4k Engine Rattle

[bill_face]

Hello all,

I have a 79 GS550, on which I recently rebuilt the engine (bored cylinders & oversized pistons). Valves clearances were checked and adjusted. Cam chain timing is right.

Problem is I get a rattle at about 4k revs. Initially, it only really did it if you gave it a quick twist in neutral, but last time I rode the bike it did it every time I passed through that rev band. I suspect cam chain, but know next to nothing about engines. I did have check that the tensioner was functioning when I had it apart and it seemed to be working OK.

I had also inadvertently put to much oil in the bike and had to let some out when I got back. When i did I discovered some small metal bits about the size of a grain of salt in the oil. I'm imagining the two are related. Due to my inexperience, I don't know how much to panic. Should I take the engine apart to clean all possible bits of metal out? Should I get hold of another tensioner and change the oil? Could it be something else?

Cheers

 

[fbody_mike]

Maybe something easier... I do not know how bad the rattle is, but on my GSF1200S I get a really bad vibration at 4500 rpm only when my carbs drift out of sync. It really shows up in the mirrors at 4500 rpm. I rebalance the carbs and the vibration disappears.
Did you balance the carbs after the rebuild?

As for tearing apart the motor, I think I would pull the oil filter and dissect it for metal shavings first.

 

[Steve]

Did you install the tensioner properly? :-k

Too many times, I have seen tensioners installed improperly. Seems that the 'mechanic' chose to read about every other line in the instructions and skipped one very important step.

.

 

[bill_face]

Thanks for the input chaps. I'll check the filter. I have balanced the carbs not that long ago, but I have had them off again since, so they could probably do with being balanced again.

I think I install the tensioner correctly. I followed the instructions in the service manual. There is a check you can do to check that is functioning properly that it passed. I'll attach a pic of the instructions I followed:

 

[Grimly]

Thanks for the input chaps. I'll check the filter. I have balanced the carbs not that long ago, but I have had them off again since, so they could probably do with being balanced again.

Cast Iron Rule - you disturb the carbs, they need balanced. That's it.

 

[Guest]

A rattle like that can be a loose heat shield on the exhaust pipe. Banging around on the exhaust system with a rubber hammer or a block of wood will usually reveal any loose aspects.

I once met a guy with a 78 750 who had come from Texas to Canada with a rod knock, nursing it along at 4000 rpm and hoping it would make it to Alaska. When he fired it up I put my foot on the exhaust heat shield and the 'rod knock ' went away. A hose clamp and he was off with a grin, making up time...

4500 is a typical frame resonance point....

 

[Big T]

As to the metal bits, how well did you clean the bores before reassembling?

My 78 vibrates the horns at about 4k. You need to try to locate the source

 

[bill_face]

I think its just a vibration. I cleaned the bores out well ( in my opinion). A local mechanic did subsequently leave a load of shrapnel in a combustion chamber when drilling out a spark plug, which could explain that...