Carb Mystery

[kypr1]

Hey everyone,

I have been having some trouble with my #2 cylinder not firing. This problem originated about 2 weeks ago when I tried to start the bike, and the engine turned once, and then nothing. So...i kept trying to start it and eventually put the kickstand up and it started for some reason with no problem. The next day I went out to go for a ride, and noticed when i started the bike the #2 cylinder wasn't firing, so i changed the plug out, which was black from carbon, but didnt look fouled, and it tried it again, and it ran fine. But the next day, I started it, and the 2 wasn't firing again. So, for a while, all i had to do was take the plug out, put it back in and it would run fine. I checked the plug caps, and wires and that wasnt it, cause i have spark to the plugs (even the ones i thought were fouled). So, i took the carbs off, noticing gas pouring out of the 2 carb, obviously flooded, and cleaned the 2 carb, all the needles, jets and adjusted the float and put it back in. The problem stayed the same. So I took the carbs back out rebuilt the 2 carb, cleaned the others (after seeing the 3 and 4 plugs were wet with gas), put it back on, and the bike fired up on all four. Thinking i had fixed the problem, i left the bike overnight and tried to ride it this morning, only to have the 2 cyl. not firing. I pulled the plugs, and as ive been noticing, the plug was wet with gas. The only thing left I thought it could be was my left petcock was leaking, but I wasn't sure if that was it, because i thought the 1 carb would be flooded too, but i pulled it out and cleaned it up, and it didnt leak anymore. So, i put the bike back together, and the #2 still wont fire. So, basically, I'm out of theories and any help would be greatly greatly appreciated. Sorry this description of the problem is so long, but I thought every detail would help. Thanks.

[TopCatGr58]

Hey there Kypr1,

Okay, your #2 cylinder is actually firing, but it's getting fouled. You've cleaned your carb, but you didn't say whether you replaced any parts in it? The 78E has the metal float needle valves and threaded in seats. A tip for ensuring that the valve seat is clean is taking a small drill bit that will just fit inside the seat, and spin it backwards to help clean the valve mating surface better than a toothbrush and cleaner can.

Are you sure your float is floating? It may have some small holes causing it to sink, and flood that carb fouling the plug? Like you said, a leaky petcock alone won't necessarily cause a carb to flood, cause it's stopped by the float valve! But a damaged petcock with rubber valve gasket breaking down, or the fuel lines corroding can cause particles to get into the carb and wedge between the float needle and seat...again keeping it open and flooding the carb.

Aside from the carbs, you can trouble shoot the #2 cylinder by swapping the plug wires with #3, and see if it moves? If it doesn't move, then it's the carbs, if it does move, then it's probably the coil wire and plug cap!? Keep at it, and don't worry about how long your post is, more info is better!!
T.C.

[mitch]

pick ups

He never did say he checked for fire! You might want to go to the tech tips on the left of this page and find the thread pertaining to the pick up coil wires this will also cause your symptoms....MITCH

[prometheus578]

