Tweaker, sounds like you have a nightmare that I cringe at when I have it in the shop. We will get through this, but it will take some time (but not two years) and I need alot more info.
The carb can handle the 686 kit with minor jetting changes. Depending on who ported the intake ports (or how well it was done) may or may not require further jetting changes.
Did you install the 686 kit and dyno-jet kit, and have the head ported all at the same time? Or, was the engine tuned with each step?
When (at what step above) did this problem start?
So I now we are taking about the same problem is your engine:
- Bogging: Loss of engine power without a miss. Engine runs smooth, just not making power.
- Stumbling: Engine cuts out like it is going to quit and then recovers either by itself or because you change throttle position.
- Studdering: Engine misses, recovers, then misses, and then recovers with the throttle in a fixed position.
What throttle position works (Idle, 1/4, 1/2, 3/4, WOT) to get through the problem?
What throttle position cause the worse problem?
Do you have the dynojet kit with all the spare and OEM parts?
Which main jet is installed now?
What is the idle mixture screw set to?
Is the air box lid installed or has the air box intake been modified in any way?
Was the diaphram spring changed to the dynojet spring?
Was the dynojet needle installed?
What slot is the clip in, on the needle? Slot 1 is the top one (fat end).
Has the needle jet ever been change?
**Can you pull the needle out, remove all parts from the needle (except the clip) and lay them out in the same order they came off in and then post a close up picture? Is this order of parts the same as it was orginally set up (refer to the dynojet instructions)?
Do you have a good place to do several cutoff tests if needed.
**Do you know for sure the float level is right (04's are really inconsistant)? Best way to check is to attach a small clear fuel line to the carb drain nipple, open the drain screw with fuel petcock on and with the clear line held up along side the carb. The fuel level should be exactly at the gasket surface between the float bowl and the carb body.
Do you need the choke on to start the engine cold?
When the engine is warm and no throttle (or choke) applied does the engine start immediately?
My gut feeling from what you described is you have a two problems: Rich on the needle and lean on the main jet. The two items marked with ** above are the usual problems that cause a rich/lean or lean/rich condition.