CARBS dazed & confused

[mack]

OK, maybe gas fumes are getting to me. So I'm trying to dial these carbs in and am getting frustrated. I have changed from plastic to brass float's with little success, merely changes which carb leaks. Starting height is 25.7 for both types.Been down to 25mm. Anyway. If I turn the carbs upside down and add fuel, just the weight of the viton tipped needle are enough to prevent flow. If I turn them right side up and add fuel, it leaks from the the "main" vent at the air side bell. Tapped the crap out of it with both the plastics & brass floats and they stop except for one. It will continue to seep. But not always the same one. Sometimes it #1, sometimes #4 and the last time was number 2. As for checking the individual bowl levels(start of this learning curve). No luck at all. No matter which style of float or height setting , the closest I can get is 1/4 inch below the washer. Now I've done this about 50 times in the last three days and while I can't get the level in the hose to hit the washer, the gasket above it is wet. WTF!!!! It must be a technique problem as I have a set of carbs someone else dialed in and I can't get the bowls on them to come up to the washers and that is the only way he sets the floats. WTF!!! Even if I put them back to 25.7mm and put them back on the bike, I'm worried that without the octy, gas will seep into the crank, albeit slowly since riding days are few and far between this year. Tell me gentlemen, what am I doing wrong?!!!!

[cywelchjr]

Ok, did you make sure you have new o-rings on the push-in needle valve seats? Those seats should go in fairly tight, if they go in easily they will probably leak around the outside of the seat in use, probably slowly. Also if the wrong size o-rings are used and they are too tight they can leak as well, of this I have personal experience.

[ccogswel]

Hey Mack.

When you had them carbs upside down did you lift up on each float to let the air out? If not do it just enough till you get some gas to come thru. Then use a Q-tip to clean up the extra gas and then let it sit for about 15 minutes. Or less your call. And then after all that wait look to see if you have any leaks. If not then check to see if your new brass floats are hitting the inside of the float bowls. Cause if you went from plastic to brass that may be your issues. Another thing you may check is your float needle pins. Make sure they are straight. If not try to straighten them. You can buy them from Mikes Xs website. But I'd say your having troubles with them hitting the inside the bowls. Good luck!

[mack]

Oh Oh

I don't remember seeing anything like that in the viton kits from z1. I used the their seat and washer, but pulled the metel washer out and put in my old fiberglass ones thinking that would give a better seal than metel on metel. Got picture man so we are in the same ball park? These are the old 79 carbs by the way

[ccogswel]

Ok so you saying you changed the float needle from the metal to the rubber tipped ones? I thought you meant the floats... But that shouldn't be a problem if you are talking about the float needle. But you may want to check the height and compare the the metal tipped ones to the rubber tipped ones. But I believe they are the same tho.

And in my mistake I called them float needle pins. I meant float post pins. The little metal pin that holds the floats. Check them for any bends.

As for using the old brass gasket instead of the metal ones you may want to check to make sure they are sealing. And actually the metal ones your talking about I believe are really made of tin or some other soft metal.

Good Luck!!

[cywelchjr]

I don't remember seeing anything like that in the viton kits from z1. I used the their seat and washer, but pulled the metel washer out and put in my old fiberglass ones thinking that would give a better seal than metel on metel. Got picture man so we are in the same ball park? These are the old 79 carbs by the way

Ok, I thought you were working on the 81 not the 79, that I don't know. I seem to recall something about the washer thing on getting the float level with those replacement ones? But I don't remember exactly what it was?

[mack]

needles and floats

I changed to the viton needles with plastic floats. Tried I don't know how many times to get the bowl levels up. No dice. Switched to the old brass floats thinking they may be more responsive. But they seep. Bowl levels still low and seepng was switching from carb to carb. When I had the plastic floats in last night I placed them upright and filled the fuel hoses. Didn't leak down over night any more than what would have evaperated. But tried again this morning to get the bowl heights up and just couldn't get it. Funny thing though is, the fuel level is 1/2 inch below the washer, how can the bowl gasket be wet? I'm just not diggin this at all. Maybe I have to just put the fuel in a trickle at a time and allow the air to escape up the needle before it SLOWLY seats.

[cywelchjr]

How are you putting the fuel into the carbs? You should be hanging a fuel cell of some sort over the carbs for a bit hooked up as if it were the gas tank and let them fill that way. Then when they have filled, you can unhook that and check the level. Of course you can leave it hooked up if you have them over something that would catch any spillage and let it sit and see if it holds without spilling over any, to make sure that the needle valves are holding.

As for the testing them with water, I don't buy that test, gas will go through places that water will not, as water in the gas will clog filters that gas will go right through, water being both heavier and thicker than gas is. If you want to know if the valves will hold gas, you need to use gas. You might be able to use alcohol, as I believe it's even thinner than gas, but water IMHO just is not a valid test leakage wise about anything but water or liquids thicker than water.

[mack]

my set-up

This is what my set-up looks like. I have four old carb boots mounted to a board then to the wall. Everything is plumb and level but fully adjustable. I can rotate the carbs 180 degree's without having to take them down.



Ok so this is how I'm trying to check bowl heights.




Not sure how the discussion about water got in there but what I do is pour gas from a beaker into the little funnel attached to the hoses.

[mack]

Red Faced

Well it finally came to me. I read someplace on here that they took the little wire keepers off the needles. So I did too. Correct me if I'm wrong, but aren't those keepers used to draw the needle down with the floats to allow air to escape past the needle while the bowls are filling? In my case the needles remained seated, so I had to over fill the bowls until the gas forced the air up through the main jet and out the vent hole. Then I would have had a syphoning effect until the fuel level dropped back down to the height of the float valve needle. This is my hypothosis and I'll test it tommorrow by putting the keepers back on.

[mack]

redder faced

nope that doesn't make sense either. Main vent tubes would have to be plugged for that to be the case and they're clear. I'm too tired to think straight. Going to bed.

[cywelchjr]

No, but with that little funnel you don't have enough fuel pressure pushing down to push down past the needle valve. You need at least about a quart container up there for that test. And the mention of the water was because I have seen water mentioned as part of the test, so since the fluid being used wasn't mentioned I raised the issue of using water.

But you do need more fuel up there pushing down for the test, that's probably why you can't get the level up, because there isn't enough pressure pushing on the needle valve so the valve is closing to easily and too soon.

[Riddle]

have you checked the upper T fitting between the carbs for blockage??

[bikerphil]

After reading this, it looks like you are working on the early type BS34 II type carbs. These carbs aren't designed to use viton tipped needles with clips or any of that. You should have brass floats, steel tipped needles with no clips with their correct seats with a thin fiber washer. The float heights should be 25.7MM give or take 1MM. If you have mismatched needles and seats they will bind up and will leak. They also may be the wrong length. Once you start mixing and modifying things in there, you are just asking for trouble, JMHO.

[TADracer]

Perhaps one other thing to consider, if your floats are allowed to drop too low they can hang open and fuel will gush forth unabated. There is a small tang on the side of the float that contacts the post and is used to adjust this. I kept my floats with only about 1/4" travel from hanging full open to fuel shut off.