Ok, you've had the carbs off too many times. (Let's work the assumption that this is carb related)
Take the carbs off again. This will be the last time.
Take the floats and a pair o' pliers up stairs to the kitchen. Dunk them in a pot o' real hot water. The water heats up the air in the floats and it expands. If one of your floats has air bubbles coming out of it, "She's a no good."
Grab one of your wife's baking/cookie sheets and sneak it back to the garage while she's watching Oprah. You'll need it later.
Look at the tips of your float needles. If there's a "wear ring" on the tapered tip, "She's a no good" (but still might seal)
Take a handful of Q tips and using some chrome polish, polish the insides of the float needle valves. Spray carb cleaner through them out the fuel line, and then from the fuel line back out the valves. HHHmmm can't recall if your valve have those little screens on them, so you may want to pull the valves and clean the screens. Also, check the condition of the fuel line. Cracked? Brittle? Chunks of rubber falling off? "She's a no good" Replace.
Clean all passages with spray carb cleaner and blow out mit der compressed air, if available.
Set the float height.
Lock the garage door so the wife can't come in, and place the cookie pan on the work bench. Place the carbs in the pan, upside down, with the bowls off. Using extra fuel line, hook the carbs up to your fuel tank, which you've prepositioned on your bench, sitting up on a milk crate or two. Turn the petcocks to prime.
The weight of the floats should stop the flow of fuel. Anything leaking past? No? Good! Go back to the kitchen and get something to drink.
"Honey, what are you doing in the garage?"
"Umm.. nothing Dearest... err , I mean, I'm making a present for you. You can't see it yet."
Back to the garage. Still not leaking?
Turn off the petcocks. Put the float bowls back on and brace/support the carbs in the upright position. Turn the petcocks to prime. Watch for 5 minutes to see if fuel wells up from the main jet/needle area or out one of the air jets at the mouth of the carbs. Nothing? Go back upstairs, passing the wife, and ask her what's her favorite color. (She will now leave you alone till you've finished the gift for her)
Check your carbs again in a half an hour. If there's no fuel in the pan, and the carbs are dry, you're done.
Leaks....? Would be from those worn float needles mentioned earlier, or the float is sticking or improperly set.
Ignore wife... ("She's a no good") as she'll be ignoring you for a few days when she finds her baking sheet missing. Small price to pay for good carbs.
Install on bike and synchronize them.
The End

[xj11john]

I'm still snickering!

What a great reply Prometheus578, very informative and Hallarious!

[skids]

I large metal roasting pan is a good thing. Buy the wife a new one and take the old one to the garage...cheapper than the cost of "hearing about it!" :-)

Originally posted by prometheus578

Grab one of your wife's baking/cookie sheets and sneak it back to the garage while she's watching Oprah. You'll need it later.

[John]

Carb repair

Make double damn sure that you sit on a blanket on the floor in the center of the garage when you do the carb work. That way when you drop something, it can't bounce and roll away under a bench or be sacrificed to the carb gods.

[xssiveone]

Re: Carb repair

Originally posted by John
Make double damn sure that you sit on a blanket on the floor in the center of the garage when you do the carb work. That way when you drop something, it can't bounce and roll away under a bench or be sacrificed to the carb gods.

Now, THIS is a great idea!!! What a neat way to trap all those pingphucks that seem to get away. Take it one step further and use a light coloured blanket so the parts stand out better.

[kypr1]

ok, so i got all four cylinders firing, and no more leaky carbs. But the bike isnt running so strong, mostly at idle, it likes to stall and then is a pain in the butt to get started again. I havent gotten a chance to sync the carbs yet, and i was wondering if that could cause the stalling. i also adjusted the floats pretty high (because of the flooding problem), all of them are at 26.5mm. could one of those 2 things be the reason for the rough riding and stalling? and by the way, thanks everyone for putting in your 2 cents, especially prometheus578, that was great!

-kypr1

[TopCatGr58]

Hey Kypr1,

From your profile, we can see you've got a 78E, but aside from that, we don't know what you've already done to the bike, or the history of it? Did you just acquire it, or have you had it for a while? Was it stored a long time? Any mods to intake or exhaust, like Indy filters or aftermarket pipes?

Have you done a compression test on it? What did the plugs look like? When you were working on the carbs, did you take the tops off and inspect the rubber vacuum diaphragms for pinholes? Did you ensure that the slides could SLIDE easily up and down, not getting hung either position?

Have you inspected your pickup coil wires closely? Have you done the cam chain slack adjustment?

On the carbs....there are upper float bowl vent tubes with "T's" just like the fuel supply lines, are these open...not clogged, even with OEM airbox, they can get clogged causing a very rich condition when trying to accelerate.

So....you see, lots of things to check, read the tech tips THOROUGHLY, and then report back on what you have done and found!
T.C.

[prometheus578]

TC's advice is solid. What do the plugs look like now?
Not synchronized could cause stallin' if the idle's too low, etc.
Is this your first bike? No insult intended, but I've had a rash of people at work lately leaving the choke on too long, foulin' the plugs.
To stall, and then be a pain in the rectum ("rectum... damned near killed him.") to restart, sounds like plugs foulin'. Pull 'em and see what they look like.