dark plug on cylinder 6

-
C

cdnEHbody

Well-Known Member
Joined
Oct 24, 2015
Messages
443
Reaction score
131
Location
regina sask canada
Good day. On my 71 Val 4 plugs one through 5 look perfect. Cyl 6 is pretty black. Clean where it's firing. It looks dry.....but I don't see how I could possibly have a rich condition. I even pulled the plug on the top of 6 intake tube and had a look. It's not wet with gas even when sitting figured maybe float was high. But the car starts runs and drives great. Running a points driven t.f.i. module with a high ouput coil. Two sets of plugs have done this. Any ideas? Or is it oil...
 
Oil is typically shiney and often will have oil on the threads but..... How is the oil consumption? If clean where firing, then it does not sound too serious. It may just be a minor rich condition on that cylinder..... fuel/air distribution is not even across all cylinders.

Maybe swap plug wires between #6 and another cylinder and see what happens. Also, adjust the valves again.
 
Haven't noted oil consumption yet as iI havent had driven it a ton yet. End of season and all here. Good idea on the wires. Also. Just did the valves. Runs a bit nicer. But still same Ole. I actually have to do tthe heater box gasket soon. So manifolds are coming off and I'll peek in 6 intake and exhaust and see what's going on.
 
Too much resistance in #6 plug wire ? Or poor fuel distribution of intake manifold.Kinda common for the slant.Try this,, drive the car at speed(50 - 60) for about 10 miles pull over and shut it off quickly. Pull that plug and see what it looks like then.Several slant guys that I was racing with actually ran hotter plugs in the #1 & #6 cylinders,me included. I believe the 71 Slant called for N-14-Y Champion number. As more smog equipment was added the plugs went to RN-12-Y(or later YC).Just a thought.
 
also check the vacuum tee on that intake runner for leaks /power brakes/vacuum canister ect.
 
Alrighty. Good step in the proper direction. Checked vacuum at the choke pull off hose. 18.5 and very steady. Good sign there. Decided to lower my float height just a hare to see what would happen. Drove for about half an hour today and it's much cleaner. All the way down the porcelain with city driving and no adverse effects of a hare lower fuel level. Idle smoothed a bit. So onto the heater box gasket next.

thanks for all the suggestions
 
Owning a vintage japanese bike with very sensitive carbs in regard to float height turned me into a systematic thinker that's forsure!
 
You must log in or register to reply here.
-

Back
Top