leaking carbs

[robsgreen]

Hi guys
I rebuit my carbs with an aftermarket kit. When I bench tested the carbs at about 22 degrees incline, they were leak free for about an hour and then started dripping. I took the carb bowls off, checked my float heights again as per Dave's method, put them back together again and they started leaking again after 12 hours. When the tang of the float is just touching the float valve tip ( the bit that is on a spring, the float is pretty much runs parallel with edge of the upper body I checked the original fuel shut of valves and they look very good so swapped the new aftermarket ones with the old ones and tried again. same result. There seems no pattern to this as its not always the same carb. The leaks are always from the over flows. The drain plugs have all got new seals, so what am I doing wrong? its my last job to sort out before I can start the beast from its 30 year sleep.

cheers
Martin

[asacuta]

No cracks in the overflow tubes?

[EMS]

As the leaking starts after a certain time and comes through the overflow, I guess you have a slight leak in one or more of the float valves. I hear bad things about the non-original float valves and their capability to seat properly after a while or even when new.

[robsgreen]

Thanks for your replies and I will check the over flow tubes.
cheers
martin

[daves79x]

My guess is you might have some cracked stand pipes also, but this type of dribbling after several hours is very common with aftermarket float valves and is what we all complain about. Get them out and reuse the original ones, cleaning them very carefully and especially cleaning the seats. You can buy OEM replacement valves here: http://www.pjmotorsports.com/keihin-mik ... tv-offroad

Dave

[Sharpie66]

My guess is you might have some cracked stand pipes also, but this type of dribbling after several hours is very common with aftermarket float valves and is what we all complain about. Get them out and reuse the original ones, cleaning them very carefully and especially cleaning the seats. You can buy OEM replacement valves here: http://www.pjmotorsports.com/keihin-mik ... tv-offroad

Dave

I purchased new float valves last fall from here......

jetsrus.com

$9.82 here compared to $14.95. Part numbers are the same and says they are oem.

PC

[daves79x]

Don't know how they compare, but I'll take your word for it. Just remember that $9 or $14 is a lot better than the $40-plus dollars Honda wants. I've used several of the $14 ones since I became aware of them (thanks Spencer!) and they work fine, as long as your seats are OK.

Dave

[robsgreen]

Hi Guys
Well, Ive swapped to the original needle valves and seats and under the microscope seem in very food condition. Fitted them all. checked the float heights again, set the carbs at around 20 degrees incline , connected the fuel, turned the fuel tap on and dry as a bone. 12 hours later, two are weeping from the over flows. I checked each stand pipe by filling each bowl with fuel and leaving them for hours. No leaks. Ive stripped the bowls off about 6 times now and Im ready to chuck them in the river! there seems no set pattern to which one starts leaking. The original seats look good, so is it worth trying the pattern needlevalves I have with the original seats? dont forget I fitted the new pattern seats and needle valves and they leaked even worse. What do I do

[asacuta]

Are the floats actually floating after 12 hours?

[robsgreen]

What do you mean exactly?

[daves79x]

The way to check for cracked standpipes is to shine them up with sandpaper or Scotchbrite, then blow brake cleaner into the drain tube, with the drain screw closed, while holding your finger tight against the top of the pipe. A minute crack will show up that way for sure. But if different ones leak at random, it's likely just needles not fully seating. Do the check for the cracks, but I probably wouldn't sweat the dribbles after 12 hours. Many do, but in actual running situations, tend to seal just fine, and you should never let the gas turned on that long if the bike is parked anyway. I'd try them as is after you are sure there's not a standpipe cracked. It is very common.

Dave

[asacuta]

What do you mean exactly?

Never had my carbs apart, so I don't know how the floats are made, but if gas can infiltrate them over long periods, their buoyancy would be impaired, and the bowls would overflow.

There's a video on YouTube about polishing the seats. I don't know how well that would work.

[swarrans]

I'd be interested in what the experts say but that wasn't exactly done under clinically clean conditions was it?! What about all the grinding paste residue?

Simon