Spark plug 3 and 4 completely black

[donald90]

I have done a rebuild on the carbs

 Carb Rebuild Kit. Contains: Float Bowl Gasket, Float Needle, O-Rings, Primary & Secondary Jets, Pilot Jet, Slow Jet, Rubber Carb Plug and Mixture Screw with spring.

Fits: Honda CB750F (1980-82) Supersport
Part #: 48-1998

So the plugs are new and not old, and i remember them being very difficult to get in.

As for the air cut off valves I am 100% positive that the o rings are in place.

As for the overflow tubes, I have had problems with my carbs leaking massive amount of fuel out of the overflow tubes in the middle of driving and waiting at stop lights to the point i had to worry about running out of gas. After that situtation and getting my motorcycle home i pulled the spark plugs out of 3 and 4 and noticed they were wet and black from gas. What i did was burn the excess fuel off the spark plugs and cleaned the carbon off the plugs and it ran well again until they became fouled again.

On Sat, Mar 14, 2015 at 5:23 PM, LukeM [via Honda CB750'S] <[hidden email]> wrote:

Based on this information, I withdraw any and all comments on this thread.
We now return you to your regularly scheduled repair discussion.  

Luke M

Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.

---

If you reply to this email, your message will be added to the discussion below:

http://honda-cb750-s.456789.n3.nabble.com/Spark-plug-3-and-4-completely-black-tp4055725p4055801.html

To unsubscribe from Spark plug 3 and 4 completely black, click here.
NAML

[donald90]

So the overflow tubes are not blocked.

On Mon, Mar 16, 2015 at 1:41 PM, Donald Rudquist <[hidden email]> wrote:

I have done a rebuild on the carbs

 Carb Rebuild Kit. Contains: Float Bowl Gasket, Float Needle, O-Rings, Primary & Secondary Jets, Pilot Jet, Slow Jet, Rubber Carb Plug and Mixture Screw with spring.

Fits: Honda CB750F (1980-82) Supersport
Part #: 48-1998

So the plugs are new and not old, and i remember them being very difficult to get in.

As for the air cut off valves I am 100% positive that the o rings are in place.

As for the overflow tubes, I have had problems with my carbs leaking massive amount of fuel out of the overflow tubes in the middle of driving and waiting at stop lights to the point i had to worry about running out of gas. After that situtation and getting my motorcycle home i pulled the spark plugs out of 3 and 4 and noticed they were wet and black from gas. What i did was burn the excess fuel off the spark plugs and cleaned the carbon off the plugs and it ran well again until they became fouled again.

On Sat, Mar 14, 2015 at 5:23 PM, LukeM [via Honda CB750'S] <[hidden email]> wrote:

Based on this information, I withdraw any and all comments on this thread.
We now return you to your regularly scheduled repair discussion.  

Luke M

Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.

---

If you reply to this email, your message will be added to the discussion below:

http://honda-cb750-s.456789.n3.nabble.com/Spark-plug-3-and-4-completely-black-tp4055725p4055801.html

To unsubscribe from Spark plug 3 and 4 completely black, click here.
NAML

[Maz]

Hi Donald,

I'm not sure if you mean that you rebuilt the carbs after the overflow problem or they are still overflowing since the rebuild. If you have rebuilt them and they are still overflowing and,as you have said, 'massive' amounts of fuel is coming out of the overflow tubes, the carbs are definitely flooding and the float valves are suspect. Only so much fuel can come out of the overflows due to the tiny hole in the end of the brass tube in the bottom of the float bowl. If the fuel flow into the float bowls is greater than that coming out of the overflow, the excess goes into the cylinders and fouls/wets the plugs. Also, in this situation, you may well find your oil level increasing as excess fuel that isn't burnt, gets into the crankcase.

If you rebuilt them and they are no longer overflowing, please ignore my advice above!

Maz