Number 4 not firing

[azr]

So I've got my 78 1000 running. So the engine has sat for a couple of years I'm sure. I've done a fairly decent rebuild/clean up on her. So the carbs have been properly dipped, cleaned, new o-rings (everything was done). New intake boots with new o-rings, new air box boots, Fresh wiring harness (everything cleaned, and shinny). Valve clearances checked and done. New dyna S ignition with green coils wires and caps. Compression starting with #1 is 160, 142, 152, 140. I know they are a bit over the map but I figured she's been sitting for a bit so ridding should even out those numbers a bit. I think that's everything with the motor side of things. I've synched the carbs adjusted the air mixtures and she idles quite well. Problem is #4 is not firing. I took her out for her first ride yesterday and knew right away on cylinder was not firing. I've tested the coils and they are fine. #4 is getting good spark as I got zapped good. Piston is moving freely. Spark plug has fuel on it. I opened the float bowl and lots of gas. It doesn't matter if the choke is on or off it just won't fire. Any suggestions?

[hampshirehog]

First thing I'd do is swap #1 and #4 plugs round and see what happens - could just be a duff plug and if it is and you don't find it you'll be chasing your tail forever.

[azr]

First thing I'd do is swap #1 and #4 plugs round and see what happens - could just be a duff plug and if it is and you don't find it you'll be chasing your tail forever.

Tried that already, no such luck. Forgot to mention as well that she's pushing a lot of blue on start up, especially from the right exhaust (mostly from the right exhaust). When I picked the bike up last year I started her up cold many times before pulling her apart and there was no smoke. I've just shot some WD-40 down the cylinder to see if that will do anything in case the rings are sticking. Arrrrrrr........so close, so close.

[Carter Turk]

I had a Dyna S with a bad 1-4 trigger, that worked intermittently. I also had a green 3 ohm Dyna coil go bad, but you said you checked that. I ended up throwing the stock plate back on and the Dyna S has been sitting in a box.

I don't know if your bike has points, but it might be worth a try, throwing the stock component on to see if it fires on all four.

Dyna took care of me, but the hassle of shipping a supposed performance part back and forth was frustrating. Maybe checking the spark plug wire for corrosion or snipping it a bit may help.

[Carter Turk]

Disregard the spark plug wire suggestion, I read your post again.

Float height? What does the #4 plug look like?

[bobthebiker88]

from the sound of things, your carbs are the culprit. verify you're getting th CORRECT quantity of fuel. frm what I'm getting, you're overloaded. does the pipe even get warm?

verify your fuel system is clean enough, and not just arbitrarily dumping gas into the cylinder.

[Octain]

Seems like you have everything covered.
I'd install a new plug and see what happens. At very least swap it for one thats working.

Does the number 4 plug look like its fired at all?

[Texas Don]

I don't like the compression on #4 cylinder at 140# but then #2 cylinder is only 142# so I doubt that 2# would cause a dead miss. The service manual says 100# is the service limit. Bear with me if these questions seem offensive, they're not meant to be.
1. Are you certain that it is fuel on #4 plug and not oil, or oil & fuel mixed?
2. If you hold the #4 plug against ground when cranking, is the spark color, volume and length the same as on #1 plug when you perform the same test? You can get a heck of a shock from a plug wire that has built up resistance but it won't be enough to fire the plug, especially with low compression. I'm wondering if the coil/wire output is so low that combined with the low compression it won't fire when combined with the low compression. Changing #4 and #1 wires wouldn't necessarily prove the coil and or high tension wire good when there is such a compression difference between 1 and 4 cylinders. Do you have access to another coil that can be tried in the 1/4 position? Hope some of this is of help. Please post your answer when you find it.
Don

[MisterCinders]

When this happened to me, I had swapped the 3 and 4 carb bodies by mistake. If you have spark, something is blocking fuel. Hunt that down.

[Octain]

Fire, air, compression and fuel and it should ignite.
Its gotta be something simple....

[azr]

I had a Dyna S with a bad 1-4 trigger, that worked intermittently. I also had a green 3 ohm Dyna coil go bad,

I know it's not the Dyna because #1 is firing just fine ( I too had a dyna trigger go once and Dyna had great service for replacement). I know these coils are working as I took them off my running 850. Weird thing is though I can't get a resistance down the wires on one of the coils. It works fine just can't get a reading. I sent an email to Dyna asking how come, I'll see what they say. I originally put the bike together with the stock coils and wires as they seemed to be ok. I swapped them out for the Greens this morning hoping it would solve my problem, no luck. I haven't gone and bought a brand new plug for that cylinder but I have swapped it out with pretty new ones, ones that I know are working just fine. The plug in #4 is a little black and wet with what smells like fuel. It doesn't look like it's firing at all. You can take the plug wire off and there is no difference in the idle, unlike any of the other cylinders which will make the bike almost stall.
So I'm thinking the next thing is to make sure the float isn't allowing too much fuel (as well I'll check to make sure the spark looks the same to #4 as the rest) I can check the float hight out side with my cleartube set up. For reasons unknown to me I threw this rack on the bike only having set the floats by measuring them, not be setting them with fuel in them and the clear hose from the drain plug. I reallllly don't want to pull these carbs, not that it's impossible but taking my carbs off my 850 is about a 6 minute job, the 1000 can take my forever, especially when it's cold like this and all the rubber is hardened.
Thanks for all the help so far.

[Octain]

Pulling the carbs is a bitch with the stock airbox. I know your feeling with that one.
My money is on the plug.
I dont think a over full bowl will cause the cylinder to not fire. At worse something will leak fuel if that were the case.

Buy a new SET of plugs and go from there.

[azr]

So I checked the two outside floats and they both were off, especially #4 so I pulled the rack. Put her up on the bench and adjusted all the floats with the clear hose and fuel. #2 & #3 were actually within spec. already and now each one is perfect. Funniest thing, I was ready to put them back in and decided just to make sure the fuel screws were set correctly.....they were never set. They were all dialed wayyyy out. Who was it that said "Its gotta be something simple...." I've put the carbs back on the bike but ran out of time to connect everything and fire her up, but will be first thing in the morning. I'm crossing my fingers tonight that's for sure. I should have known when I pulled the carbs and said "geez that's strange, each intake boot has some gas pooled in it".....like I've said before, "not the sharpest tool in the shed but definitely the fastest"

[Charlie G]

I know the feeling! Good luck there, getting it going.

cg

[Nessism]

Sounds like you might have figured it out but a couple of things that come to mind are: make sure the pilot jet is open by holding it up to a light, and make sure the pilot fuel screw tip isn't broken off in the carb body.