Very hot number one cylinder EGT

[bvolcko38]

Mike,
I leaned, slowly, until the engine ran smooth. Any richer and it runs rough.

[XenosN42]

These are the CHTs from the same flight.
1 and 3 are hot. Probably need to put a little baffle on the front of 2 and 4 to deflect more air to 1 and 3

Based on that information I'm pretty sure you're running too lean. You may also need to retard your secondary ignition a bit. I likewise had a couple cylinders that looked "good" and a couple very hot. It doesn't matter so much that you have two that don't look bad. The voice of experience speaking :-)

I agree with Mike. I had a similar situation with a large spread between the hottest and coolest clylinders. It was caused by running too lean.

-- Michael

[lutorm]

Based on that information I'm pretty sure you're running too lean.

On which cylinders? ;-)

On our engine, if the mixture was adjusted so the back cylinders didn't run lean, the fronts became so rich so as to barely run...

[lutorm]

I leaned, slowly, until the engine ran smooth. Any richer and it runs rough.

What did the 4 EGTs do when you did that?

[bvolcko38]

1 and 3 got hot.

[lutorm]

1 and 3 got hot.

What about 2 & 4?

[bvolcko38]

2 and 4 stay cool

[lutorm]

2 and 4 stay cool

They did not change at all? That seems quite strange.

If you continue leaning from the point where the roughness goes away, do the EGTs on the hot cylinders continue climbing or do they drop. Do the cool cylinders start climbing?

The only thing I can imagine is that the front cylinders are running so rich that their EGTs basically don't change. But at *some* point, they have to start climbing as you lean out. Knowing where that is in relation to where the rear ones peak will tell you something about how uneven your mixture is.

[bvolcko38]

After checking, with a timing light, and comparing to the fixed primary ign, the secondary was very much advanced... about 40 degrees btdc! Fixed now but symptoms are the same

[mike.smith]

Which needle are you currently using? If you're not getting positive results then you might try another needle. I ran with the #2 for too long, trying to sort things out. I changed to the 2.5 needle and after a few trial and error adjustments got the numbers I needed.