I installed Shorty Tapered Paughco Duals. I also went from stock cam to an EV13 cam along with Velva Touch Lifter Blocks.
Still running stock low compression on a 1983 Shovelhead.
Running .028 intermediate jet and .072 main jet.
With these jets plugs were off white with stock crossover exhaust, now they are black and soot covered. The idle air fuel screw is less than a turn out.
It smells really rich but no black smoke that I notice.
My gut tell me to drop down one size on both but Nightrider recommends not going lower that .028 on intermediate jet size.
Will main jet size affect idle or low speed at all?
No, but a missing oring, or a hanging float might...
O-Ring new, reset the float height last time I had the bowl off.
I re-watched S&S carb tuning video and they made mention a low restriction exhaust will cause a rich condition. They were running a 2-2 exhaust in the video with lower number (leaner)jets than the common suggested .028 and .072.
Main is high rpm only. If it needs leaner it needs leaner. Never hurts to try. The suggested jetting is normally on the rich side.
A couple years ago I installed some Paughco tapered muffler staggered duals and found them to be very quiet and restrictive like stock harley mufflers. If yours are like the ones I got that could be contributing to your sooty plugs. I've never got a set of aftermarket exhaust that was a quiet as the Paughco's, maybe they have to comply with some new EPA decibel rule. I opened the baffles up and they started sounding and flowing good.
I ve been helping a guy with a new build. .0265 & a 68 main This thing has new pipes from ??? and it will gas foul a set of plugs in no time. The pipes turned blue from the head down to the first bend. About to give up. He already had the shop try and get it to run leaner that built the motor and they gave up. They think the carb is worn out Been on since 89. Hate to go any lower on the intermediate but guess we can try it. Running out of ideas to try.
With jets that lean in it there is likely something wrong with the carb. Float level is high?
Float level is high? Now you lost me. Can you explain how this would make it foul out the plugs if the bike is running like nothing is wrong with it? Plugs are black from gas so I am guessing you are saying it is getting too much gas. But if it is getti8ng that much raw gas wouldn't it be running a little doggy? Like falling on its face when you open it up?
Quote from: DresserDan on June 17, 2019, 08:08:39 AM
The pipes turned blue from the head down to the first bend.
Late spark timing will do that.
How about running after switch is off? It has done it a few times.
Lots of things come into play for run on. It usually takes a combo of these.
High head temps
High idle speed
Rich idle mixture
Quote from: Burnout on June 17, 2019, 07:40:36 PM
Lots of things come into play for run on. It usually takes a combo of these.
High head temps
High idle speed
Rich idle mixture
Poor fuel
Burnout,
I will re-check timing and rejet the carb back to standard. I road bike with the lean jets and is was scary lean.
Quote from: Hossamania on June 18, 2019, 07:45:31 PM
Quote from: Burnout on June 17, 2019, 07:40:36 PM
Lots of things come into play for run on. It usually takes a combo of these.
High head temps
High idle speed
Rich idle mixture
Poor fuel
This for sure.
Old fuel will exhibit many symptoms, too many and too varied to list.
I will add that old fuel cannot be fixed with additives or snake oils.
Adding anything to a tank of bad gas just creates a fuller tank of bad gas and taps into your beer money.
The best solution for this problem is to drain the tank, flush and refill with fresh premium fuel.
Any fuel that is over 6 mos old should be suspect.
Any tuning done with bad fuel will likely result in a bad tune when the old fuel is replenished.
I don't mess with old fuel, I don't even put it in my mower after sticking the valves in one of my old mowers due to crappy fuel I was trying to dispose of.
I have a 5 gallon can full of it in the garage I'm looking to find a use for or get rid of. Starting burn piles does not use enough!
With today's fuels you cannot read the plugs as they do not color like they used to.
Many guys today have straight pipes, and tuning with them is futile.