carb problems i think

I have a 1981 honda cb 650 costum,it idles fine but when you go down
the road it cuts out real bad around 3500 rpms. It ran fine last
summer but this morning it went south. does any-one out there have a
recommendation on a home fix for this problem?

 

<Holds head in hands and whimpers>

 

Maybe you should go on the wagon for a while?

 

Pull the fuel hose off the carburetor and drain some gasoline into a
clean container. Is there water or rust in the gasoline?

If not, your idle jets and idle passages and ports are probably just
getting plugged with gum and varnish.

Riders who store their motorcycles over the winter without
putting Stabil in the gasoline notice that the engine will start and
idle, but won't run above about 1/4 throttle without cutting out due
to fuel starvation...

Run down to Wal*Mart or any good auto parts store and purchase a can
of Berryman B-12 Choke and Carburetor Cleaner for about $3.25.

The 15-oz. can of liquid B-12 works best, but if you can't get that,
buy some B-12 or STP or GumOut carburetor cleaner in the aerosol can.

They all contain xylene, methyl alcohol, toluene, acetone, etc, and
those solvents will clean gum and varnish out of the carb as you ride.

Don't buy Techron, or any fuel system cleaner that contains "petroleum
distillates". Those cleaners are for fuel injectors.

Carefully measure about 4 or 5 ounces of the carb cleaner into a
container and pour it into a full tank of gasoline and go for a slow
ride, using as little throttle as possible to make the carburetors
suck gasoline through the idle jets.

After several miles, you should notice that the engine is idling
faster, so you can turn the master idle knob down.
It's probably located between the two carbs on the right hand side of
the motorcycle.

If cleaning the carbs doesn't "get 'er done", it's possible that your
spark plugs have reached the end of their service life. Spark plugs
cost $2.50 to $3.00 each, so you're looking at $10 to $12 for spark
plugs.

But modern motorcycles with electronic ignitions don't
have a lot of problems with spark plugs, rough running at low RPM is
caused by dirty carburetors and cutting out at
very high RPM is caused by old spark plugs.

 

There, there, TOG, 3 fingers of single malt will set everything aright.

As for the OP, did you happen to drain the gas out of your carbs before
letting the bike sit for 6 months? If not, they're almost certainly
plugged, and you're going to have to clean them out. You might try the
Yamaha or seafoam cleaner that you fill the carb bowl with, let sit for
30 minutes, and flush out, but more likely it's going to require pulling
the carbs, disassembling them, and thoroughly cleaning them. This
procedure has been posted on this list _many_ times, so search the group
archives (e.g. via a google-groups advanced search) for details.

--
Later,
John



'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.

 

<Hopeful>

Are you offering?

 

Man, you live closer to the stuff than I do! I'm more of a rum drinker
in any case. I will toast you next time I have a sip, though.

--
Later,
John



'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.

 

I was sipping a lovely cask strength (56% ABV) Bowmore the other
day.... Nectar, it was.

 

Funny. I've had two friends talk to me recently about Bowmore (one was
referring to their double barrel, IIRC. the other has a bottle of their
"Legend"). I'll keep an eye out for the cask-strength next time I'm
shopping.

--
Later,
John



'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.

 

Afraid not. The battery will put out slightly over 12v and it will run
happily on that. The charging system generally puts out over 13v, but it
doesn't need this much to run properly.

 

OTOH, I chased a problem like this for quite a while with a CB750, and it
turned out to not be the carbs at all, but the damn spark plug wires.
Ran fine at low RPMs but cut out at 4-5K.
Still, the carbs are probably more likely, esp. if he hasn't tried the
Berryman's yet.


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