Honda 919 Bafflectomy DRAFT
Coring the Stock Exhaust Canisters
Many
have sought an answer to the less than inspiring exhaust note heard at idle on
the stock 919. Still others have sought
a lower cost alternative to the $500-$700 slip-on options for the Honda Naked
Bike and now here both needs are answered for less than $50 in parts; here it is, Tested and Proven by many
9’r/Hornet owners we present, The
Bafflectomy Procedure!!
The
coring of the stock exhaust cans is one of several exhaust modification options
on the 9’r, it is known as at the Bafflectomy.
The Honda 919 is not the first exhaust system to be modified in this
manner, VFR owners have been using this method for years. Once cored, your exhausts will flow more
freely and have a different sound at idle and throughout the RPM range though a
modest performance improvement is possible, it is not the goal of this
process. A Power Commander 3
(http://www.dynojet.com/) is NOT required for this modification. Should you happen to already have a PC3 for
your 919/900, gains of 3-4hp have been reported after Dyno Tuning and
re-mapping of the ECU. Honda 919 Owners
have reported 15+ thousand miles with this mod in place and no ill effects. As always, if you don’t know what you’re
doing with FI tuning and a PC3, spend the $250 and have someone Dyno Tune your
bike for more power and improved throttle response.
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Proceed at your own risk, no warranties are expressed or implied, consult local laws and regulations as to the legality of exhaust system modification of road registered vehicles.
Parts List:
Safety Glasses
Ear Plugs
3/8" Drill
Vice Grips or Pliers
Magnet on a Stick
2”x2”x4” block of wood
1 1/4" Holesaw (bimetal)
2 1/8" Holesaw (bimetal )
1 ¼“ Deep Well ½” Drive Socket (alternatively a 3/4"x2ft threaded rod)
Hammer (or Mini-Sledge)
Round File or ½ Round File
Flat Head Screwdriver
Dremel
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Painter’s Tape
Newspaper
Hi-Temp Flat Black Paint
Overview:
Drill out the Inner Pipe
Drill the outer edge of the flange
Remove the newly created 'washer'
Use 1 of 2 methods to Remove Center Pipe
Use Round File to clean up edges of exhaust can
Use Dremel to finish the edges and prep for Paint
Spray Paint
Procedure:
Step 1 - Drill around the Center Pipe
Put on your safety glasses and with the stock
exhaust still in place on the bike, use the 1 ¼” Holesaw to the cut the end cap
of the exhaust around the perimeter of the Center Pipe. Try using the Ear Plugs at this point unless
you enjoy the sound of grating metal.
If the centering drill bit of the holesaw begins to hit the inside of
the center pipe, stop and remove the drill bit. Normally they can be removed by loosening an allen screw in the
holesaw adapter shaft.
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Step 2 - Drill the Outer Edge of the End Cap Flange
creating the “Washer”
With your safety glasses on, now use the 2 1/8”
Holesaw to cut the outer edge of the exhaust flange very near the inner edge of
the canister itself. When finished, you
will have a ‘washer’ shaped piece of the exhaust flange to remove. Remove the washer, use the Flat Head
Screwdriver if needed to pry the washer out.
While removing the washer, be careful not to bend the outer lip of the
exhaust can. If for some reason you
have trouble getting the washer out, it’s possible to leave it in but in so doing,
you will make the next step a bit more difficult because movement inside the
can will be limited.
Step 3 - Remove the Center Pipe
Here is where you earn your money, it can be over in 2 minutes or it can take 15, depends on your intensity, focus and the lb sledge you’re using. You will need to break loose a couple of tack welds at the base of the Center Pipe without damaging the lip of the stock exhaust canister. There are two easy methods for this part of the process;
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A) Place the Block of Wood over
the Center Pipe and then strike a dead blow with the Mini-Sledge/Hammer. You are attempting to break the tack welds
loose and it’s not likely to happen with a single blow so take your time and
give it a couple whacks. Then you want
to remove the Center Pipe but those annoying tack welds will be hindering the
progress so Insert a length of Threaded Rod (or the handle of a ½” Drive Socket
Wrench) into the Center Pipe and work the Center Pipe back and forth until the
welds break. You will hear them ‘snap’
when they give way. Then use some
pliers or even better, vice-grips to remove the center pipe. If the welds seem to be hung up on the inner
flange, use the long shanked Flat Head Screwdriver and a Hammer to bend back
the flange down inside the exhaust can where the Center Pipe is hanging
up. Don’t get messy, just enough to let
the mini-flanges on the center pipe pass thru.
B) Another method is to use a
1” socket from a ½ “ socket drive set, place it over the end of the center pipe
and strike a dead blow with the Mini-Sledge or Hammer. Same as above, a couple whacks is likely to
be required and even then, you’ll need to work the center pipe back and forth
to crack the tack welds. Leaving the 1”
socket on the end, you can attach a ½ “ drive extention and use that to
leverage the center pipe back and forth.
