Lean Issue - 205 Main and Still Lean - HELP!!!

[Quadzilla]

Hey guys,

I have a lean issue that won't go away. I got my 416 motor back (ported, valve job, Hotcams stage 2, etc) and bolted on a used FCR 39 that I got. Went all the way to a 188 main and it was still too lean. Checked for air leaks by shooting carb cleaner around air boots and carb while idling. Nothing happened. Thought I bought a bum used FCR so I went and ordered a Service Honda 40mm FCR and a bunch of jets. Even with a 205 MJ and needle on 2nd clip from bottom, it's still a bit lean. Anybody here ever fight an issue like this? For the life of me I can't figure this out. Intake manifold appears tight and no visual cracks. Sprayed carb cleaning there also while running and nothing. I know the carb cleaning thing works because one of the times that I had the carb off, I left one of the boots a bit loose and the rpm instantly shot up with the carb cleaner hit the boot. Could this motor really just want that much gas (again a 205 main or larger)?? Look at the list of what I got done below and you tell me. The plug is just barley greyish with a little darkness to it, but not quite tan. I'm afraid that I will blow it up if I ride it too much. What could this be? Help!

[MIKE400EX]

'Zilla,
It's conceivable that a 205 main might be right but not likely. Have you checked the slow/pilot jet, slow air jet(or slow air screw setting if applicable), or the main air jet? A main air jet that is too big will also lean out the upper rpm range. Also, pump unleaded fuel is almost impossible to get a good plug reading with. Try running some leaded race gas to help diagnose the problem(s) and get it in the ball park. Was the porting done by an experienced person or is it a "home dremel" job?
You have an email!

[Quadzilla]

Thanks for the info Mike. On the gas, I'm running Sunoco Race 100 Octane. Not sure if it's leaded or not, but I imagine so. I'm going to pick up some 110 today or tomorrow.
On the porting, a local, experienced motor builder did the work. He did not polish it, just cleaned up the intakes (smoothed out flat spots) and matched the intake manifold to the head and opened things up a hair (not much).

[MIKE400EX]

I think Sunoco sells a GT unleaded that's 100, at least that's what some places advertise around here. Try that 110 and see if you get more color.
Doesn't sound like the head could have been hurt too much with only that porting. If not done correctly, the air flow will slow and you'll have to up the jetting because of the poor carb signal.

[zephead400ex]

Do check the pilot jet. Mike is right on, the pilot can affect the main jet or upper rpms. I have had experience with this before, but not quite as lean as your running:p

[Quadzilla]

Originally posted by MIKE400EX
I think Sunoco sells a GT unleaded that's 100, at least that's what some places advertise around here. Try that 110 and see if you get more color.
Doesn't sound like the head could have been hurt too much with only that porting. If not done correctly, the air flow will slow and you'll have to up the jetting because of the poor carb signal.

That's the stuff (Sunoco GT) and as you pointed out, it's unleaded. I'll pick up the 110 leaded and see what my plug looks like then. Thanks for the assist. I'll be wrenching this eve....