Cylinder #2 not firing

My number 2 cylinder is not firing. I switched between the #2 and #3 plug wires and the problem did not move, it stayed at #2 regardless of which wire addressed the spark plug. The plugs are all brand new. I think this is probably something to do with fuel starvation of sorts then. I have never cleaned my carbs, should I take them apart and check them all out? Also, I ran Sea Foam in the carbs last fall, I suppose that could have dislodged some crap that ended up fouling somewhere in the fuel delivery for #2.

Some others overruled the possibility of valve clearances being an issue since I have good and equal compression in all cylinders.


Additionally, can someone verify: Is it a bad thing to run 91 octane gas in these old bikes??????

Just my opinion,

Is it only not firing at idle? If it starts firing when the revs get up higher it is related to the pilot circuit.

Mine was doing the same and I found the pilot jet plugged on #4. The only way it would fire was if it was choked/revved up higher than 3k.

Good luck

Just to amuse an old man really trying to be patient, your new and spiffy spark plugs... ever heard of a BAD SPARK PLUG? I see bad spark plugs frequently. Wasn't one of the troubleshooting 101 steps, swapping the 2 & 3 plugs? If not, it should be. When you have done that, see if the problem moves... hate to have you rebuilding your carburetors when a spark plug is internally shorted. Does it happen with new plugs? YES or I wouldn't have recommended it.

Sorry, didn't mean for you to think I was disregarding something you had suggested. Ummm, through out all the compression testing I did(4 different times), I had ended up mismatching all the plugs around and had figures mathematically that #2 hadn't been the same the whole way around. Anyway, just to be safe I did as you suggested, #2 still didn't fire, and where I switched the #2 plug to DID fire. So that I guess narrows it a little.


So now we are to the carbs being the only problem left??

I reason that I might as well take apart whatever is typical for a good tuneup and do that while I'm at it since it has never been done before.


I began by taking apart the float bowls for all of them, so as to clean them out. Weirdly enough, the #2 carb had like a calcium deposit looking stuff on the inside of the bowl. All the other 3 looked pretty much brand new, but #2 looked old and some mineral is for sure crusted up around in it. So I bathed all 4 in carb cleaner..... and I don't know what to do next..... just start taking the whole thing apart slowly?


I don't have the $$ to get this done professionally, so thanks for the patience and time helping me out.






NEW NEWS ON LABOR DAY:


I have my carbs in pieces. I have bathed all of the parts in a real nasty paint can of some special carb cleaning fluid. After the 20 + minute bath I cleaned additionally by spraying all the small tunnels and jets with carb cleaner. The calcium like deposit stuff will not come off unless I scrape at it with a metal screwdriver. Is this normal? Nothing loosens it up, I have to literally chisel it off the metal. It gets me thinking that if this stuff is built up in some of the tunnels as well and in the same manner, there is no way I can get it off and that might just be my problem with fuel supply. I am attaching an image of what the deposit looks like.


Additionally, that 20 minute bath stuff, is it horrible to leave metal parts in it for 2 hours?

Post edited by: b4schroer, at: 2006/05/30 00:17

The pic

That stuff is oxidation. You can't clean it with carb cleaner. You need to use a fine wire brush. You need to clean the inner passageways with a dremmel tool with a wire brush and make sure the inner passageways on the pilot circuit are cleaned... not just the outside. Find the hole on the intake venturi edge associated with the pilot jet. You can spray carb cleaner into that hole and keep your finger over the mixture screw and pilot jet well and carb cleaner SHOULD come out the small hole in front of the needle jet on the bottom of the main venturi. This way, you will know the pilot circuit is all clear of the white debris. You may have to alternate between blasts of compressed air and the spray cleaner. If you don't have a compressor, buy a couple cans of compressed air at a place that sells computer supplies. There is little chance that the #2 carb is starving as far as the gas supply goes because the #1 carb is getting gas. Carefully set your float level on all the carbs using the Service Fuel Level method.

Thanks for the answer WiredGeorge. I am assuming that this oxidation is to some degree normal. I still think it is interesting that it only is in the #2 carb and that is the cylinder with the problem. My manual says not to use wire brushes to avoid damaging the jets. I will be sure to use a soft one I guess. Anyways, when I have brushed the tunnels and once I have set my fuel service level, can I get by with just the mechanical adjustment since I don't have vacuum gauges to fine tune? And one more question for you, you suggested that fuel starvation isn't likely the problem..... it seems to me that this carb cleaning hasn't done a whole lot to change anything from the way they were previously.... Is there another way this oxidation could POSSIBLY be affecting the #2 firing?

Post edited by: b4schroer, at: 2006/05/30 16:13