Any alternative to that @#$% airbox?

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macx
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Any alternative to that @#$% airbox?

Post by macx »

Being I've had the back half of the bike apart "more than once"
lately, with trans & clutch work, I have found that the airbox is
the biggest hassle in the whole process. Just plain likes to argue
about coming out.

Seems I saw some time ago a setup that substituted some different
intake tubes and a small cone shaped filter on the end of each one
basically in the area where the airbox is now.

Anybody ever seen anything like this?

Even with just lubing input and clutch splines periodically, it would
be worth getting rid of that pesky airbox!

Those cone filters are widely available in different sizes, so the
intake tubes into the TB's would be the make or break in that
scenario.

BTW I'd never use a filter that had to be oiled, they've been proven
in controlled tests to allow more grit into the engine. There is one
brand that doesn't require oiling and does a good job filtering. AEM
Have one on my hot rod and one on my suv. They make cone filters,
too.
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Re: Any alternative to that @#$% airbox?

Post by AirForceDirt »

Boxermania's 1150R had the airbox removed. He'd be the best one to ask about this. I'd like to do it just for the looks and because I want to put a storage box of some flavor in it's spot.
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Re: Any alternative to that @#$% airbox?

Post by iowabeakster »

What do you do with the PCV valve and temp sensor when you use those cone filters?
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Re: Any alternative to that @#$% airbox?

Post by boxermania »

I did a lot of experimenting both off and on the dyno with fuel, exhaust and air mods. The stock airbox has been fitted within the available confines and it's not the best design, also it clutters the area. That being said the least expensive mod that can be done to the bikes that will result in a more responsive and crispier engine is the following:

UNI filters, mine were slightly larger in diameter than the TB intake and either 4 or 5 inches long (will have to find the catalog number, $11 each). As a side note, the filters alone make the A/F ratio slightly leaner than stock, even with the limited adjustment of the Motronic 2.4. Since it was a week before BB II (2005) I chose to mask 50% of the filter element and read my new plugs and that satisfied the needs for the trip. The bike performed flawlessly and if anyone has any doubts, ask Chibbert when he and I were returning from the logging town on WV 15 back to the motel.

Once the airbox is out of the way one can easily replace the FPR 3.0 Bar with a 3.5 Bar from a prior generation K 1200 bike, $36 from Chicago BMW. This will get the fuel pressure at the injector from 44 psi, stock, to 51 psi, in essence injecting a bit more fuel to complement the added air at the intake (this is without maskng the filters above)

Advance ignition timing to the max, which works out to about 3 degrees. Ran Autolite 8923 plugs gapped at .032" and ran any gas 89 octane. Mileage stayed pretty much around 44/46 mpg and the bike ran GREAT!!!!!

http://www.r1150r.net/pics/user_rides/boxermania1.jpg

The engine vent hose (there is no PVC) was routed upwards from the air box fitting to the tank side support and fitted with a common 1/2" motorcycle crankcase vent filter. The intake air temperature sensor was removed from the airbox and positioned in the horizontal plane on the left sub frame tube. I don't know if the pics can still be accessed on the old photo hosting site, but Cyclerob took some pics of the setup at BB II.
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Re: Any alternative to that @#$% airbox? EDITED

Post by macx »

Now THAT's a neat looking setup, and obviously well researched so
that it runs properly!

Thanks so much!

I can see the next mod to my bike "from here" :D

Found the site

http://www.unifilter.com/

Just wondering - it appears from that (very nice looking!) picture
of your setup that there may be room for a short tube between the
TB and the filter, just thinking about a possible benefit from
straightening out the airflow going into the TB & reducing turbulence.

I know that's a big deal on efi hot rods, but of course that's also
with a mass air meter.

The OD of the TB flange appears to be 2-1/4". There are filters
available with both 2-1/4 & 2-1/2 ID flanges, with all the other
dimensions of both filters the same. That would allow
room for a short 2-1/4 ID tube of some sort that, if the tube
mat'l was 1/8" thick, would just fit nicely inside the 2-1/2" ID
filter.

