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Message started by splash07 on 09/20/07 at 22:02:43

Title: fowled plug and black smoke
Post by splash07 on 09/20/07 at 22:02:43

whent to start the bike for the first time in too long, and it wouldnt start. I ran down the battery trying to get her to crank, once the battery was dead i decided to check the plug. Got it out and found it covered with black soot. I threw in the spare from my tool box and with a jump she fired right up. As it idled faint black smoke puffed from the pipe. No smokeonce it got warmed up. I had only put 200 miles on the last plug. What could be causing this? Is/ should it be a concern?

Title: Re: fowled plug and black smoke
Post by YonuhAdisi on 09/20/07 at 22:58:37

Black soot on plug and black smoke from exhaust usually means you are running extremely rich.

Title: Re: fowled plug and black smoke
Post by Reelthing on 09/20/07 at 23:05:15

If the carb slide is getting a little dirty it will sure act this way - the slide starts to hang a bit and won't close off the mainjet as well as it should

Title: Re: fowled plug and black smoke
Post by splash07 on 09/20/07 at 23:55:01

carb was just completely cleaned so i dont think it is the slide. I tuned the carb a bit and will check the plug again in a few days.

Title: Re: fowled plug and black smoke
Post by demin on 09/21/07 at 06:19:35

Maybe flooded it trying to start it.

Title: Re: fowled plug and black smoke
Post by splash07 on 09/21/07 at 06:55:03

seems a likely possibility, but would it create that much soot by just flooding it once?

Title: Re: fowled plug and black smoke
Post by justin_o_guy2 on 09/21/07 at 08:02:18

If you take the bike out & run it for a while, get it all the way warmed up, go play, then, after its been parked & is cooled off, run a finger in the pipe & see how sooty the exhaust is inside. If your finger comes out all black & filthy, it's rich. If it comes out with a bit of grayish looking stuff on it, thats normal, a lighter color. Closer to a gray, than black.
Here's an idea..
If you look at the exhaust pipe on, say, a Honda car, it is fuel injected & you can bet the mixture is about right, look at other exhausts & get an idea what is good, then check yours. But, they do have a catalyzing exhaust system & it will be a cleaner pipe, but the general idea is still gonna lead ya closer than no clue at all.
200 nmiles on a plug isnt a good thing, & just because the carb was recently cleaned is no comfort. It is normal to go straight to the last place worked on when things go badly, just because that was the last place a person coulda made a mistake. I hear just fingerprints on a slide can make them stick a bit.

Title: Re: fowled plug and black smoke
Post by Savage_Greg on 09/21/07 at 09:22:34

splash07 wrote:

seems a likely possibility, but would it create that much soot by just flooding it once?

Not likely that you flooded it, simply by trying to start it. That's sort of a misconception that applies to older carburated cars because when you pumped the pedal you were operating an accelerator pump that squirted raw gas in the intake. We don't have that kind of device on our CV carbs and simply opening the throttle doesn't do that much.

(I do have an XT250 in the garage with an accelerator pump. Different Mikuni though)

Actually, you do not need to open the throttle at all to start the bike. If it's setup correctly, the pilot circuit will do it all. However, it can still be too rich for a few different reasons.

Time to find out why it is too rich...assuming that all was just fine when you parked it...

Clean fresh gas in carb and tank too?

Was choke on?

How's the float height?

Oh yeah, charge the battery so that you have a good spark before the next try.

Title: Re: fowled plug and black smoke
Post by justin_o_guy2 on 09/21/07 at 09:41:38

The easiest float level check is a tube from the bowl drain held up next to the bowl. The height of the tube end when gas drips out is the level of the gas in the bowl. No disassembly, no callipers. SCHweet!

Title: Re: fowled plug and black smoke
Post by demin on 09/21/07 at 13:14:44

You're right Greg.I'm thinking of the S&S on the ol' H.D.
:-[

Title: Re: fowled plug and black smoke
Post by Savage_Greg on 09/21/07 at 13:23:00

[quote author=demin link=board=RubberSideDown;num=1190350963;start=0#9 date=09/21/07 at 13:14:44]You're right Greg.I'm thinking of the S&S on the ol' H.D.
:-[/quote]
Yep, an old pumper.

