Mohawk

Looks like the ecu fault shunt connector under middle left of seat. You put a wire across it to read the stored fault codes.

I take it that those white plastic bottles in the airbox are NOT connected to anything, right ? If so they are sound resonance chambers, probably there just yo reduce intake noise for passing tests. Take them out & see if it affects the sound.

5th & 6th gen vent the tank via a tube welded in to the bottom of the tank with its top just under the inside of the top of the tank. Thus you can fully fill the tank. There is NO vent in the cap. I assume 8th gen is the same, but don't know for sure. Either way there shouldn't be any hissing.

Or if they followed the service schedule & removed cleaned & repacked the rear axle. Normal rear ends get stripped every time you change a tyre., just like your front wheel. But SSSA don't, they should get stripped & cleaned every 2-3 years & then they wouldn't need a hammer !

That sounds like a starter clutch engagement issue, either low amps from battery or a mechanical issue.

So you say the crank lube oil way for #4 rod may have been the issue. Its a straight through drilling, was it blocked when removed the rod ? Where were the shells relative to each other when you separated the rod ? Re the journal being under size once ground to smooth. Why not just have it welded up then ground to a standard size ?

The front centre is the engine crankcase breather. And if bike is normally stored on its side stand then any oil residue will run to the front left plastic intake trumpet & seep down between the plastic & metal throttle body. When engine runs the vacuum pressure will suck it on to the butterfly & into the intake. My 5th gen does the same on #3 pot, as the breather is in the rear right corner of the airbox. Don't worry about it.

Anyone that can get 50mpg (US) on any VFR just ain't trying. Fuel consumption figures are pointless in & of themselves without a riding profile for speed & flat/climb/descent info. Plus rider style (aggressive/relaxed). If the OP never had Vtec engaged then it was a slow relaxed ride. On similar profile I have managed 50mpg (Imperial). That said the 8th gen was reworked for less peak power, more torque & better fuel consumption to ass emissions testing. As always YMMV

Sorry to hear of your issues. There is obviously some fault with those engines if after some hard use they grenade their bearings. I guess not many get a good thrashing so just keep going. Hope you find a replacement or a.another solution.

Drill it out & replace with new. Every bad one I've done was seized in the alloy, once the head was drilled off the fork popped apart & the threaded remains unscrewed by hand.

Whats wrong with the existing crank ? Theres not much that a weld up & regrind can't fix ! Just need to find the right engineering shop !

86 = 1st gen, then easy, use CBR600F2/3 wheels. I did that to my VF500 many years ago. Everything should just fit, but might require a spacer or two to get wheels central.

That sounds like G induced gray out. I've experienced it in a jet pulling 5.5g with no G-suit. But if it happens at the 1.5-2g acceleration on a bike would indicate you have a blood pressure or flow issue. Go see a Doctor, especially if you get same standing up quickly. Better safe than sorry ! 🤔

Re the earth block, mine was spotless so I discounted it. When I revisited it to replace it in desperation I cut up the plastic block & most of the earth wires were badly corroded in their metal crimp connectors. I cut them all off splayed the wire strand end & mechanically cleaned them then soldered all together in a block & heat shrink covered them & taped back in to harness. No random errors afterwards 👍😁

Aha, if you have higher replacement bars. Try adjusting the weight. Take the existing weights off & see if its better or worse. That will give you an idea if you need more or less weight. But its likely to be weight related. The VFR does have a roughish vibration in the 5-7k range, but its barely noticable with the standard bars & weights. Keep us posted.