I can't find anything wrong! And yet...I still have problems

I rebuilt my carbs. New air and fuel jets. New float needles and seats. All floats set at 23mm from gasket surface to bottom of float. Everything cleaned and tested within an inch of its life. Floats tested to see if some are more bouyant. Air/fuel mix at 3 turns. Carbs bench synced. On the stand and on the bench, they are DEAD level.

Whenever I add fuel from a small source above the carbs on the bench or from the tank on the PRI position, carb #2 and sometimes #1 overflow. If the carbs are on the bike, those 2 cylinders get full and some fuel even makes it to the airbox. It seems to do this regardless of my float settings on those carbs. As expected, putting the bench fuel source below the carbs or moving the petcock to "ON" when it's on the bike stops the overflow. Carbs 3 and 4 are set perfectly according to the clear tube test.

I can see NOTHING wrong with either float, needle, seat or other part. I took off the bowls and turned the carbs upsidedown and blew through the fuel line. All 4 needles stopped air from leaking until I manually lifted the floats. So, I know they will seat properly. Ordinarily, I'd think a float(s) was stuck but can find no evidence that one is. Everything seems to move freely.

The only thing I can think of is that the fuel is pushing past the springs in the (brand new) float needles. The needles I've seen in cars are solid with no spring. Does anyone know why they have the spring in the first place?

I also notice that carbs 1 and 2 are closest to the fuel source. Could that have anything to do with it? Any other ideas out there?

 

Re: I can't find anything wrong! And yet...I still have prob

I set my float heights using a fuel source with the carbs on a bench setup. This tells me which carb is leaking so I don't waste time. Two things will cause new float valves to leak. One is the new float seat is just slightly rough. This can be polished out with a wooden golf tee. Press it into the brass float seat and polish it with a back and forth rotation. Second is friction on the float valve rubber tip. It simply sticks while trying to rise up and seat. So if the carbs are still on the bike turn the fuel on and tap the carb bowls lightly with a rubber hammer or the handle of a screwdriver.
One thing confuses me. There are no springs on the float valves. There is a spring clip on the float hinge but that is all I remember. I do remember springs on the pilot mixture screws but I doubt it is those you refer to.

 

Re: I can't find anything wrong! And yet...I still have prob

the float needle / seat is a simple valve, if you are getting too much fuel in the carb-s the valve is not closing. it's possible, that when you did the blow test you exerted more pressure manually that would be exerted by the bouyancy of the float.

 

Blue, I suppose it is possible that your bike doesn't have the float needle spring I'm talking about. In mine (new and old), the part of the needle that contacts the tang on the float is in actuality a spring loaded pin. Then, there is the loop or hook of wire that actually goes around the tang. My guess is that the spring prevents the float from applying too much force to the needle and seat. Once the needle is seated, the spring absorbs any further force applied by the float. Just my guess.

As for the golf tee idea, I'll try it next. I have some bamboo skewers that are similiar in size. I'll just need to make sure they aren't long enough to put a hole in the screen on the other side. Maybe a bit of cooking oil on the rubber needle tips.


Wizard, I'm with you. It SHOULD be simple. This isn't rocket science, it's a damn valve. I'll swap that needle and seat to a different carb and see if the problem moves or persists in #2.

 

I had the same problem. I took some polishing compound on a q-tip in my dremel tool and polished the needle seats. Hasn't done it since. Make sure to get the entire inner surface, not just the part where the needle seats. On mine, the needles were actually sticking on the walls of the seat.

 

Get a piece of 1500 Grit Finishing Paper.
Cut a strip and ROLL it TIGHT so that it will stuff into the Float Valve Seat.

Twist the Roll and put a new finish on the Inside Diameters of the Float Valve Seats.

When you remove the twisted roll of finishing paper from the Seat it will have a brass tinge on it.
Use a set of Diagonals to cut-off the Brass tinged area before you do a succeeding Valve Seat.

 

Bamboo is a HARD wood ! Just thought you might want to know. . .

