BF30A Bogging under load mid to high RPM

Engine is a BF30A 1997. Bogging only happens under load; when not in gear the engine will rev up to the limiter just fine no issues. When under load the engine will rev to mid rpm no problem, but as soon as I give it the beans it just bogs down and won't put out any more power. Sounds like the engine is choking. If I do gas it and let it bog out, there is significant power decrease across all rpm for a short time before returning to the normal full power up to mid rpm.
Carburetors have been completely rebuilt, new jets, new gaskets and orings on all carbs and intake. New fuel lines, new fuel filter, new fuel pump. 98% sure there should be no issues fuel side. Compression is good across all cylinders. Checked, doubled checked, tripled checked and it's good. If anyone is wondering, it is 120 psi across all. I know it sounds low, but it is a pull start model and has been that same compression reading since I bought the engine long before I ever had this problem. New spark plugs, old ones not fouled, resistance check on ignition coils showed they are all within spec. Did the old school pull the plug on each cylinder while its running test and all cylinders are firing.
I'm thinking its the CDI, but I can't get a new one and would have to buy used and I really don't want to have to check resistance on all the CDI components. Any thoughts before I pull the trigger on a used CDI?

Timing good? Belt not too sloppy and "floating" under load? I doubt it would cause this within actually jumping a tooth or two but worth looking at.

I'm going to have to assume that the carburetors are flowing correctly since you covered that already.

Pull the cam pulley cap and check the pulsar coil. It can get dirty and wet in there. That could cause it not to advance the ignition timing correctly.

This sort of sounds like a cylinder dropping out under stress and that could be a number of things. Could be a bad ignition coil breaking down. Not sure how you check that without an oscilloscope though. But do look very carefully at the wires and fitment of the replaceable plug boots to the wires.

Other than those things, a weak/ broken valve spring might act like this and not be indicated on a static compression test. If it were a car, I would try a running compression test but not sure how that would work in this case with just the three cylinders. So pulling the valve cover and inspection is your option here I guess.

You could very well be right about the CDI but check those other things out before putting out that money.

Good luck.

Sorry, my experience has been if you have something like this going on there's about a 90% chance it IS in the carbs, and because you've gone through it once DOES NOT mean there's a 100% chance you didn't miss something. Please don't take this personally, but you most likely DID miss something somewhere. I have literally done hundreds of these carbs, and though it's now pretty unusual, I am STILL quite capable of missing something somewhere on occasion. For that reason, there is no hesitaion on my part to pull them down again, for an even more careful cleaning/inspection. "Careful" cleaning/inspection would be blowing air/squirting carb cleaner through EVERY opening in that carb, and wherever possible, sighting through the passage to confirm it IS clear, beyond any doubt. FWIW, -Al

Thanks for the response! Timing is good and there is no slop. It is tensioned correctly. I replaced the timing belt a couple of years ago, and the first time I had it just one tooth out and the engine could barely run even under no load, so I'm positive it's not the timing. Will check the pulsar coil and take a good look at the coils and plug boots again. And I'll take the valve cover off and take a look at the valve springs. Out of curiosity, do you think that even with resistance being within spec on all ignition coils that they could still be the problem?

Thanks for the response! I am totally with you on this seeming like a carb issue, which is why I have actually taken them apart and fully cleaned and inspected every passage three times. Carb cleaner, compressed air, super clean work area with no dirt or debris, the works. Checked the main jets for tiny cracks and couldn't see anything. All passages totally clear before I put the carbs back together and almost all new components installed. I suppose it is possible I missed something, but I feel like after triple checking it is likely something else. Let me know if there is a specific part (or parts) of the carburetor that you think could be the cause of this issue, and I would have no problem tearing them down one more time.

Did you check both primary and secondary resistances? If yes and it revs up ok in neutral then I think you can only assume the coils are ok....for now anyway.

I wouldn't be surprised at all if you do find it's a carb problem. As Alan suggests, it could just be something you missed on just one of them.

Did you clear the low and high speed air jet passages at the forward mounting flange? Lots of people miss that.

Are all the orifices at the top of the throat above the throttle plate flowing pressurized cleaner freely? At full load, every one of those contributes fuel, even the idle orifice.

You never mentioned the low speed "jet-set". Those are hard to clean and they often crack.

Alan does these way more than I do anymore so he probably has some good ideas for you.

Standing by and hoping you slay the beast!

My experience has been that Honda's ignition is rock solid. It's actually the LAST place I look for trouble.

What about your idle mixture settings? Is there ANY chance you may have set them too lean? Going half a turn richer might be worth a try, to see what happens, even if it doesn't run as smooth as it does when set slightly lean.

Bottom line, my thought is the engine is lean. You just need to figure out why.....

Primary and secondary resistances were in spec. Thanks guys for your recommendations, I'll recheck everything to do with the carbs and try to figure out if the engine really is running lean. That being said, I took the valve cover off to take a look inside the head and found something pretty unfortunate. Looks like the caps of 2 of the intake bolts cracked off inside the head...... here is a picture: https://imgur.com/a/kh7Iw7a
Im thinking maybe some of the debris from the head has damaged my valves but I figured that if that was the case then the compression test would have shown it. Thinking I'll perform a leak-down test just to be sure. Let me know what you guys think and how bad of a problem this is/could be.

Wowee..... That's certainly not something you want to see when having a quick look inside. Clearly caused by the use of too long a bolt. That said, I doubt it's the kiss of death. Hopefully the chips are resting in peace in a little niche they found in the oil pan, with any smaller particles handled with screens and filters.

What it does point/hint at, may be the source of your lean condition, which COULD be a vacuum leak where the intake bolts to the head. Have you had that apart?

Actually it was caused by repeated anti-sieze use on my part... really mad at myself about that one. Looks like it just kept packing in there until it burst... theres a lesson learned right there. I've had the intake off quite a bit recently, just put it back on when i did the carbs with a new gasket and didn't notice any cracks or anything awry. I did just hook up my vacuum guage to the intake runners to tune the carburetors and and synced them all up to the parent carb. All read around 6 psi at the end which seems a bit low to me. Let me know what you think.

Ouch! But I don't believe those pieces could damage the valves. Just make dang sure no pieces are tangled up in a spring. They could also clog the oil return passage but you would have probably had excess oil come out when you removed the cover if the oil wasn't getting back to sump.

I might pull the drain plug and see if I could fish anything out with a hook shaped piece of wire.

Run it at idle with the cover off and see if you can detect vacuum leaking at those broken bosses. Yes, it might get messy but a quick squirt of carb cleaner at each one might show it up for you. If no vac leak then you're probably ok.