Cylinder#4 not firing?

Hello! I have a 1985 Yamaha Maxim xj700 that I am having some problems with. I recently tore the carbs down and cleaned them (twice, the second time actually done right), installed new dyna coils, new air filter, new plugs, new wires and caps, new pilot screws... but now cylinder #4 is not firing. I know this because the pipe is cold, where the others are blisteringly hot. I know THIS because I am currently nursing a 2nd degree partial thickness burn... anyhow, I am wondering what my next step should be.

There also seems to be some fluid shooting out of the drain holes in the exhaust on the same side. I can't tell if this is gasoline (because it only leaks when the bike is running and the smell of exhaust in the closed garage is making me loopy... are those really flying Q tips? They're attacking!!!

Anyhow, I am sure someone has seen this problem before and hopefully can shed some light on this problem.

I have air, I have fuel, I have spark... resistance is within spec for caps, coils are within spec...

HeLP!!

 

If #4 is not running, and you know you have spark going to it, then you most likely have junk clogging that carb, or that float is upside down blocking the flow of fuel. How does that plug look? Wet with fuel or im guessing its dry.

Im glad someone else has brought up the flying q-tips... i noticed they perfer pez over human flesh... so ill always bring a couple packs with me to keep them distracted while wrenching.

Also you should check the wires and make sure theres good wire to bite into the plug cap, and thats its securely screwed on.

 

Hey Schmauster, that burn looks a lot like yours! You two related?
Looks painful Madmaxim!

 

It's a lot bigger now... I've named it Schmauster.

So, my crank case was full of fuel. Drained it, replaced with new oil. Cylinder 4 is still not firing, but MAN is there a spark. Note to self: Don't touch the bike while testing the plug.

If the crank case is full of fuel, that means a float is stuck open, yes? Or do I see a tear down of carbs in my near future? :twisted:

 

Fuel in the oil is a classic symptom of a hung float or sticking fuel needle. Time to pull and clean some carbs. Don't worry, you'll get good at it before too long (third time is a charm, or so I'm told...).

 

Yeah uh.. Robert, i told you i was testing the air fuel ratio by comparing my skins burning point to the relative humidity, ambient air pressure and the color of the leaves on the trees.

maybe i should put up a picture of my arm and it can be a show and tell.

I wanted to use my wrist since its more sensitive. I now know that i need bigger pilot jets... small price to pay.

I was swearing at the rubbing alcohol gods today.

 

I figured it out!

Of course, it took a tear off of the carbs again...

The little brass bolt that holds the emulsion tube in place was sitting in the well all by it's lonesome. But don't worry... the other brass fitting on the post next to it were all having a grand old time with the copper washer just splashing around in the bowl.

Must have forgotten to tighten the little suckers down. *sheepish grin*.

Well, I'll have the bike running tomorrow for sure!

oh yeah... the blister says hello.

 

Let's see.....
1. don't grab hold of a hot exhaust pipe
2. don't grab hold of a sparkplug while holding the frame
3. I sure hope you don't do something with a whole lot of gasoline nearby when you try getting a spark.

4. Please make sure you are sitting on the bike when you start it.

Dave
ps: yep, I've gotten blisters that look like that, too.

 

5. Not a smart idea to ground the battery charger to the carbs
No, I did not do this but I know someone who did....

My battery acid burn isn't as impressive

 

I'm considering changing my name to Firemarshall Bill. "LeT Me Tell Ya SoMeTHin!!"

It brings to mind all those things dear old mom, in her infinite wisdom, tried to impart. "Don't touch that, dummy, it's hot."

Yeah, testing all 4 plugs against the frame was a good time... especially when I went to shut the bike off. "Spark.. SPaRK...SPArK!!!"

I'm going to ride the tires off that bike once I get the fire put out.