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Old 07-12-2014, 02:54 PM   #1
twistylove OP
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Curious crank seizure?

Hey folks-

So I’ve got a seized 2-stroke from a 1978 Suzuki DS100.

A buddy helped me pull the engine apart and the piston itself slid right out of the cylinder, so that wasn’t the problem (though there were some vertical scratches on the piston and in the cylinder; visible, but not much more than surface deep, see below).


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After popping the piston off, we noticed that there were some small pieces of shrapnel that were resting on the crankshaft (they're all collected in the corner closest to the top of the image):


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Looking around for the shrapnel’s source, the only thing that caught our eyes was maybe some had chipped off the bottom of the piston itself:


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At this stage, the kick-start is still frozen about half way down and manual pressure won’t move the connecting rod.

I suppose I’ll also mention that once we removed the cylinder, it became apparent that the piston was making physical contact with the crankshaft and there are scratch marks on the crankshaft from where the two make contact.

Cruising around the forums has left us a little high and dry on what’s going on with the engine.

Thoughts on where to look/what to do next? Time to open up the crankcase?

Much thanks in advance.
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Old 07-12-2014, 03:49 PM   #2
anotherguy
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Post a photo of the piston dome please.
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Old 07-12-2014, 04:35 PM   #3
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Post a photo of the piston dome please.
Happy to try to grab pics of anything else that'd be helpful.

Front of bike is to the left:


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You can just see the forward facing arrowing point left in this one:


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Old 07-12-2014, 05:41 PM   #4
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OK. No impact on the dame rules out a big end bearing. Time to take it apart. More then likely a crank main bearing. Easiest and cheapest to replace the crank,bearings and seals along with a piston/rings. While it's apart go through the gearbox. Could be cheaper yet to find a used engine on eBay.

A lot of the parts seem to be available on Bikebandit so they're out there. Prices aren't out of line. Some stuff on eBay too.
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Old 07-12-2014, 07:02 PM   #5
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Originally Posted by anotherguy View Post
OK. No impact on the dame rules out a big end bearing. Time to take it apart. More then likely a crank main bearing. Easiest and cheapest to replace the crank,bearings and seals along with a piston/rings. While it's apart go through the gearbox. Could be cheaper yet to find a used engine on eBay.

A lot of the parts seem to be available on Bikebandit so they're out there. Prices aren't out of line. Some stuff on eBay too.
Excellent, thanks for the knowledge! We'll do some poking around and update with our course of action.....
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Old 07-12-2014, 08:44 PM   #6
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with the old oil injected Suzukis you must run the injector and not switch to premix, the oil enters the engine through the crank bearings and then to the top end. Running premix starves the crank even though the top end is getting lubed. Is this what happened to yours?
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Old 07-13-2014, 08:37 AM   #7
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Looks like you may have bent the rod as well. Is that damage from the rod at the center of the opening on the top surface? Also, that would explain the piston skirt contact with the block. Good luck, I feel your pain.
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Old 07-13-2014, 07:33 PM   #8
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Quote:
Originally Posted by 380Viking View Post
with the old oil injected Suzukis you must run the injector and not switch to premix, the oil enters the engine through the crank bearings and then to the top end. Running premix starves the crank even though the top end is getting lubed. Is this what happened to yours?
that's entirely possible- when I bought the bike it didn't have an oil injector, so maybe the previous owner took it off? thanks for the tip, I'll do some research to see what I can dig up on this one
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Old 07-13-2014, 07:40 PM   #9
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Quote:
Originally Posted by vtwin View Post
Looks like you may have bent the rod as well. Is that damage from the rod at the center of the opening on the top surface? Also, that would explain the piston skirt contact with the block. Good luck, I feel your pain.
Thanks. When we have a chance to get back inside, we'll check the rod for damage as well.
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