1976 HONDA CB750 K6 Carb Sync

Finally got the carbs synched! Airbleed screws set at 3/4 turns out. Number four was a pinch high (1/4"), but spec in the manual is all to be within 1". I adjusted it anyway. I knew I would.... UPDATE: found #1 idle jet plugged. Recleaned and it sounds a LOT better. In this video, the bike is idling on 3 cylinders only.
Next is tires, then RIDE!
UPDATE: Exhaust sounded a bit choppy to me, so I investigated. Found two pipes cooler than rest. Found those to have bad plugwire caps. Resistance too high. (Should be about 5k ohm) Replaced the plugwire caps (from e-bay) and it sounds better. Had no effect on the sync settings.

Category:

Autos & Vehicles

Tags:

• honda
• cb750
• 750four
• 750k6
• cb750k6
• k6
• streetbike
• motorcycle

[creuter85]

Could you better describe the carb balance? This is a project I will be taking on soon and would love some tips. Could you walk me through exactly where to hook up the carb sync gauge hoses and where the adjustment screws are? There is a nice video called "How to sync carbs on 1977 CB550, but that is nothing like our bikes! Thanks for the help.

[chargerdrew]

@creuter85 SORRY so late with response. Copy this into you seach engine: Sohc CB750 1969 - 1976 Carburetor Synchronizing

Then click on the 'salocal' link which has the 'carburetor_synchronizing' document. That's a good one. i wish I could post the actual address here, but it is not permitted

[wanderer1031]

what is the advantage of having four individual carbs? it seems a lot easier to just have one big one to mess with.

[chargerdrew]

@wanderer1031 I agree. It would be easier. Not sure if there is any advantage

[TheRiversDark]

how do you check the plugwire resistance?

[chargerdrew]

I used a digital multimeter to check the resistance across the plugwire cap after unscrewing the cap off the wire end. Also beware that since the resistance is built into the cap itself, don't use resistor or "R" type sparkplugs. This will double your resistance and make the spark weak. I'm going to post a vid af what the bike sounds like now. This one just bugs me. Good Luck!

[vipexperformance]

@wanderer1031 The advantage of multiple carbs is eneormous - the intake runners are very direct (compared to one carb) and as a result make dramatically more power. Carb sychronization is a snap and well worth the effort.

[yellowbusguy]

@wanderer1031 With four small carbs you can maintain good intake velocity . The air needs to pass through quickly to promote proper fuel air mixing. You can't keep good velocity through a big hole until the rpm's are really high. Too big of a carb results in sloppy low speed throttle response and poor running at low rpm's.

[chargerdrew]

Put in a new set of plugs, no difference. Started reading my service manual and discovered the plugwire heads have resistors built into them which can burn out. Bought a new set on E-bay, and it sounds great!

[chargerdrew]

The exhaust didn't sound right to me. Way too rough. I pulled #1 plug and it was wet. Getting a new set of plugs. Stay tuned.