High oil temperature 912UL

Re: High oil temperature 912UL

by Kevin Stewart » 7 years ago

Kevin Stewart

3 432 1.33k

Here's a further update. I've discovered that the oil burn only seems to occur during the warm-up. Also there is very little compression when the engine is cold, it is very easy to turn the engine. This is not true when it is hot, when it feels like each stroke has good compression.

Re: High oil temperature 912UL

by Rob Seaton » 7 years ago

Rob Seaton

3 1.32k 251

did the pistons get replaced? The clearance tolerances are very small and too large a clearance is the likely problem.
The pistons are grouped into two sizes, as are the cylinders.This makes it easy to get good clearances but you have to know what piston to order.

Re: High oil temperature 912UL

by Kevin Stewart » 7 years ago

Kevin Stewart

3 432 1.33k

Pistons and cylinders are original, only the rings were changed. I'm going to try to measure the crankcase pressure as per the SI, I just need to make up some suitable plumbing first.

Re: High oil temperature 912UL

by Rob Seaton » 7 years ago

Rob Seaton

3 1.32k 251

easiest way is to drill a small hole through a long M8 bolt, braze or loctite a nut at the top of the threads and then cut the head off.
Use this fitting in the crankshaft lockpin hole

casepressfitting-1.JPG (You do not have access to download this file.)

casepressfitting-2.JPG (You do not have access to download this file.)

Re: High oil temperature 912UL

by Kevin Stewart » 7 years ago

Kevin Stewart

3 432 1.33k

I don't have the means to make on up so I bought a brass fitting to do the job. What I didn't realise is that the thread in the crankcase is recessed, so my fitting almost didn't reach the start of the thread!

Anyway, I managed to make some measurements today. It was quite a cold day and I could only get the oil up to about 80 deg C on the ground. At 4600 RPM I had a pressure of about 3 PSI or 0.2 bar, which is within the permitted limits so no smoking gun there!

Any ideas on where to look next? If I had an excessively lean mixture that would give rise to higher temperatures but I guess that would also be seen in the cylinder head temperature as well as the oil?