GS500 Knocking

[yamahonkawazuki]

well  youd end up tearing into the engine. at this point. ( to examine Big end bearings) seems daunting but tbh it isn't. if damage at some point proves terminal, , an engine swap might be worth considering.

[adidasguy]

So, will you remove the oil pan and see what metal fragments are there? I'd do that next. It can help identify what bearing is bad if there are lots of metal bits in there.

[sledge]

So, will you remove the oil pan and see what metal fragments are there? I'd do that next. It can help identify what bearing is bad if there are lots of metal bits in there.

How?

Balance shaft, big-end, mains.....they are all the same. We already know the oil contains debris and it could be from ANY bearing 

Bottom needs to be stripped, examined and measured up.....unless someone has got a set of x-ray specs the OP can borrow!

[Alan_nc]

If there were metal bits in the oil you are going to have to rebuild the engine (or put in a new one) so you don't care about taking thing apart at this point.  Take the engine out of the bike and put it up on a bench where you can get at everything easily.  Follow the book on taking the engine apart.  Label all of the parts as you pull them out.  Everything is going to have to come out of the lower end so that you can clean all of the metal bits out - every bearing will need to be replaced.

The fact that you can't wiggle a part doesn't mean it doesn't have to much clearance.  If things were loose enough to wiggle you probably would have put a rod through the block.

Would be nice to know what caused the problem.  Do you know the entire history of the engine/bike?  Someone before you may have run it for years with no oil change or gotten water into the crank case at some point.  If bikes are stored outside in changing temps (winter/summer) condensation can cause quite a bit of water in an engine.  If the  engine had  been overheated at some time in it's life this will cause rubber seals/gaskets to become brittle.  Also metal expands when hot so the bearings may have rubbed when it overheated causing wear....this then makes the bearing loose when it cools down.  Might not cause a problem with the engine until much later in it's life.

[sledge]

Excellent (and realistic) comments above 

The subject of bearing failure and replacement is another one that many in here like to comment on but very few have actually done or have hands on experience of.

Some points.....For longevity and reliability its absolutely vital that the correct size bearing is identified and used, there are four to choose from and markings on the cases and rotating parts will identify the size. Too tight and the oil cant get in there leading to overheating, too loose and it will rattle and wear prematurely. Its also vital that the journal is measured up accurately and found to be within service limits, this includes both diameter and concentricity and that when fitted the clearance between the shell and the journal is also within limits. We are talking about figures down to 0.01mm (or 0.001" in old money) and an accurate micrometer is a must, as is plastiguage to check and confirm clearances.

What's also important is that the root cause of failure is identified and removed. Your don't want to pour time and money into a major repair and then find it fails again in a weeks time in the same way.

Degraded oil, low oil pressure, overheating, oil starvation, dirt or debris, manufacturing faults........all are in the frame and without careful examination and evaluation of the parts its only possible to speculate on the nature of failure at this stage.

O/P??
You can carry on wasting time and effort pulling covers off, peering at the oil and trying to wiggle bits! etc but what's that going to prove or achieve? Its obvious you have a serious internal issue that is going to need `major surgery` to correctly identify and rectify and there is no way to sugar coat it. You now need to ask yourself a question......Are you up to carrying out a repair of this nature, have you got the skills and confidence and have you got the tools and equipment needed? Many find they haven't and go down the second-hand engine route which will probably work out cheaper anyway.....perhaps this may be your best option.

[Kyromatic]

I am definitely no professional when it comes to this. I have been tinkering in order to save myself the money of an engine diagnostic at a shop. I have been talking with some local dealerships and getting some opinions on it, but everyone says something different.

I think the best thing at this point would be for me to go ahead and buy that used 2004 GS and attempt an engine swap. I'd hate to go through all the trouble of tearing down the engine, maybe even replacing the damaged part, just to find out that there is still another thing causing the failure of said part.

Thank you so much for all of your suggestions. I have class and work all day, but I will reply to posts later tonight.