Have you ever thought of replacing the nylon fuel lines
with efi hose & clamps? Esp with the higher fuel pressure?
I've read some posts it may have been on AdvRider where
some folks experienced cracks in those lines,
or leaks at the connections, and replaced with efi hose.
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Re: Any alternative to that @#$% airbox?

Post by CycleRob »

Attaching Uni filters directly to the TB is not good for the power curve. Doing so usually creates a big dip in the power curve at lower RPM's where most of your riding is. At least use the stock intake tubes and maybe the velocity horn inside the airbox.

After DynoJet dyno testing hundreds of bikes over a 9 year period, we found that removing the stock airbox or "modifying" it with drilled holes or large cut off openings always harms some portion of the power curve. You kill off some very expensive rocket science that utilizes sound waves and the dynamics of the pulsating intake pressure waves to create good airflow while snuffing excess noise.. At the same time, the little bit of "no airbox" extra power that may be generated is so close to redline it becomes an unworthy sacrifice. Carburetted bikes were especially harmed as the smaller intake back pressure affected the CV slide height, lift rate plus the slide needle and main jet fuel mixtures. A Honda VFR-750, Suzuki SV-650, Kawasaki 500 Ninja and a Ducati 900-S all come to mind because of owners that either modified or removed the stock airboxes and lost power somewhere within the most used 3K--6K RPM range. Without the stock airbox, good fitting earplugs are absolutely required to ride those bikes. The high sound wave amplitude intake roar generated at full throttle is painfully damaging to your ear drums.

EFI bikes are less harmed with airbox removal because the fuel injected bike's engine does not depend on a small airbox generated intake vacuum to control the fuel mixture. It is best to leave the airbox in place, and look for extra power or storage space with some other bright idea.

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Re: Any alternative to that @#$% airbox?

Post by ASQTec »

CycleRob wrote:Attaching Uni filters directly to the TB is not good for the power curve... It is best to leave the airbox in place, and look for extra power or storage space with some other bright idea.
Good advice.
I did this with my old (carbureted) Guzzi SPII. It looked awesome, and made the intake sound like a small block Chevy with a Quadrajet! Unforunately, the engine became anemic below 3000 RPM's. Back went the air box. At that point, I came to realize that there is a threshold at which too much spare time begins to backslide into counterproductivity and money wasting. Wish I learned that lesson when I was in my 20's.
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Re: Any alternative to that @#$% airbox?

Post by Ric »

CycleRob wrote:Attaching Uni filters directly to the TB is not good for the power curve. Doing so usually creates a big dip in the power curve at lower RPM's where most of your riding is. At least use the stock intake tubes and maybe the velocity horn inside the airbox.

After DynoJet dyno testing hundreds of bikes over a 9 year period, we found that removing the stock airbox or "modifying" it with drilled holes or large cut off openings always harms some portion of the power curve. You kill off some very expensive rocket science that utilizes sound waves and the dynamics of the pulsating intake pressure waves to create good airflow while snuffing excess noise.. At the same time, the little bit of "no airbox" extra power that may be generated is so close to redline it becomes an unworthy sacrifice. Carburetted bikes were especially harmed as the smaller intake back pressure affected the CV slide height, lift rate plus the slide needle and main jet fuel mixtures. A Honda VFR-750, Suzuki SV-650, Kawasaki 500 Ninja and a Ducati 900-S all come to mind because of owners that either modified or removed the stock airboxes and lost power somewhere within the most used 3K--6K RPM range. Without the stock airbox, good fitting earplugs are absolutely required to ride those bikes. The high sound wave amplitude intake roar generated at full throttle is painfully damaging to your ear drums. EFI bikes are less harmed with airbox removal because the fuel injected bike's engine does not depend on a small airbox generated intake vacuum to control the fuel mixture. It is best to leave the airbox in place, and look for extra power or storage space with some other bright idea.

