Number One Cylinder Not Firing

[Spiderman11]

Okay guys, I need some help. I've got a 1979 XS1100F with 15k miles showing. The bike is a fairly clean beauty. I'm the third owner. All fluids are fresh, the carbs have been cleaned, the plugs and caps are new. Other than being the cold-blooded beast these darlings can be, the bike starts and runs fairly decently once warm. That's actually quite surprising since I have now realized the number one pipe is not getting hot. The number one plug is, however, soaked with fuel. Yes, I have read the tech tips for the coil/wire replacement and the pick-up wire repair. But, since it is only the number one cylinder, I thought I'd get some help from greater minds before I start cutting and splicing. I would greatly appreciate your thoughts on the most likely culprit. Thanks in advance.

[Ken Talbot]

Start by swapping #1 sparkplug with any other - bad plugs, even "new out of the box" are not all that rare. If #1 is still dead with a swapped plug, remove the sparkplug cap, trim it back about 1/4 inch and reattach. That should do it...

[Spiderman11]

I trimmed back the wire and reinstalled the cap this afternoon with no change. I'll try the plug swapping next. Thanks for the suggestion.

[skids]

It might be easier to swap plug caps and wires with No. 4 and see if the problem "moves" from No.1 to No.4.

Originally posted by Spiderman11
I trimmed back the wire and reinstalled the cap this afternoon with no change. I'll try the plug swapping next. Thanks for the suggestion.

[Ken Talbot]

Ah right, Skids' got a point there. #1 and #4 fire off the same coil. If the problem moves, you look for a problem with that coil and one of the two wires coming out of it.

[Spiderman11]

I've swapped the plugs around with no change in results. Soooo...it looks as though I'll be making the modification to install new plug wires into the coil next. Thanks for the continued advice.

[uk1.1s]

Desperation.....one Idea

If you're getting desperate try something that worked for me earlier in the year.

#4 refused to fire and left the pipe cold...although the bike sounded fine at idle..a quick trip up the road revealed the truth (and surrounded me in a cloud of unburnt fuel fumes at a junction...yipe!

So...I tried the old single trick of heating the plugs (or just one) in the oven for 20minutes and then (using bike gloves) tried to get it all back in whilst still nice and hot.

Fired up - ran a bit ragged and then chimed in OK and has been working ever since. Dunno what the trouble was, but once the bike got the idea it seemed to sort itself out.

Not very scientific I know (and with me with the word 'engineer' on my business card too - don't tell the boss!!)

[Spiderman11]

Sounds like an interesting idea. A little shake and bake. I won't tell your boss if you won't tell mine.....of course, my degree IS in M.E. and not E.E.

[uk1.1s]

Shake and bake

Yeah - try and work those breadcrumbs in really well tho'!!

[TonimusMaximus]

Maybe I've been working for CSK Auto Parts for too long, but baking plugs really does work. As far as I can tell, the heating allows the coils inside the plugs to expand and seat properly rather that just shorting out on each other producing little to no spark. (And me only starting work on my M.E. degree... ) Hope it works out for ya. Have fun guys.

[uk1.1s]

Wow scientific backing

I'm impressed.

I thought my homespun remedy 'snake oil' approach to maintenance, getting sulking bikes running and garage therapy was just a result of an old bikers many moments of desperation over the years with old heaps of scrap in the garage

At last - engineering reasoning behind my 'finger in the wind' mechanicking!!

[schpiff]

I have found that once a plug gets fuel soaked and wont spark/fire, a faster and very effective way to get it clean is to use a propane torch. Just heat the business end up good and hot. You will see the fuel burn off. Just dont melt the electrode!

[Hobbit]

You would have to get it really hot to hurt it. The center electrode temperature is normally around 1200 and 1400 degrees F.

The main problem is that the chemicals in the fuel permeate the insulator and act as a conductor so the voltage just discharges to the shell rather than arcing. (I use to work for Autolite Sparkplugsas a technical rep.)

[Spiderman11]

Here's an update. I have now replaced the plug wires, using the tech tip "new wires in old plugs", and I'm getting a healthy looking blue spark at the #1 plug. However, the number one pipe still isn't getting warm. When I remove the plug, there does appear to be fuel present. However, and here's my question, is it possible that I am not getting ENOUGH fuel to that cylinder for it to fire? If so, what is the most likely cause/fix?

[s38310]

My guess is that the cylinder is running very rich which will keep the exhaust cold. Is the bike running rough? Do you have dual exhausts with the #1 side having light blue smoke? Its possible the float is higher on that cylinder or the seat is seeping allowing raw fuel to enter the cylinder. Since you now have spark I would start looking into the carb as the culprit especially since the plug is wet after shutdown. Hows the compression?