My slow jet screw stock settings, read 12/18/03:
Cyl 1: 3/4 turn
Cyl 2: 1 1/4 turn
Cyl 3: 1 1/2 turn
Cyl 4: 1 1/4 turn
Remove the seat (two bolts left and right and one on the rear fender).
Remove the left side air box cover (one screw on bottom). Remove the rest
of the left side fake air box (two phillips head screws). Turn off the
fuel at the petcock and disconnect the fuel line at the automatic fuel
shutoff valve. Remove the tank (one bolt front and one back). Remove the
right side air box cover. Remove the bolt holding the thermostat housing
to the bike. Remove the two screws holding the rest of the fake air box
to the bike, then pull up a little - it will be free from the bike but the
coolant line will hold it in place. Remove the plastic covers (left and
right) by the tripple tree (one screw each). Remove the top of the air
box (six phillips head screws). Remove the air filter and clean or
replace it if necessary. Remove the bottom of the air box (six phillips
head screws).
To remove the carbs - there are four rubber collars that hold the carbs to
the heads of the engine with two screw calmps on each one. Loosen all
eight screw clamps. Pry the front of the carb assembly up and then pull
the back up. (I use a long flat head screw driver and pry against the
back of the front head to get them out.)
You may need to remove the choke cable, but you can leave the throttle
cables attached and work on a stool at the lft side of the bike.
Steve [Hawk] Hardi
--- Steve's Carb Class 101 ---
Lesson 1: Stock Information
Identification Numbers:
1987 VF700C - VD-ECA (VD-EDA, California Model)
1988 VF750C - VD-ECB (VD-EDB, California Model)
Main Jets:
1987 VF700C
Front - #108 (105 California Model)
Rear - #105
1988 VF750C
Front - #110
Rear - #108
Slow Jets (all):
#35
Float Level:
8.9mm (0.35in)
Idle Speed:
1987 VF700C - 1200 RPM +/- 100 RPM
1988 VF750C - 1000 RPM +/- 100 RPM
Pilot Screw Initial Setting:
1987 VF700C - 1 and 7/8 turns out
1988 VF750C - 1 and 3/4 turns out
(California Model) - 2 and 1/8 turns out
Pilot Screw High Altitude Adjustment:
1987 VF700C - 1 turn in
1988 VF750C - 3/4 turn in
(California Model) - 1 and 1/8 turns in
Source: Honda Service Manual 87 VF700C/88 VF750C Magna
Published March 1988
Steve [Hawk] Hardi
Black '88 [Wicked Black Maggie]
Dallas, TX
-------------
2886.4 in reply to 2886.1
Lesson 2: Carburetor Cleaning and Float Valve Adjustment
Cleaning the carbs has been outlined by 87MAGNAMAN in post 2872.11, and I
added a few notes in post 2872.18
While you're cleaning the carbs it will only take a few minutes to check
the foat level and adjust it if needed.
The foats close off the fuel flow for each carb when the float bowl is
full by pressing the float needle into the seat. If a float is out of
adjustment it can cause either too lean or too rich of a mixture. (Note:
too rich of a mixture will be indicated by a "carbon fouled" plug).
The float level is checked by tilting the carb's up (in the direction of
travel of the float) so that the metal float tab just touches the needle -
also called the "float valve". Measure the distance from the side of the
carb housing to the top edge of the float, perpendiculat to the carb
housing. See attached file "FloatAdjustment.jpg"
The float level should measure 8.9mm (0.35in).
To adjust the float bend the metal float tab either toward or away from
the needle. That's it - Super easy (sorry about the pun).
------
Lesson 3: Pilot Screw Adjustment
(I'm putting this one in early for reference later on.)
The Pilot Screw adjusts the Pilot (or Idle) Jet. It is just a tapered
needle in a hole, and how far it is backed out determines how much fuel
flows through the hole for each carb at idle.
The Pilot Screws are covered by plugs from the factory. The recommended
method for removing the plugs is to drill a small hole through the plug
(Note: the plug is only 1/16 inch thick) but do not drill past the plug or
you will damage the Pilot Screw, then screw a self tapping screw into the
hole, and use plyers to pull the screw and plug out. See attached file
"PilotScrews2jpg".
Now the fun part:
1. Turn each Pilot Screw in until it seats lightly, and then back it out
to the Pilot Screw Initial Setting:
1987 VF700C - 1 and 7/8 turns out
1988 VF750C - 1 and 3/4 turns out
(California Model) - 2 and 1/8 turns out
2. Warm the bike up to operating temperature
3. If available, attach a portable tachometer with 50RPM increments
4. Adjust the idle speed with the Throttle Stop Screw (See attached file
"PilotScrews2jpg") so that the idle is
1987 VF700C - 1200 RPM +/- 100 RPM
1988 VF750C - 1000 RPM +/- 100 RPM
5. Turn all Pilot Screws out 1/2 turn from the initial setting.
6. If the engine speed increases by 50RPM or more, turn all Pilot Screws
out by 1/2 turn each until engine speed drops by 50RPM or less.
7. Adjust the idle speed with the Throttle Stop Screw.
8. Turn the number 1 carburetor Pilot Screw in until the engine does not
increase. (No. 1 is by your left thigh as you sit on the bike)
9. Turn the number 1 carburetor Pilot Screw 1 turn out from the position
obtained in Step 8.
