CX500 GL500 CX650 GL650


Just When You Thought It Was Running Well ...

a gallery of Things That Went Wrong

1. CX650 Eurosport - (John Zarecki and Ian Shearer, Scotland)

This 650 Eurosport suddenly lost almost all engine power, and then appeared to free up. It soon afterwards developed a rumble from the rear of the engine, with a flickering oil light. These ominous symptoms almost always mean a failed big end or main crankshaft bearing. The owner managed to get home and shortly thereafter, the engine seized up. Not in a position to effect repairs, he sold the bike to a friend who dismantled the engine and sent me the following photographs of the carnage he found inside the crankcases.



You are looking down the cylinder bore, after the pistons had been removed. The steel shaft is part of the crankshaft, where the big-end joint of the connecting rod is bolted over the crankshaft journal, with the two semicircular shell bearings in between.

See that the journal is fatally scored after the big-ends have disastrously failed.







The two semicircular shell bearings which fit closely in between the big-end and the journal. Oil is pumped at high pressure through the lubrication holes and acts as both a lubricant and coolant, so that the big-end never actually touches the shells.

Here, the oil supply has failed for some reason - possibly cam chain wear which has sent aluminium shavings into the oil supply - and the shells have suffered fatal damage. Their faces are almost completely worn away, sending the dreaded copper flakes into the oil sump, which further contaminates the oil. Soon after that, the bearings get white hot and weld to the journal, causing the engine to seize.

This kind of damage is only repaired at very considerable cost and effort. It requires a new crankshaft and bearings, but the main problem is removing all the contamination from the oilways inside the engine. In most cases, a replacement engine is the only answer.

Apparently the 650 engine has an extra oil feed jet to the rear crankshaft journal, to improve oil feed and cooling, but the CX/GL engine, when seizing, nearly always suffers a rear bearing failure, as this one seems to run hotter than the front one.



The much-dreaded tell-tale of both aluminium and copper flakes, in major quantities, at the bottom of the engine sump and crankcase covers.

Ah well, engine, it was nice knowing you ... this picture is the under-engine oil sump of the 650s and Turbos.





Similar picture showing silver and copper flakes in the oil sump area. This is inside the lower right of the rear crankcase, just by the gear selector drum.











2. CX650 Oil strainer woes - (Ian Shearer, Scotland)

Ian noticed that his oil pressure warning light was flckering on tickover and that an oil flush showed specks of dirt in the oil. Suspecting the worst, he removed the front engine cover. Inside, he found that accumulated debris has almost completely blocked the oil strainer, fortunately without the engine having suffered any damage.

The photo (left) shows the upturned strainer, with its gauze almost completely blocked.

This could have been seriously nasty - Ian changed the oil pump and flushed the engine, and so far appears to have got away with it.






3. Cam chain carnage - (Jon McComb)

Jon reported major rattling from inside his engine and diagnosed a very loose cam chain, which did not prepare him for the carnage he found inside the rear casing.


Quite a substantial portion of the internal aluminium casting has been eaten away.











And here's more evidence - a thoroughly mangled cam chain tensioner and guide blade.










This is the end of the tensioner arm through which the locknut passes. It too has been chewed up by the slack chain thrashing about. And you still ignore that rattle inside your engine ... how can you sleep at night?








4. Broken connecting rod - (Richard)

This engine threw a connecting rod. This is a very unusual fault on the CX engine, and resulted in major internal damage.

Here you see the totally smashed piston, the remains of the connecting rod and journal, the mangled shell bearings and a pile of debris recovered from the bottom of the engine.

















Severe damage to the (upturned) piston.









This is the lower engine space, with the gearbox removed to reveal the gearbox bearings in the rear casing. A large portion of the internal webbing has been smashed away.








5. Oil Pump Fatally Damaged - Trev Hadley

Trev rebuilt his 500 Custom into a 650-engined version and thoroughly cleaned up the engine before modifying the C frame to accept it, and changing to transistorised ignition as well as making other necessary modifications. The engine ran very well and sounded superb, but we were worried when its oil warning light flickered when idling below 900 rpm and we decided to check out the oil pump. Trev had obtained a new low mileage 650 oil pump in the meanwhile, and we planned to install that.

On removing the radiator, front cover and sump bowl, we found that the oil strainer, despite having been thoroughly cleaned no more that 1,000 miles before, was almost completely blocked with what looked like animal hair. Since the engine had previously lived under a blanket which the owner's cat had used as a bed ... well, YOU explain how so much fur walked through solid metal and invaded the engine!

More tellingly we discovered that the oil pump was fatally damaged, with the inner and outer rotors deeply scored, although technically within tolerance. The pictures below show you what you DON'T want to find your oil pump like ...

(Left) the pump outer rotor, showing visibly deep scores along the perimeter. The flat faces were similarly marked.








(Right) the pump body has matching damage. It seems that the engine had been run (in a previous life) without the so-necessary spring and steel washer inside the oil filter housing, and which ensure that the filter is held tightly against the front crankase body. Failure to fit this essential part allows oil to bypass the filter.

Apart from this hitch, the 650 conversion went well.










6. CX650 Differential Failure - Steve Case

Steve says "This was a 650ED, 1986 29000 miles. It was used regualy for 600 miles per month commuting then - no tell tale signs or warnings - just the drive failed as I attempted to pull off at the lights. .There is a small crack across the teeth, this may have caused the failure or was a consequence of it - I'm not really sure."

This is a very unusual fault on the otherwise sturdy CX differential unit.




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