1987 Savage, with about 17,400 miles on the clock, and SuperTrapp.

Riding back from Pa last night, I noticed black smoke in my rear view mirror on a heavily traveled Rt. 78. The sun has just set, my mirrors were vibrating and there were two 18 wheelers up ahead on an incline blowing black smoke, so I thought that the odds were good that it wasn't me.

I just finished cleaning the bike and added about 1/3 of a quart of oil. Also, I was backfiring like crazy on decel yesterday, so I richened up the mixture about 1/2 a turn counter-clock-wise on the carb mixture screw.

After I was done with everything, I fired up the bike and didn't notice any smoke. After a few minutes I gave it more throttle (bike was on the stand), but not too much, and noticed a puff of black smoke while letting off (decel). It smelled pretty bad too. It's not "steady" black smoke, just a puff.

Did a google and found black smoke=fuel problem, maybe too rich. My previous experience tells me; black smoke=engine problems ie: blown engine on my old Cutlass belching steady black smoke.

The only changes I made were switching from Castrol Syntec to dino oil (don't want to start an oil war, but need to tell all for potential diagnosis). I checked the oil before leaving Pa. for a 120 mile ride home, and it was just above center between the two marks. Checked it this morning and it was just above the low mark.

If Fido or TMack noticed any black smoke coming from my bike while riding behind me yesterday, please let me know.

I'm going to take a ride in a little while with Shar following in her car looking for smoke.

Thanks in advance for any replies.

Synthetic oil burns clean, no smoke.  That's one of the reasons I love the stuff -- I have an original Acura Legend that I have owned since it was brand new (over 215,000 miles and it drinks a quart a month easy.  Drive it hard and that will double or triple.

It would be an undriveable mosquito fogger if it wasn't for synthetic oil burning clean.  Very rarely do I see smoke on a hard take off.

Think about it, were you burning oil before but just didn't know it?  You switched to smoking nasty old dino oil, you know.

Next option, Justin had a consumption issue he tracked back to tired oil -- he changed his oil to fresh and his consumption went much lower (until the oil got tired again).  Just info -- I have not noticed this myself.

My bike didn't use any oil until I went to the mountains -- it uses a quarter quart a month now.  I ragged it pretty hard on the mountain trip and now it uses some oil -- surprise surprise.

I feed it synthetic Rotella diesel oil which does not smoke.  I top it up as needed.  I change it twice a year, but if consumption gets high enough that will go to once a year at filter change time.

You just joined the oil users club, that's all.  

Switch back to synthetic and see if your smoke stops.  I bet some 20-50 Mobil 1 would stop both your smoke and oil use.

Was writing post while you replied OF. Just changed the oil before leaving for Pa. Noticed that the dino oil does burn faster. With the semi-synth, it seemed like I was hardly ever topping off.

Thanks Serowbot.

I just took a blast with Shar following me. She didn't see anything, so seems I'm fine. Did some 0-50 quick rips also. Backfire's pretty much gone. Don't know if it was adjusting the mixture, but it's back to abnormal.

Thanks again for the replies.

thumperclone wrote on 09/21/08 at 12:46:42:

8 blocks from the Atlantic Ocean. I'm at sea level.

Hi Joe,
   I didn't notice any black or blue smoke coming out of that un-trapped supertrapp.    

The black smoke on a quick rev is due to the slide which is vacuum operated.  In a perfect world it would close as soon as the throttle does.  But, since the world has friction, it lags a little.

You're best bet is to look at the sparkplug.

T Mack