Float bowl question

[dbeardslee]

So Betsy's been giving me fits on the launch up to 3k. I've changed float heights, needle heights, jets - I've been in the carbs at least 15 times. I've been through the wiring, the pickup coils, the coils, the high tension wires, the charging system, the battery, and the valves, but I continue to get this coughing and sputtering up to 3k. As I think back to when this problem started it was coincidental with a carb bowl cleaning, IIRC. I was cleaning out the little jet in the bottom of the bowl - squirted it out with carb cleaner, and then hit it with compressed air. Something was ejected from the bowl along the flange, and at the time I just thought it was a big drop of carb cleaner. Now I'm wondering if that little jet came loose. It's very difficult to see what's down in the hole - even with a boroscope. When I fish around with a bread tie, one of them 'feels' a little different than the rest. My question is this - has anyone ever seen or heard of one of those little jets coming loose?

[bikerphil]

DB, I know you use the colortune to set the mixture screws and I remember you mentioning bunson blue color. My 79 Standard likes the mixture set to an orange color or she'll stumble like a drunk off the line. JAT. You'll know you've gone too rich if you quickly blip the throttle and the RPM's drop below the set idle level. JAT. Can't help you with your original question though.

[egleaves]

I just made a float adjustment yesterday and while I had the bowls off it occured to me that I had never given that little jet you are talking about a good cleaning. I shone my little flashlight into the port in the bottom of the bowl and I could look down that tube and see a little speck of light shining through the oriface of that jet. A couple of them were kinda dirty so I gave them a good shot of brake cleaner and they opened right up. It looked to me like that jet was a seperate piece that could come out if it had enough persuasion (read: compressed air) behind it. You'll need a smaller flashlight than the one you keep there on the workbench, but I think I would check to see if you have a little pinhole worth of light or if the passage is wide open.

[dbeardslee]

Phil - I've had 'em rich, lean, sideways - you name it. Floats have been everywhere from 28mm to 24mm. I managed to make it worse by lowering the needles one notch, but I put them back where they were. No matter what I do I still get that stumble, and she never did it before that fateful cleaning. I can watch it on the tach and it always clears up right around 3k, which keeps bringing me back to the low idle circuit. I might be grasping at straws here, but for some reason the rediculous seems oddly plausible.

[dbeardslee]

Eric - I tried sticking the end of my boroscope in the hole, but even with that it's difficult to see. Maybe it's difficult to see 'cause it isn't there? I've got some '80 float bowls, but I don't think they'll fit on 79 carbs. The only other thing I can think is that I have viton tipped needles and plastic floats. I'm wondering if those needles close with less pressure due to the viton. I'm also wondering if that's why the 80/81 carbs need the floats set at 23mm. I've got them at 24mm right now (tried them at 28,27,26,and 25mm prior), so I might try raising them (running orientation) another mm to see what happens. That will make it richer, and what I'm hearing Phil say is that the problem could be a lean one. I'm also going to try looking down the holes again and see if I can verify my suspicions.

[DiverRay]

The float bowels SHOULD interchange between the years. Go ahead and try the 80 in place of the early ones.

[tarzan]

DB,if you have the floats set at 24mm,wouldn't that make it lean?
I thought I read if you run the plastic floats, you have to run them at 23mm.
JAT
Rick

[red bandit]

78-79 bowls will not swap w/ 80-81 bowls. The enricher tube is moved over slightly. Might be able to blow the jet out of bowl, I don't know?? But that shouldn't effect anything when the choke is off.

[dbeardslee]

Tarzan - up for rich, down for lean as the carbs are mounted (running orientation). If you have them upside down on a bench, then yeah, down for rich. At 24mm I'm still getting good color on the plugs with just a slight black ring around the outside. The insulator is a nice deep brown. The interesting thing about the plastic floats with the viton needles is that at 23mm that tab is almost unbent - kind of like it wants to be set there. With the stock needles and the plastic floats I ran at 25-26mm for a long time with no problems.

Ray - I don't think that little brass tube that goes down into the bowl will line up with a '79 carb, and an '80 bowl. That's why you always have to nibble a little off the gasket hole when you use the 80 gaskets with '79 carbs. The ones off the '80 have a little nib inside the bowl that isn't there on the '79 as well.

