03 vstar 650, 27k~ miles. Cobra drag pipes, RAK intake mod with K&N filter. 130 main jets, 2 #4 washers on each needle, mixture screws 3.5 turns out. Symptoms present before and after mod, but has gotten worse as time has gone by. I'll try to be straight and to the point with what I've tried and whats happening.
I can ride for about 30-45 minutes of gentle riding before the engine begins to hesitate, misfire, spit, sputter, backfire/pop- she gets noisy. Or if I'm aggressive with the throttle, it'll happen after about 15 minutes. This starts slow, like I need to switch to reserve, and will progress and become severe and make riding hazardous. Present throughout throttle range. While severe, the bike struggles to idle and might even die. Choking and throttle seems to help at first -slightly-, and briefly.
I've tried removing the fuel cap when this happens and ride for a bit- no change.
Replaced fuel filter. Lots of fuel flow with hose disconnected. Fuel pump seems to be working ok but, but haven't disconnect hose to check for pressure increase.
I've cleaned and synced the carbs. Used propane to search for intake leaks. Found one, and sealed up intake joints with RTV on reassembly. No change.
Pickup coil was out of tolerance- in the 500 ohms or so while cold. Symtoms remind me of last time my pickup coil went out- except symptoms and complete failure occured in the same day. Stator was in tolerance but had one coil that was charred. I replaced both with new OEM parts.
Ignition coils out of tolerance around 17kohms, i think the limit is about 15kohms. I have not replaced these yet.
I do have some excess blow by passed the rings, air and oil will launch out of the crankcase if I take off the oil filler cap while running (not normal, right?) Compression in the mid 120s psi hot, which I know is below factory spec, but I've been told if I'm over 100 dont worry about it.
Charging voltage normal, don't remember the numbers but can do it again if needed.
There is exhaust discoloration mostly on the rear cyl exhaust. Yellowing on the outside cover, blue underneath on the actual exhaust. See pics.
I've fired the bike with the igntion leads disconnected and not grounded in the past, before I knew this can be harmful to the ignition system.
Front carb main jet oring blown out, I can see a small edge of it looking through the main jet. I have new orings, just havent swapped them yet.
Carb heat shield missing- vapor lock?
The bike does take longer to warm up after my mods.
Slight hesitation and pop while shifting gear with aggressive throttle during warm operation- does not seem related to issue when the bike gets hot--- and need to mention, night riding greatly extends my riding duration, even with aggressive throttle. Sometimes night riding I'll have no symptoms. Hot florida afternoon on the other hand- beware how far and where you're riding!
Hopefully thats everything....
Where should I continue from here? Not sure if the mixture is a part of the problem, but I'm suspecting mostly electrical? Just wanted some second opinions before I start swapping parts again (the stator and pickup coil were a chunk of change
) Thanks for any leads