Guess what caused my sooty plugs

I hav'nt been riding much recently. Just a few km around town on Saturday was all I could manage the past few weeks. Also, the beast has not been running quite at 100% I first noticed this about 2 weeks back that it just did'nt feel right. At 3,000 rpm it felt like it had a very slight stuttuttuttutter and right there the exhaust sounded like a long string of little f*rts. I pulled the plugs and they were really black and sooty.

So....got new plugs and saw no change. Last Saturday I decide to tackle it seriously.
Checked the voltage at coils 12 V. No surprise since I had done the coil mod the season before last
Checked the plug caps and ignition wires for continuity and resistance - everything seemed in spec.
Checked the primary and seconday coil windings - all in spec.
Electronic ignition which so nothing to check but I did make sure the advancer was working and lubed it up.
Compression on all cylinders was 125 to 135 - no reason for suspicion.
Pulled the carbs and spent a morning cleaning them out - no change.
Screwed out the air mix screws a half a turn which made minimal difference.

Hmmmmmmm. I spent last week thinking about it and wondered if I should get new ignition wires or maybe even pull the carbs again. Last night I realised that the only thing I did different in the past few weeks was buy gas at a different filling station (Macs) from my usual. Worth a look. So first thing this morning I emptied the gas tank into the van and filled a container at my usual Sunoco filling station. Once I fired up the bike with regular form my usual Sunoco I could feel it. No more stuttering or f*rting at 3,000rpm and everything back to normal.
Pulled the plugs this afternoon and they too are back to normal.

Who'd a thunk that different gas would make for sooty plugs? Guess I wont be filling up at Macs anymore.

Post edited by: JR, at: 2007/10/13 20:17

They may have had water in their underground tank and their tank may have been low enough to suck some in. I had this happen years ago with my BSA. It was running great, and when it went on reserve I stopped and put in gas at a Shell station. I drove about a mile up the road and the engine died. I dumped the gas on the side of the road (I was not environmentally conscious in my youth) and carried the tank to another station. Put in different gas - problem solved. Ed

Same here. I filled up at a station, and within 5 miles thought I had shelled the cat in my bronco 2.

Drove 30 mph all the way to the funeral I was missing, and then continued on in same fashion to in-law's house so I could use some tools. (500 miles from my house)

1 a.m. I finally ran that tank of gas out, filled up, and Whoa! what a difference! (made me feel kind of dumb though)

I own a gas station in Florida.

In my experience the greatest risk of getting water in your tank occurs the first 2 hours after a gas delivery by the tanker. At that point the water is agitated and dispersed in small globules all over.

After that the water settles to the bottom of the storage tank. The pickup in the tank is above the very bottom so you don't get water when you buy gas.

If there is even a 1/2" of water at the bottom of the tank (well below the pickup) I will detect it before it becomes a problem for you.

Preventative?
1> Don't buy gas if you see a tanker making a delivery. If you are paranoid ask if they had a recent delivery. If you do it right (casual conversation) the attendant will not have a reason to lie to you.
2> I recommend a cap full of rubbing alcohol in the gas tank at least once a week. It bonds chemically with any water and gets burned by your engine without problems.
3> Keep your tank full when your bike is stored. (Water will condense in your tank during periods of high humidity)

Post edited by: FloridaBiker, at: 2007/10/14 07:39

Thanks for the view from the other side of the counter. This is good stuff I will remember and use.

Yeah, thanks! When I had my problems, there was a weights and measures inspector there. Might that be related?

I've bought bad gas quite a few times over the years. Mostly at the discount gas stations .... but not always .... I bought bad gas at Sunoco before. So thanks for the tips FloridaBiker !!! I'll keep an eye open for gas tankers on the lot and avoid that station that day !!!

One thing I do try to do is stick to one local gas station as much as possible. My local Marathon gets 90%+ of my gasoline dollars .... and now Marathon gas has STP in it ....... just ask Richard Petty I do this because if I do get bad gas I know who to complain too !!!

Thanks for the tips floridabiker. The rubbing alcohol sound like a good one. All in all with my recent experience I was thinking more along the line of gas quality rather than water. I've had water in the gas before and this episode seemed different. When I removed the carbs to clean I drained the gas from the bowls into a clear dry plastic bottle and did'nt spot any water in the bottom - usually ends up as globs. I did think the colour was darker than usual but it was just a passing thought. Wished I had made more of a note and then I might have dumped the gas a week earlier.

I guess I could always experiment and fill up next time at Macs and see if the problem returns. Hmmmmmmmmmm I'll have to think about that

Gotta warn that rubbing alc. has water. Some is only 70% alc. some 91% alc. I poured in a bottle to see what would happen. Never checked the percentage and didn't have any bad gas either, see cuz i'm that way. The motor did not want to run till 8,000 rpm or more, then after choking and sputtering back and forth it took off like a rocket. Fun but one can't drive like that in town. Some of the additives do not mix with water as well as they are supposed to, i've seen tests with heet and it did not mix with water. Maybe now days it's better. :woohoo: