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Bent rod... now what?

Cherryriver

Cherryriver

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Guest
Certainly an well-hammered topic, let's see if there's any new great thoughts.
I picked up an '01 in halfway decent shape apart from a predicted hydrolock issue. 0nly 28,000 miles and some nice parts, including brand-new Avons. I am a sucker for new tires.
The bike was being sold only a few blocks away and the price was right.
So I actually rode it home and it ran pretty well, indeed, apart from that fairly fearsome clatter from the port side. It was much smoother-running, less vibey, than my long-ago '86 and more recent '99 junker, even at over 6,000rpm.
But danged if cylinder #2 failed the depth-gauge bent rod test by about 3mm. And the compressions were 165, 121, 170, 173.
So what next? I looked around for Ebay motors and that path looks to be a thousand bucks. I don't mind the labor changing it out, tinkering with bikes is what I do for fun.
I can't see, though, splitting the cases and changing a rod. That looks pretty crazy for an inexpensive bike that isn't in otherwise mint condition.
My plan is to stick it in the storage unit and just sort of wait until an inexpensive motor or crash bike comes along.
The devil on my shoulder says, ride it. Yeah, but what happens then? Flying internals?
Bill
 
Thank you for the replies.
Any guidance on the rod-changing process would be appreciated.
I figure to have to remove the cylinder head and oil pan, unbolt the rod and remove the piston/rod assembly out the top. Is that correct?
 
All of your compression #s are low but reasonably close other than #2.

Was the throttle was wide open when you did the first compression check??? If not, do the compression test again with throttle wide open.

Then before investing $ adjust the valves and do the compression check again. With only 28K on the clock it wouldn't surprise me if the valve clearances were never checked/adjusted.
 
brooke.benfield said:
All of your compression #s are low but reasonably close other than #2.

Was the throttle was wide open when you did the first compression check??? If not, do the compression test again with throttle wide open.

Then before investing $ adjust the valves and do the compression check again. With only 28K on the clock it wouldn't surprise me if the valve clearances were never checked/adjusted.
Click to expand...
You may be right on the compression numbers being a little low due to valvetrain issues, but if the rod is bent ("But danged if cylinder #2 failed the depth-gauge bent rod test by about 3mm.") then shouldn't this be fixed if you intend to run the engine long-term?

That is to say, if the rod is bent at all, but the engine still runs ok, doesn't that pose long-term risk of further rod damage since it's weakened? And worst case possibility that it breaks and ruins the crankshaft/case/piston?

I'm asking not to be snarky, but because I've never had to deal with a bent rod, so I truly don't know whether you can safely expect the rod to hold up under 'normal' running conditions.
 
Don't ride it with the rod bent that bad. (Think you sed; 3 MM / approx. 1/8")
If it breaks, could be a rod thru the case. :eek:

Haven't done this, but can guess.
You will have to remove the head as the piston comes out the top.
Also remove the exhaust and pan.
Inside I think you have to remove a few pieces including the oil pump to get to the bottom of the Rods.
Then remove that rod cap and push the piston/rod out of the top.
You should see the weight on the rod. Use that and find one on Ebay.
Prolly good to get a piston/rings too as it's possible the piston is damaged.
After the rod arrives, assembly will be in the reverse order.

Ride safe, Ted
 
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Here's a piston Rod. Note that the rod appears that it might be slightly bent?
www.ebay.com

1998 98 Kawasaki Concours ZG 1000 ZG1000 piston connecting rod Rings Std.bore | eBay

Find many great new & used options and get the best deals for 1998 98 Kawasaki Concours ZG 1000 ZG1000 piston connecting rod Rings Std.bore at the best online prices at eBay! Free shipping for many products!
www.ebay.com

Here's a set of 4. Might be a better deal as you could compare and pick the best (and have spares).
& (before you buy) The seller could possibly look at weight.

www.ebay.com

94-96 KAWASAKI CONCOURS 1000 ZG1000A ENGINE MOTOR PISTONS W CONNECTING RODS | eBay

Removed From: 1995 Kawasaki Concours 1000 ZG1000A. We are human, mistakes happen and will always make it right.
www.ebay.com
 
Thank you, I have begun to contact Ebay sellers asking about the weight letter code.
It's looking as though I might be spending five-ten times as much on gaskets as rods.
Still, if this succeeds, I will be in decent shape overall on the bike and can move on to other things it needs.
 
