Cylinders 1&3 not firing

[Larrym]

Shocking Development

I have to refer to the manual every time I forget which coil fires which plugs...You're right!!

If you are getting spark on all 4 cylinders then......

Back to the carbs/fuel system you go! (Electrical/fuel/mechanical...)

Maybe there's something wonky going on in there. I know that if there's spark in a cylinder with a gas/air mixture then something happens: Ka-Boom! (Hopefully on the downstroke, please!)

I'm using OEM coils right now and I'm not impressed with the spark. The bike runs great, of course. But I've seen the light shows from some of the aftermarket coils and it's scary. Bright Blue sparks with a sharp CRACK that makes you step back and hope that it doesn't jump out to get you. Like I said, the stock coils appear "weak" but they do the job.

Try idling the bike for 5 minutes and then misting the pipes with water from a spray bottle. (Confirms which cylinders are really running.) Which cylinders are being lazy???

No problem, Doug. This'll all be a fuzzy memory soon and you'll be back to trying to figure out why bugs keep hitting you in the face instead of being drawn in to your headlight...

[Blackdog]

It is definitely 1&3. I still think I should be getting 12v to the coils.

[TopCatGr58]

Hey Doug,

Yes, you should be seeing close to 12 volts at the coils, and with them only getting 8-9 volts, that's why you are loosing spark on 1 and 3, the other end of the line for each paired coil!

Check your main ignition switch and wires(Key switch), you can take it apart, may find some corrosion, broken or partially soldered connections and such!
Still say you need to replace your fuseblock!

Cy, the coils get a constant supply of voltage/power thru the red/white wires, it's the Orange and gray wires that switch the ground on and off, so with a tap on the red/white wire, he can measure the proper voltage with it running.
T.C.

[Larrym]

Weak?

Yeah.. But if the coils are getting enough juice to put out spark then the fuel in the cylinders would ignite. That is if there is fuel getting in those 1+3 cylinders...

May be multiple bogies. (Yet to see a 30 year old bike which doesn't have multiple issues...) Like TC said, there is a replacement fuse block available which would likely eliminate any problems which would be caused by a faulty stock fusebox. But the question is whether or not your "misfiring" cylinders are due to a faulty fuse block which is "dropping" the voltage to your coils. You could get the new fuse block and install it. It may or may not fix the misfiring problem. (It's a great upgrade regardless of whether it directly leads to fixing your immediate problem, IMHO.)

The fusebox is important but people who have done this upgrade have also to some degree gone through their bike and cleaned up rusted/corroded connectors and contacts as well. You may have some "Iffy" connections leading to and from the coils which may be causing the readings to be less than perfect. If you want to clean them up and see if that improves the voltage readings then there's no harm in that.

But as long as the coils are producing spark equally in all four cylinders it would appear that there's something else which is different about #1 and #3. Ruling out mechanical failure (pistons/valves/etc..) leaves you back at fuel.

Really makes you wish you had an extra set of carbs to swap yours out with, don't it? I've got a "test carb" bank but I bet you could find out what's happening in your fuel system way before my carbs would be at your door.

[TopCatGr58]

Yeah.. But if the coils are getting enough juice to put out spark then the fuel in the cylinders would ignite. That is if there is fuel getting in those 1+3 cylinders...

Hey Larry,

There can be enough juice to spark the plugs in OPEN AIR laying on the head, but it's a different story when it's under pressure inside the cylinder.

I still think it's the low voltage to the coils. He could do a test, run a pair of wires directly from the battery to the coils at the red/white wires and see if it then hits on all 4...ensuring that he's seeing the same voltage at the coils that the battery has...close to 12 volts!
T.C.

[Larrym]

Show of Hands, Please??

TC,
Now that would be a real "eureka!!" moment!! Real do-able way of verifying what's wrong and telling us which way to go.

"All those in favor of running TC's temporary By-pass say aye...."

AYE!!!

[DiverRay]

AYE!!! Just remember to have some type of quick disconnect on the wire! I would use the clips you got when Larry said to, and just un-clip the wire to STOP the engine! Remember, it will run as long as it has spark, and if the coil is direct to the battery, it has spark!

