col535 Posted August 13, 2008 Share Posted August 13, 2008 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! Link to comment Share on other sites More sharing options...
fosdyke Posted August 13, 2008 Share Posted August 13, 2008 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! I would run a compression test first and go from there - let us know what you get - if the problem is top end it may not be a new engine! :D Link to comment Share on other sites More sharing options...
yoda Posted August 13, 2008 Share Posted August 13, 2008 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! If it was significant it would not idle. You will however destroy the engine if something has come adrift. The lack of power and the knock look like broken piston but it would not idle unless the idle adjustment was increased. I would not ride this bike incase the engine suddenly locked up. Link to comment Share on other sites More sharing options...
col535 Posted August 14, 2008 Author Share Posted August 14, 2008 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. Link to comment Share on other sites More sharing options...
col535 Posted August 20, 2008 Author Share Posted August 20, 2008 I would run a compression test first and go from there - let us know what you get - if the problem is top end it may not be a new engine! :D 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? Link to comment Share on other sites More sharing options...
fosdyke Posted August 21, 2008 Share Posted August 21, 2008 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? OK doesn't sound like a top end problem if you are getting 140+ psi, If you haven't run the engine at high revs I would expect the plug to be sooty - have you cleaned and check the carbs and settings? This could be a fuel detonation problem - I would check: 1. Spark on plug to rear cylinder 2. Ignition timing 3. Valve clearances 4. Cam chain tension Don't right off the engine yet - BTW waht is the mileage on this bike? Link to comment Share on other sites More sharing options...
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