Does this problem sound like a sticking float to you? I think so but dunno

[JeremyL]

I have a 79 Special (with 80 motor, 79 carbs). I have just did the "new wires in old coils" mod, which seemed to make the bike run smoother, fixed the coil pickup wires, put new plugs in, new jets, cleaned carbs, new plastic floats set to around 25 1/2mm, and cleaned all the wiring connections, and removed the Octi.

After replacing the floats with plastics I was getting a little fuel seeping out if I left the petcocks on. I figured out it was just a drip from #3 carb so I planned on getting new float needles and seats. It didn't leak before but I DID get the float needles mixed up when I pulled the carbs apart (stupid, and I knew NOT to mix up parts)... Now the bike will start and run excellent and will almost pull me off the seat at WOT, BUT I'll be riding around and in an instant I lose a cylinder, I think. let's say I'm cruising along... I can rip the throttle and it will charge forward like a beast. Well 10 seconds later I can rip on the throttle and the speed will SLOWLY increase, like 1mph per 5 seconds, and the engine is just making a BOGGGGGG sound like air in a tunnel. It doesn't sputter or die but its just like I'm running on 3 cylinders. I thought it was maybe an spark problem so I redid the wires and checked the coils but it's still doing it.

It may do that for 3-5seconds then suddenly it'll run fine again, and as quick as it switched back to fine it will switch back to being low on power. I'm thinking the float is getting stuck and either flooding out or starving a carb. I've noticed that if I hit a bump or pothole it may trigger this too so it kind of makes sense. Also, sometimes when it's running low on power it will backfire (like a cannon shot sometimes) but when it's running normally it runs great and doesn't backfire. I'm thinking that means its running lean so the float must be getting stuck closed and starving that one carb.

Any ideas? I need to order the float needles and seats from Mikesxs.com (I need the 5019 part number right?) but want to make sure there's not something else it could be. I thought maybe that carb that was dripping gas when the bike is shut off could be flooding out that carb (and the float isn't getting stuck at all) but if the leak is just a drip at a time I would think the carb would just burn that fuel off and not completely flood out enough to kill a cylinder for a few seconds then clear up perfectly fine.

[DGXSER]

With the spark system these bikes use, it is very uncommon for a single cylinder problem to be electrical in nature, since each coil fires both spark plugs every time. You could try riding it until this problem appears, then try stopping somewhere before it goes away and spray water on the headers to see if one is cooler than the others, that would at least tell you where the problem is.

I would look at your floats, gaskets, and the tang on the back of the floats.

Some of the new plastic floats have been reported to have ridges on them which could hang up on something.

Also, I always, always, always cut the gasket material off on the sides of the float bowl, matching the gasket edge to the inside edge of the bowl. This eliminates an edge of the gasket for the float to catch and hang up on.

On the back of the floats there is a tang on one side bent up to hit the float post to stop the float from dropping to far. Check that all are at the same height.

[GLoweVA]

I had a similar issue on my 80G. I found it was the vac advance wires.
One bump and vroom, off I'd go again. If I were you I'd check those wires and move them around a bit to see if one (or both) open when you wiggle them around. You can do this with a volt/ohm meter. I read somewhere in here that you can pull on the wire and if it wicks out then the copper is broke and that's where the break is.
My thought on the float thing, is it would slowly die away as it gets starved for fuel.

[GLoweVA]

After re-reading your post again, maybe it may be a float thing.
Ditto what DGXSER said about checking all that stuff in the carbs.
I did have an issue with my floats sticking open and I used that tab to limit the travel on how far the float drops so it wouldn't get stuck on the bottom of the bowl.

[DGXSER]

Hey George, I think you meant the pick up coil wires (vacuum is strictly a tube) .

The engine or cylinder could be flooding just as much as starving. I would definitely agree, that if it were a starving issue, it would be at least two cylinders as the floats almost if not always never get stuck in a closed position. Therefore it would have to be a fuel petcock issue, or tank vent for the cylinder to be starving for fuel.

[cywelchjr]

Something that occurs to me. The wires in the coils were replaced. That is the one place IIRC that you can get ONE cylinder not working electrically is at the plug wire. Somehow it seems that one plug wire can provide enough to let one plug fire but not the other. Then again, without checking, these engines have enough power that it could be TWO cylinders dropping that causes the bogging, which could be the pickup coil wires. It's not unknown for the repair to have to be re-done at least one time. It's at least worth checking, both the pickup coil wires since that is affected by throttle setting and the spark plug wires since those were replaced/grafted in.

[JeremyL]

I would look at your floats, gaskets, and the tang on the back of the floats.

Some of the new plastic floats have been reported to have ridges on them which could hang up on something.

Also, I always, always, always cut the gasket material off on the sides of the float bowl, matching the gasket edge to the inside edge of the bowl. This eliminates an edge of the gasket for the float to catch and hang up on.

On the back of the floats there is a tang on one side bent up to hit the float post to stop the float from dropping to far. Check that all are at the same height.

I have read about this (after I put the floats in) but I'm going to check the floats and the gaskets and make sure there's no overhang when I pull the carbs off.

I had a similar issue on my 80G. I found it was the vac advance wires.
One bump and vroom, off I'd go again. If I were you I'd check those wires and move them around a bit to see if one (or both) open when you wiggle them around. You can do this with a volt/ohm meter. I read somewhere in here that you can pull on the wire and if it wicks out then the copper is broke and that's where the break is.
My thought on the float thing, is it would slowly die away as it gets starved for fuel.

I had redone my vacuum advance wires I thought but I went outside and checked them and remembered only one side failed the test where you tug on the wires so I only did one side. That was a dumb move because it sounds like they're almost guaranteed to mess up eventually so I'm going to go ahead and do the other side too because it may still have a bad connection in it. I may check it with my multimeter to see if there's any breaks in there and to make sure my soldering is good enough.

Something that occurs to me. The wires in the coils were replaced. That is the one place IIRC that you can get ONE cylinder not working electrically is at the plug wire. Somehow it seems that one plug wire can provide enough to let one plug fire but not the other. Then again, without checking, these engines have enough power that it could be TWO cylinders dropping that causes the bogging, which could be the pickup coil wires. It's not unknown for the repair to have to be re-done at least one time. It's at least worth checking, both the pickup coil wires since that is affected by throttle setting and the spark plug wires since those were replaced/grafted in.

I was thinking back and I think you might be right... being down 1 cylinder would be a noticeable decrease in performance but not this bad. And so far it's always been a problem only when riding, when I'm revving it up in the driveway it's perfect. Also, it's a very quick on-off-on kinda thing. I can be riding along with a very strong almost scary fast motor when a few seconds later when I go to grab the throttle it just maintains speed and has that hollow BOGGGGG sound. And then I'll let off the throttle and grab it again and it'll be full power again just like that. It runs with full power most of the time but just has "fits" with running at partial power... it may run slow for a few seconds then go back to fast again or it might run that way for 30 seconds before instantly switching back to fast again.

It's a big enough of a drop in power so that I couldn't climb a steep incline and even on flat roads can barely maintain speed or barely gain speed.




Thanks for the ideas guys, it gives me other ways to look at it.