Originally Posted by
Glowgeek
If the valve lash is normal and a valve on that cylinder hasn't developed a leak that would be an interesting/strange problem. ASP boxer?
Valve lash is normal, the intake valve is maybe a touch wide but then I am talking 0,01~0,02 mm so really nothing;
I do not hear hissing, so I doubt it is a leaking valve. That cylinder has always had a slightly lower compression than the other one but that also is not really significant and has been the case from new.
oh... and yup... ASP. Still running very strong, just a weird problem. Without Telemetry I would not have ever known, because I can't tell by its power or running behaviour. It runs the same and pulls the same RPM as ever.
Originally Posted by
Raleighcopter
Which cylinder is hot? Is it the same one that ran lean before you modded the intake? I recall you drilled a couple air jet holes somewhere. Might one be clogged?
The airjet holes were done with the radial, not the Boxer.
My memory is blank about which cylinder was rich and which one was lean before that mod (I would really have to go through my notes for that) but the weird thing is, the one cylinder remaining basically constant in temperature while the other follows the throttle, would suggest a lean running cylinder (less fuel, less heat) which would mean that simply tuning a touch richer or leaner, at least one of the two should shift the bias: if the cold cylinder would be cold because of running a touch lean (it can't be much since the engine still ran nominal power) a bit richer tune would restore that cylinders temperature, and if it was rnning colder because of a rich conidtion a richer setting should increase the difference. Neither happened.
One click richer dropped ground RPM by about 200~300 RPM, but the temperatures as well as their difference basically remained the same.
That is why I suspect an obstruction: up to a certain throttle position both cylinders follow the throttle, up to the point where the throttle opening becomes larger than the restriction, from there one cylinder would run constant while the other follows the throttle. At least, that is my theoretical reasoning. Whether that reasoning is correct really remains to be seen.
A (partially) blocked exhaust would IMHO result in excessive rising of that cylinder's temperature.
As said, so far, I could just as well consult my ouji-board or crystal ball...
Tomorrow.... I will pull both heads and runners tomorrow