10. Adjust the idle speed with the Throttle Stop Screw.
11. Perform Steps 8,9, and 10 again for each of the numbers 2, 3, and 4
carburetor Pilot Screws.
If you want to replace the plugs - the part number is 07942-8230000
Source: Honda Service Manual 87 VF700C/88 VF750C Magna
Published March 1988
------------
Lesson 4: Carburetor Synchronization Procedure
One or more cylinders may be wasting power helping one or more of the
other cylinders function, because each cylinder is not performing the same
amount of work. Correcting this is accomplished by balancing the vacuum on
each cylinder by adjusting the throttle-stop screws so that each cylinder
is performing the same amount of work.
Disclaimer:
I have tried to include as much information as I have available. Adjusting
the carburetors incorrectly can make things much worse than when you
started.
Tools:
1 Carb Sync tool either a mercury meter sync tool (for a 4 cylinder
engine) or a 4 gauge sync tool (mercury is poisonous follow the
manufactures warnings)
1 Small Plastic T-fitting for the hose on the carb sync tool.
1 small Zip-Tie
1 Carb throttle stop screw adjusting tool for flat-head screw or 7mm
socket head. (I use a 7mm socket, universal joint, and 8 socket extension)
1 Hand Vacuum pump - optional
The cylinders are numbers as follows as you sit on the bike:
1 back left - by your left thigh (the one that will burn you in shorts)
2 front left
3 right rear
4 right front
Carb Sync Tool:
The carb sync tool will include fittings that must be screwed into the
vacuum ports for each cylinder, except the number 2 cylinder which already
has a fitting for the vacuum line from the automatic fuel cutoff valve.
The Number 1,3, & 4 ports have Phillips-head screws with washers in their
ports acting as plugs you will unscrew them and screw the provided
fittings in. You will still need to pull a vacuum on the automatic fuel
cutoff valve do this either with a hand vacuum pump or put a T-fitting on
the number 2 cylinder so that both the meter and the cutoff valve can be
attached. The vacuum port fitting on the Number 2 cylinder is a smaller
diameter than the carb sync tool hose, so use the zip-tie on the end of
the hose to get a snug fit.
Throttle Stop Screws:
There is no adjustment for the Number 1 carburetor you are synchronizing
the other 3 carburetors to the Number 1 carburetor. The number 3 throttle
stop screw is accessed from the left side of the bike, and is located
between the Number 1 and Number 3 carburetors. The Number 2 and 4 throttle
stop screws are accessed from the right side of the of the bike and are
located between the Number 2 and 4 carburetors.
Note: The Pilot Jets adjustment procedure outlined in Lesson 4 must be
performed first.
Procedure:
1. Start the bike and bring it to normal operating temperature
2. Shut the bike off
3. Place a block under the kick stand to get the bike level
4. Remove the vacuum port plugs and attach the vacuum port fittings from
carb sync tool
5. Connect on vacuum line to each cylinder using the above numbering
(remember your T-fitting for the Number 2 cylinder for the automatic fuel
shutoff valve).
6a. Synchronize the Number 3 carb to the number 1 carb using the Number 3
throttle stop screw, by turning the screw either in or out in 1/8th turn
(or smaller) increments. *
6b. Synchronize the Number 2 carb to the Number 1 carb using the Number 2
(inside) throttle stop screw, by turning the screw either in or out in
1/8th turn (or smaller) increments. *
6c. Synchronize the Number 4 carb to the Number 1 carb using the Number 4
(outside) throttle stop screw, by turning the screw either in or out in
1/8th turn (or smaller) increments. *
7. When the reading on the carb sync tool is balanced (or as close as
possible) your done. Shut the bike off, remove the sync tool fittings
from the Numbers 1, 3, & 4 vacuum ports and reinstall the plugs, and
reconnect the vacuum line from the automatic fuel shutoff valve to the
Number 2 cylinder vacuum port.
* As you adjust the throttle stop screw for one carb, the other three
carbs are affected you will find it necessary to go back and forth
between the carbs. After you make an adjustment to the throttle stop
screw, twist the throttle slightly to reset the reading on the carb sync
tool.
----------------
2886.24 in reply to 2886.20
I would like to add my two cents.
I recently went through this proceedure.
I purchased a 1987, bone stock 8000 mi bike recently, that had not been
run in some time.
I read through Brent Fisher's web site (which was quite informative on
this subject) armed with a factory manual, I dissasembled the bike and the
carbs.
One of the areas most people over look is a discussion on how the carbs
back on, which I found quite difficult to do. I soaked the manifolds (or
rubber bands) in armor-all for a couple of hours. I had read on the
Sab/Mag web site about using nylon tiedowns with rachets in the ends.
Similiar to what you would use to tie a bike down in the back of a
pick-up.You need four (4) tie-downs. I stabbed the front two (2) carbs
into the manifolds. I used one tie strap on either side of the bike
pulling the carbs down against the frame of the bike. The racket action of
the tie downs made it easier to get the rear two carbs aligned with the
rear manifolds. Once Aligned, Iused the other two (2) tie-down straps To
pull the carbs rearward (strapped to the rear foot pegs) Once you start
applying some rearward force the carbs, the carbs "pop" into place.