col535

Took your advice and ran a compression test and all seems OK with the top end... Pressure built up within 5 strokes to 147 front and 153 rear, which I think is acceptable? The spark plug of the rear pot was quite black and sooty, which I think means the fuel/air mix may be too high, but that still wouldn't account for the knocking sound. Any help on a diagnosis?

Guys, thanks for your help. My logic in replacing the engine is that I've found one second hand off a '98 Virago for £230, and if I decide to repair the current engine, then for the gaskets alone (before you've even replaced the broken part) it's going to be getting on for £100.

Hi all, I've recently bought a 1991 XV535 Virago, not run for over two years. There's a hell of a knock coming from the rear pot and although it idles fine, there's no power in it. It won't go above around 40mph, so I decided to put it in for MOT first to find if it's worth trying to fix it. Although it passed its MOT, the mechanic said I'm as well replacing the entire engine rather than attempting to repair it due to the cost involved. What I want to know is whether an engine off a 1998 will fit directly into my 1991. Were there any changes to the engine in this time? Thanks in advance for any help you can offer!