. WTF.
I'm getting pretty tired of subjective butt-dyno nonsense, especially when an alternative has been available since Bosch came up with the wideband O2 sensor... I can guess that the system is running rich/lean but really that's as far as it goes/
It might be time to splurge...
As the datalogging technology becomes cheaper and more widespread, maybe we can finally find some way of posting realtime mod results in lambda terms that don't require high-cost dyno time. Eventually, maybe, there might be a way that the forum can post actual graphs from stock exhausts, alternative carbs and muffler systems, and finally get close to what this 1100cc engine is truly capable of.
Then one can hope that the rider has the skill to make the best use of the info..

I would like to give some data logging a try too but at the time I only have the original double walled headers and do not want to put bungs for the O2 sensors in those. Maybe I will see what I can do this winter and see if I can get ahold of a crappy set of undented rusty single wall headers to use. It would make tuning WAY easier instead of the current guess and test method.

[gareth]

Well today I drilled four 1/2" holes in the center of the airbox and it helped a bit. Later on I added four more. Which made things better. I am going to ride it around for a while like this and see if the newly oiled filter dries out a bit and becomes a bit less restrictive. The new airbox came with a fairly decent original filter which looked like it might be a better option but I stuck with the oiled K&N.
I might raise the needles on the weekend to lean up the mid-range and see what happens. Still happy with the performance up until 4k...bit iffy after that.

[XS1100_OEM4ME]

Oem

Yeah, the farther we get from OEM, the more questions/problems we have Drill it, cut it, change it and see if you can ever get it to run right again