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Discussion Starter · #1 ·
I figured I should deviate some posts to here to stop spamming my Project Logs thread:
viewtopic.php?f=5&t=105&start=220 :lol:

Backstory for the new guys: I have been running CB450 carbs on a CB360 because that is the way my PO set it up. It runs ok, but its a PITA sometimes to start it up. I scored a nice set of CB360 carbs that I am trying out. So far, I have a lot of work ahead of me.

Right now:
The bike has jets set at stock sizes, diaphragms are in AWESOME condition, no binding in the linkage of the cables, cleaned carbs this week and replaced old float valve and seat with a new set from a rebuild kit.

1. The bike starts up extremely easily, which is the one thing that really keeps me motivated.
2. Bike idles ok but not great at 1,300 rpms
3. When throttle is given, the bike revs up really nicely, but upon release of throttle, the revs SLOWLY come back down.
4. The right header pipe gets "warm" a lot slower than the left header. I get sputtering from the muffler from time to time. I do NOT think it is backfire since backfire sounds like an explosion, the sound I hear is almost like a "cough". Sometimes when the bike "coughs" at idle it sounds like it is coming from the carburetor and the idles drop down really low and sometimes the bike cuts out.
5. Upon removal of carburetors, when I disconnect the right carbs' fuel line, fuel drips out of the nozzle for quite a bit. When the carb is removed, I see fuel inside of the rubber carburetor boot (right side of course)

Now I am trying to plan the work ahead:

#2 and #3 - Seems to be a carburetor synch issue. I can get my hands on one and try to do this myself
#4 and #5 - I am guessing this is due to a float being set too "low" (by "low" I mean if you flip the carb upside down and measure distance from lip to top of float). Right?

Any input is greatly appreciated!!!
 

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Discussion Starter · #2 ·
Ok so I adjusted float levels. The crappy carb was modified to be set higher than spec (i.e. shuts off fuel sooner than the previous adjustment). The pipe warmed up almost as fast as the good side.

I bothered my roommate to try the carb synch....BUT NONE OF THE NOZZLES FIT! The threads were all so small that they twirled around the port. Sigh....

I took the bike for a test ride around a few blocks to raise my spirits. The bike performed nicely with mid-high range throttle, but whenever I clutched it in the bike would hover at 3.5-4k rpms. I found that I can roll through the entire powerband without stumbling, but idle is just screwy. I have to blip the throttle every 15-20 of seconds to keep the bike running.

I really need to get this carb synched up, maybe guess and check?

EDIT: With a digital caliper I measured the "block" screws to be 6mm and there is a 6mm adapter set available from the carb tune manufacturer. I think I will be ok
 

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In the meantime have you tried the old time method of putting your thumb behind the pipes and trying to equalize the exhaust pressures?? It may show some small improvement..


GB :mrgreen:
 

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Discussion Starter · #4 ·
Hmm....not a bad idea GB.

I also realized as I was giving up the other day that Honda designed a hole in the frame just below the fuel tank so that one can synch the carbs easily. I will definetly take advantage of this next time. I probably will also need to find a super long screwdriver as well :D
 

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NOTE: Before syncing carbs, always check ignition timing and valve clearance. If either of these are off you will never get a decent carb synch. . . . I learned this the hard way. :(

I eventually learned to synch mine by exhaust pressure & engine note. Both sides will have the same pressure & note when everything is right. (The engine note thing is hard when you are half deaf though) :roll:

You can also set the idle so that the bike runs about 1000 on one cyl then adjust the carbs so that you get same results alternately running the bike on first the right, then the left cylinders. Then, once running on both simply set the idle speed normally.

The closer you get to perfectly synced, the better the bike will idle & the more even the mixture settings will be from side to side.

BTW: You have a leaky float needle or a fuel soaked float if you cannot set the float level to specs. That needs fixed before syncing the carbs.
 

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Discussion Starter · #6 ·
Sigh...

I think I will put this carb swap project off for next winter. It was too damn nice out! I went back to the oversize carbs in 15 minutes of garage time and went for a spin around Evanston
 

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krukster86 said:
Sigh...

I think I will put this carb swap project off for next winter. It was too damn nice out! I went back to the oversize carbs in 15 minutes of garage time and went for a spin around Evanston
Keep plugg'in away at it man. I'm sure you will figure it out.
It took me a lot of work to get my stock carbs to work decent. (not right though) ;)
It took a fair amount of messing to get my 34mm Mikuni CVs to work too, but they sure are nice now.

If you were closet to me, i'd tell you to bring the bike over & i'd help you with those carbs.
I'm not so sure I couldn't rebuild a CB360 carb set in my sleep now. :shock:
 
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