I like the Q-tip and polishing idea - - more tricks up my sleeve!

 

Holy Cow Rick! I need access to the places you get sandpaper. I've been all over town (home depot, lowes, true value, etc.) and can't find much above 280 grit. If I'm lucky, they have some coarse emory paper. I don't think I've even SEEN 1500 grit anything!

Is this one of those times where toothpaste on a q-tip will work? Or, is toothpaste too coarse?

I've got some 0000 steel wool and Nevr Dull. I used the Nevr Dull to get the mirror shine in my diaphragm bores.

I'm off to do a combo of Blue's golf tee trick and Broke's polish job. If that doesn't get it, I will hunt down some 1500 grit finishing paper.

Time, no bamboo this time. My wife has a soft wood "Orange stick" as she calls it. It's something to do with fingernails and cuticles. Looks like just the thing.

 

q-tip with a bit of 0000 steel wool spun with my fingers
i've got the little spring plungers too and got no idea what they do

 

Toothpaste will work just fine. As long as it is tooth paste and not tooth gel.

 

Re: I can't find anything wrong! And yet...I still have prob

Auto parts store. Look in the paint section.

 

cps2) Aftermarket high-quality WET-OR-DRY FINISHING SHEETS. Since these don't contain "sand", we really can't call them "sandpaper", but you get the idea. A large assortment of ultra-fine finishing paper is just the trick to polish the vacuum pistons and piston bores in your carbs, or master cylinder and brake caliper bores, ridding them of any surface oxidation and minor imperfections that will create interference or friction and prevent the pistons from moving freely---causing all sorts of high-idle (and other problems) in your carbs, or dragging brakes in your calipers. Our recommendation is to start with with the 400- or 600-grit paper and move up 200 grit at a time until you get the bores micro-polished to an incredible smooth finish. One 9.5" x 11" sheet of each size will be enough to do four carbs or one pair of calipers; use two sheets of the 5-1/2" x 11" super-fine grit paper.

Of course, this premium finishing paper is just the thing you'll need for prepping any painted surface for painting,


HCP8594 Aftermarket premium grade 400-grit FINISHING PAPER, single sheet, 9.5" x 11". Each:
$ 1.95

HCP8594SET10 Aftermarket premium grade 400-grit FINISHING PAPER, single sheet, 9.5" x 11". Set fo 10 sheets:
$ 14.95


HCP8596 Aftermarket premium grade 600-grit FINISHING PAPER, single sheet, 9.5" x 11". Each:
$ 1.95

HCP8596SET10 Aftermarket premium grade 600-grit FINISHING PAPER, single sheet, 9.5" x 11". Set fo 10 sheets:
$ 14.95


HCP8597 Aftermarket premium grade 800-grit FINISHING PAPER, single sheet, 9.5" x 11". Each:
$ 1.95

HCP8597SET10 Aftermarket premium grade 800-grit FINISHING PAPER, single sheet, 9.5" x 11". Set fo 10 sheets:
$ 14.95


HCP8598 Aftermarket premium grade 1000-grit FINISHING PAPER, single sheet, 5.5" x 11". Each:
$ 1.50

HCP8598SET10 Aftermarket premium grade 1000-grit FINISHING PAPER, single sheet, 5.5" x 11". Set fo 10 sheets:
$ 10.95


HCP8599 Aftermarket premium grade 1200-grit FINISHING PAPER, single sheet, 5.5" x 11". Each:
$ 1.50

HCP8599SET10 Aftermarket premium grade 1200-grit FINISHING PAPER, single sheet, 5.5" x 11". Set fo 10 sheets:
$ 10.95


HCP8600 Aftermarket premium grade 1500-grit FINISHING PAPER, single sheet, 5.5" x 11". Each:
$ 1.50

HCP8600SET10 Aftermarket premium grade 1500-grit FINISHING PAPER, single sheet, 5.5" x 11". Set fo 10 sheets:
$ 10.95


HCP8601 Aftermarket premium grade 2000-grit FINISHING PAPER, single sheet, 5.5" x 11". Each:
$ 1.50

HCP8601SET10 Aftermarket premium grade 2000-grit FINISHING PAPER, single sheet, 5.5" x 11". Set fo 10 sheets:
$ 10.95

 

To find an ample supply of 1200 and 1500 Finishing Paper, you need to shop at an Auto Body Supply Shop.