[Blackdog]

I like it!

Great idea, I think this really has promise. I don't think it's in the fuse box because it's only getting 10.8v to the fuse box, 10.8 leaving. BTW I think it would be a good idea to change fuse box, but I don't have or want PayPal. I also wouldn't mind sending a little something to help maintain this site. Anywhere I could send a check? Thanks again and I will let you know what happens tomorrow.

[Ivan]

What are your compression numbers? I looked back through the thread quickly and didn't see them.

[Blackdog]

Darn

Did the 12v shunt to the coils and 1&3 still aren't firing. Guess it's coil replacement time. Looked at Mike's XS and they had several different coils, not sure which coils to order or whether to probe more with what I have. I still have a hard time believing that both coils could go bad by just sitting there. I haven't checked compression because I don't have a compression gauge. It is a very low mileage bike that never was frozen up.

[Larrym]

Drat!!

Well at least you've got some "evidence" to guide you in that direction. (I'm not a big fan of just swapping stuff in a "shotgun effort" to solve problems.)

There's been a few threads recently about the "longevity" of those Mike's coils. If you do a search here on the site these threads will show up.

There's also a tech tip here on the site which shows how to replace the high voltage wires coming out of those "suspect" coils you still have.

Remember that if the new coils don't work then we can head back into fuel systems.

[Blackdog]

Update

Went out and probed some more, pulled plugs and got much healthier spark. While I was delving into low tech diagnostics I decided to go really low. Spit some gas in cyls. 1&3, put plugs back in, and fired it. For a brief moment it fired on all 4. So while I think I definitely have an electrical problem that needs fixing, I think my carb rebuild sucked. Carbs are coming off and gone over again. Keep you posted.

[Larrym]

Up the tree?

Blackdog,

Looks like following the scent and crawling under logs is gonna pay off! You've got them varmints up the tree, have you? Good instincts and tenaciousness you got there. I'd go hunting with ya anytime.

I have some Ether/Starting fluid that I keep on hand for this sort of thing. I don't like to use it. I don't even like having it around. (Part of being a firefighter once, I guess...) I tend to block out that I even have it. But there are those times when it proves itself useful....

[Blackdog]

Fiddled with carbs, not complete breakdown. Made initial test run, idling on 4 cyls. with max choke on at 1000 rpm. Running with coil shunt in place. Dies when I take it off max choke, even to middle choke. Guess I am going to learn the definition of triple clean. But I am making progress.

[Larrym]

Nervous Breakdown

Doug,

I didn't want to go "invasive" on My carbs either. It's the natural reaction to want to minimize things and do only what's needed to make the bike run. But at some point someone has to go "in" and luckily it's you.

That nervousness means you care and will likely be very cautious at every step of the way. That's a good thing when you contrast it with someone who's gung-ho and casual about this operation. You are the technician here and so any "TIE's" (Technician Induced Errors) are not gonna be cause you were careless or in a hurry: broken float posts, stripped screw tops, Buggered threads, torn gaskets, the list goes on.

The site here has a great general guide with all those hardwon tips like filing down a flathead screwdriver so it fits perfectly in the Idle jet slots or taking some fine emery cloth to the float pin so it'll come out easier the next time. My favorite is to take a plastic credit card and cut it in the shape of an "L" to make a float level gauge. (I use those CC's which come in the junk mail. "No. I don't want a MasterCard but thanks for sending the plastic!")

While you're testing your ability to dodge a stream of carb cleaner aimed at your face, consider this:

The carbs are only as complicated as they need to be. Lots of orifices for air and fuel. Little pin holes in the ends of those jets and sometimes more even tinier holes along the sides of the darned things. Every one of them important and without each one doing what they're s'posed to do the bike doesn't run right. Multiply that times 4 and the Eek factor skyrockets. There's a point where you might wish that things were a lot simpler. Why not have fewer carbs? That would make it easier, Right??

It would also be taking a giant step away from being a superbike and heading in the same direction as a Harley Davidson. I'm not opposed to heading in the same direction as a Harley. I just wait for the safe opportunity to pass them. That's what a superbike with four carbs does.

Just filling in the dead air here on channel 11.....