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Connecting Rod Bearings Worn Down

  • Thread starter Thread starter William Groebe
  • Start date Start date
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William Groebe

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So here's a quick recap. I bought this bike for $300 running, but slipping out of second gear. Turns out the shift drum had gouges in it at the 2nd gear spot, so I replaced the transmission.
You can see the thread on that topic here. http://preview.tinyurl.com/nll4wd8

The bike ran great for 2 weeks, then one day a banging sound started coming from the engine. I thought I had a valve problem but ended up ruling that out now that I know what the real problem is.
You can see the thread on that topic here. http://preview.tinyurl.com/mgljkny

Now that I know that I know what the problem is I figured I'd post a new thread with a more accurate title.

Ok, here we go. I had play in the #4 connecting rod. Once I opened up everything I found the rod bearing looks like this. Yikes!




 
By the way, this a 1982 GS650GL.

So obviously I need a new set of bearings for that rod, and my mechanic recommends I buy a new connecting rod as there is some scoring on the inside of the rod. He says he's replaced stuff like this before and it works out fine. That seems nice and simple, but it sounds almost too easy. I suppose I could always try that, and if there are any more problems with this engine I can just sell it for scrap and buy a new one.

Others have recommended buying all new crank bearings as well as they've been sloshing around in oil full of metal shavings from the bad rod bearing. I probably should do the whole plastigage thing to test the crank and bearings measurements as well. That'll be a new adventure.

If all else fails I've found a parts bike nearby for $100 that's been for sale for a while. That would be my backup plan..... or I could just go ahead and buy it and drop its engine in and hope it runs great. tempting.....

I'll keep you all in the loop. I'm out of town for the long weekend and will get back to moving forward with the wrenching sometime next week.
 
Sorry mate but that crank is gone !, change the rods also. Your oil pump is most likely gone and all the oil galleries will be full of metal bits. Sorry to bring bad news.
 
".....If all else fails I've found a parts bike nearby for $100 that's been for sale for a while. That would be my backup plan..... or I could just go ahead and buy it and drop its engine "
Take this route, the chances of getting another disaster are reduced- maybe not the $100 baby , but must be others out there suffering from carb and/or electrical neglect which are easy fixes after what you've gone thru.

Mine at 45 k is still mechanically excellent, though she ain't no beauty queen!
 
tom203. Yeah, that parts bike is looking pretty good right about now.
 
$100 parts bike is a no-brainer if the engine is good.

I don't think you'll be able to find the crank alone on ebay for less than that. Certainly not shipped.
 
Ok. So I've been pretty busy over the holidays and am only now getting my head above water to be able to spend time in the garage.

I've decided to give this bike one chance at a simple fix, and then if it does not work, I'm going to buy a parts pike and replace the engine.

I bought a set of bearings and used some scotch brite pads to smooth out the surfaces of the rod and crankshaft at the point where the old bearings were. I'm going to put the new bearings in the rod and hope that's all she needs.

Here's a pic of the worn down bearings next to the new shiny ones.
Wish me luck.

 
I figured it'd be fun to show how messed up my engine got from all the tiny particulates of metal that wore off the bearings. I had to clean out the upper and lower halves, the oil filter, all the bearings and more. It took a while, but I think I got it all.

Here's an example of how bad it was. My oil pan had it worst, but is clean as a whistle now.


 
Your persistence is excellent. But I'm still worried about metal bits that have jammed up oil holes in this engine. A parts bike has better odds, so keep your eyes open for something close by.
 
I put the new bearings in the rod and connected the rod back to the crankshaft....

There's a lot of play. Side to side, and up and down. Dammit. Oh well. It was worth a shot.

Time to buy the parts bike and throw a different engine on here. That's probably not going to happen until next weekend, so I'll update you all then.
 
Stuff happens. Just scanned looking for 650 shafties, not much pops up, hope you get luckier!
Member gs650mann sounds like he's about to ditch his 82 650 and upgrade to other model- I have no idea where he lurks, but sometimes stuff happens!
 
With your oil pan off, this would be a great time to fix something or upgrade it now. The oil drain hole. Those threads will eventually strip and off the pan comes again. Have a threaded steel insert installed in it. Never have to worry about stripping those threads. Just make sure the steel insert is flush with the pan on the outside and cut two grooves into the insert inside the pan so all the oil can drain out. It's easy do and worth while. Go to a NAPA store or any parts store and get a new oil plug to fit and some copper crush washers.
 
For funsies I put a good rod (#3) on the bad spot (#4) on the shaft and the known bad rod (#4) on one of the good spots on the shaft (#3). Neither worked out. Both had play. Which means both the known bad rod (#4) is bad, and the crankshaft at the spot (#4) is bad too. Like I said before, I'm going to try to find a replacement engine. If it comes along with a complete parts bike, then so be it. It looks like I'm going bike shopping this weekend. I'll keep you informed.
 
Can you not get the crank throw #4 reground and replace with an oversized bearing shell? A typical regrind shouldnt be more than $100... Even the connecting rod can be refinished for an oversized shell. Seems a shame to scrap an entire motor because of a single spun bearing shell.

Just speaking from previous small blocks I have dealt with. American scrap iron may be a different story however.
 
Doing a shaft regrind is not feasible as there have never been any undersize shells available for this model. Suzuki did offer undersize shells for the first plain bearing 750 but as far as i know there are none left - unless you find old stock somewhere..
Yes rods can be resized but the problem here is the shaft. If it doesn't measure up round within .0005in and within .001in of the nominal size, it's a throwaway.
Then of course there's cracktesting...9 out of 10 suzuki shafts which spin a bearing also crack....

So yes, hope the spares motor is a good one.
 
Picked up the parts bike

Picked up the parts bike

So, I went ahead and picked up that parts bike yesterday for $100. Now I'm the proud owner of two non-running motorcycles. There is going to be a lot to do on this, and it no longer qualifies as a problem with a connecting rod bearing so I'm going to start a new thread.
http://www.thegsresources.com/_foru...cement-for-1982-GS650GL&p=2152310#post2152310

Wish me luck on the engine swap. This is going to be some real Dr Frankenstein fun.

 
I bet that parts bike will have a sound engine in it. You can find out in a few hours time.
 
Good score. You've got $100 plus in those pipes alone by the look of things.

Hope the new engine is fine. I would lift the cam cover and the sump and have a look to see what the insides have been up to before fitting if I were you.
 
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