|
Hop-Ups
for Dummies - Advanced
Honda 50 Tuning by Chad Baird and Stanton High
In
Honda 50 Carb Tuning,
Stanton High gave us a thorough view on what it takes to do
a basic carb tune. In this article, Stanton and Chad Baird
team up to bring you some advanced tuning techniques.
Chad:
Whether your bike is coughing sputtering and popping like
a three-pack-a-day smoker or you just not sure what it should
run like after you spend big bucks on an engine kit, Stanton
and I are going to try and help you “git er done”
and make that bike run like it should by using the dyno everyone
comes with from birth, the seat of your pants.
Here’s a list of stuff to be done to completely
tune a bike:
1. Adjust the valves
2. Clean the air filter
3. Change the oil
4. Select a main jet
5. Check the float height
6. Set the needle height
7. Select the pilot jet
8. Set the idle
Let's
start with step four for this article. We’ll cover 1-3
another time so we can get right to the meat of things now.
Step Four: Select a Main Jet
Scrounge up some masking tape. You need two pieces - one for
the throttle and one for the handlebar.
On your tape, mark out ¼ increments starting from zero
throttle opening. Stick one piece of tape on your throttle
and one on the handle bar. The zero position should match
up on both pieces of tape - as in zero throttle input. Keep
an eye on your tape increments and keep a mental note of where
the motor feels anemic.
Now,
warm up that motor and do some full throttle runs. The engine
should pull HARD all the way to redline and keep pulling to
the rev limiter. NO sputtering, surging or crapping out.
Lean/Rich
Test --- Try accelerating hard and letting
off the throttle, if it surges or power picks up after backing
off the throttle a little bit, your main is too small. If
your engine sputters on the way to full throttle your main
is too large. Ignore off idle symptoms until your main is
the correct size.
Step
Five: Check the Float Height
Refer to your manual for this one. If you have never messed
with this then it’s probably okay. Basically, you measure
from the base of the carb to the very top of the float without
compressing the float needle. You make the adjustment by bending
the tang found in the center of the float.
Stanton:
For the stock carb its 7/16". Carbs that come with bore
kits are almost always set correctly from the factory. If
you are doing big jumping it might get thrown off. Mine did
that :)
Step
Six: Set the Needle Height
Raising the needle enriches the mixture and lowering it leans
it out. This is the tricky part… normally you can leave
the needle in the stock position and shim it with a small
washer to raise the needle if you haven’t swapped out
the stock exhaust pipe. The needle basically meters fuel and
helps transition from your pilot circuit to your main. If
your bike is acting up from idle to the main jet, it’s
going to be here.
Step
Seven: Select the Pilot Jet
Warm up your engine. Set the idle to a higher rpm. Find the
air screw and turn it in until it seats lightly. Back it out
until the engine gets to it’s highest rpm and then turn
it in until the engine starts to miss.. Go back about a ¼
turn and it’s set. NOTE:
You will know if your pilot is too large if you have to turn
the air screw out more than three turns. Go one pilot size
smaller. Having too large of a pilot is one reason why plugs
get fouled.
Step
eight: Idle Adjustment - Back the idle screw out
until engine settles back down to a nice lope.
Some Extra Notes On Tuning:
Chad: Your base line is your stock setup but there
are steps that should be taken and not changed in order to
get consistent results. I hear the stock pipe is the best
for producing torque.
Stanton:
aftermarket pipes make more of a pop off the throttle but
drag the low rpm power down. In other words, the after market
pipes cater to a higher RPM range and bring the peak HP and
TQ higher into the power band.
Chad:
About Plug Chops (or plug reading the old
school way): This method isn't as good as it used to be because
of the unleaded fuel we use today, it could be very misleading.
Don't count on it.. This should be mentioned as an exception
and not a rule. It's good to keep clean plugs for max performance
anyway.
From past experience the best way to dial in a carb is to
change the main jet first and work your way down low. Especially
if you deviate from both the stock air cleaner and exhaust.
Otherwise your chasing symptoms right??
Contrary
to popular belief the main jet DOES affect low speed operation
as does needle height then float height and finally the slow
speed circuits; pilot and air screw. These circuits don't
work alone but transition smoothly into each other depending
on the desired end results.
About
the authors:
Chad Baird - My riding/wrenching obsession
started in the summer of 88-89. My Dad got me a used $50 Sears
minibike with a seized 4hp Tecumseh. I spent hours upon hours
in the garage hooking up throttle cables/linkages, kill switches,
changing tires, swapping engines and of course riding and
crashing. Dad would hand me a repair manual, show me how to
do something once (mostly how to use a tool) and then was
pretty much hands off except to yell at me about loosing his
tools. He would also cuss me out for taking off without making
the bike 100% ride-able or fixing something half-assed. So
that's basically how I learned, lot's a trial/error and getting
yelled at. heheh.. Now my whole life revolves around working
on, riding, talking about and teaching others who are interested
and even some who aren't, how to do the same.
Stanton High has ridden on wheels for as
long as he can remember. In 2003, he discovered the xr50 and
was instantly hooked. Recently, Stanton was in a bad accident
and half his body was burned. "It was hell," Stanton
recalls. But after four months and 13 surgeries later he got
back on the xr50 and is now riding harder than ever. These
days Stanton rides as much as he can and is looking for a
job in a machine shop. You can check out some of Stanton's
riding in the Rider Gallery.
Related
Links containing How-tos:
Honda
50 Carb Tuning
Carb Theory 101
Eric
Gorr's Carb Tuning
Mikuni
Performance Guide
Mikuni
Tuning Guide
Night Rider Tech Tips
|
