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Discussion Starter #1
I took the rear cylinder and piston off of my engine this afternoon.
I soon realized why the engine is so hard to turn over.
The rear rod is seized to the crank, and the front rod bearing is gone.
There is a good 1/8 play in the front rod, so now I know where the copper shavings come from. I had a good idea the rod bearing was bad, but not that bad.
I'm waiting to find a bolt to pull the stator so I can get the front cylinder off so I can split the cases.
Damn! I was hoping for a better find, but I knew in the back of my head otherwise.
I will post pics as soon as I get the cases apart.
Back to court I go.
 

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If only it had 6th gear..
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Wow man. Hope it goes smoothly for you. Best of luck.
 

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Discussion Starter #3
I have found a crank and rod assy from another member. I just need to get the funds together to get them.
 

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Welcome to the club Bill. That's just what we found. Both rods frozen but, no copper filings. We should be able to just replace inserts.

I think what happened in our engine is that all the filings from the counter-balance grinding pieces up clogged the oil filter. When the oil pressure got high enough the relief valve popped and let all the filings into the oil passages. Filings were every where. The oil holes in the crank shaft were full leading to bearing failure. There were even filings in the little oil filters that protect the HLA's. TGFT's.

I have a question about rod play. With the old inserts in and the rods on the crank. The rods have noticeable linear movement. Didn't have plasti-gage. Do you think you could feel the oil gap move? There is some rocking movement side to side. How much is tolerable?

Thanks and Good Luck Bill
 

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Discussion Starter #6
I'm not sure about the side to side movement. I know there will be a little bit, but it can't be too much, or it wouldn't allow oil pressure to build up.
I know on a car, if the rods & mains have too much clearance, the oil pressure will be low.
I will have to read in the manual to see what the specs are.
The rear rod is frozen to the crank, but it will turn with a quite a bit of force. The front rod flops around on the crank. I think the bearing is gone.
All I know is that it's going to cost me a lot of money to get it going.
 

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When we first got this bike(2001vn750) it would not turn over. Both side engine covers were AWOL and a majority of the innards.

We tried turning it over with a breaker bar on the primary nut but it wouldn't budge.

Then we added a strap wrench around the rotor. It took both of us to break it free(and we're no lightweights 245lbs and 250lbs).

Had hoped that with exersize it would start turning more easily.

Didn't happen.

The starter would turn it over very slowly and only 1 or 2 times before it needed a boost.

After wasting way too much time trying to free it up by hand we finally took the plunge.

I have new respect for that starter.
 

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Discussion Starter #8
I finally got the engine torn down.
The front rod is toast along with the crank.
The bearing spun on the crank, and tore the crank up pretty good.
The rear rod is still intact, the bearing is good other than a scar mark from metal shavings on the bearings themselves.
I thought it was seized to the crank, but it wasn't.
A piece on the front rod bearing had wedged itself between the rods, and after I pulled the piece out the rear rod moved fine.
 

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Discussion Starter #10
I believe they are interchangeable. I will look at the manual to see, but I don't see any difference in them.
 

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With that kind of damage to a VN750 engine, I would just start looking for another engine, or sell the bike for parts, and buy another. A car engine with that kind of damage could be repaired, because there are replaceable bearings everywhere, the cylinders can be rebored, and the crank and cam can be reground. Japanese motorcycle engines are not built that way, they do not have undersized bearings, the cam has no bearings at all, and if there is damage, the heads, cams, and cam holders all have to be replaced. Those shavings could have gotten anywhere, including the crankshaft main bearings, the cam chains, and anywhere in the transmission. Motorcycle engines are not designed to be rebuilt, and trying to rebuild one can involve replacing virtually every part in them.
 

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Your lucky you got 31K miles out of it without a problem. I recently picked up an 02 750 with an engine knock. As it only had a little over 4600 miles, and it didn't sound like a rod knock I took a chance. Well, after much tinkering, and finally deciding that the engine would have to come out, I found that it had indeed spun the bearing on the front connecting rod. What was left of the front bearing was paper thin and the connecting rod had scored the journal (or crankpin as they call it). The rear bearing didn't look that good either. I seriously think that this was caused by something they did or didn't do during manufacture. When you rebuild, pay close attention to the bearing size and clearance!!
 
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