Loss of Power and Knocking Noise

I was riding my SV650s 2001 home from work last night and I suddenly lost power and a knocking noise developed from the engine, the higher the revs the more knocking…Just wondering if anybody has a clue what this could be or any tests I should do to diagnose the problem.

In order to help narrow the search down I will add that I had the carbs balanced last week and last gave the bike a full service 2000 miles ago, oil, oil filter, air filter and plugs. There was no metal apparent in the oil and the spark plugs looked to have been burning clean…I have also already checked the current oil level which appears fine.

Many thanks in advance.

That could be a number of things really. What is the bikes mileage? Is it smoking at all? Is it still firing on both cylinders? Has it had any other problems leading up to this?

My initial instinct suspects your big end bearings could be shot but could do with a bit more information. How much power has it lost? 50%/60%? etc

Total mileage is just over 32,000, not smoking at all, still firing on both cylinders, apart from the knocking sound as described above it sounds like its running well...as to power loss it was like I had hit a rev limiter at about 70mph and it just wouldn't go any higher and that is when I pulled over and noticed the knocking part, not sure how much power it has lost exactly as limped home but I would imagine it has lost about a third if not more.

Can you tell which area of the engine the knock is coming from? Front/back cylinder and top or bottom of engine?

It is probably worth dropping the oil out and checking it for any metal bits as a first step. It still sounds a bit like the big end bearings to me. I had a simlar thing happen on my old ZXR400.

For the bearings to go at 32k however would suggest your bike has had a tough life! Has the bike had reguilar oil changes do you know?

on a slightly simpler note.

has one of the rubber bungs fallen of the carb where the vacuum gauge hose plugs on?

this would throw your carbs well of of sync, a massive loss in power and a pretty bad knocking.

Certainly since I have had the bike I have been following the maintenance schedule in the Haynes Manual, for the first 14k miles the book has been stamped so can only assume it has been done properly...can certainly check the oil for metal bits.

As I have just had the carbs balanced I guess it is possible that one of the bungs could have fallen out, I will get the garage who did the carb balancing to look at the bike, although the bike idles fine which I would think if the carbs were off then it would sound rough...

I had this happen on my SV, turned out to be the big end bearing for front cylinder conrod.

The cost of a new engine left quite a sting

Valve service?

I'd say unlikely to be the valves as that would be more of a tap getting progressively worse over a few thousand miles. Sudden loss of power would indicate a dropped shim which would leave more than a knock.

out on a limb... snapped cam chain ?