Topic: CB750KO Carb Question

[Johnie]

My KO is all original with the 4 cable carbs & HM300's.  I know some of you have converted over to the K1 carbs for improved running.  I would not mind being able to adjust my idle at a stoplight which is not possible with the 4 cable carbs.  When I bought my K1 the PO gave me 2 extra sets of carbs and I was thinking of trying a set on the KO for kicks.  I know I will have to change the throttle cable, but am asking those of you who have done this to chime in with your story and what you had to do.  How do you like the set-up.  The good thing is I can always put the 4 cable system back on as I do not plan to rob any parts from that system.

[kghost]

Hey I've never done it.

I sold the 4 cable carbs I had for big money.

Just comparing the 2 systems side by side.....

The unified cables are the way to go.....have them on 2 K2's and they work.

[736cc]

 The quirks of tuning the K0 carbs are half the fun. They look cool, too w/ all those cables and oversize adjusters. Plus you are now an expert on carb tuning if you ain't afraid to mess around w/ these funky things.
  Synching K0 carbs actually ez; hook-up vac gauges, bottom-out the brass adjusters on top of all 4 carbs, get a hi-idle at the throttle housing adjuster (2500-3000 rpm), get a balanced reading by adjusting the brass screws on top of the carbs, back-off the throttle adjuster at throttle housing to get a little play at throttle grip, then set idle w/ the individual large carb idle adjusters, getting equal vac readings. Actual vac readings don't really matter; same readings across the board what you want. Should last a season or so.
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[Johnie]

Ah...so you guys want to talk me out of it? 

[Bob Wessner]

Come on, John, what's an extra cable or two, or three, or four.   

[Johnie]

I was waiting for you to come after me Bob...

[kaysystems]

What better way to spend a Sunday afternoon.

I found that that 4 cable system doesn't really go out of adjustment after everything has settled in. Say 39 years or so.
 Seriously, after spending the time to set up the 4 cables, I have no problems at all. You need a good grip on the twistgrip though. I think the throttle return springs are stronger than the push pull setup.

David

[Old Scrambler]

Johnny.......Its a good question if your going to be riding the bike long-distance and you don't want to mess with the carbs while on the road.  Otherwise, the original carbs are not a problem.  If you have trouble with the idle being to low after the bike is hot, just turn up the idle adjuster on one carb.  Then remember to set it back when you park the bike.  If you have the opposite problem, your pilot jets may be too large or the air mixtures are not all in sync.

These carbs are esentially the same as used on Hondas since 1959.  I use a somewhat different approach than 736cc suggests.........The most important thing to have in sync is the height of each slide.  Back off the idle screws and  place a thick string in each carb so its secure at the slide.  I have it attached to a pencil or piece of cardboard and lightly tug to get an even pull on all 4 strings.  While watching and feeling the strings, slowly open the throttle to feel for any one string that releases first or last. Adjust the tops of the carbs (brass) accordingly.

Now you attach the vacuum lines and start and warm the motor. Hold the throttle to set the idle on each carb while maintaining the same desired RPM.  Then up the RPMs to about 3,000 (fan in place) and read the gauges.  Adjust the vacuum by very slightly moving the air screws until all are balanced. The motor should be very smooth and you should be able to balance a nickle on its edge on the case next to the ID.

Button everything up a take the bike for a ride. If the idle is too high, turn down each carb one click at a time until you have it where you want. If you find that one carb is very difficult or impossible to get in sync at speed, check the compression for uniformity.  If all is fine, you may have to pull the needle and clean the emulsifier.  I have found slides that are slightly binding will cause big problems.  Sometimes the carb body is warped. Sometimes the needle on one carb may need to be lifted or lowered to get the best mixture for that one cylinder.

Anyway.......I like either set up for tuning, but the later version is a lot easier on the hand.  A clean fuel system and a little cable lube keeps me happy for a long time.