If the gas isn't too old, I'd just charge the battery, clean the plug and go blow it out...:P

Title: Re: fowled plug and black smoke
Post by splash07 on 09/25/07 at 12:57:47

well, I put 100 miles on it and then my exhaust tipfell off. I got it home now and since i had the exhaust off to fix the wrap (no visible leakes in the gasket) i decided to check the plug. Really black plug, no smoke any more when it fires up but the plug is fowled beyond all belief.
155 main, 55 pilot, Drag pipe with single baffle, 650 ft above sea level, Cone air filter, 1.5 turns out. Any thaught, suggestions?
I did notice some backfire as well, not much though.

Title: Re: fowled plug and black smoke
Post by splash07 on 09/27/07 at 12:17:34

also it has shut down a few times when i let off the throttle. Starts right back up again, is the idle too low maybe? Perhaps i should go down a size on the pilot? suggestions comments?

Title: Re: fowled plug and black smoke
Post by bill67 on 09/27/07 at 12:31:19

I think if you jet for the most power you are going to be to rich on normal drive conditions. I havent change anything other than pilot jet Im going to go one richer on high speed and low speed A little more power and should still get good gas mileage.

Title: Re: fowled plug and black smoke
Post by WD on 09/29/07 at 23:02:51

Yep, 155/55 is too big for normal riding, even with a free breathing set-up. That is the combo I have, will downsize as soon as I can score a 150 main jet. Got a 50 pilot, still need to swap it out (raining and no garage).

Worst part? I'm only getting around 40 mpg right now... when stone stock it was getting mid-70s mpg commuting. The wimpshield, apehangers and bags don't help, but a 30+ mpg drop in mileage? That ain't right...
-WD

Title: Re: fowled plug and black smoke
Post by barry68v10 on 09/30/07 at 04:25:03

I tend to agree with WD. 155 main seems extreme when you consider the stock is 145. Going up 4 sizes in jets might be ok, but you'd want to get there 1 at a time. I've got the stock pilot and main, and simply got rid of the white spacer, and my mpg dropped from mid 70's to high 50's (got 58 last tank.) That's a pretty big drop, but my throttle response is soooo much better, that it's worth it to me.

"Ideal" air to fuel mixture is around 14.6:1, but an engine will "run" from about 11:1 on the "crazy rich side" all the way up to 18:1 on the "make your nose bleed lean side." You're definitely better off at 15 or 16:1 than 12 or 13:1, so I'd err in that direction if at all. My personal preference is 14:1 for "hot rod" applications, and 15:1 for "daily drivers." I don't have my exel spreadsheet out right now, but I think a stock S-40 runs around 15 or 16:1. Can anybody confirm or deny?

Title: Re: fowled plug and black smoke
Post by Savage_Rob on 10/01/07 at 06:49:16

When I had the stock carb on mine, along with a MAC muffler and K&N air filter, a #55 pilot and #152.5 main worked perfectly for me. Many folks don't need the #55 pilot though.

Title: Re: fowled plug and black smoke
Post by barry68v10 on 10/02/07 at 04:34:26

Rob did you notice the ceramic headers required a richer mixture? I noticed when I wrapped my header with heat tape the bike acted like it was running leaner...

Title: Re: fowled plug and black smoke
Post by Savage_Rob on 10/02/07 at 04:58:33

barry68v10 wrote:

Rob did you notice the ceramic headers required a richer mixture? I noticed when I wrapped my header with heat tape the bike acted like it was running leaner...

Odd hijacking of topic but nope, didn't notice that at all.

Title: Re: fowled plug and black smoke
Post by barry68v10 on 10/02/07 at 14:19:35

Not trying to hijack, trying to provide quick alternatives to test a leaner mixture since I thought we were pretty convinced we're dealing with an over-rich condition...

Title: Re: fowled plug and black smoke
Post by splash07 on 10/02/07 at 17:16:41

got the 152.5 main in today and fired it up, she runs a lot better now. Although i am on the sidelines again for other reasons.

Title: Re: fowled plug and black smoke
Post by splash07 on 10/03/07 at 21:32:52

well I ran for a bit today, and it seems that the backfireing is worse. Also it seems to be at max RPM at about .5 to .75 turns out. is this odd.
since the pebble ordeal, i cant help but wonder if it is related. So much work on the bike in so little time it makes me dizzy. I due for a 400+ ride this weekend and I am sure all my questions will find answers on the road.