Smoking 912

[Jerry1]

I have a 67 912 with a 1720 big bore rebuilt about 9000 mile age runs great but I catch a smell of the exhaust every once and a while. I had a friend tell me to night he could smell my exhaust when following me. Is this typical or should I be concern

[Jerry1]

I pulled the # 2 and 4 spark plugs I'm not running rich there is little carbon build up on the top.


Here are some pictures

[Jeff Trask]

Why don't you ask here: 912 BBS - Welcome to 912BBS

[Rick Becker]

Compared to emission control cars 912 engines are pungent; however if the engine rebuild only has 9K,
1) have you considered upgrading the ignition system; for many years 912 owners have been upgrading the distributor and adding a capacitive discharge unit
2) are the size and jets of the carburetors optimized for the big bore setup

[WFBowen]

It's hard to tell from a photo, but that plug looks like it's seen some abnormally high cylinder temperatures. I'd check the heat range of the plug then look to timing and jetting issues. Running slightly rich (vs too lean) is preferable in these early aircooled motors.
JMO
Bill

[Jerry1]

Thank for your input do I need a hotter of cooler plug

[Jaems]

Unless you are burning leaded gas. You can not use the old - 'look at the plug routine' - anymore. The only exception if you are burning oil the plug would look oily. It would also help if you told us what plugs you are using. Even with the big bore the standard plugs should work.

You could have have oil leaks that could cause your car to smoke.

[C. Clark]

Smelling exhaust and seeing smoke are two different things. Does it burn any oil, how often do you add oil?

[Jerry1]

No it does not smoke uses very little oil and run great. I'm not sure the spark plug I forgot to look when I had them out. I will let you know
Thanks

[Jerry1]

I finally got around to investigating the smoke problem a few days ago. As I was checking the Idle mixture adjustments I found that #3 the left front was out of adjustment about 3/4 of a turn to rich. 1 and 1/4 turn out worked out to be good on all of the adjustments. No more stinky exhaust and runs better off the start.

Jerry