Cherryriver said:
Thank you, I have begun to contact Ebay sellers asking about the weight letter code.
It's looking as though I might be spending five-ten times as much on gaskets as rods.
Still, if this succeeds, I will be in decent shape overall on the bike and can move on to other things it needs.
Click to expand...
I have found buying an entire ZG1000 engine set of gaskets is cheaper than à la carte buying just needed gaskets. This was years ago, likely still applicable.

Wayne, Carol & Blue
 
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connie_rider said:
Don't ride it with the rod bent that bad. (Think you sed; 3 MM / approx. 1/8")
If it breaks, could be a rod thru the case. :eek:

Haven't done this, but can guess.
You will have to remove the head as the piston comes out the top.
Also remove the exhaust and pan.
Inside I think you have to remove a few pieces including the oil pump to get to the bottom of the Rods.
Then remove that rod cap and push the piston/rod out of the top.
You should see the weight on the rod. Use that and find one on Ebay.
Prolly good to get a piston/rings too as it's possible the piston is damaged.
After the rod arrives, assembly will be in the reverse order.

Ride safe, Ted
Click to expand...
Only one change - you don't have to remove the oil pump.
 
Cherryriver said:
Thank you, I have begun to contact Ebay sellers asking about the weight letter code.
Click to expand...

I have some K and L marked conrods. But you need to know what letter is on the conrod in question. Once determined, you only need to match that one with a straight one with the same letter / weight designation.
 
Back from a nice little vacation riding the coulees of the Driftless Area of western Wisconsin with the Missus.
One thing that isn't clear to me: do I remove the cylinder block to do the replacement? Or can I just work the piston/rod assembly out the top of the bore? Might save a little work, I guess.
Hoping to get things apart in the next day or two.
 
Again, I haven't done this. But I suspect that you can push the piston/rod in thru the cylinder.
I know that the bearing end of the rod fits thru the cylinder easily.
NOTE: You don't want to remove the cylinder. {So that you don't have to re-stab all the other pistons into it}.

Ride safe, Ted
 
connie_rider said:
Again, I haven't done this. But I suspect that you can push the piston/rod in thru the cylinder.
I know that the bearing end of the rod fits thru the cylinder easily.
NOTE: You don't want to remove the cylinder. {So that you don't have to re-stab all the other pistons into it}.

Ride safe, Ted
Click to expand...
This is correct!
 
CORRECTED after memory kicked in.

You would have to reuse the base unless pulling the cylinder block, which requires all four pistons to be reinserted into the block from the bottom up while attached to the crank and cases intact. Did that before on a Suzuki GS1100 and it was a Rubics Cube to get it all back together.

Both the C10 base and head gaskets are multi layered metal.

The base gasket and block were never removed and simply tightened back down when the head was torqued back on.

CORRECTION: I originally stated I reused the base gasket in place as is, but my memory kept nagging me. I checked my notes and sure enough, I swapped out the block and the base gasket which was also sprayed on BOTH sides with Copper Gasket spray just like the head gasket.

Mind you, this was on a Frankenstein engine project using various parts from 2 failed engines make one good running engine.

One engine had ACT damage to the main clutch drive gear (missing teeth) on the crank where it interfaces the clutch basket, the other engine had hydrolock damage with 2 bent rods to the point of being unable to rotate 360 degrees.

YMMV
 
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Stasch said:
CORRECTED after memory kicked in.

