B&W 150 airfilter/exhaust upgrades

[jbignell]

Does anyone know of a good combination airfilter/exhaust upgrade for the B&W150?  I've searched around a bunch and found a few decent looking exhuasts (no idea how they actually perform or sound) but very little on air filters - filter boxes etc.  While I'm at it, does anyone know the compatibility of GY6 150 parts to the B&W150? 

Thanks

JB

[MotoRandy123]

I found the airbox on my Yager is very well designed but the tube letting air into the
dirty side reduces in the center and is fairly small in inner diameter, it also has a 90
degree stub pipe inside the box (for noise). I removed the 90 degree hose and replaced
the with external one with a hose from my vented heater for more flow. The output
side of the airbox goes into a bellmouth which it the termination of a tuned pipe.

A scooter is a bit different from a motorcycle in that it has a limited rev range. The tuned
pipe can gain 10% over even a pod filter so I left that part alone (for now, it is tuned to
the torque peak, you could try it 2" shorter to tune to the power peak...).

Here's a picture of the new pipe going in;


Here's the bell mouth;


This is the tuned pipe with possible tuning;


This keeps it fairly quiet but revs smoothly with no delay...

If you get a muffler try to find one with a long headpipe. They are generally too short to tune correctly.
Here's one that works well;

[jbignell]

Thanks for the information.  I've since pulled my airbox off and on the B&W it appears very restricted.  Inside the airbox there is only a small opening from the initial intake pipe and allows only a small amount of air to contact the air filter.  I drilled holes all along the inside tube in the airbox to allow more air to contact the air filter.  It's winter here, and although temps have risen sharply to be at a comfortable riding level, my scoot is uninsured so I haven't been able to test the affects of drilling the air box.  It does run smoothly and revs through the rpm range with no hesitation and no noticeable difference in sound. 

The biggest restriction, as you have pointed out, but as it applies to the B&W is the small initial intake tube diameter.  I don't know the actual specs but for comparison sake it visibly appears to have a 1" pipe going into a 1.5" - 1.75" air box hole.  This afternoon I'm going to dive into this issue and see if I can't make something work that will not restrict air flow. 

I'm wondering though, if I do manage to achieve the full breathing potential of the air box would there be a necessity to re-jet or otherwise tune the carb? 

JB

[MotoRandy123]

 Well mine is fuel injected, though it might lean out a little it's probably not enough to
change the mix by much. If you got a lot more air into the motor I'd look for a way to
add some fuel. If your's has a carb some tweaking might help even without any mods.
Most vehicles are a bit lean from the factory these days.

 If you look at the tuning pic above that is the stock tube going in. The inside diameter
is probably 1" but it also has a connector that reduces it more in the middle. The new
tube is probably 1 1/4" and the rippled tube allows more flow. A smooth 1" tube will flow
about 1/2", a rippled one will flow 3/4" as drag on the walls is reduced.

 I think it is just enough so the motor doesn't starve for air during quick acceleration.
It's difficult to add a new input and have it seal properly on the organic shape of the airbox.

 

[jbignell]

So I tore into my B&W with vigor and found that the air box input winds its way around several corners and ends up just under the middle floor boards in a medium sized white plastic box, with an even smaller air inlet hole that is shielded by another big plastic flap.  Many couplings, many 90 degree turns, many size reductions.  I haven't got a camera at present that I can find ( there are three in the house, but between my wife and the cat, who knows where they've gone) or else I'd show a few pictures of what I'm explaining.  I'm thinking now that I can fabricate some form of intake that would seriously better this system, kind of a ram-air intake, utilizing the screened sides of the scoot just behind where your feet go.  There is a nice screen for styling, but behind it there is a plastic panel that renders the screen totally useless (like a hood scoop on recent model american cars).  The panel is screwed in place, so It makes possible the removal of the screen and it's adoption for use as a template to construct a more useful, derestricted yet stock looking air-filter. 

Also, behind the air filter there is that 90 degree piece of pipe on the B&W that with very slight pressure pops out of place. 

JB

[MotoRandy123]

  Wow it's funny they routed it like that. Packaging is tricky on scoots. My scoot has smaller wheels
so there is a lot of storage under the seat. They hid the fuel tank under the floorboards, which is nice
except it's a little unnatural to raise your feet higher to clear it.