.
Anytime you provide more air you have to rejet carb bikes and check the engine controller on FI bikes. (Among many other bikes) I owned an 01 SV (normally aspirated) and went from 67 to 73 RWHP by installing a new header/pipe system, desnorkling the airbox and REJETTING the carbs. Both power curve & torque curve came in quicker down low, were smoother than stock across the rpm range and finished higher. That did come from many many dyno runs testing various combinations of air filters, filter mods, and jets.

No. You can't just go and drill holes in your air box ! You can't modify like this unless you do a lot of dyno runs or use someone elses dyno work on an exact same bike.

As for ear damaging sound...., you hear a bit of growl from the intake but it's low level and you'll forget about it after the first mile or two.
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Re: Any alternative to that @#$% airbox?

Post by boxermania »

CycleRob and I are extremely good friends, that being said, we don't have to agree on everything. His post dwells primarily with carbureted bikes, which by just removing the air box you can barely get them to rev up unless the idle and midrange jets are increased in size, FI bikes are a different breed.

As Ric indicates more air, added fuel and a less restrictive exhaust equates to added horsepower. Likewise on the other hand there might be a slight loss in torque down low, except that this is masked by the ability of the engine to rev up faster. By the same token, when have we had issues of torque down low on our bikes, with 2 cylinders displacing just under 600 cc each.

Like I said many times before, I respect everyone's opinion and my philosophy is to each it's own. I enjoy the "state of flux" with my bikes until a reach what I consider a happy medium and then I'm done.

In this case the question came up and I chose to share my experienece........... 8) 8) 8)
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Re: Any alternative to that @#$% airbox?

Post by Ric »

I was agreeing with CycleRob....just expanding on his point that you can't just modify the air box....other issues have to be addressed...namely your air/fuel ratio but also air streamline flow too.

Well...I wasn't agreeing with him on the sound issue ;)
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Re: Any alternative to that @#$% airbox?

Post by macx »

Being I've got my airbox out at the moment, I took a flashlight and
looked in thru the filter grid, and down the intake tubes, just for
curiosity sake to see how long the tubes are and if they are constant
diameter inside or whatever, both of which would impact the tuning
of the air flow and hence the torque curve, and also if the airbox
contains anything in the way of flow control or enhancement versus
just being an open plenum from which the intake tubes draw air.

I see the tubes are fairly long, extending well into the airbox plenum,
which aids building low & mid range
torque versus short intake paths. Also the relatively small diameter
aids flow velocity which also aids low & mid range torque as it
contributes to better cylinder filling in those rpm ranges, at somewhat
of an expense to higher rpm flow volume.

With my hot rod & race engine tuning experience, I'd have to believe
that those intake tubes contribute the major portion of the torque
building in the low & mid rpm ranges, versus torque improvement
from what is basically just a relatively large open plenum in the
airbox.

I'd still like to try getting a pair of just the intake tubes and fix the
small filters to the ends of those. Being they're slightly curved,
I think they could be angled so that the intake ends & the individual
small filters end up one above the other in the space currently
occupied by the airbox.
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Re: Any alternative to that @#$% airbox?

Post by omg1010 »

As said earlier your bike will lose a lot of power when using these cone filters instead of the airbox. No matter whether you continue to use the intake tubes or not. On the intake side a certain volume (which is an ingenious process to calculate) is necessary. Same on the output side the exhaust system also needs a certain volume.

Hence I can only suggest to you to leave the box in place. Also don't drill any holes into the box as you will not increase the confined volume and thus only lose power.

Believe me here in Germany a lot has been experimented with the intake and the output and your best bet is to stick to the box.

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Re: Any alternative to that @#$% airbox?

Post by macx »

Thanks.

I will defer to experience and research.
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Re: Any alternative to that @#$% airbox?

Post by omg1010 »

My friend,

if you want to improve the output of your bike you have plenty of choice, a tuning chip, modification of the intake tubes, different mufflers, different pistons and camshafts, etc. But don't remove the airbox. That does not help at all. An improvement would be a mod (called "Volair") developed by a German oilhead aficionado. This is opening up the lower part of the airbox to fit in a larger airfilter ... This is the only mod (in conjunction with other mods) which makes sense. Even polishing the intake channels in your cylinder heads is apparently not a good idea - which some members of our local boxer-speed forum have found out ...

