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Knocking engine - engine rebuild experts needed

  • Thread starter Thread starter flyingace
  • Start date Start date
F

flyingace

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I've had prior threads about a knocking noise from my GS850 engine. Today, I pulled the #2 plug wire while the engine ran and the noise went away. The bad news far outweighed the good news.

Only pulling #2 makes it stop. Does this mean a rod bearing is bad or could it be a main? Are there ways to determine the exact cause of the noise apart from a teardown? Also, can the bike be ridden without too much risk to the rest of the engine?

Thanks,
Ace.
 
I'm only guessing but if the sound goes away then I'd think it's a rod bearing. Maybe it's piston slap??

I'd check the exhaust for leaks and carbs and boots too.

Good luck and I hope it's something simply.
 
Thanks Jake.

Piston slap is the only other possibility I can think of too. Earl seemed to think the engine wouldn't even run if you can hear pistons slap - I don't know if that's true. I know my compression is pretty low.

Just in case, is there a good crankshaft exchange service you know of?

Thanks again.
Ace.
 
flyingace said:
Just in case, is there a good crankshaft exchange service you know of?

Thanks again.
Ace.
Click to expand...

I'm afraid it will be much cheaper to find a parts bike/engine than to have the crank rebuilt. I don't know of any 'exchange' services.
 
I would just go ahead and pull the head, cams and jugs and see what the problem is. With any luck, it wont be anything worse than a wristpin. You never know until you get in there and you have to know in any event.

I wouldnt run it with it knocking. I could be something easily fixed but that if breaks will cause major damage.

Earl
 
Have you removed the cam cover and check around the #2 area for any broken valve springs, cam lobe wiped out, etc.

If it's a bearing problem drain the oil and you'll know for sure when you see all the brass/copper color piece's.

You might be able to use a good flashlite and look inside the sparkplug hole as you turn the motor only by hand and look for metal to metal contact on top of the piston.
 
I used a small flashlight bulb soldered to leads to look in my cylinders before I found out the bad news.... Anyway with a small bulb you can just drop it in the bores and really get some light in there.

Just make sure you can pull it back out!

/\/\ac
 
Their is a GS1000 G motor on ebay !!!!!! Weather it is a rod or main wouldn't matter It's still crank time
 
Thanks all for your help in this trying time. To add gasoline to the fire, my #4 carb problem came back with a vengence as well. The plug is so sooty, the bike barely runs.

Earl, I agree that the thing to do is determine for certain what's making the noise, then go down whatever road that dictates. The rest of the bike works great (except the #4 carb), so an engine swap is very temping.

Lynn, will that GS1000 motor fit into the 850 frame?

Jake, I've looked at the cams, cam bearings, cam chain, tensioner, etc. The engine turns over fine without any noise with plugs removed using the starter motor.

Thanks again,
Ace.
 
Need to do minor mods to the motor mounts & change the driveshaft that's all to install 1000
 
I'm having a really difficult time making a diagnosis on this knock. I've done both 'conclusive' rod bearing tests and got different results. Pulling the #2 plug wire stops the noise, but when I shove a dowel into the spark plug hole (after going past TDC), I can't move the piston at all - it's solid.

What I do with this engine is entirely different based on if the crankshaft is OK or not. And I don't want to tear the whole thing down just to trace a noise.

Anybody have ideas on what else the noise can be or how to confirm/deny it's a rod bearing?

Thanks in advance,
Ace.
 
Did you change the oil and look for the sparkly metallic bits as Racin Jake suggested? That 's a dead giveaway if it's a big end bearing. You'll see it.

I went thru a couple of CB 450 engines. :oops:
 
Yep. I saw a few tiny bits of metal gathered around the drain plug magnet, but not enough I think for a bad bearing. I ran a clean magnet thru the oil and got nothing. Neither did I see any metal bits on the bottom when I poured the oil back. And I didn't see anything like metal flakes floating on the surface.

I'm starting to believe there's something else going on with #2 that stops when you pull the plug wire. I hear it best directly on the bolt on the starter motor cover, but it's really hard to ID an exact location.

Thanks,
Ace.
 
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