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What can you really expect from mods?
- From: "Tom Brown" <tbrown@xxxxxxxxxxx>
- Date: Mon, 26 Nov 2007 16:47:53 -0600
- Subject: What can you really expect from mods?
The GS tubes work great on an RT or RS. You have to mind the little
alignment mark on the tube. Make sure it lines up with the little seem on
the back of the throttle body. Get the rotation a little wrong and your
bike will run rough. This gives smoother lows and stronger mids at the
expense of highs. Peak HP drops about 2 HP, but torque is better and it
helps with surging about 25%.
Increasing valve lash is a bummer in my opinion. The valve noise is
ridiculous. Mileage suffers as well as performance. I did not notice any
plusses with this one.
I wouldn't advance the timing. The late Bob Lencini did that and also
advocated using mid-grade gas because it was "fresher" than premium in most
cases. That guy was a peach of a fellow, but he eventually blew a piston by
doing this. Bad gas plus advanced timing equals detonation. If you tour
the bike and don't always have control over the quality of the fuel that
goes in it, I'd stay away from changing the timing settings from factory.
I had pretty good luck with one of the older Fuel Nanny setups. You have
to unhook the 02 sensor, then you jump the cat code box in a prescribed way
to give a consistently lean fuel curve. I think it's one from the 850 boxer
or something. Then you hook up the fuel Nanny to a ground and one of your
FI leads. It extends the time that the fuel injectors squirt and it's
adjustable for high RPM and low RPM. You can set it for performance and
get wheelies, but it really sucks gas if you do that. I set it just rich
enough to avoid surging and had no problems with it save a broken wire on
one trip which I was able to diagnose and fix on the road.
K&N filters do nothing on RTs and RSs unless you make cuts in the air box to
let more air in. The air filter is not the limiting factor in the boxer air
stream, it's the trumpet nozzle thing. Changing this air intake to let in
more air can confuse the computer and cause lean running too, so stay away
0=0 procedure is good to do if your bike surges. It will not give more
performance, but it cuts surging about in half if you do it correctly.
Critical to a good throttle synch is a really perfect valve adjustment. You
must get this right or you will have "sweet spots" and "rough spots" in the
behavior of the bike at different RPMs if the valves are set accurately
side-to-side, you won't be trying to correct that imbalance with the
throttles. The idea is to get the throttle butterflies to open exactly the
same on both sides. If there's an offset for a bad valve adjustment, the
different angles of the throttle bodies will let in different amounts of air
(from each other) at different throttle plate angles. You're bike will be
smooth at 4,000 but not smooth at 3,000 (as an example).
While on a long trip, I discovered that I could fine tune the synch through
the hole in the right side of the RT fairing. My valves were a little off,
so I moved the right air screw to make the bike smooth at my cruising RPM,
which was near 4,000. It suffered smoothness a bit at lower RPMs, but I was
out west traveling long distance and was spending very little time around
town. With the right screwdriver, you can do this while running the bike
down the road, or you can just pull off, make a small adjustment and try it
for 30 minutes or so, then pull off and try again until it's nice.
>I've been reading about a variety of low buck things to do that will
>improve midrange, and it seems that advancing static advance 2-3
>degrees, installing the GS intake tracts, and increasing valve lash a
>bit optimize low and midrange performance. I'll not be replacing the
>exhaust or doing anything to extend torque above 6000 RPM so this work
>seems to be the thing to do. Who has done these things, and what
>tangible difference did these changes make? This sounds like something
>I could do over Christmas (If I get the manual) if there are real
>benefits to it.
What bike? I recall that R1xxxR's have the GS tubes alreads.