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Re: Any alternative to that @#$% airbox?

Post by boxermania »

Oliver

I just have two things to share with you

1) Have you tried similar mods and collected data to back up you claims.....don't think so!!!

2) You appear to be a smart man and I'm sure you understand that regarding IC engine design there are a miriad of parameters that have to be dealt with such as: available space, expected performance, expected economy, expected emissions, all within a budget. Ultimately the design is a compromise that leaves some element of performance on the table.

That being said, it has been proven and I can confirm that there is about an 8% to 10% performance improvement on ou ... components, nothing more to be had because of the dated air cooled design.
Last edited by boxermania on Tue Nov 16, 2010 12:22 pm, edited 1 time in total.
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Re: Any alternative to that @#$% airbox?

Post by CycleRob »

Eliminating the stock airbox has 1 very big disadvantage. The exposed filters get wet! Then they feed the motor soiled water and don't work so well. A very bad thing under way in a heavy rainstorm. They also do not work as well as the stock paper filter at providing clean air.

Drilling "breathing" holes in the airbox -or- going to external filters destroys the expensive engineering dynamics (Rocket Science) that was expertly designed into the limited available space. More power everywhere with external filters is elusive, even after making mainjet size and slide needle height adjustments needed that are indicated by the dyno curve results. That's right, by comparing the before/after curves and recognizing the type of faltering squiggly line the "after" curve has tells us if it's too rich or too lean. They look different. With carburetted bikes the RPM where the faltering squiggly line occurs defines whether it's the slide needle or the main jet. On EFI bikes the same lean/rich indication is not as well defined by changes in the power curves displayed, with smoother, smaller deviations that are almost always in the "too lean" direction. Even though closed loop EFI can compensate for some modifications, removing the airbox is not one of them. There will be big dip downs at lower/mid RPM's at low/mid throttle settings with a too lean power peak. That's where the airbox Rocket Science does it's magic while also being able to register increases nearly everywhere. Boxermania dealt with the lean fueling by cleverly changing the fuel pressure regulator to a higher pressure one intended for another BMW. That makes it richer everywhere in addition to the range it was needed. With or without utilizing the O2 sensor to control the fuel injection is another decision that requires being "decision right" even more important.

On carb or EFI bikes, changing to a free flowing aftermarket exhaust system often requires a length change (replacement) in the velocity stacks on the TB inlets to gain the most HP where you need it most, be it mid-range (street) or peak (racing). The newest SportBikes have computer controlled systems that do just that with their motorized velocity stack length changing mechanisms. Changes them on the fly with the RPM and the throttle opening. There are a lot of variables to consider and without an experienced dyno testing facility to dial it all in for you, you'll just be spending time/money to "look different" or "sound better" while making sacrifices you may not be measurably aware of. Loud volume power gains are usually just deception. I was always entertained by the surprised expressions of owners that just installed their new exhaust with glowing Power Commander fuel/ignition curves from the internet only to see there were some losses and little or no power gains from stock. Well over $1400 went POOF.

My R1150R mods consisted of 1st internally relieving the muffler internals (Pic 1, Pic 2, Pic 3) and it dyno tested at 80.3 rear wheel HP. Unfortunately, it was never dyno tested with the stock muffler by me. I later completely gutted all the internals (Pic 4), but being 720 miles away from the shops (free) in house dyno, it was not tested to confirm it improved the peak HP. I made the radical muffler mod anyway because the stock exhaust torque curve's increasing downturn at high RPM's did indicate either mild cams or too much exhaust back pressure.

My F800ST will remain stock, because I like the deep muffled sound the stock satin finish SS exhaust makes, heard even over the wind noise. There's plenty of passing power and it is well spread out. If you need more power, you prolly bought the wrong bike.

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Re: Any alternative to that @#$% airbox?

Post by macx »

I apologize for apparently starting somewhat of a row, here!

