New exhaust, now bike smokes. Why?

Fjfreude

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OK so ive read a bit into this and have some thoughts but am still confused. To begin heres what ive got

1976 xs650c. Bs38 carbs with 25.5 pilot, 132.5 main, 4m1 needle second clip from top. Im running UNI pods.

I had some leaking exhaust problems so I decided to just replace them since I found a set of MAC TT exhaust on a good sale. The new ones have a little larger headers (1 3/4).

The bike starts just fine and stays running no problem. However, if i blip the throttle a bunch of smoke comes out especially when I let go and more on the right side. I cant really see smoke on idle. It did this a little bit with the stock exhaust but not nearly as much. My first thought is that im running too rich but with bigger headers, that doesnt quite make sense to me. I did note the fuel screw was out ~2.5 turns on the right hand side and a little over 3 on the left.

I figure ill go back and tune the screws to start and see where that gets me.

Any thoughts from the collective?
 
With the new exhaust? Just enough for the muffler seal to cure. 15 min or so. I didnt like all the smoke so i shut her off to be cautious.

I do know its not the film on the pipes themselves. Well at least the outside isnt smoking. What im talking about it coming out of the mufflers.
 
pretty common to oil the innards of pipes.
but yeah 15 minutes is a while did you actually ride it or just in the garage?
If you can run it up and down the road.
If it persists pull plugs see what they look like. You have a leaky head gasket? Have you retorqued the head studs?
Burning oil is ugly but won't hurt much while you try to track down the reason.
 
No ride, just the garage revving now and again.

No signs of leaks on head. Ill take a look at the studs. Ive got the factory manual so im sure i can find the procedure.

Oh and the plugs. Not pretty. Seems rich. Heres where they were with the old exhaust. I know the PO fiddled with the idle speed a lot on startup (almost every startup) so i think they may be a false read.
20201031_124030.jpg
20201031_124036.jpg
 
mebbie rev it a bit shut it down with the kill pull and sniff the plugs, that soot might be more oily than gassy.
Smelled your dip stick? Gas contaminated oil...
 
Yeah, Im a little worried about the plugs. Im still not sure why the smoke is worse with the new exhaust. It wasnt bad before. Well, not for a 40+ year old bike. Im crossing my fingers on valve guide/piston/ring issues. I reaaally dont want to have to do a top end rebuild. The bike was supposedly rebuilt in the last 10 years (not sure to what extent but if the ignition system is any indicator the guy was a competent mechanic) and not ridden much, so I have some hope.
 
Running revving without a load tends to create high intake vacuum increasing oil sucked though old hard intake valve seals........
 
You never said what color the smoke was, I assume black and I assume both cylinders. Black is a mixture problem, blue smoke is burning oil for whatever they reason. Those plugs look awful, I'm surprised they fired at all. A clog in the pilot jet circuit will produce a puff of black smoke when you blip the throttle. The smoke won't be there at idle (idle circuit) and if you let the revs build the smoke will go away because you're into the main circuit. To try to get a handle on the problem I'd pull the air filters unless they're brand new, put a set of fresh plugs in it, ride the bike and look at the plugs again. Please don't ride long without the filters.
 
I dont think it was blue. More greyish. It was night in a poorly light garage. Im trying again in the daylight to make sure.

I know what you mean about the plugs. Im not sure how they are working but they do. Ive been waiting to figure some other things out before i put fresh plugs in and probably foul them too. Changing one thing at a time.
 
How many miles are on the engine?
You need to determine whether the smoke is fuel mixture related or oil consumption.
Unknown miles. And yes, the fancy plugs were what I bought it with. Im going with the simple ones.

I think a compression test is in order soon.
 
Update: did a compression test. PITA because the NAPA rental tester was broken (read 30psi on each side) so I had to pick up another one.

120psi on each cylinder. Seems a bit low but not too bad considering it was stone cold.

Also, as recommended by @gggGary, re torqued the head.

Seems like I can narrow it down to valves or tuning at this point. Easier said than done but at least Ive done those before.
 
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A cold motor will read lower too. Best results are had testing a warm motor and holding the carbs wide open (or remove them).
 
Your jetting seems good for that carb set and the mods you have. I have similar mods and set up a carb set like that exactly the same. Question - what did you oil the pods with? If you used the special foam filter oil, that can be too thick and clog them. It's recommended to use just a 50-50 mix of gas and motor oil.
 
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