I'm still wondering if one of those tiny jets came loose from a bowl. I've got one plug (#4) that's slightly darker than the rest, and IIRC that's the same bowl I thought I saw something go flying out of. When I get home from work tonight I'm going to try the boroscope again, and see if I can get a good view of the bottom of that hole. Like I said, the bread tie 'feels' different down in that bowl, so maybe that's another indication of a missing jet. I might be able to tell by the stream that's produced by shooting carb cleaner in from the bottom. Seems to me like it didn't atomize as well coming out of that bowl either. One way or the other, that's the last time I use compressed air on a float bowl .

Red - we must have been typing at the same time. When that little jet gets plugged up it will sure affect it when the choke isn't engaged, so I'm thinking it may affect it when too much gas is going through it. That's kind of the classic symptom of the bottom of the float bowl as well - sub 3k problems. I've tried so many different combinations on these carbs I'm left with something outside of the 'normal' range of issues. Who knows, maybe another mm on the float height will do it, but that will be the first time I've heard of anyone going to 23mm on '79 carbs, but with the floats and valves that are installed, maybe that's where they need to be.

[81xsproject]

The tiny jet in the float bowl is the starter jet. It supplies fuel only when the choke/enricher is on. It WILL make it run like crap if one of the jets comes out (which I have had happen), but only when the choke is on. Below 3k, you have a problem in the pilot circuit, or and intake leak. Have you changed the pilot jet? Have you checked for an intake leak (with something FLAMMABLE, not WD40 or some other crap that's only flammable when aresolized). Get that float level and needle height back to stock and start focusing on these two things.

[dbeardslee]

Jessie - I bumped the pilots to 47.5, but went back to the 45's as I had very little adjustment in the mixture screws with the fatter pilots. I had an intake leak, but I installed brand-new carb boots with permatex ultra copper gasket sealer two weeks ago and that problems gone. I've tried running it with the vacuum advance disconnected and plugged at the carb with the same results, so I don't think the ATU dashpot is leaking. I've had the floats set to stock, above stock and below and I keep getting the same issue. It did seem to get a little better going from 25 to 24mm. Haven't tried them set to stock level for an '80 yet, so what the heck - might as well try 23mm too. I may have a couple more float bowls by this evening, so I can try them too. Thanks for verifying that those little jets can come loose. This problem is a weird one.

[dbeardslee]

So tonight I pulled the carbs and checked the float bowls again. This time I secured them in a vice so I could use both hands with the boroscope. Looks like all the little jets are still there. I set the floats to 23mm and it seems to have improved some, but it still isn't right. Course I haven't colortuned and synched yet, so we'll see...

[psycoreefer]

Hey I've got the exact same issue, to lean just off idle. I've replaced all the jets, including new emulsion tubes and its still there. I've also got the plastic floats from mikes xs and I've set mine up to 23mm and the stumble goes away once the bike is warm, so i think if I go a little further I'll have it solved.

I did check the fuel level in the bowls when the bike is running and its about 8mm below the top of the bowl with the floats set at 24mm, however I have no idea where it should be, I tried setting it up way higher like the later carbs need but that was way to rich. I think the plastic floats just act a little differently, I say keep adjusting those floats richer until it runs right, thats what I'm going to do.

[Ivan]

try going down a size on the pilot jest, if you have them, just for grins. I have been fighting the low end stumble for some time and have found my low end to be way too rich, until it gets on the needle. I am really wondering if my needle jest are just worn out. I was able to get it somewhat back in like with smaller pilot jets and drilling out a set of pilot air jets. Still not there yet.

[dbeardslee]

Ivan - I already stepped down one notch on the pilots. Didn't make any difference. Tried two different sets of needles too - same story. I put a new battery in it this evening just to make sure it isn't a weak spark causing the trouble. The one I had needed a considerable amount of water several weeks ago, and I was getting somewhat low readings at the TCI. I'm afraid the tops of the cells in the old one may have been exposed to the air. The guy at Walmart said the old one tested OK, but he didn't really look like a battery expert. Didn't get a chance to try it cause it started raining. Got my fingers crossed. With all the stuff I've done tracking this gremlin down, the one that yielded the best result so far was repairing the pickup coil wires. Ran better after the valve adjustment too. I've adjusted the carbs every way I can think of and I still wind up with that 2-3k stumble, so maybe it is electrical. The other weird thing is that it was running fine with the carb floats at 25mm, the needles in the center slot, and the same jets it has now. It's just when you see a problem like that in that rpm range you naturally think carbs, but who knows. Sooner or later I'm going to run out of stuff to fix .