Pls help diagnose RPM/power issue on RVF400

[SimonCNZ]

Hi. So a couple of weeks ago, I was attempting to ride home on a hot summers day in heavy traffic. As soon as I got on the motorway, I realised I'd forgotten to gas up, but thought I still had around 20K's before it needed to be switched to reserve (I didn't switch it at the time due to my RC211 Tyga kit which makes it hard to change on the run). I figured i'd pull off 3K's down the road after crossing the harbour bridge. Stuck in traffic though, and suddenly the bike felt like it wanted to die if I let the RPM's get too low. I managed to push on and get off to gas up, but following this the whole way home, there was absolutely no power below 5K RPM. I ordered up 4 Carb gasket kits and associated O-rings (geez do Honda make a profit on those), and proceeded to clean my carbs - there was quite a bit of gasket goo throughout them, guessing the previous owner left the original seals in the carbs and used gasket goo. At the same time, I changed the oil, oil filter, 4 plugs, air filter, and the air filter cleaner element which was disintegrated beyond belief. In cleaning the carb's, I found the pilot screw to be two turns out vs the standard 1 5/8 turns out, and none of the piston needles had a washer present. In re-assembling it, I thought I would try the standard pilot setting (as it has definitely been running rich). In trying this setting, it wouldn't hold rev's and kept dying. So I put it back to two turns out and started it with full choke. It needed some throttle to keep going until the engine was warm and the choke off when it idled fine. In riding it, power seems OK (slightly lower than it should be but consistent in rev's), but between 5-7K RPM it feels like it's really struggling to - like it was almost getting too much petrol. It smells rich and there is a small amount of black smoke when starting. I'm thinking I should get some washers now to put in the piston needle and set the pilot screw back to 1 5/8 turns. Any advice? The air box is standard, and the bike has a carbon exhaust, about 26000KM's on the clock. Sorry for the novel. Thanks

[Neosophist]

Theres a seller on here who sells new full carb gasket kits (including o-rings) for about 30 dollars that are made to very good quality, but thats a bit late now.

Perhaps there was some crap or water in the tank that made its way down to the carbs when you switched to reserve? Theres a filter in the tank so nothing major should get in the carbs.

(Have you had a look in the tank?)

It seems unlikely that you will need to start retuning the carbs to make it like it was before this happened

[SimonCNZ]

Thanks for the reply. I drained the fuel tank and disassembled the tap to look for any deposits but it looked pretty good. Also replaced the vacuum tube from tank to carb's because it was quite brittle. Although the power band is not what it was before, I think it's always been running rich. When I changed the plugs the old plugs looked quite carbon fouled...

[Neosophist]

The outsides can get a bit black, what about the tips?

What jets do you have in the carbs now? float heights / pilot screw settings?

[SimonCNZ]

Both tips and outsides looked very fouled. Identical to the carbon fouling image in my good old Haynes manual. Pretty sure the jets are all standard. Float height measured to 12.5mm as per Haynes as best as I could measure them. Pilot screw currently set at 2 turns out.

[Cammo]

You really need to check what sized jets are in there, the previous owner/s could have fitted anything.

[SimonCNZ]

OK. Can you tell me how to check what sizes they are? Thanks

[CMSMJ1]

Take the jets out and have a look - they will have some sizes stamped on them.

[Neosophist]

Both tips and outsides looked very fouled. Identical to the carbon fouling image in my good old Haynes manual. Pretty sure the jets are all standard. Float height measured to 12.5mm as per Haynes as best as I could measure them. Pilot screw currently set at 2 turns out.

Pilot is only 1 5/8s on NC35 or something like that.. but if I recall properly turnng that screw out leans the NC35 so it should be running leaner, not richer.

Sounds like you have an issue somewhere, like you said over over-rich.

Hmm, I will have a think

[SimonCNZ]

I'm wondering why the piston needles would be missing the washer - what would be the likely result of adding the washer and turning the pilot screw back to the correct setting, assuming the jets are standard when I check the size?