Author Topic: Trying to balance carbs. Simple question. (Read 2242 times)

strangedaze39 · « **on:** May 09, 2009, 05:01:11 PM »

Ok so I hope your smart or I'm dumb. I'm trying to balance my carbs again and for the life of me can't figure out what I need them set at on the vacuum pressure gauge!

My manual say's 16cmhg-24cmhg, what the heck does that convert into on the vacuum gauge?

I see mm vacuum and vacuum inches.

First answer gets a beer,
-SD

fmctm1sw · « **Reply #1 on:** May 09, 2009, 05:40:50 PM »

Mine were all between 18 and 20 on my Morgan... I like Iron City...

robe0531 · « **Reply #2 on:** May 09, 2009, 05:41:07 PM »

i would go by the number 2 carb and set the others to that seeing how u cant set it
so what ever it says is what i would go by
not sure if it is right though

OldSchool_IsCool · « **Reply #3 on:** May 09, 2009, 05:49:11 PM »

Throw your manual away, at least the carb balancing section. Pick one carb as your standard (quite often the #2 carb is not adjustable, so that becomes the standard). Now, adjust the other carbs until all 4 guages read the same. The absolute value means nothing, the fact they are all pulling the same is the important thing. Note that adjusting one carb will affect the others, so you may have to mess with several carbs at once.

strangedaze39 · « **Reply #4 on:** May 09, 2009, 05:50:39 PM »

It's a CB350F, I think I just made it worse. Before when I started they were roughly around 100-150mm vacuum so I upped then to 200mm, I must be making it richer. Anyone know what I should set this at. The manual says 16-24cm HG (damn hg...) I have no idea where it needs to be set at and it's running like crap. I guess the old saying "if it's not broke don't fix it" would be appropriate.

Any info on this would be greatly appreciated. What do you guys set your cb350f's to on the vacuum gauges.

@oldschool: I agree I'm about to burn this carb synch page in this manual.

Johnny5 · « **Reply #5 on:** May 09, 2009, 05:57:24 PM »

Quote from: OldSchool_IsCool on May 09, 2009, 05:49:11 PM

Note that adjusting one carb will affect the others, so you may have to mess with several carbs at once.

Several?

Like OldSchool said, dont worry about the number on the gauge, but just make sure each carb has the same vacuum.

OldSchool_IsCool · « **Reply #6 on:** May 09, 2009, 06:00:05 PM »

there are 10 mm in a cm, so 16-24 cm is the same as 160-240 mm whether its Hg or H2O or jell-o.

But again, setting the vacuum to an absolute value is folly. Go for a matching RELATIVE vacuum across all carbs.

strangedaze39 · « **Reply #7 on:** May 09, 2009, 06:00:49 PM »

I can have them all read the same now but they are all set so off the correct mark it's running like crap when i give it anything over 4k rpms

Johnny5 · « **Reply #8 on:** May 09, 2009, 06:04:45 PM »

Quote from: strangedaze39 on May 09, 2009, 06:00:49 PM

I can have them all read the same now but they are all set so off the correct mark it's running like crap when i give it anything over 4k rpms

Have you done a complete tuneup? If not, start there and do the carb sync last.

strangedaze39 · « **Reply #9 on:** May 09, 2009, 06:18:08 PM »

@Johnny: My bike is always tuned :p I've done multiple carb synchs and complete tune jobs on it and never ran into this problem where it wants to give me a hard time. like i said anything over 4k is a no go. I'm going to let it sit for a while now, don't want the thing to over heat.

Anymore idea's are welcome

Johnie · « **Reply #10 on:** May 09, 2009, 06:23:20 PM »

Agree...sometimes you need to walk away for a bit. If you have everything else in tune like you said, and you completely have it out of wack now, then I would pull off the air box and bench sync it. That way you are at least at a good starting point again. Then warm it and hook up the vac guages again and start over.

OldSchool_IsCool · « **Reply #11 on:** May 09, 2009, 06:30:08 PM »

And blow a fan over the engine when ever you are running it and not moving. Your engine will thank you.

strangedaze39 · « **Reply #12 on:** May 09, 2009, 06:48:42 PM »

The beer goes to old school. I'm such an idiot. The problem why it wasn't going over 4k is I had a towel under my tank this time, since it has a new paint job on the tank. Hence that thing was starving for air/overheating. I caught it quick enough before any damage was done and threw some semi warm water on the engine while turning it over.

Note to self: Don't be such a idiot next time.

Thanks for the replies guys.

Also if anyone else is trying to figure this whole cm hg to mm it's all the same like oldschool said, so 16cm hg is 160mm on a air vacuum gauge.

Steve F · « **Reply #13 on:** May 10, 2009, 07:08:06 AM »

Where in IL are you?

OldSchool_IsCool · « **Reply #14 on:** May 10, 2009, 08:09:16 AM »

MMMMMMMMMMMM BEER!!

Duke McDukiedook · « **Reply #15 on:** May 10, 2009, 09:50:45 AM »

Yeah but 20cm of Hg is not the same as 20cm of H20 just so you know.
Quite a big difference between the two.

OldSchool_IsCool · « **Reply #16 on:** May 10, 2009, 10:02:46 AM »

Quote from: Dukiedook on May 10, 2009, 09:50:45 AM

Yeah but 20cm of Hg is not the same as 20cm of H20 just so you know.
Quite a big difference between the two.

If ur measuring pressure, yea, but if ur measuring 20 cm of length, not so much!

Unfazed · « **Reply #17 on:** May 10, 2009, 10:11:24 AM »

Did you adjust the carbs with the air screws or the adjusters next to the top covers?

mystic_1 · « **Reply #18 on:** May 10, 2009, 01:19:37 PM »

Both! Depending on what you're adjusting

Sync adjustment is via the top adjusters that pull the slides up, if you have mechanical carbs.

Air screws are for adjusting idle mixture.

mystic_1

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Author Topic: Trying to balance carbs. Simple question. (Read 2242 times)

Unfazed