after market exhaust

 

I have a Yamaha V-Star 650 Classic, and was wondering how much of a
difference, it would make by purchasing an after market exhaust, and
rejetting it, with either a slip on or total exhaust system?

 


Want more power? Buy a bigger motorcycle.

Want to go really fast? Buy a motorcycle that's designed for high
speed sport touring or track days, instead of a cruiser.

If you look through the catalogs, you'll notice how damned expen$ive
aftermarket systems are and you may even conclude that exhaust systems
for cruisers mostly change the style of the bike.

You'd be lucky to get two or three more horsepower
out of an engine equipped with a loud aftermarket system.

Slip on cans don't do a thing for power, except maybe reduce it,
because a can with less restriction lets the heat out too fast.

The way modern sportbikes get a couple more horsepower out of an
engine with a titanium slip on can is to re-map the fuel injection
system. They make the low speed idle mixture a little richer and maybe
advance the ignition a few degrees at lower RPM.

What does the slip on have to do with the extra power?

Nothing.

Back in the mid-1980's, we could get 20 more horsepower out of a
GSXR-1100 by installing $500 worth of aftermarket carburetors and $500
worth of aftermarket exhaust system.

We changed the exhaust system and the carbs and added a $50 ignition
advancer to the GSXR-750's to help the mid range power band.

We wound up with race bikes that were too loud for the street and
weren't much good for cruising the boulevard.

About the cheapest and best recommendation I can make for tweaking the
carburetors is to tweak the carburetors as they came jetted from the
factory.

Screw re-jetting your carbs. Dynojet kits are for suckers who think
they will get more low end power by putting bigger main jets into the
carburetors.

That's just plain stupid. Dynojet makes tons of money off of stupid
riders.

Dynojet makes special jet needles that have a radical taper at the end
so the carburetors will come onto the mainjets a little sooner. But
you really don't need radical needles any more than you need huge
oversized jets.

You're running down the highway most of the time using about 1/4 or
1/3 throttle.

The vacuum on top of the slide determines how high the slide will
rise.

The jet needles don't get pulled completely out of their holes so the
carbs come onto the main jets until the vacuum gets high enough to
raise the slides and that only happens when you're using full
throttle, which you rarely do.

Constant vacuum carburetors like your Yamaha has run off the idle jets
95% of the time, so tuning the idle mixture screws is what makes the
engine run better.

Find the EPA anti-tamper plugs on the carburetors and very carefully
drill a pilot hole in the brass plugs.

The EPA plugs may be on top of the carbs or underneath the carbs, just
foward of the float bowls.

Drill the pilot holes very carefully so you don't hit the end of the
idle mixture screws with the drill.

Then screw a sheet metal screw into the plugs and pull them out with a
pair of pliers.

Then you can turn the idle screws counterclockwise about 1/8th or
1/4th of a turn to get quicker starts, faster warm ups and better
throttle response.

The idle screws only control idle fuel/air mixture coming out of one
hole. There are three more transition holes near the edge of the
throttle butterfly.

Getting the idle mixture screws set just right involves
opening them just far enough so you don't need to turn the master idle
knob to raise the idle speed back to factory spec.

If you have to do that, you've turned the idle screws too far out and
the throttle butterflies will uncover the
three transition ports prematurely and the engine won't idle down
after you blip the throttle.

 


 Damned well said FB...all of it.

 


Wow. That's called schoolin'. Great advice.

 

FB

thank you very much for the info