All I was looking for was an easier time of it getting at the
trans / clutch / splines by possibly substituting something for
the airbox and thus eliminating what is, for me, a major
aggravation. I've had plenty experience building & tuning high performance
cars, so understand intake and exhaust manifolding, tuning,
basic airflow, etc. and have modified the efi on my street car
significantly and it runs better than it did stock. I used the stock
mass air system as the base, matching it with a freer flowing yet
still good street torque type long runner intake. larger throttle body
and mass air meter, and larger inj's with a matching computer tune.
It's on an engine with 50 more cubes, a considerably bigger cam and freer
flowing heads, and with headers and a freer flowing exhaust.
It starts, idles, accelerates, and runs as good or better than the
stock motor did, has nearly 70 lbs more torque and 90 more hp
under full throttle on the dyno and still gets the same if not
1 mpg better fuel economy on the highway with 1 step
deeper gears and a high stall converter, all because it is a system
where all the components match targeting an ample mid range torque
curve for daily street use and I don't have to run it at 4k just to
get around without bogging.

On the bike I'm not concerned about a few hp one way or the other,
the only thing I'd not want is to significantly detract from mid range
torque so that it is noticeable from the seat of the pants, not just
on a dyno. This is far from a high performance bike, let alone a
race bike, so a few hp one way or the other makes no difference
to me whatsoever. I've already removed the muffler and substituted
just a short turndown because I like the sound, not because of any
power considerations. And there hasn't been any reduction in
throttle response in my 3k to 6k rpm range that I've noticed from
that. The chip was remov'd from my bike before I bought it,
which I understand is to somewhat alleviate the really lean US
Motronic configuration, so perhaps that helps make up for a little
added airflow without the muffler. I don't get any lower rpm
surging, or backfiring, and it seems to pull as well from low rpm
as it did before, so it must be within tolerable range.
In that there has been no change from when the muffler was on.

The only thing I might consider some day is the advanced cam
sprockets, which of course are said to improve the lower rpm
torque and throttle response. But I have swapped gears in my
roadster trans to the Enduro lower ratio 1st & 6th and, even with
the 2.62 FD I'm going to install this spring, will still have a 7%
lower 1st gear which will take care of starts. With that combo
I'll have my idea of a perfect 5th gear rpm range of between
3k & 3600 from the low 50's to near 65 mph for the 2 lane roads
I primarily drive on. So at that rpm range the engine has plenty
torque as is for enjoyable cruising.

Again, thanks to all for their input, I understand what you're saying
and know full well how easy it is to have mods end up detracting
from an engine's performance.

Oh, I don't ride in the rain. I very rarely go over about 30 miles
away from home, watch the weather, and avoid bad weather.
I ride for pleasure, and riding in the rain gives me no pleasure.
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Re: Any alternative to that @#$% airbox?

Post by AirForceDirt »

CycleRob wrote:
My R1150R mods consisted of 1st internally relieving the muffler internals and it dyno tested at 80.3 rear wheel HP.
Either you cutting breathing holes in the muffler did absolutely nothing to your power, or by replacing the cat and pipe with a freer flowing exhaust, I was able to increase power to nearly the exact same numbers. As I never put the bike on the dyno prior to removing the exhaust system, I have to basis for comparison. With the full remus system, My R turned the exact same rear wheel power.

Now, if the exhaust did nothing to change the power and torque output, its still much better than the factory exhaust if for no other reason than to remove around 20 pounds of dead weight.

While I agree that trying to make gobs of power with the 1150R motor is an exercise in futility, I do not believe for a second that every part on the bike was meticulously engineered to be the best the bike will ever be. Were that the truth, it wouldn't be 530 pounds wet and only crank out 80hp and about 80ft-lbs of torque while having a lottery of which clutch, transmission or final drive part is going to miraculously fail. I know that there is some serious engineering that went into the design and function of this bike, but to believe that there's no way anyone other than BMW can possibly improve on it is narrow-minded at best.

