Obviously too much time on my hands, as checked the
compression pressures on my newly acquired 1984 K100RS with 70k registered miles.
The Haynes book states 135 to 145 psi is “normal” and over 145psi is “good”. My bike measures 195psi on cylinders 2, 3
& 4 and 190psi on 1. Engine starts and runs well with no pinking etc.
Question; are the Haynes figures correct and if they are, do I need to think
about de-carbonising the head?


Any experience or advice gratefully received.


Cheers, Robert

Less than ten psi variation between cylinders is not enough to worry about, nor is what some would consider a 'high' reading. If it doesn't smoke (beyond the typical sidestand start-up cloud), doesn't make strange noises, runs down the road with ease and puts a smile on your face, no worries. Haynes is talking about the normal range for infernal combustion engines. Ours are not even close to 'normal'. As the sage said, if it ain't broke don't break it.

Two Wheels Better wrote:Less than ten psi variation between cylinders is not enough to worry about, nor is what some would consider a 'high' reading. If it doesn't smoke (beyond the typical sidestand start-up cloud), doesn't make strange noises, runs down the road with ease and puts a smile on your face, no worries. Haynes is talking about the normal range for infernal combustion engines. Ours are not even close to 'normal'. As the sage said, if it ain't broke don't break it.

Many thanks for the advice. Will keep riding and smiling. All the best, Cheers

TWB has nailed it don't worry just enjoy!
Regards,
K-BIKE