problem with number 4 cyl - with pics

[kevxs]

Hi Gurus, having a problem with my number 4 cylinder. The bike likes to run on 3 cylinders, when i remove the #4 plug it is very wet, i clean/dry it and the bike runs on all 4 again. Also on the right tailpipe there is wettness, see below, the left one is fine. any ideas?



2 shots of the number 4 plug . . .

[randy]

Well, could be just a fouled plug that's not firing properly, give you a few shots and then fouls up again. The wetness is gas from the non-firing cylinder. how well did you clean the plug? Did you clean all the way down the insulator? When plugs misfire from fouling, they like to do it deep in that well so you can't see it, the dirty bastards.

If you've tried a new plug and it happens again, i'd say it's a stuck float that's flooding that cylinder, then fouling the plug.

[blue giant]

How many times have you cleaned that plug? I'm thinking it just might be a bad plug. What is the gap on that plug? Looks a bit much to me.
Have you snipped the coil wire back 1/4 of an inch and reinstalled the plug cap?

Randy could be right too! Park your bike on a slight incline and check to see if carb 4 leak fuel back into the air box

Just a few ideas.

Paul

[oldyam80sg]

And another thing i noticed-is there a cotter pin for the nut on the axle? If not would be wise to put one in there!

[Ivan]

To reuse a fouled plug, you need to burn the fuel off with a torch. Get it glowing hot for about a minute and make sure the insulator is burned white again. If not you will just foul it again.

Another thing, I don't see any anti sieze on the threads. Antisieze doesn't just make removal easier, it vastly increases the ground path of the plug to the engine. I have fought miss fires before that were remedied by antisieze on the plug threads. Mostly happened on fords with iron heads, but aluminum heads on Yamahas aren't exempt.

You also need to look at the outside of the plug insulator. If there is a very thin black line that looks like a hair that will wipe away with your finger but doesn't, its carbon tracked and you need a new plug.

Other possibilities are a bad spark cap connection to the wire, a stuck float on that cylinder, a loose main jet allowing too much fuel, the choke plunger not seating, possibly a sticking slide. It may not be ignition related...

[CatatonicBug]

Other possibilities are a bad spark cap connection to the wire, a stuck float on that cylinder, a loose main jet allowing too much fuel, the choke plunger not seating, possibly a sticking slide. It may not be ignition related...

Wow, Ivan! Now you sound like an OBDCII computer!

[kevxs]

update

Thanks for the help guys, i took your advice,

did the spark plug wire trim fix on #4
fixed the sp gap on #4 (all set to .30 now)
put anti seize on all the plug threads
checked for cotter pin in axle (it is there)

I dont think the plug wire was the problem as I was already getting decent spark when I would test it on the engine block. I assume this means the plug and wire are ok . . .

took the air filter off, parked on an incline, checked for gas leaking ...
nothing leaked, however it was wet on carb air intake and there was a semi dried puddle of (i assume) gas in the airbox.

not wanting to take the carbs off if possible, i put a 3rd of a can on seafoam in the tank and filled up with shell 92, went for a short rip, bike ran well checked the plug after it had cooled and it seems dryer, probably too soon to know if the seafoam is working (see pic)



there is also evidence of gas leaking right below the airbox onto the exhaust.
(see pic)



Just drove into work and noticed some hesitation getting back up to speed after sitting at a red light for a bit, maybe its just the seafoam clearin out the junk, other than that its running fine for now, i'll keep an eye on it and see how it is after a tank or 2 with the seafoam.

hopefully i start getting better than 17mpg

anyone know what mpg a healthy 11 gets in the city?


btw here is the beast in question
again, thanks for all the help, keep it comin

[cywelchjr]

I don't know how "healthy" mine is, but with fairing and bags I get 29-30 around town and around 37 out on the road.

[DGXSER]

My 11 had a needle valve issue and ran no1 rich at anything below 3k rpm. I was getting 30 MPG then, since I cured that, it gets about 35-37 avg.

[oldyam80sg]

I get around 33 to a gallon.

[jetmechmarty]

I didn't want to pull my number four carburetor either. The float mount stud was broken and repaired by the PO. The repair failed. The float stuck. The engine backfired. I had a big fire!

Had my daughter not been extremely quick to grab a fire bottle, the bike would have quickly been a total loss. I will never again ignore a problem like that, or try to fix it with SEAFOAM.

[dbeardslee]

Kev - Having your float height too high (in the installed orientation - too low when they're upside down) will cause plugs to fowl. Have you checked your float heights? Are you still running stock coils? Do you have the proper plugs installed (ngk bp6es)? I've seen people go to the bp7es's thinking they were going a heat range higher, when in fact that's a heat range lower on NGK's. They're numbering scheme is bass ackwards for some reason.

[Trainzz]

30-35 mpg

Like the car commercials say " Your mileage may vary"

Depending on the angle of my throttle hand, I get 30-33 in town, 35-38 highway. So far my best mileage is running 75 mph, some trips at that speed I will hit 40-41 mpg.

I have learned that trips in excess of 80-85 mph reaaaaaaly lowers my mileage per gallon.

[kevxs]

hi dbeard

running stock coils with the ngk bp6es, bought the bike back in feb, had a mechanic tune it all up, but i haven't had the carbs off myself. just drove into work this morning, bike is running well on all 4 but the right tailpipe is wet again, would the incorrect float height cause this? wish i had a garage or even a driveway to work on the thing, looks like i gotta take carbs off on the street

ahh toronto living

[dbeardslee]

If a float is set to high (in the running orientation) it will cause plug fowling, and can cause them to look black and shiny. If they're wet it's probably not getting fire. If you remove the plug wires from 1&4 and put a multitester between the plug caps you should get a reading of 15k ohms resistance. More than that and you might consider new plug caps. Unfortunately the wires arent' replaceable. If you get it running in a dark place you can throw some water on the plug wires. If you see sparks arcing from the wires to the top of the motor your plug wires are shot. With 30 year old high tension wires the chances are pretty good you'll see sparks. When I replaced the coils on Betsy I thought I would keep the old coils - just in case. I was going to keep them in a 3lb coffee can, and when I bent the wires to put them down in the can they snapped in two! I'm pretty sure they're not supposed to do that .