Topic: Plug reading - Need advice

[joeyvans]

It's my understanding that an exhaust leak actually reduces the combustion temperature and pressure, resulting in a less efficient burn, thereby deposits. I wouldn't say your "introducing" air as that comes form the intake side, but you certainly aren't "sealing" the combustion event fully.

Yes... Completely makes sense, Cal.  Thanks for the explanation!

Side note: My dry compression readings are all within 10% of each other with only 1 or 2 PSI difference across. The wet test only increased my readings by 1 PSI across the board.  Any recommendations on the #4  head?

[flybox1]

Be sure #4 header is sealed well
recheck your #4 bowl fuel level
redo your vacuum sync

[joeyvans]

Thanks fellas. I re-torqued the exhaust collars a few days ago. Had a slight tappet click, so re-adjusted tappets last night, then re-checked timing. All good there.

Definitely running good, but will clear tube all carbs again. I did it off the bike last time. Maybe I wasn't level. 

I'm going for about a 120 mile ride tonight. Am going to squeeze in the 2/3 chop, but aside from that... Will open it up in the wide open country I'll be in.

[joeyvans]

Update: 

What ultimately fixed the minor stumble in the low throttle range was the fuel level in #2 still being a bit too high even after clear tubing and thinking it was perfect.  After a ride, I noticed #2 spit out fuel from the overflow.  So, I cleartubed it again and it was too high.  Once that problem was resolved, and the needle clip was raised to middle position again, the stumble was completely non-existent.

Carb settings - 087a with UNI replacement filter in stock airbox:  105 mains, 38 slows, Needle clip - middle notch, IMS - 1.5 turns.

As said before I am NOT a short shifter and love to hear this exhaust.  Given these riding conditions, on any given tank, I typically get around 35 MPG.  I did a high speed run at the end of my 2015 riding season (60 degrees).  GPS verified that I hit 99.6.  I had to let off as I was quickly approaching a speed zone.  But, from a stop all the way to 99.6, there was no stumble and I believe I could hit 100 - 105 mph.

Thanks again everybody for the help with this.  Hopefully I'll be able to enjoy the bike more in 2016.  Cheers!

[flybox1]

Sweet    Glad you figured it out.
Thanks for the update.

[Redline it]

Update:  Since the airbox drain plug is obsolete, I rigged up a tube with a cap on the end for the time being.  I will periodically pull the cap and make sure nothing is accumulating in there.  I also added a tube on the air chamber breather nipple that extends towards the right side of the bike.  I'm guessing this doesn't make a difference as others have said they have never had anything hooked up to the chamber breather nipple. 

Anyways.... intake is now about as stock as I can get it, aside from the Uni Foam replacement filter... which I believe restricts airflow.

Warmed up engine yesterday, returned and put new plugs in.  Then road for 40 miles..... again speed typically between 60 and 80 and accelerating hard from stops.  I can guarantee my tach is off because when I'm riding in 5th at 75 mph, it is only showing 4K.  Still stumbles a bit in the lower RPM range, but nothing that cracking the throttle can't fix.  It has always run strong in upper throttle ranges.  I'm hoping the install of the 4-1 exhaust will make things more uniform across the board, as I have eluded to different backpressure across each pipe due to rotting.  Here are my plugs after that ride in order of 1-4... I'm curious if others think I'm ok to run as is.  Thanks in advance!  - Kyle

I had a few 1970s 750's and a couple 76 400f's, one running right now.  Runs bad ass, then the next day, it's doing other things. I run a home made foam element that wraps around the screen of a stock filter holder, it's oiled also, I quit buying air cleaners in the 80's. The last 400 motor ran #$%*en 60mpg at any speed with that foam air cleaner, up until 32000 hard miles and a ring broke.  Carbs, synced or not, always will do different things, out of nowhere, the air screw settings are all very different that each other,  sometimes I'll adjust them at each stop light, for how much time the light gives me, fuel levels adjust themselves from gear to gear. I use to be somewhat interested in them running super clean. I give it time now to find it's own settings, and then out of nowhere it runs #$%*en. Still have the 2 400s. Idling I don't care too much about it, when you roll it on, and hold it, that's where they always run good. Got a fresh motor with couple thousand miles running now with the foam air cleaner. I watch the ignition, mostly. Jets are probably all worn way out, I'm lucky it runs. My plugs look like yours. Maybe it'll keep all that carbon from building up. 

[flybox1]

I had a few 1970s 750's and a couple 76 400f's, one running right now.  Runs bad ass, then the next day, it's doing other things. I run a home made foam element that wraps around the screen of a stock filter holder, it's oiled also, I quit buying air cleaners in the 80's. The last 400 motor ran #$%*en 60mpg at any speed with that foam air cleaner, up until 32000 hard miles and a ring broke.  Carbs, synced or not, always will do different things, out of nowhere, the air screw settings are all very different that each other,  sometimes I'll adjust them at each stop light, for how much time the light gives me, fuel levels adjust themselves from gear to gear. I use to be somewhat interested in them running super clean. I give it time now to find it's own settings, and then out of nowhere it runs #$%*en. Still have the 2 400s. Idling I don't care too much about it, when you roll it on, and hold it, that's where they always run good. Got a fresh motor with couple thousand miles running now with the foam air cleaner. I watch the ignition, mostly. Jets are probably all worn way out, I'm lucky it runs. My plugs look like yours. Maybe it'll keep all that carbon from building up.

There's a few priceless quotes in there 
I'm partial to "give it time now to find it's own settings, and then out of nowhere it runs #$%*en"

[joeyvans]

My plugs look like yours. Maybe it'll keep all that carbon from building up.

One thing I failed to mention.... My #4 plug still has dry fouling, even after I installed a Pamco with Dyna coils. I was hoping it was due to weak spark, and the revamped ignition would cure it. But now I believe the combustion chamber has a ton of carbon buildup from the exhaust leak (Cal explained this possibility earlier in the thread) I found before the 4-1 install. So.... Next summer, I rag the #$%*e out of the motor and hopefully burn some of that carbon off.