Once you feel the welds break, again, same as above, use the long
shanked Flat Head Screw driver and a Hammer to widen the flange down inside the
exhaust canister, this will ease the removal of the Center Pipe.
C) Use a long handled round
file to shape the inner port left exposed down in the can after the Center pipe
was removed. Not required, but a nice
finishing touch.
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Step 4 - Clean up the Inner Edges of the Exhaust
Canister
With your safety glasses on, Now use the Round File
or Half-Round File as needed to begin cleaning up the inner lip of the
canister. After removing most of the
rough material with the Round File, use a Dremel, or similar rotary tool, with
cutting tip to remove all burrs and excess material. Switch tips to the sandpaper wheel and prep the inner lip of the
Exhaust Can for paint. You can achieve
a nice finished edge using the File alone but using a Dremel or similar rotary
tool allows for a smoother finish.
Step 5 - Clean up Filings and Excess Material
Once you have completed the finish work and the
surface is prepared for paint, remove the filings and excess material that has
fallen down into the Exhaust Can itself.
Using the Magnet on a stick, drop the Magnet down into the Exhaust
Canister and collect filings from original cuts and edge finishing. If you are not satisfied that you have
removed all the material, take a few minutes to remove the rear cowl, loosen
the exhaust pipe clamp and remove the exhaust hangers. This will allow you to remove each can
individually for a thorough cleaning if desired. Many folks have reported satisfactory results without removing
the cans at this stage.
Step 6 - Paint
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Make sure the paint used in this step is Temperature rated
to 1200 degrees and it will likely say that it is safe for automotive exhaust systems
right on the can. Do not use the
lower rated 600 degree paint intended for other engine components such as intakes.
Using some painter’s tape and some newspaper, mask
the perimeter of the Exhaust Canister and provide enough coverage to protect
the tail section from any over-spray during the painting process. Spray the inner edge of the Exhaust Can
with the Hi Temp Exhaust Paint staying 10”-15” away, using a sweeping side to
side motion and repeat a half dozen times with 30 seconds drying time between
each coat. Let the Paint dry overnight.
Note: do NOT Paint the canister while the exhaust system is Hot, just
in case you were tempted to fire the bike up after Step 4 or 5
Step 6 - Test Ride
After completing your Bafflectomy Procedure, fire
the bike up and listen to the exhaust note at idle. You should notice a significantly different sound as compared to
the stock cans. Listen for any
rattling or buzziness that might indicate some excess material is still down
inside one or both of the canisters. If
all sounds well, go for a test ride and listen for the same thing again. If you have any doubts about material left
in the canisters, go ahead and remove them, dump them out and re-install, it’s
a 15 minute job start to finish. If you
have a persistent buzziness and you have checked for metal bits floating around
inside, you may have a loose weld or bent flange inside the can where the
Center Pipe attached, time for the Hammer and Screwdriver again.
Hints:
Use
Safety Glass when drilling and filing
Use
Ear Plugs while drilling
Remove cans from bike to ensure all filings are removed
During
step 3, be careful not to hit the outer lip of the canister
Options:
Drilling
the End Caps – the Swiss Cheese option
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SweepUK’s Drilled End Cap Solution:
I have started to drill out my
exhaust.
I originally did 8 x 7mm holes in a circle around the centre outlet, it sounded
O.K under acceleration but a bit too quiet at tickover with a pff pff sound.
I have now drilled out all of the centre bit (removing the outlet) as per the
piccies that "Ratdog" referred to on another forum. I am taking it
step further though:- my mate is going to make up a disc with a centre outlet
and braze or weld it in the end. This will still give the sound (hopefully) but
without the large open, and ugly, hole in the end of the exhaust. My mate, who
has made quite a few racing exhaust systems from scratch, thinks that it will be
better to do what we intend to do from a gas flow / back pulse point of view.
He used to race European F1 sidecars sucessfully and made up all his own
exhausts.
See my picture of where I am at so far (half way through !)
Info sourced from: http://www.motorush.com/forums/messageview.cfm?catid=93&threadid=29618&highlight_key=y&keyword1=stock%20exhaust
Pic courtesy of LMCCdoggy from the Nest
Sweepuk’s website: http://members.lycos.co.uk/sweepyuk/
Full
Baffle Removal – why stop at the end caps? Gut the whole thing!
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SweepUK’s Race-Can conversion:
Why stop at removing the Center Pipe? Why not just gut the entire can? Sweep did and shows you how over here: http://members.lycos.co.uk/sweepyuk/exhaust%20debaffle.htm
Check the website for full baffle removal, end cap removal and custom race can
creation with new end caps.
Credits:
Many have contributed to this effort
including but not limited to; PerfectPower, sweepUK, Sniper, motocycho, Don I.,
ratdog, Typhoonblue919, Skipman, wphistory and many others. For support goto Nakedbikes.net and post in
the forum.