Carb syncing

I checked the sync on my 2-cylinder Honda today and it didn't seem right
but before I go adjusting anything, I'm wondering if this sounds like a
simple sync issue or if there's something else going on.

I made one of those inexpensive vacuum balance tools from 1/4" OD clear
vinyl tubing and 2-stroke oil and my carb balance is way off at idle by
about 15 inches but it balances out at about 2000 rpm and then goes the
other way as the rpm goes higher until, at about 4500 rpm, the balance
if off by about 8 inches in the other direction.

Is it normal for the carb balance to vary like that?

Tia,
Ken in Albuquerque

 

Sorry not going to touch this one.

 

I lied, sorry
cant help myself.

Rigth tool for the job, and a book with spec's.

 

IF, and thats a big IF, your measurement is correct, it sounds
like an internal problem with one of the carbs,
(one vacuum piston moving faster, or more, than the other).
IIRC Hondas use Kehin dashpot types.
Check that the butterflys are moving evenly and that one choke or
the other is not hung-up somehow. (easy & simple).
Check both carbs for free movement of the pistons. (easy & simple).
If one or the other is hanging up you've found the problem, you might
be able to cure it with Gum-Out spray.
Beyond that, carbs are finicky beasts to work on and it's hard to
restore
the settings to 'status quo ante`. If you do it, its a full carb
tune-up.
If you feel up to it,strip down the offending unit, (if you found one),
or both,
(if you didn't), & clean the hell out of it, (them).
Check that the vacuum passages are clear and the piston(s) are clean &
smooth.
Look for vacuum leaks.
Best of luck,
MadDog
"R75/5 Forever !!"

 

Ues, it is normal to have variations off idle. Differees in cabs,
linkages, makes their response to throttle opening slightly different.
Your difference is greatly magnified because you're using oil instead
of much heavier mercury, or properly calibrated gauges.

 

Which one?

 

What he said. Get the proper tools and/or knowledge or don't faff with
it.

 

Depends on the age of the bike, and even some modern small twins use
old-fashion slide carbs. There's one sitting outside my house right now.
And of the CV type, by no means all used diaphragms.

 

There is nothing wrong with the "tool". Yes, the home-made oil vacuum
gauge will be much more sensitive than a store-bought mercury one, but
that does not make it wrong. It makes it *better*.

 

What he's built is a differential manometer. Why would
that not be an appropriate tool for the job ?

Perhaps it should also go "ping" ?

Might be worth starting with a check on the throttle cable
synchronization, a check for air leaks and a compression
test. If it's CV carbs, the diaphragms might be in need of
replacement.

 

An easy way to deal with the sensitivity is to add a crossover
tube with a shutoff valve. This can be constructed out of $1-$2
worth of drip irrigation parts.

The drill is to start the engine with the crossover open, then
gradually close it until you see a difference in fluid heights.
Useful because it prevents the fluid from being ingested if
things get seriously out of balance.

 

Ken,

Since nobody else gave you any kind of reasonable reply, let me chime
in. What you are doing is comparing the intake vacuum on the two
cylinders. Before attempting to balance the carbs you want to be sure
that the engine is in a good state of overall tune. This means fresh
(or recent) plugs, clean air filter(s), ignition timing and valve
clearances adjusted and/or determined to be in spec.

The main thing that will effect the vacuum will be how far open the
throttle slide/plate/actuator is. At idle, this is usually adjusted by
some sort of a mechanical throttle speed adjustment on each carb. You
would do this with any linkage or connecting cables loose.

Once you have that balanced fairly close you would see what happens as
you open the throttles. If they become unbalanced you have to adjust
adjust the cables or linkage that connects the two carbs together so
that they will remain at a fairly equal vacuum at all throttle openings.

 

Thanks much. I suspected my homemade tool might be contributing to the
funny results but since I had never sync'ed carbs before, didn't
really know what to expect. (All my previous carb experience has been
Rochester Quads and Holleys on Chevys and Mopars.)

Now that I know what to expect, my $5 carb sync tool will do me just
fine, thankyouverymuch!

Ken in Albuquerque
(Reply address works as is.)

 

Which one?[/QUOTE]

'83 GL650 Silverwing
(Reply address works as is.)

 

'83 GL650 Silverwing[/QUOTE]


Right.

Yep, CV carbs with steel pistons rather than rubber diaphragms.

 

Sure PING ? Needs spec's.............. What's the f'n use! I'm not
going to educate without pay. Got beter things to do, so I'm out of this
one.

 

You're just being argumentative or you don't know what you are talking
about. You don't need "specs" to balance carbs. There are no "specs".
You get it the best that you can and that's that.

What's the "spec" when you're using a Twinmax (about the best electronic
instrument their is for carb balancing)? Oh, that's right, there are
none. You just get it the best you can...

 

No shit, just being argumentative. Just no mater what you say sometimes its
like talking to a wall. The backyard so call meter is not the way to do it.
No mater what they say... Let them learn the hard way. I said need spec to
see if anyone says yes? Like fishing. Like I said who cares... Take Care,
Later.

 

Monthy Python, "The Meaning of Life", a machine that goes "ping".

When a twin cylinder engine draws the same vacuum on both cylinders
as indicated by his homemade differential manometer, it is "balanced".

End of spec.

Perhaps I could add pictures or other some learning aids if you like.

 

What's a "backyard so call meter"?

Ken
(Reply address works as is.)