CB360 carbs


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I dont claim to be the expert so if you have anything to add or if I made an error please let me know.

ANY Adjustments made to carbs must be done w bike parked level and on center stand. I place a block of wood under front tire to get bike as level as if I were sitting on it.

Pods added And/or Exhaust change.

If your machine is popping, sputtering or cutting out. And you insist on running pods of any brand. Send them to crazyPJ for modifications He will also ultrasonic clean, inspect, repair (if possible), set floats, and syncronize.

In the event you have JBM diaphragms installed...

And have stock air boxes w good filters OR sent your carbs to PJ for pod filter modifications and the rich midrange rpm issues persist, popping, sputtering & cutting out. I suggest NEW diaphragms from Honda parts dealer.

My bike runs like shit w JBM diaphragms. Even decent old Honda diaphragms are better.


I have made a list of things to do before tuning carbs.

Carbs can not be clean enough, clean them. Clean tank and fuel tap. Things to check while cleaning carbs. Float condition and height (holes, cracks, leaks) make sure the jets are installed properly. Good bowl gasket and any other o-rings.

1 are your carb diaphragms good? It sucks to tear an old one halfway through this process. like I did.

2 do you have the original stock Keihin air/fuel adjustment needle springs installed (BEST) OR Did you file sharp edges off new carb rebuild kit air / fuel adjuster springs ?

3 Do you have clean inline fuel filters or screens on fuel tap? clean tank ? vented gas cap venting properly?

4 Do you have good stock coils or new coils ? good condenser ?

5 Good plugs set proper gap (.7 - .8 mm), NGK B8ES, (NOT NGK BR8ES) and 5 or 10 ohm plug caps ?

6 Timing set properly w timing light (engine hot) ? (using a light to set static timing, is a preliminary set up, that will get bike running. Not properly. Once bike is running use a stroboscopic timing light to set timing). good points ? properly adjusted .3 - .4 mm gap
Also, check mechanical advancer is clean, lubed and advances properly and smoothly.

7 cam chain adjusted properly/ with engine hot? trap crank w wrench while re-setting cam adjustment bolt.

8 Valves adjusted properly w engine cold?

9 Rubber carb insulator boots and gaskets in good shape (no cracks or leaks). Best price I found for New boots and gaskets is my local Honda shop.

10 carbs properly synchronized w gauges? (PJ makes the manometer adapters for this.

11 throttle cables properly adjusted and lubricated?


12 Bubbles forming in fuel lines? Ensure fuel lines/filters do not contact engine, engine mounts or frame. Cheap transparent fuel lines getting hot can cause fuel to boil and a myriad of problems.

13 make sure carbs are level to engine. Here is a link to help prevent carbs from sagging in boots.


14 Tank or tap not getting hot. From what Ive read online, the boiling point of most gasolines is 90 - 400 degrees F

15 Good battery, properly charged? Properly charging... 12.5 - 14.5 volts

16 Clean all wiring connections and coat them w dielectric grease.

17 Properly adjusted clutch? Engine not trying to pull when stopped in gear and lever pulled all the way in.

OK Now your ready to start working on carbs.

Check for leaks. Heres some I have had on my bike.

Insulators warped. So they were leaking at the gasket. I filed them flat and used a little Hondabond on the gaskets.


CrazyPJ makes replacement plugs for the LEAKY throttle shafts.


possible leaks around diaphragm caps


Filed carb tops to make em flat. Not so much that they could pinch or cut diaphragm, just enough to squish thicker o-ring edge.


Also flattened diaphragm top cover.


Next is carb health.

Springs measure approx 5.25 inches.


My bike runs rich w the JBM diaphragms installed so I got the kits Brand new from Honda. It includes New diaphragms, slides and springs.


The 754A model carbs have non-removable pressed in air correctors.


The 745B model carbs have removable screw in correctors.


When cleaning the carbs you need to pull the removable correctors to ensure they are installed in the proper locations.


Also, check to ensure the vents in the slides or on the FILTER side of the carbs.


If the AIR/FUEL mix adjustment needle springs have been changed out. Make sure they are filed flat on the ends just like the original stock springs.

Popping on decel

Can be aggrevated by an exhaust leak at the head and leaking exhaust valves and timing.


Popping on decel is completely normal for any carb'd engine. Its louder w some exhaust than others. Thats why you dont hear an old Cadillac do it. But, you can hear an old Chevy w glasspacks do it.

It is caused by a lean condition, the rpms are up and the butterflies are closed. It can still draw some air around the closed butterflies but cant get enough fuel through the idle and pilot circuits.

W my O2 sensor installed I can see the A/F ratio jump from 12.8 to 1 all the way up to 20 to 1, when I roll off the throttle and thats when the popping really goes crazy.

You can lower the amount of popping by installing a quieter more restrictive exhaust and larger pilot jets. But, probably wont eliminate it completely.

As long as everything else is good it wont hurt anything.

If your bike doesnt return to idle speed of 1200 rpm.

Check that the throttle plates (butterflies) are centered in the body and not hanging up or dragging on the walls of the body.

Check to make sure throttle cable isnt to tight or binding and properly lubricated. New cables are shipped dry.

Lubricate the linkage and springs between the carbs.

Hesitates on Takeoff or doesnt idle smooth.

Usually caused by a lean condition.

Make sure the idle and pilot circuits are clean and operating properly.



Dont remove this plug.

On this junk carb I wanted to see what it looked like under this plastic plug, covering the A/F mix and pilot circuits.. So, I drilled it out to see. This cavity is what makes it so hard to clean properly. Plenty of room for stuff to get trapped in there.



Atomized fuel is fed to the A/F and pilots circuit through the main primary jet, then onto the pilot jet, then in to the cavity.


Tuning carbs


for a/f adj. and its important to have her fully warmed up to operating temp. Cold engine will cause the atomized fuel to re-condense to a liquid state. The hot engine helps to keep the atomized fuel...atomized. If you adj a/f mix cold it will change as the engine warms and need readjusting. Thats the reason they install a choke on it. The choke IS the adjustment for starting and running the engine when its cold and the atomized fuel is condensing.
So warm bike, adj idle speed to 1200, then adj a/f mix on left carb to fastest idle, re-adj idle speed back to 1200, then adj right carb a/f mix to fastest idle. then adj idle speed to 1200, repeat...go through them twice to to be sure you got it good as you can. Mine is happiest at 12.8 to 1 a/f ratio.
and remember it may just take a tweek on them the second round like 1/16th of a turn.

Also, the reason they made these easily adjustable to start with is, the mix will change w outside air temp. and altitude. So, if you set em up in the spring when its 50 degrees it will need re-adjusting when its 90 degrees.


If you listen real close. you may notice the rpms vary slightly and rythmically during this process. That is actually caused by the fuel level in the bowls dropping and raising w the floats opening and closing feeding fuel. And they get a little lean and richen back up as they fill.

More to come as a I get time and think of things to add.


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crazypj said:
That's a good article, should be a 'sticky'

Thanks bubba !
Its a work in progress. If you got anything to add. by all means please do.

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