not firing on left/drivers two cylinders

[gauthierdustin]

i have a 1985 fj1100 and it doesn't seem to fire on left two cylinders? any ideas where to start???

[gauthierdustin]

i bought it foolishly and thought it was running right, until i painted the headers and realized the paint never changed on the left two pipes, there is no heat therefore no fire??  does one cdi run two cyclinders next to each other, or do i have a carb problem?

[1tinindian]

I think irishluck should be able to help you out!
He knows all about this issue...

[gauthierdustin]

ok so i have spark on far left cylinder, so it's obviously a fuel issue or carbs i think?? i have pod filters and 4 - 1 headers with a shortie exhaust plugs are all new!! should i rebuild carbs? the engine was just rebuilt by the previous owner? did i get ripped or what?

[andyb]

Spark is routed from two coils.  One fires 2+3, one fires 1+4.  The one you're seeing fire on is 1 (l-r as you sit on it).

The coils fire two cylinders at a time, one appropriately and one spark is wasted during the exhaust stroke.  Rationale is that two coils are cheaper than four.

Starting assumptions :  You have fire on 3 and 4, to start.  Now it sounds like you are just missing on 2, if 1 is firing also.

So, to start.  Swap the 2 and 3 wires to the plugs.  If that moves the cold cylinder to 3, I'd suspect that the spark wire, cap, or something in the coil between the outputs is bad. 

If swapping 2/3 doesn't move the cold cylinder (#2 still not firing), then you are likely not getting fuel to it.  Pull the plug and smell it, if it smells like gas the plug is bad.  If it doesn't smell like gas, the carbs are gummed up (most likely the pilot jet and idle mixture circuit).

How long has it been sitting?  With the proper combination of crap gas and staying parked, carbs can get crappy in a week or less.  If there's rust and crap in the tank, they can get killed off even quicker.

[irishluck]

ha yeaa i know a little about this one. As far as i member your left coil should be on cylinder 1 and 4 and your 2nd coil on 2 and 3 (if im wrong correct me)

check that first and make sure those are hooked up right, if so, then you got maybe some bad wires or something


idk how to really check if engine rebuilt or not but try to turn the crankshaft with a wrench and see how it feels and sounds.

mostly its prolly going to be the carbs,  they may have sat for awhile, may have bad gas. tear into them and see what ya find.

[gauthierdustin]

So I've found the left two cylinders only fire at 3000 rpm I screwed around with the carbs a bit it still don't idle right though

[irishluck]

did you open the carbs up at all and see if gunked up?

[SkyFive]

Dustin,
Be sure your coils are well grounded before you "tear into" your carburetors. The coils ground an a painted surface, install a star washer and retighten the ground just for the hell of it and see if that helps.

ETA; This is assuming you have a "firing" problem. Test with a uninstalled well grounded spark plug, the spark should be bluish.

[gauthierdustin]

Do I need a carb kit before I start tearing into them I think they are just gunked up?

[gauthierdustin]

And where do I start tearing in? The top cover first?  Yeah I have spark no problem there??

[irishluck]

well me, id start by taking the bottom of it off, thats where you'll find your jets and such that would be gunked up, and i never used a rebuild kit for mine and my carbs still work fine. its recommended to get a new main jet and gasket if its gunked but they can still be cleaned if ya got an ultra sonic machine or something along those lines.

[Klavdy]

Hi Dustin, welcome to the site.
Please don't follow any advice offered by that Irishluck boy, he's not quite right in the head.
Andy B, Slow Old Guy and Randy from RPM(among many others) would be your best bets, listen to what those experienced men have to say and you should be fine.
Your machine worked once, it will work again.

[irishluck]

nope, aint gota listen to me, listen to the guy who wants to talk crap, thats a great thing to do

[andyb]

If you can troubleshoot it to the carbs (which is what it totally sounds like, incidentally), the guide you want to follow is here.  Explains the lot.

I strongly suggest buying this kit, also.  It'll make your life...oh... a zilliontybillion times easier if you ever need to go back into the carbs again.