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Discussion Starter #1
Hi gents
I did several searches but can't find a similar issue
I recently restored a very low mileage (4K miles) 95 CBR 900 that was garage neglected for 15+/- years

The carb was completely packed with varnish. I overhauled the carbs and replaced all o-rings and jets. Reassembled bike and have an intermittent gas leak out of the "far left" carb. Sorry I don't remember the carb numbers and my 5 y/o has replocated my shop manual for me :D

When I open the petcock and start the bike it may OR usually won't leak and it idles and runs beautifully up to 55 mph. When I return and park the bike it usually will start leaking fuel when turned off OR a while into idling..

The fuel appears to be dripping off the bottom of the carb onto the starter area. When I turn the petcock to off after a few moments the leak will stop. Initially I thought the float needle was stuck open and causing an overflow - BUT I think I've learned that this condition would drain fuel out an overflow hose? Or does the overflow from a stuck float/needle cause leaking at the bowl cover itself?

Could this be as simple as a bad seal in the bowl cover itself? when the fuel in the bowl gets to a certain level it's leaking past the seal? I rebuilt the carb a second time and the float and needle appear to be working fine. The bowl seal is new and appears to be seated in the grove properly.

One other thing happened of note. Yesterday with the bike off, no leaking, petcock set to "off" and on a track stand. When I transitioned to the kick stand the carb started dripping immediately. Is it possible the fuel in the supply line shifted to the carb in question when it was leaning on the stand?

The restored bike is running and working like a charm with the exception of this fuel leak. Thanks in advance for any advise as I'm getting ready to pull the carbs again - I just don't know what to troubleshoot while it's apart and am DYING to go for a long ride sans any fuel leaking onto the engine.

OB
 

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Bike with 4k does not need a float adjustment. Did I move the tang? No = Change needle and seat as a set.

Did I move the float tangs at all? Yes = Bad boy! Must be a tang you bent too much.
 

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Varnish on the seat can be cleaned, the fuel leak is from this point in the carb. You can replace the float needle. I've used Colgate toothpaste and a q-tip to clean my float seat when rebuilding mine. (I have 18k miles and didn't need to change the seat out. Compression is good, I just know.) Learned that cleaning trick on another biker forum. Saved me $100.
 

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Check the fuel filter, i had this issue and found tiny bits in the fuel, i put the old fuel filter back on the wrong way round and little bits got into the carbs and stopped the float valve from seating properly, made even worse by the fact the fuel pump puts the fuel system under pressure. I had to clean out the carbs again and replaced the fuel filter. The bits were almost invisible, i could feel the bits in my fingers but not see them. After that i have no problems.
 

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Varnish on the seat can be cleaned
Varnish is more a chemical etcher and eats brass.

I've used toothpaste and a q-tip to clean my float seat when rebuilding mine.
You have a machined taper that has a 45° edge to it and you polished it out. The needle too has a taper and band-aid fixes are just that. You probably didn't dip the carb in vinegar, clean away with gunk carb clean... sounds like???

You know how squids steel brush their inner caliper machined finish, and sand away the piston as well? What is the difference between a brushed out finish is that I read it on the net :rotfl:



:rolleyes: :hmm:
 

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Discussion Starter #6
Gents
Really appreciate this!

Can you clear one thing up for me: A stuck float needle will cause floodingf of the bowl. Where does this gas go? Does it drip off the bottom of the leaking carb OR does it travel out the series of black lines connected to the carbs?
 

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Varnish is more a chemical etcher and eats brass.


You have a machined taper that has a 45° edge to it and you polished it out. The needle too has a taper and band-aid fixes are just that. You probably didn't dip the carb in vinegar, clean away with gunk carb clean... sounds like???

You know how squids steel brush their inner caliper machined finish, and sand away the piston as well? What is the difference between a brushed out finish is that I read it on the net :rotfl:



:rolleyes: :hmm:
It was only after pulling it out of a short period of storage, mine wasn't deteriorated, more ethanol than varnish.
Mine doesn't leak last 8,000 miles of riding. Not every bike needs an overhaul Catch, not every diagnosis involves new parts, you can recondition them. Actually works for squids and professionals alike.
 

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Gents
Really appreciate this!

Can you clear one thing up for me: A stuck float needle will cause floodingf of the bowl. Where does this gas go? Does it drip off the bottom of the leaking carb OR does it travel out the series of black lines connected to the carbs?
It travels UP towards an orifice at the top front of th inside of the float bowl, and if it can't go out the overflow vent tubes from this passage (which are the 2 tubes between 1-2 and 3-4 by the slide tops) it can leak out the butterfly through the needle jet passage.

Check your float bowl drain screw for proper o-ring seal/debris and make sure it's not too tight that it cracked the bowl itself.
 

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Discussion Starter #9
THANKS for the help, gents!

Fixed it! I found a hairline crack in the bowl area on the outside of the carb. JBWeld to the rescue. Cleaned and roughed up the surface. 100 miles ridden and no drips or breakdown of the "weld". Going to look for a replacement but in all honesty I think it's good to go. Not always a fan of patching something but I really think this should last a long time

It looks to me like some used a pry bar of some sort to loosen the carbs :eek: as I noticed gouges on the inside of frame directly next to the cracked area.
 
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