Not new to the forum scene, amazed this one is still as busy as it is though! (seems to be IanDohaan keeping it alive) I work on carbuerated and EFI
Japanese cars so I'm not completely helpless, but I'm a mite bit stuck.
Three days ago, I encountered my first mechanical issue on my 3-week-old purchase, a maintained 1994 Honda CBR900rr. I have read through a collective 30 threads that have any keywords related to an overflow problem and am convinced it's time to make a post.
The bike ran quite literally perfect for the three weeks I had it. Rode it home from work and then set it on the kickstand after shutoff. Fuel started dripping out a hose of the left side.
It only stopped with the petcock being switched off.
I then started it to move it to a buddy's house. It ran for a minute until it just chugged slower and slower, then died out. It eventually stopped turning over.
I hit r/Fixxit on Reddit after reading up here, just to avoid annoying y'all with what looked to be a stuck float needle. You can read that small thread here
The bike sat with float drains open for a day. I tore out the carbs, cracked the floats open, and the interior/needles were pristine. Ran Gumout carb cleaner through the entire system, but I did NOT open the vacuum diaphragms. Reinstalled, got the same leakage. It then stopped turning over, as if it's flooded.
I read that it's possible a cylinder (or several) aren't getting spark, which would cause excess fuel to enter the cylinder and then stop it from turning over; however, that does not explain the leakage, does it?
I've attached all related pictures.
Edit: My FSM is coming on Wednesday, woohoo! Been using the '96-'98 PDF version so far.
Hey BV, thansk for the mention, there are a few of us here that try to keep the forum going in the days of Facebook, etc. In regards to your issue, I have a few (ok maybe more) questions/comments.
I see in your pics
(great job adding them, they help a ton), that the hose you are mentioning drains out by the kickstand. That hose should connect to the underneath of your tank. Does you bike only leak the fuel while in the side stand? If so, its leaking from a corroded/disintegrated internal vent line that vents the tank. Inside the tank is a small steel tube (only noticeable with a dentist/inspection mirror inside the tank. If there was ever nasty fuel left in the tank, it eats away at it, and a full tank of fuel will usually enter the steel tube and drain out the vent hose shown in your picture by the side stand (I cant see what it goes up into, but just using deductive reasoning, as there are only 4 hoses on the old 93/94's). Those hoses are the carb vent hose 45 degree angled open air hose on the right of the carbs, the fuel tank vent, the fuel tank overflow, and the coolant overflow (small opaque tank behind fuel pump). On the SC28's, there were no other drain/vent hoses I can think of (but I'll be honest, It's been 30 years since I've seen a stock enough 900 to remember). Anyway, what is attached to your cabs to believe they are the leaking though that hose? Pics of that? Another thing I see in your pics (unrelated), is that your air-box grommets (the 4 parts with the clams on them that are still attached to the carbs by the velocity stacks should be sealed onto the air-box itself, not left on the carbs as yours are. Common issue with the old bikes in that the old liquid gasket material tends to lose its grip. You'll want to remedy that as well.
That leads to my next comment which is that it seems like a coincidence that turning the fuel valve off stops the leak, as the fuel pump will handle that (and again, your awesome pictures show the pump and the filter (albeit not mounted properly, but I'm not judging
). On the newer models SC33's, there is a vacuum operated fuel valve to stop flow because of the deletion of the fuel pump. Anyway, a more definitive picture of the where that hose is connected to at the top of it would give me a better idea. Obviously you've had the tank off, so you would know if that vent hose from the tank is the one, but I can't make assumptions (its the internet buddy, don't discount anything lol)
It MAY be hydro-locked (cylinder full of fuel), but a quick check of your oil level may confirm or deny that as the level will be high due to it being diluted with fuel. Its a possibility.
When you said "eventually stopped turning over", what exactly did you mean? Not turning over is the starter has power but doesn't crank the engine. Is that the case, like the motor is seized? Or does it crank but not catch and run? Try pulling the plugs and cranking it. JUST BEWARE IF THE CYLINDERS ARE FULL OF FUEL SO WILL YOUR FACE if you're not careful.
Very interested to see more pics
and if any of that helped you out.