E: Engine Post war motorcycles

robin

Well Known and Active Forum User
VOC Member
I have oil in the rear inlet stub.
The sealed lower valve guides are new, cylinder compression is good, ignition is good and on cold start up the exhaust is clean. However, after about 15 minutes warm up, at a fast tick over, the rear cylinder cuts out and investigation shows that the inlet stub has a puddle of oil in it.
If a paraffin test is done, whilst the cylinder is cold, there is not any leakage.
Any ideas please.
New cylinder heads are expensive and welding an invisible hole is problematic.
Thank you.
Robin.
 

chankly bore

Well Known and Active Forum User
Non-VOC Member
Have you had the inlet port opened out or had the rocker tunnels sleeved? Failing that then porosity is another possible explanation.
 

robin

Well Known and Active Forum User
VOC Member
Inlet port has not been opened up. The rocker tunnel has been cleaned up to accept long rocker bearings.
 
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