Overflow not fixed by carb rebuild on '94 CBR900rr - Honda Motorcycles - FireBlades.org
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post #1 of 30 Old 09-16-2019, 10:19 AM Thread Starter
 
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Overflow not fixed by carb rebuild on '94 CBR900rr

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.
Attached Thumbnails
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3fb075b95717dd3ba4431f7448e5bfdabd6415d5-1.jpg‎   2.jpg‎  

Last edited by bv9900; 09-16-2019 at 10:33 AM.
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post #2 of 30 Old 09-16-2019, 10:57 AM
 
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Re: Overflow not fixed by carb rebuild on '94 CBR900rr

Could be the O rings on the hoses that run between the carbs and seal the plastic T's that those hoses bring fuel into the carbs. I have that issue every year when I start the bike up for the 1st time in the spring. It seals itself in my case but if those are original plastics, o rings, and hoses it could be your issue. Good luck with your repair.
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post #3 of 30 Old 09-16-2019, 11:13 AM Thread Starter
 
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Re: Overflow not fixed by carb rebuild on '94 CBR900rr

Hm, how would that go into overflow though? It drains through a hose to the ground, not just spilling everywhere like a loose O ring. I think I'm missing something here.

Would that also see the motor bog down like it's doing?

Thank you for the reply, I'm in classes and trying to find time to quickly get back to y'all. Much love
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post #4 of 30 Old 09-16-2019, 1:38 PM
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Re: Overflow not fixed by carb rebuild on '94 CBR900rr

Quote:
Originally Posted by bv9900 View Post
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.
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post #5 of 30 Old 09-16-2019, 4:06 PM Thread Starter
 
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Re: Overflow not fixed by carb rebuild on '94 CBR900rr

Yup, I come from tech forums where all supporting data is basically mandatory. Upon re-tearing down the bike, I'll upload more pictures (if it isn't too dark out).

There's only one hose connecting to my tank. Two out of three pipes are just hangin' around. ...so where in hell is this gas leak coming from if that hose isn't connected there?

It leaks at all times, not just the side stand thankfully. I can't believe I didn't trace that kickstand-area hose to where it started from.. Will do that when I get back to the bike. And yeah the grommets are pain in the *ss to get back on, knew I did that wrong. I'll check the oil level and then crank it after the plugs are out but yes, even it cars being in the way is a baddd idea. The engine simply stopped cranking, as if the starter couldn't keep it going. I'll check battery voltage but chances are it's hydrolocked...

Just wanted to say thanks mate. This is my daily (low on funds for the next month) and I'm kinda dead in the water without further thought. Shoulda got an EFI moped if I was smart, huh?

Totally exhausted so I may disappear for a bit to pass out, don't worry. I'll be back with results/pics
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post #6 of 30 Old 09-19-2019, 12:49 AM Thread Starter
 
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Re: Overflow not fixed by carb rebuild on '94 CBR900rr

Didn't even have to tear down the bike again. Traced the hose like my logic told me to the first time ("it's a stuck float needle!") and found it went to the fuel pump. The pump does not look to be stock; online, it says the hose (shown in pictures, at the bottom of the motor) is an air-only vent. Apparently, when the internal gasket breaks, fuel can leak through.

Guess what the little monster sounds like? (hint: click link for the recording)

Sounds just like a Mallory automotive fuel pump that locked up. The engine cranks fine, kept doing it with no fuel pump until I was afraid I'd kill the battery (stays at 11.88-12+ volts).

New fuel pump and inline filter on the way; will post results.

Thanks Ian. You're a G bruv
Attached Thumbnails
9551609eb5eb03c946b1f386241cbe0bf89fe1a7-1.jpg‎   3624a1bf4392c673529299e2d8581c6804bf425c-1.jpg‎   3d0e660dd015a882c61fec146bef381624e9fd09-1.jpg‎  
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post #7 of 30 Old 09-19-2019, 4:30 PM
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Re: Overflow not fixed by carb rebuild on '94 CBR900rr

Quote:
Originally Posted by bv9900 View Post
Didn't even have to tear down the bike again. Traced the hose like my logic told me to the first time ("it's a stuck float needle!") and found it went to the fuel pump. The pump does not look to be stock; online, it says the hose (shown in pictures, at the bottom of the motor) is an air-only vent. Apparently, when the internal gasket breaks, fuel can leak through.

Guess what the little monster sounds like? (hint: click link for the recording)

Sounds just like a Mallory automotive fuel pump that locked up. The engine cranks fine, kept doing it with no fuel pump until I was afraid I'd kill the battery (stays at 11.88-12+ volts).

New fuel pump and inline filter on the way; will post results.

