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Discussion Starter #1
Hi guys, I have been a member for a long time, but I don't think I have ever posted anything.

It would be nice to start posting under better circumstances, but it is what it is...

I have a 1988 GSXR750, bought in 2003 (my first bike), it has 65000km/40000miles now. Since I have several other motorcycles it hardly gets used.
The last time I used it regularly was in 2016, since then its been on display in my living room.

Decided to get it running again this summer, so I got a new battery, cleaned the clogged carbs and put in some fresh gas. Didn't change the oil but it has done less than 500 miles since it was changed.

When I used it in 2016 (and before) it ran perfectly, no issues or sounds from the engine.

Started it up a couple of days ago, it ran well, a bit of coughing in the beginning but nothing much. let it run on the choke for about a minute. Decided to go for a test ride, turned of the bike, pushed it outside and put on my riding gear. Started it up again about 5 minutes later, ran on the choke for about 30 seconds, pushed it in one notch, revved the engine a few times, just a couple of quick on/off, maybe up to 4-5k, everything seemed fine. It had been running for about 1 minute at this point, revved it one more time, didn't look at the tach, but maybe it went to 7k, either way far off the redline.

A brown smoke cloud blew out of the exhaust and rattling noises came from the engine. I turned it off immediately.

At first inspection, no external damage or oil leaks. But emptying the oil and dropping the oil pan revealed a lot of debris and there seems to be a "hairline" fracture on the back on the second (from the right) cylinder.

I do have a spare engine I can take parts from, but because of the sentimental connection to the bike I would like to rebuild it instead of swapping the engine.

Now it seems pretty clear that the revving caused this, maybe I got over excited to hear it run after several years maybe I didn't let it warm up long enough?
I am not a reckless rider and I have never been close to the redline with this bike, and I wasn't now either, so I am asking myself if there was already an issue that was inevitable and I accelerated it, or did one revv kill the engine?

Hopefully I'll be able to get her back on the road rather quickly.

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First off..
13 years and no posts?? :eek::eek:

Secondly..
Dayum, that looks pretty FUBAR, but I'll let someone familiar with internals answer your questions.
 

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Looks like it will need a complete disassembly to see what all is damaged inside. That will give you a better idea on whether or not it can be repaired.
That is a lot of debris. If there are cracks in the block, I would replace rather than attempt to rebuild...
 

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what a co-incidence! i have an 86 750 track-only bike with a damaged carrillo rod, and was wondering if i did something or was it inevitable? if i did something, i want to know, so i don't do it again.

hopefully, someone with engine knowledge will chime in. i should ask the engine builder, since the engine is going to be repaired.
 

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Discussion Starter #5
I have started the tear-down, tomorrow we'll see the full extent of the damage.

So far we can see that the valve rocker arm on the intake on the 3rd cylinder is broken.
Maybe the connecting rod broke and the piston hit the valve and that broke the arm?

86gixxer, yeah, I feel terrible about this, and I am very curious to learn what caused it.
If one revv of the accelerator broke my engine after riding for 20 years without a mechanical issue, well that would be the bad-luck of the century.
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Discussion Starter #6
Well, I'm not much wiser now, with regards to cause... The piston is gone, the debris in my first post matches the bottom part of the piston that connects to the rod.

The connecting rod itself seems fine, it's still attached to the crank and moves normally.

The cylinder lining is broken and at least 1 valve looks damaged..

I still wanna rebuild it, it just doesn't feel right to do an engine swap, it is my first bike, my first love after all.
Anyone care to speculate with regards to the cause?

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There isn't always a reason. Sometimes things just wear and break.
Could be an oiling issue. Running with low or old oil can cause issues like this.
From that picture, it looks like you might be able to get away with re-sleeving it.
For sure will need a new piston and rockers.
Will want to check all of your tolerances tho and make sure the other pistons aren't worn beyond specs as well.
 

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Would be nice to see the underside of that piston, looks like the rod has been pulled out/off of the piston pin which would indicate that the piston itself failed. On the up stroke of the rod, it looks like the piston has come into contact with the underside of the head, which has been in the inlet stroke hence the valves may have been open, and forcing the valves back into the cam rocker arm....and smashed them. I would put this down to the piston failure as the probable cause and not something that you could have foreseen. The ensuing damage all stemming from that piston. To say the rod looks fine would be pure speculation, I would think there would have been some damage caused to that too, particularly if it still had the piston pin in it and it was smashing up against the cylinder.

Either way, it will cost lots of $'s to get this one working again. Best of luck.
 

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That is some real carnage. if youre going to rebuild that you will need to check everything over very carefully. I know you're attached to the engine for sentimental reasons, but if your cases are cracked I think its a loosing battle.
 
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