You can also find 3M Brand Polishing Compounds there, too.

Buffing-out your Paint with one of the 3M Finish Restorers will give your paint job a whole second life and the bike will look great.

They have a Hand-Rubbing Compound ... but, I don't remember the exact name of it.

 

Re: I can't find anything wrong! And yet...I still have prob

They keep the float from pounding the needle against the seat when you go over bumps.

 

Preliminary SUCCESS!! No fuel pouring out during the bench test. We'll see what happens when they are on the bike. I "Nevr dulled" the bores using my drill, a q-tip stick and a few small wads of Nevr dull. Then I polished them to a mirror shine with plain qtips. Then I gently cleaned the seat area with the wood (golf tee) stick. It made an excellent seat area.

 

The Spring-loaded Float Needle Pins are ... in theory ... supposed to last longer than the Solids because the Spring helps prevent the Float Pin from becoming warn-out as fast as a Solid Pin would ... over time.

Since some of the OEM Solid's that came with the Bike, from where they got made, in the Land of The Rising Sun, are still on-the-job and doing just fine ...
I'd say they were invented to "Cost More"

You know how them Biker's are!

"We got these-here regular Float Pins which work just fine and will for a couple of decades ... or, iffen you want, you can get THESE special spring-loaded baby's for a zillion dollars more. They got your anti-stick action. They increase fuel economy by 40-percent. You get an additional twelve horsepower. They are guaranteed against everything and you can have an extra one in case you lose one someday. Just keep the sales receipt for your grandchild to bring-in as proof of purchase. I'll be dead before you ever need another one!"

 

Keep it up and you'll be Graduating with an "Old School Diploma"

Nice work!

 

Road test!! It still really needs to be tuned properly. BUT! No fuel leakage, no runaway throttle (new throttle shaft seals) AND it started with NO choke.

I'm getting some popping from the exhaust. There are missing clamps and the seals are wasted so I'm not surprised. The other issue was the fact that I have trouble hitting second gear. Either I miss it or sometimes it pops out right after I get it there. The weird part is, when it jumps out and I've already hit the gas (I've basically revved it in nuetral), the RPMs stay high. Around 6k. I've not tried to blip the throttle to make it go down. I just hit the kill switch, turn it back on, drop to 1st and pop the clutch. It fires right up at idle. Any thoughts on why it wants to stay at high RPMs in this one instance?

 

Re: I can't find anything wrong! And yet...I still have prob

throttle linkage sticking?
exhaust popping = too lean.

 

Re: I can't find anything wrong! And yet...I still have prob

Just keep in mind that the float height in these carbs (according to the manual) have to be set with "volume" rather than a specific float height. The float height you mentioned is just a starting point. The "book" recommends using a clear tube on the bowl drains the set the floats so that the bowls hold an approximate amount of fuel. I had to remove my carbs 3 times and remove/install the fuel bowls about 8 times to get this right.
Now all four cylinders will pull very strong except at an idle. I still have a miss until it gets to a certain RPM. I have rebuilt a many a set of carbs over my life time and never had to disassemble/assemble, check and recheck carbs like I have on this bike.
I have had enough of these carbs for a while. I plan to do a top end overhaul this winter because of low compression on the cylinder that has the miss.
Good luck on your ventures with the carbs.

Ed

 

Wizard,

When I say "popping from the exhaust", I mean from places where there should be no popping. Like where the headers meet the motor and at the joints that are missing clamps. Still the tune isn't dialed in.

You said it Ed! I'm tired of carbs. I'm gonna take a few days away from the carbs and work on other items like exhaust and why my new brake pads in my fully rebuilt caliper still sqeak. The sqeak makes it sound like a POS.