You would have to reuse the base unless pulling the cylinder block, which requires all four pistons to be reinserted into the block from the bottom up while attached to the crank and cases intact. Did that before on a Suzuki GS1100 and it was a Rubics Cube to get it all back together.

Both the C10 base and head gaskets are multi layered metal.

The base gasket and block were never removed and simply tightened back down when the head was torqued back on.

CORRECTION: I originally stated I reused the base gasket in place as is, but my memory kept nagging me. I checked my notes and sure enough, I swapped out the block and the base gasket which was also sprayed on BOTH sides with Copper Gasket spray just like the head gasket.

Mind you, this was on a Frankenstein engine project using various parts from 2 failed engines make one good running engine.

One engine had ACT damage to the main clutch drive gear (missing teeth) on the crank where it interfaces the clutch basket, the other engine had hydrolock damage with 2 bent rods to the point of being unable to rotate 360 degrees.

YMMV
Click to expand...
My only experience was with the GS1100GK that I still own. IIRC the guys on the GS forum said if you replaced the head gasket the base had to be changed as well. Of course they also swore that the vesrah gaskets I used were trash and that I shouldn't have used them. I had my son help with getting the cylinders back on. It wasn't that tough a job really. She still runs great.
 
I would have to wonder about the condition of the other 3 con rods with this one so bad. The forces that bent the rod so severely would seem to very likely result in other unseen damage. Must have been one heck of a burn out!
 
If your going to invest in putting this back together, definitely install overflow tubes in the float bowls. I did my own but if you don't actually work in a machine shop, I don't recommend doing it yourself. Steve at Shoodaben engineering does this for a reasonable price. You won't sleep well if you don't do it.
 

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Relievenski, It's less common that 2 fail at the same time. (But not impossible)
It's probable that only one carb allowed gas to get into a cylinder.
That gas, had to fill a cylinder (that had intake valves open) just before a compression stroke.
As liquid is not compressible, that rod bent when the piston couldn't move.
When that one cylinder stopped movement the other 3 stopped to, but they were not on a compression stroke.
 
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connie_rider said:
Relievenski, It's less common that 2 fail at the same time. (But not impossible)
It's probable that only one carb allowed gas to get into a cylinder.
That gas, had to fill that cylinder with liquid just before a compression stroke.
ie; The intake valves had to be open.
As liquid is not compressible, that rod bent when the piston couldn't move.
When that one cylinder stopped movement the other 3 stopped to, but they were not on a compression stroke.
Click to expand...
could have been a repeat event.
 
connie_rider said:
Relievenski, It's less common that 2 fail at the same time. (But not impossible)
It's probable that only one carb allowed gas to get into a cylinder.
That gas, had to fill a cylinder (that had intake valves open) just before a compression stroke.
As liquid is not compressible, that rod bent when the piston couldn't move.
When that one cylinder stopped movement the other 3 stopped to, but they were not on a compression stroke.
Click to expand...
Thanks for the information. I was not aware as mine is a C14. Hope he is able to replace the parts and get her back on the road.
 
I have to say the seller was exceptionally forthright, and he even lived across the way from us.
He said there was one hydrolock occurrence, and my check of the piston heights tends to confirm it.
Here's the really weird part: I rode it a short distance home, in this case about 1.2 miles, and it ran very smoothly and vibe-less-ly. Noisy, but no buzz.
Now I wish I had trailered it home, because I was under the incorrect impression that he'd changed the oil completely after the event, but such was not the case.
Still, I've seen bearings hurt worse than this and keep going. Plain bearings are incredibly tolerant.
 
