99 katana 750 stalling

This is about a 99 katana 750... the bike was sitting in the shed for a
week or so... when I tried to start the bike today morning, it would
start but the engine sounded kind of rough... it was struggling to idle
and died when I tried to throttle... thought it was due to the cold
start but, even with the choke on, it was struggling hard to idle...
after a minute or so I smelled gas and so I turned it off... it sounded
like something is blocking / stalling the engine... I checked the oil
level and it looked fine... I would like to fix it myself if it is not
something big... my first guess was air filter (coz it's pollen season)
and then carburetor... I'm new to motorcycle... so, I don't want to
mess it up without knowing anything ... any tip would be greatly
helpful.

thanks!

 

The problem has nothing to do with the fact that it's a 99 Katana 750.

It's a generic problem that happens to all motorcycles that are
equipped with constant vacuum carburetors. The tiny idle mixture
passages get plugged up with gum and varnish and when you try to
increase the engine RPM by twisting the throttle
grip, the vacuum downstream of the throttle butterflies is too low to
either suck gasoline out of the idle ports or suck mixture past the jet
needle/needle jet orifice.

The engine does not have a choke plate like a car, it has a small valve
in the side of each carburetor that is opened when you move the "choke
lever" to the ON position.

Raw gasoline is sucked straight out of the float bowls and into the
engine through the starting enrichener.

When you open the throttle to nurse the engine to higher RPM, vacuum is
too low to suck enough mixture through the starting enrichener bypass
port and what does get sucked into the engine doesn't get atomized
properly and you smell gasoline fumes.

So, you're in the strange position of trying to troubleshoot an engine
that's starving for burnable mixture while you smell raw gasoline!

You don't need to start tearing the carburetors off the engine to clean
them out though. You must live in the UK or Oz or NZ if you park your
motorbike in "the shed".

I don't know what brands of carburetor cleaner you have there, but I
use Berryman's
B-12 Chemtool Choke and Carburetor Cleaner, which is a mixture of
xylene, acetone, and methyl alcohol. I put 3 or 4 ounces into a tank of
gasoline and go for a ride to clean out the carburetors.

The exhaust will smell awful with the aldehydes breaking out of the
polymers, but, if you notice that the engine suddenly starts idling too
fast, you're cleaning the idle ports and jets out. You'll find a master
idle knob between the #3 and #4 carburetors and you can turn the idle
RPM down with that knob by turning it counterclockwise.

If you're using something like B-12, the best bet is to ride slowly to
make the engine have to suck the cleaning mixture through the idle
jets. High speed full throttle runs with alcohol in the fuel may tend
to wash the oil off the cylinder walls, so I recommend burning the
whole tank of gasoline before trying to set a land speed record.

 

Thanks! I'll try it out...
Do you use the additive regularly? is that good practice?

 

Yes, I have been running B-12 through the gasoline every spring after
bringing the machine out of winter storage for the last 30 years. And,
here in the central valley where the temperature is 100 degrees F every
day for six months, the additive needs to be used more often, since the
fuel system cleaning alcohols in pump gasoline evaporative rapidly.

I have seen no evidence of permanent damage to rubber parts or plastic
parts exposed to the alcohol at such small concentrations.

B-12 comes in 15 ounce aerosol cans fro spraying through jets and in
liquid form to mix with gasoline and it costs less than $3.00 a pint.

 

Great! Thanks

 

Whoa, is this krusty rediguised? I didn't think I'd ever hear someone
else talk about B-12 that favorably . I have the exact same problem,
94 Yamaha XJ600. It was stuck in the garage while I waited to replace
the chain and sprockets, and the gas got gunked up again. Weird twist
though; I was able to clean the carbs a little (pulled them off quick,
looked through the idle jets, sprayed some stuff and put back on) and
then went for a long (1+ hr) drive. The power slowly got better, but
it was running with a good push at 1/8 throttle (very tiny), but would
loose power and almost bog above that. Finally I got it to operate
mediocre at 1/2-full, although there was no difference in running 1/2
or full, just the same push.

I took it out again a week later. This time it had trouble, and
finally stopped itself. Would start barely, but would die every time I
gave it throttle. I'd forgotten about the symptoms of plugged carbs.
I'm going to pull it off and give it a thorough cleaning, every
jet/hole/passage. Then I'll try again and see.

This bike is on it's last leg. It's had the carbs gum up on my 2 times
now (although those were my fault, I admit), it's broken a chain, the
drive sprocket nut wore itself to the point where there were no threads
left (I have no idea how the drive sprocket stayed on the drive shaft!)
and the tires and muffler are going bad. For a $1000 starter bike,
it's lasted long enough. I figure I'll give it one last go, then junk
it and get a new one. Anyone ridden a 2003 SV650 or a 2000 Triumph
TT600? Both are for sale locally, both are cheaper than the racer
bikes. Hmm.... 2, 3, or 4 cylinders?

 

No, but a new e-mail was in order to defeat killfiles in other NG's as
certain self-important people tried to dominate them with elitist
cliques of riders who know nothing about motorcycles beyond taking them
to the $tealer$hip for the silliest reasons.

 

My ethical belief system tells me not to keep silent when
self-appointed tyrants shout slogans.

Obviously, nobody has to read anything anybody else posts. But changing
e-mails and nicknames will occasionally get through to a liberal bigot
trying to force "political correctness" as viewed in, say Canada or New
Zealand, upon a group.

And, when a bunch of users gets together and claims that they are the
only "actual riders" in the country and tries to dominate a newsgroup,
sets up a private elitist newsgroup called "Actual Riders", and *still*
comes back to the newgroup that they claimed to hate so much and tries
to run out everybody they disagree with *again*, then that challenges
freedom of speech and free speech will always find a way through the
noise of liberal bigotry and "political correctness".

(What "new clothes"? The king is *naked*. It's time to change e-mail
addys and nicknames again. I'll do it now.)

Well, I should certainly hope that some of the liberal bigots are
irritated. The very nature of Usenet invites trolling and gatekeeping
and controversy and angry arguments. I figured out what Usenet was all
about the first week I had internet access.

My newsreader doesn't even have a killfile feature. I can see all
targets and zero in on their weaknesses and pull their strings and make
them dance. It's good interactive fun, while I look for real bikers
that appreciate free and honest advice.