Thanks Ian. You're a G bruv
Thanks BV. You don't have to use the pump if you don't want to, but that might be moot as you have one coming. I don't have on on my 93, took it off for 1: weight and 2: issues that you now have 3: it was just a cool thing to do at the time lol

Obviously the low fuel issue from the bad pump would generate your other issues. Here's how it mounts with the filter. Curious to see how it goes when you get the new one.


Click image for larger version

Name:	Fuel pump 93.JPG
Views:	6
Size:	133.1 KB
ID:	94764
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post #8 of 30 Old 09-19-2019, 5:34 PM Thread Starter
 
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Re: Overflow not fixed by carb rebuild on '94 CBR900rr

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Originally Posted by IanDoohan View Post
Thanks BV. You don't have to use the pump if you don't want to, but that might be moot as you have one coming. I don't have on on my 93, took it off for 1: weight and 2: issues that you now have 3: it was just a cool thing to do at the time lol

Obviously the low fuel issue from the bad pump would generate your other issues. Here's how it mounts with the filter. Curious to see how it goes when you get the new one.


Attachment 94764
Oh! I forgot we could do that. Hell yeah. I may try that.

And thanks for the mounts! I have the FSM and memorized most of it upon disassembly but that's very helpful.
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post #9 of 30 Old 09-19-2019, 8:34 PM Thread Starter
 
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Re: Overflow not fixed by carb rebuild on '94 CBR900rr

Stupid battery dead. Couldn't jump start it on my own. Will have at it tomorrow.
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post #10 of 30 Old 09-21-2019, 11:11 AM Thread Starter
 
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Re: Overflow not fixed by carb rebuild on '94 CBR900rr

Right, so it ran last night! Started fine, but took a lot of throttle at first. I rode for a minute and then it died out over a period of 10 seconds.

Fuel starvation because it's used to having a pump? Did you have to change anything after deleting your pumps, Ian?
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post #11 of 30 Old 09-21-2019, 12:36 PM
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Re: Overflow not fixed by carb rebuild on '94 CBR900rr

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Originally Posted by bv9900 View Post
Right, so it ran last night! Started fine, but took a lot of throttle at first. I rode for a minute and then it died out over a period of 10 seconds.

Fuel starvation because it's used to having a pump? Did you have to change anything after deleting your pumps, Ian?
Didn’t add or change a thing. Just a straight hose from the fuel valve to the carbs. Well, to be concise on that I deleted the fuel filter, because that was only there to catch debris from the possibility of the pump pumping sh!t into the carbs.

I run my 93 and 99 (the SC33 96-99 didn’t use a filter or a pump) without both. Never had a running issue. Maybe you need to pull the bowls off the carbs and check them for schmegma aka dirt etc lol

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post #12 of 30 Old 09-22-2019, 4:02 AM
 
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Re: Overflow not fixed by carb rebuild on '94 CBR900rr

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Originally Posted by IanDoohan View Post
Well, to be concise on that I deleted the fuel filter, because that was only there to catch debris from the possibility of the pump pumping sh!t into the carbs.
Ian, my RR-P fuel circuit seems to be: Tank Tap > Filter > Pump > Carbs ......
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post #13 of 30 Old 09-22-2019, 6:50 AM
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Re: Overflow not fixed by carb rebuild on '94 CBR900rr

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Ian, my RR-P fuel circuit seems to be: Tank Tap > Filter > Pump > Carbs ......
Right you are sir, I had it backwards. Filter then pump then carbs.

Glad I’m not the only guy here who knows a thing or two

Clean fuel into pump makes for clean fuel out of the pump.
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post #14 of 30 Old 09-22-2019, 1:35 PM Thread Starter
 
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Re: Overflow not fixed by carb rebuild on '94 CBR900rr

Hm, I could try shooting some carb cleaner in and see if it revs higher (meaning a fuel flow problem) but yeah I hope to high heavens it's not clogged! A full rebuild, not just a float check, would really suck haha.

I'll do a filter delete as a last chance check and swap out the piece of hose, as it could be too long for the gravity feed connection.

Any other ideas, haha? Willing to test most anything. Bike's down for the count it seems. Tuning issue perhaps?
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post #15 of 30 Old 09-23-2019, 4:04 AM
 
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Re: Overflow not fixed by carb rebuild on '94 CBR900rr

Hello bv9900, can we just confirm where your leak is coming from, I believe (Help please, Ian !?!) that if the Carb Float Chambers are overflowing, that the fuel will spill out here ......... <see photo>. Is that what you are seeing?
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Last edited by Duncan893; 09-23-2019 at 4:34 AM.
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