To the airbox and external filters: There are some downsides, as always, with any modifications to the bike. Sure, external air filters are exposed to the element's more, and they may let more water into the engine, but that's nothing that can't be overcome with some ingenuity and further modification.
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Re: Any alternative to that @#$% airbox?

Post by omg1010 »

boxermania wrote:Oliver

I just have two things to share with you

1) Have you tried similar mods and collected data to back up you claims.....don't think so!!!

2) You appear to be a smart man and I'm sure you understand that regarding IC engine design there are a miriad of parameters that have to be dealt with such as: available space, expected performance, expected economy, expected emissions, all within a budget. Ultimately the design is a compromise that leaves some element of performance on the table.

That being said, it has been proven and I can confirm that there is about an 8% to 10% performance improvement on ou ... components, nothing more to be had because of the dated air cooled design.
To 1) No I have not. I am just an enthusiast and greenhorn. But I am a member of the German boxer-speed-forum where a few gurus of the oilhead tuning scene contribute. One of the oldtimers in this business is Mr. Kurt Roesner who happens to be the organiser of a little event called "days of thunder" where a large number of oilhead adicts meet and get their bikes dynoed in his workshop. Kurt happens to be the exclusive distributor of Woessner pistons in Germany. To cut a long story short Kurt says the removal of the airbox and replacing same with the cone filters you don't gain anything. To the contrary. And I have no reason to question this as Kurt always dynoed his bikes and he is a known and proven expert in oilhead tuning ...

2) Thanks for the flowers. I may be smart when it comes to running my business but I am not an expert in oilhead tuning. I am just sharing knowledge from reliable sources (wome of which I have applied on my bike) and I am sure you will agree with me that the cradle of oilhead tuning is located in Germany. Yes I agree that there is a myriad or parameters need to be looked at. All I am saying is that replacing the airbox by coned air-filters is a dead-end street, no matter what other parameters you deal with at the same time.

But anyway the original question was if the airbox can be removed and replaced with other filters for the sake of easy accessibility of the rear frame. The answer is a clear yes but at the cost of a few horses.

You may want to have a look at this article which provides a good insight view. http://www.calsci.com/motorcycleinfo/Airboxes.html
Or this one http://www.thunderproducts.com/AirboxesDynotech.htm

Brgds
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Re: Any alternative to that @#$% airbox?

Post by boxermania »

Oliver

As mentioned before the intent is to share my experience, not to lock horns with applied theory and the compromises that need to be made, which is also part of my training.

Torque, leaving cam timing as a constant is based on the velocity of the air filling the cylinder at low engine speeds, the faster the velocity the higher the torque (within limits). For instance the transition tubes between the airbox and the TB on the GS models are slightly longer and of smaller diameter than those on the R variant to increase the torque down low. Some users have chosen to swap the GS intake tubes for those on their R's. In my case, I can tell you with some certainty that if there was any torque loss down low it was not noticeable at all (with the filter and fuel changes)

I finally found some of the pics to show...

Stock R1150R dyno results, do remember thatvthere are differences between dynos

http://r1150r.smugmug.com/Motorcycles/b ... vdyf/Large

Stock R1150GS (red traces, zoom in for better view), note the very slight difference in torque and HP

http://www.sjbmw.com/service.asp?s=charts&did=43

Location of the engine vent, using existing line to the airbox

http://r1150r.smugmug.com/Motorcycles/b ... ntKE/Large

Relocation of the test plug and air temperature sensor on top of the filter cover

http://r1150r.smugmug.com/Motorcycles/b ... U9ts/Large

Stock FPR (3.0 Bar) and upgraded one (3.5 Bar)

http://r1150r.smugmug.com/Motorcycles/b ... nbwq/Large

Masking of the filter before the addition of the higher FPR to insure A/F ratios remained in a desirable range

http://r1150r.smugmug.com/Motorcycles/b ... zrey/Large
Last edited by boxermania on Thu Nov 18, 2010 12:01 pm, edited 2 times in total.
Member #312
06 Suzuki Burgman 650 "state of flux"
79 CBX
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