So my carbs have been running a bit rich since I installed the new airbox but wanted to try something with the airbox before readjustment of the carbs as I believe it’s starving the airflow a bit. I’ve been running on the Costco premium unleaded. We went to the track and I topped off my gas tank from 1/4 tank of the premium unleaded to 163 octane leaded track gasoline. I knew she was running rich due to the slight black exhaust tip but after adding the track gasoline the the tips are a distinctive gray.
Did I screw up with the track gasoline or? My engine is a 2.4 stroker 4 cylinder and runs well with about 2,000 miles since the build. Click to view attachment

led baby, your guides are extra happy

I know the lead is good for our engines the but the unleaded premium mixed with 163 leaded octane and my now Grey exhaust tips was what I was wondering about.

Most would wish for tail pipes to look like those.
I run race fuel in a few bikes and it's the only time I get a non-sooty exhaust.

Original plates to the car and what year is it?

oh yea!

Not original plates to my car I bought them and had them reassigned to my car a “74”.

So sounds like gray is good!

I always liked gray. Gray is good. Black is too rich.

Bob B

What I’m wondering is she was rich with Costco premium but gray with 163 leaded, is that showing the lack of quality in the Costco premium or just how much better the engine Preformance is with higher octane leaded?

wes...
grey is from the leaded race fuel..your 2.4 hp engine should love the 163 race fuel
you didn't do any thing wrong to the engine by using this.
if you start using the Costco premium unleaded again the tips will turn black again
and that does mean it is running rich. Also it has alcohol in it.
The race fuel does not have alcohol unless you are running a dragster.,.
pull the plugs and take a look for running rich...better yet find some one with a wideband o2 sensor meter

Thanks that’s what I wanted to hear.