Black, oily (?), plug.

[Gyrogearloose]

OK, 79SF has black plug in #3. I've done the carbs cleans (3), and switched wires (2&3), and tried new spark plug there. Still black...missing at steady throttle below 3500 rpms, then goes like a bat! The black is kinda' oily looking..smears on my finger, but it is burnt, like, it is carbon. The other plugs have white tips. Oh, and I bench sync'd via the butterfly over first hole method. The idle mixture screws are all set at 1 1/2, but I've turned in #3 to 1 1/4; still with no change. It starts readily without the choke. If it is oil in #3, where could that come from? ...Rings?...valve guides?...er. Hope I'm describing things right. Thanks for your help.

[Da-Bubble]

Gyro,

I have the same problem with three whites and one black plug. If the black is powedery, that is not oil it's just running rich. As for how to fix it, you're guess is as good as mine. My carbs are fully disassembled on my work bench for another go thru. When I pulled them, all the floats were within a few 10ths of a millimeter of each other. I am giving mine one more chance before I beg/pay TRBIG to come up here and help me with them.

Good Luck,
Scott

[egsols]

Probably not the problem but always worth a try....swap plugs and recheck just in case you have a bad plug, it can happen and is a lot easier to fix then tearing down carbs.

If it is still black then you are probably running rich on that carb, could be high float but you say others are white, indicates lean. Sounds like time to double check float heights in all and do a proper sync including idle mix set up.

[bikerphil]

fuel filters?

Make sure you run in-line fuel filters so no more crap can get in the carbs.

[Gyrogearloose]

Thanks for the replys. I am running inline filters without the octy. I've set and rechecked the float levels on each carb clean; set at 25.7....? so, I'm kinda' at a loss here. I've used two new sets of plugs getting her this far, and have swapped plugs from other firing cylinders; still to find #3 black after each run. It sounds good when I fire it in the shop, but when I take it out on a test run, it doesn't take long to start missing.

[bikerphil]

fouled #3

Just for the heck of it, put in a clean plug & turn the #3 pilot screw (mixture) in a bit more. Don't tighten it all the way, it could break. Check the plug color after running it some. I've got one carb on my Standard where the pilot screw is in much more than the rest of them for it to run properly. Pilot screw affects fuel mixture up to about 4K RPM. HTH.

[Gyrogearloose]

Hey! Thanks BikerPhil, I wasn't aware that the idle mixture was used up the rpm range that far. I'm shaggin' my but- bones right out there and crank'er in some. Let you know what happens!

[wa407mpp]

Did you make sure all your floats float, or shake them and listen for fuel inside? Also it's very important to keep all the carb. parts separated and not mix them up, from carb. to carb. They all wear different and mixing them can cause problems, and the only fix is to replace everything with new, and at the price of jets, seats, and towers, can be expensive.

[Gyrogearloose]

Just got back from a ride. Huh. No change. I had swapped in a new plug, and turned in the idle mixture screw 1/4 turn. It's now out 1 full turn. Yup. I'm beginning to suspect a faulty float as Fastmover suggested, because it doesn't take any time at all to start missing. Well, I guess another carb tear down was in the mix after all...at least that's what the last tossing of the bones suggested. Heh.

[dbeardslee]

Gyro - my plugs were all getting oily 'till I changed the valve stem seals. Put new ones in and haven't had that problem since.

[cruiser]

Suggest you go back to the basics.
Compression check of all 4 cyl. with throttle wide open to verify condition of rings and valves.
Any blue smoke from exhaust on start-up?

[dbeardslee]

Gyro - I agree with cruiser. In your original post you said 'oily ?'. If they're just sooty (carbs) they won't be shiny. If they're oily they'll be shiny and wet looking. If you're getting oil on the plugs it's coming from one of two places - the top (valve seals) or the bottom (rings). You can tweak the carbs all day long and it won't fix either of those problems. How many miles does your machine have on it?

[Gyrogearloose]

well, the bike has 18K plus on it, no reason for that kinda' wear, at least that's what the speedo says. The black is not that shiney looking, but it smears easily. I thought, "Well, if it's not been firing by the time I get home, of course it'll seem moist....?" It's definitely not dry or powdery. Hmmm. I'll pull off the carbs again and check the float and it's level in relation to the rest of them. I hate having to pull the head off. Thanks for the comments!

[DiverRay]

Geno,
When you pull the carbs, do a compression check while they are off. Check ALL FOUR and keep in mind anything over 10% in difference IS a problem. If that looks good, when you pull the float bowls off, look at the main jet, and then at the tower just in front of it. There should be a screw WITH A WASHER on the tower. IF that is missing, you will be getting WAY too much fuel into the pilot circuit, and that will cause your problem.

[Gyrogearloose]

Thanks DiverRay, you've always got good advice. I should have this evening free; let's see...put a few more plants in the ground, feed the pigs, get the eggs and lock the chickens up for the night, split a coupla' pieces of wood for the eve., stir the rhubarb jam..ah...busy here on the farm!