Technical Loss of compression?

[Alex1985]

Hi all, I recently got my 1985 X1/9 back from having a full service and it drove fine for about ten miles then started to run awful. It wouldn’t idle properly, sounded like a lawnmower and I lost a lot of power.

Checked when I got home and I’ve lost compression on my 3rd cylinder =[

Any ideas what could be wrong?

Hoping for an easy cheap answer….

Cheers.

Alex (Leeds)

 

[sledgehammer]

Have you checked it with a compression guage to get to this conclusion?
Could be a stuck valve or worse a dropped valve.
Have you checked the valve clearances recently? No valve clearance will give no compression.

 

[jimbro1000]

After a service the most likely cause of compression loss is a faulty spark plug, especially if the engine suddenly goes noisy and is only losing compression on one cylinder.

I know it is hard to do on these engines but see if you can clean the spark plug seat on the head, along with the threads. It could be some debris in the bottom of the recess is stopping the plug from seating correctly.

Failing that it is, as already mentioned, either a valve, valve seat, gasket, piston or piston ring. I'm ignoring the really horrible possibilities of cracked head or block for now...

 

[Alex1985]

So my head gasket has gone =[ Not the worse news to hear but could have done without the cost.

Cheers for all the suggestions.

Alex