Engine trouble with 2004 SV 650S

Hi everyone!

First of all, I'm not very mechanically inclined, so I am sorry in advance if I don't know what I'm talking about.

The trouble started about a year ago, when I went on a longer trip through some twisty roads. Lots of accelerating, decelerating and braking and when I came to a stoplight, the engine just stopped. It wouldn't start unless I also accelerated. If the revs dropped below something like 2500. I managed to get a few more miles like this until finally it wouldn't start at all. The mechanic I went to found there was motor oil in the spark plugs, which had to be replaced. I don't remember if he did anything else.

When I took it to my usual mechanic to check it, he said the engine was fine, except the compression for one cylinder was lower than for the other. Something like 10.5 and 8.5. Just a few months ago both were over 10.

Fast forward one year and the same symptoms presented themselves. This time after 30 minutes of 140kph highway usage. The engine works really rough and if left at idle it stops. If I let it be for 1 hour or more, it starts OK, but after some usage it can present the same symptoms.

Can someone enlighten me with what is going one? Why does the problem go away if I don't use the engine for some time? And what could have caused this large loss of compression? The temperature displayed is the same as before.

The model is a 650S from 2004. Thank you!

Closed up valve clearances will affect the compression and cause poor hot running/starting. Under hard use not uncommon for them to need adjustment.

what sort of milage has the bike done,and does it still seem to oil up the plug/s

It has 45.000 kms. I took it to a a mechanic and indeed it has oiled up one of the spark plugs. He suggested that the valves should be adjusted soon. And some things were pretty worn in the engine and he replaced them (some engine lids). For now, it's working again properly.

if the plug is oiled up and not wet from petrol,then its more than just a tight valve,and whats a engine lid!

and at 28000 miles you would like to think it have had the valve clearances done at least once,and if it had a valve that was not shutting completely,then after a year of use you would have thought it would have got worse an lost compression on that cylinder completely by burning the valve