  I thought your air intake was over the CVT like most other bikes but I see it feeds forward through
the black tube. Get some pics and let me know your plans and maybe I can help. Reduceing restrictions
and right angles will defiantly help the bike to accelerate smoothly without holding back. Most are there
to kill the noise. Most gains will be on top which is perfect on a scoot. A bike might gain at the 120 MPH
redline, a scoot stays within a 3000 RPM range so gains all the time.

[MotoRandy123]

  Here's a chart to show you the tuning on the input. There are 3 harmonics with the 2nd being the strongest.
You measure from the bellmouth to the intake valve and tune according to the chart. 20" is 7000 RPM's on the
second harmonic. You can tune, like on the scoot, for a peak at 6500 and another at 8000 to gain intake power
over that range (one will be a lesser harmonic). 16" gives us 6500 and 9000 for peaks so would work well.



  What you need for this to work is a continuous tube with no significant diameter change along it's length. The throttle
body on my scoot doesn't change diameter so allows a nice long tuned intake. I'm not sure how the venturi in the carb
affects this...

 My scoot has a 20" or 21" tuned intake tube (from the factory) and it's tough to change it so I haven't messed with it yet.
I could shorten it but would need to move the airbox closer to the throttle body somehow. I might do some experiments
come spring.

[jbignell]

Thanks.  I haven't got pictures yet, maybe this coming weekend.  The scoot is kept at a garage away from where I live and access is a bit of a pain sometimes. 

I think I have, in theory, figured out how to route the intake properly using 2" ID tubing.  I've drawn crude pictures to help illustrate what I'm up to.  What I most like about what I'm proposing is that I can hack away and cut some holes etc, without destroying any of the factory intake hardware.  So if my attempt doesn't work I can change back to the stock set-up with no difficulty. 

A $2 pipe and a little plastic welding and the set-up will be done. 

Bear in mind this is all PRE-filter hose routing.  After the filter is as good as it will get for now or at least until the day comes when a flat slide carb arrives and I get more serious about tuning. 

Thanks for the information.  I'll get proper pictures in time. 

JB

[wordslinger]

...that's bad-ass!!!...

[jbignell]

Sorry, it's taken some time to sort this out, work always gets in the way of good fun. Regardless, I've sorted out my cold air intake system and it only cost me $8! 

I've got some pictures of what I've done so far.  I am going to paint the hose black.  The last picture shows the factory intake hose that I replaced.  It was 15/16" inside diameter.  The hose I replaced it with is 1 9/16" inside diameter, with a gradual bend.  The scoot runs smoothly with the new set-up and has a pleasant intake "honk" sound when I get on the gas.  Some people may not like this, but I certainly do. 

I'm going to "enrichen" the fuel mixture a little to compensate for the increased air flow. 

I dig it.

JB

[MotoRandy123]

Looks good! I believe that is the first natural restriction to these scoots.
Mine is a touch louder at times too but not too bad. Might be why it's restricted - noise.

I tickled the air temp sensor so it thinks the air is 10 degrees colder to richen it up a little.
Not sure it does anything once it's warm but she seems to run smooth!

Here's the inside of my air intake point;


The hose sits in there loose and draws through these slots;


I wanted to make some sort of scoop and open up the slots some but I haven't come up with a good looking
soultion yet.

[jbignell]

What about enlarging the two holes into one big one with the same trapezoidal shape and put some expanded aluminum screen behind?

The B&W has a CV carb, although efficient, practical and easy to operate, sucks hugely for tuning.  Unless I'm missing something, there appears no way to enrich the fuel/air mix i.e. no c-clip on the needle to adjust one way or the other the fuel/air.  So, this carb has got to go and a flat slide or equivalent will be on order shortly.  The CV carb is covered in hoses that go all over the place.  I'm sure there is a reason for the whole mess, mainly emissions, but the way I see it I'm riding a scooter and not driving a V8, so no big deal if a little C02 escapes my little .15L engine. 

JB

 

[MotoRandy123]

  Well CV carbs are self correcting to some extent. We used to get the Dynojet carb kits,
they had jets and needles and sometimes a drill for the slide. Usually just accessing the
mix screw (and turning it out a turn or so) and going up 2 sizes on the low speed and
main jet would wake them up.

 I thought of cutting between the slots but want it to look finished. A better bet would be
some sort of scoop or something so it looks factory. The other possibility is to move it
behind the screen as seen here;