Honda CB500T Problem

 Hello all and thanks in advance for any help you can provide.  I have a
Honda CB 500T.  I have changed the plugs and points and the bike runs pretty
good for a day.  The plugs start to foul after that.  I think it is an
electrical problem.  The carbs have been redone recently.  Any ideas what
may be wrong?

John

 JMM wrote:

Yep, it's running too rich, it is not an electrical problem.

I have no idea what sort of carbs you've got so my advice
is generic, but you can't assume the pervious owner didn't
mess with things.

Take the carbs off and check:

Float level, if the fuel level is too high it will make the
mixture rich.
Main jet size, if not stock, replace with stock size.
Pilot jet size, if not stock, replace with stock size.
Needle jet clip position, if applicable.
Float needles and seats for wear.
Look for missing rubber plugs inside the bowls, if any.

Also look for rust or sediment in the float bowls, if you've
got rust it's time to flush the tank and at a minimum install
a fine mesh filter, at worst you will have to have the tank
acid etched and sealed.  POR-15, KBS, and Kreem kits will
all work fine IF YOU CAN FOLLOW DIRECTIONS.

--
'01 SV650S  '99 EX250-F13  '98 ZG1000-A13
OMF #7

 

What do the deposits look like?  Bad valves or rings can cause deposits
too.  Does it use a lot of oil?  Were the carbs worked on because of this
problem?

Robert

 JMM wrote:

What do you mean, when you say that "the plugs start to foul"?

Is it dry, fluffy soot? That indicates the mixture is too rich.

Wet, oily fouling indicates that oil is getting past the piston rings or the
valve guides.

If the fouling is wet and smells like unburned gasoline, the engine is being
flooded with excess gasoline due to a stuck float valve or high float level,
or, I have actually seen this, the jet fell out of the bottom of the carb and
is laying in the float bowl.

Are you sure that the spark plugs are the right heat range?

The air filter might be dirty, the choke might be slightly closed, the floats
might be set too high, the float valves might be leaking, the needle jet
might be worn egg-shaped from the jet needle banging against it.

http://www.bikebandit.com/partsbandit/showschematic.asp?dept_id#25824

The idle mixture screw is shown enclosed in the box, item #6.

It's a GAS screw, turning it clockwise will lean up the mixture. Turning it
too far counterclockwise will make the idle mixture so rich you have to
increase the idle speed.

Then the engine will idle too fast when it's hot and it won't idle down after
you blip the throttle to check for proper response.

--
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http://www.motorcyclekb.com/Uwe/Forums.aspx/bike/200706/1

 

 Had exactly the same problem on a CB500T I restored a few years ago.

http://www.chateau.murray.dsl.pipex.com/images/CB500T.jpg

These things have *terrible* carbs, with non-adjustable needles and all
sorts of other shit.

Basically, all the interior pasageways of the carbs get clogged with
stale fuel. Ultrasonic cleaning might work. That gunk you pour in the
tank might.

In the end I sourced a pair of carbs, guaranteed to be sorted by someone
I trusted, and that was the problem sorted.

It's the carbs. Not electrics, although I agree it sometimes feels like
it.

PS - it's a horrible bike anyway. Throw it away.




--
BMW K1100LT  750SS  CB400F  CD250  SL125
GAGARPHOF#30 GHPOTHUF#1 BOTAFOT#60 ANORAK#06 YTC#3
BOF#30 WUSS#5  The bells, the bells.....