Topic: Bike dies and really badly fouled up plugs after only 150miles

[tommychains]

Hi guys, I've had constant issues with my '78 CB750F running poorly and eventually 1 then 2 cylinders quitting altogether. It seems to run fine again when I change the plugs. I've attached a pic of the plugs taken out after only 150 miles. They're really fouled. Is this likely just due to overly rich mixture? I will be looking at taking apart the carbs and taking the jets down one or two levels. Can there be something else causing this though? I have air pods, electronic start, and 4-1 aftermarket exhaust on the bike.

[PeWe]

Look like floats are floading. Verify float heights, floats not blocked, float valves can close.

[flybox1]

when was the last full maintenance performed?  valve adjustment, timing/advance, carb clean/vacuum sync...etc?

what jets are you running for your pods?
clear tube test your fuel height....its easy on your PD carbs.

[tommychains]

Thanks for all these tips folks!

-cylinders 1&3 die, so it's not likely related to ignition
-I haven't done any valve adjustment, timing/advance maintenance done, so I'll look into this

My first step will be a take another close look at the carbs and check floats.

Flybox1, can you elaborate what you mean by "clear tube test your fuel height"?

[flybox1]

its a test of the fuel level in your carb bowl, and is very easy for PD carb bowls.
Fuel level is important.  too much and youre rich.  too little and youre lean.

http://forums.sohc4.net/index.php/topic,135470.0.html

http://forums.sohc4.net/index.php?topic=166447.0

[tommychains]

its a test of the fuel level in your carb bowl, and is very easy for PD carb bowls.
Fuel level is important.  too much and youre rich.  too little and youre lean.

http://forums.sohc4.net/index.php/topic,135470.0.html

http://forums.sohc4.net/index.php?topic=166447.0

hah very cool thanks

[MicahDT]

Plugs look like the engine is running too rich. I had the same problem when running rich. Mine was caused by float level as mentioned above.