Time for a bit of an update.
Partzilla has been extremely slow nowadays on "processing" orders. I waited a long time for the gaskets and so forth I figured I needed for the job.
Stasch so very kindly sold me a perfect match rod, both the bearing and weight codes matched. Very reasonably; thank you, sir.
Doing the #2 rod change with the engine in place requires some extraordinary body contortions to get done. Even with my (beloved) Harbor Freight lift, I had to do some exotic twists to get that rod cap up there and the nuts on the bolts.
Finally, today, I was ready for a test run. I decided to get new oil cooler line crush washers at the last minute and the local Yamaha dealer, Rich's in Lockport, IL, came through.
Yeah, but you're supposed to remember to torque up all of the banjo bolts. It's amazing how much oil that thing could pump out in a quarter-minute.
So it started right up, but ran a bit rough and not so happy, not like it was running before the teardown. But with oil gushing out of the lower end and coolant oozing out of the intake-side water pipe manifold (because I didn't order out new O-rings for it), it was a short run indeed.
Plus, I tried getting away with re-using the old exhaust header gaskets, and that didn't work, either. I've had luck with that in the past, but not this time.
On the other hand, the engine itself sounded pretty good, no clanking or banging. So, at least for the moment, I'm encouraged.
Now, to settle in and wait for some gaskets to arrive so I can enjoy pulling and replacing the carbs one more time.
 
Another update; not as much time has been available for this project as might be wished.
With the #2 (straight) con rod in place that Stasch so generously shared, getting everything else back in order was a slow haul between real-life events.
Today, after some family doings, I was finally able to get back to putting things back together. I was saving the joy of carburetor re-installation to near the end.
With the various new gaskets in place, things were buttoned and with the greatest of trepidation, the fuel valve was turned to "PRIME" for a minute. A yank on the enrichener lever, a press of the starter button, and with only a few turns of the crank, it fired off fairly nicely.
Two minutes of warming on the lift with lights being pointed everywhere and then, rolled it off onto the drive. Another few minutes of running and blipping, no weird noises from the crankcase. I rode it around the parking lot and honestly, to both my wife and myself, it sounded downright good.
We put the upper fairing on to gain some lighting and lit off down the road, stopping every quarter mile or so at first, looking for those devil leaks.
Still good, we went a little bit further- you can get a little bolder when you have a trailing rider with a passenger seat- and then turned back. I rolled the tach around to 10,000 in first and second gear, holding it there for a while, listening. Still okay down there.
My impression of engine smoothness was good. It seemed at least as smooth as my long-gone '86 was, if not better, even at 5,000 rpm.
Being our temps are over 90 F today, the engine got good and hot, a long red-light wait included. The last bit I zoomed a little bit at 70mph before stowing it in the garage so we could go out for dinner. On our bikes, of course, just not this one.
I am hesitant to say so, but the motor sounds downright sweet. Having listened to my first Connie motor for near a hundred thousand miles back in the late '80s-early '90s, it's a sound I really like.
Tomorrow, I will begin putting on the rest of the bodywork and commencing a few upgrades and touches, things I didn't want to do before knowing the engine would at least run.
My wife is hoping for a victory happy dance, although that may have to do with watching a geezer act goofy.
Who knows, I may get to that.
 
That would be the advice I would have given to the gentleman who sold me the bike- he forgot to take it off of PRIME and left it for a week or two.
 
I've pulled spark plugs more than once because I left it on prime. The float valves did their job so far. It's tough getting old!
 
100 miles covered so far. No internals have gone external yet.
I have not been gentle, either.
This just might, might be a win.
A bit premature, but still.
 
This might bear another update.
So now I've covered a bit more than 800 miles with the bike and the engine continues to hold together and run pretty decently.
I even splurged on a few upgrades to both make it more interesting to me, and to a potential buyer.
I can't really decide just how many miles of non-explosive running is required to convince myself the engine is actually fixed. After all, an old C-10 motor is not the quietest, least-clashy motor ever. In fact, I can recall describing my back-in-the-day '86 as sounding like a garbage can rolling down a gravel hill.
A description, by the way, that brought gales of laughter from the jaded old service manager of the local Yamaha dealer. Broke through the grump right well with that one.
So I just keep riding it around, not going hundreds of miles from home but not being shy, either.
Thanks again, Stasch, you were the key player.
 

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