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REPOST Enforcement Mod
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This is a general question regarding spun bearings since a friend of mine had this happen on his Triumph Speed Triple. I won't go into how it happened other than he was running the motor with about 1qt of oil in it. :rolleyes: Once the bearing spun the motor started knocking pretty badly and was shut down quickly.

Anyway, we pulled the motor out of the bike and split the crankcase. The #2 (center cylinder) definitely spun the bearing due to the oil starvation. The bearing halves were still there and it looked like just the sheared off holding tab is the only damage to the bearing shells. The conrod and crank journal have a faint black mark from where there was metal to metal contact, but it's not anything like I would've expected. I kind of expected to see some type of scoring on the crack journal, which was not there. There's no blueing from excessive friction or anything either. I don't really have any personal experience with spun bearings.

So my question is, what level of tolerance is there on the crank and conrods in this situation? Is the motor going to grenade itself on startup if we just use a little crocus cloth on the journal and replace all the bearings? Is the reliability of the motor compromised if we reuse the major components (crank and conrod) and replace the other items (bearings, conrod bolts, etc.)? What do people usually do to repair this type of failure?
 

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:headshake id def send the crank out to be checked,all the tolerances are in the service manual.its just me but if i split the cases im def gona put all new bearings in it.id rebuild the oil pump and replace the oil cooler as well.once those bearings start to come apart that matter goes through everything in the engine.im sure others will chime in and explain alot better than me...thats just mo
 

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Supercharged Mod
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Use a good micrometer to very thoroughly check that journal for out-of-round and out-of-tolerance. The shop manual has the specifications in it. Also, very carefully check the affected con-rod for out-of-round and out-of-tolerance.

Sometimes you can be lucky. Other times, not.

Oil pump and oil strainer screen should be checked for sure. If the oil filter did its job, everything downstream of the oil filter should be OK.
 

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:headshake id def send the crank out to be checked,all the tolerances are in the service manual.its just me but if i split the cases im def gona put all new bearings in it.id rebuild the oil pump and replace the oil cooler as well.once those bearings start to come apart that matter goes through everything in the engine.im sure others will chime in and explain alot better than me...thats just mo
Use a good micrometer to very thoroughly check that journal for out-of-round and out-of-tolerance. The shop manual has the specifications in it. Also, very carefully check the affected con-rod for out-of-round and out-of-tolerance.

Sometimes you can be lucky. Other times, not.

Oil pump and oil strainer screen should be checked for sure. If the oil filter did its job, everything downstream of the oil filter should be OK.
Thanks for the advice guys! The plan was to replace all of the bearings and the affected conrod. The problem is a new crank costs almost a $1000 for that motor. I was going to check the tolerances to be sure the existing crank journal wasn't trashed, but it's going to be hard to check for out of round given the tools we have access to. Guess we're just going to have to mic it about a 1000 different times to get a feel for it's roundness.

I guess if we're within the service tolerance, we'll polish the journal with a little cloth to knock down any potential peaks on the score mark and put it all back together to try it out.

The oil system will get a cleaning prior to assembly and a good flush once we get it back together and running.
 

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if bearing spun, it did damage.... it needs rods and crank, smoothing w/emery cloth will just increase tolerances , maybe they have oversize bearing then you can turn crank and resize rod and/or replace both...when motors lose oil pressure, it loses o.p. on the top end first..check cam also.. long term low aerated oil is bad.. wears everywhere... you might be better off finding a used motor , those are popular bikes ...
 

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thanks i have just spun a bearing in mine i really thought it was no hope but yall proved me wrong.

But wanted it be easier and cheaper to just buy another motor
 

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Have you tried APE? I've used them for all of my crank work with great results. You'll often be better off than before (balancing, tolerances, and such).
 

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I used to work in an engine machine shop. If they make oversized bearing for that engine you can just have an engine shop regrind and polish the crank and recondition the rods... you need to have them all done not just the busted one. Will be A LOT cheaper than buying new parts.
 

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Have you tried APE? I've used them for all of my crank work with great results. You'll often be better off than before (balancing, tolerances, and such).
No, I have not tried APE yet. I know they do crank work :lol:, but it's typically not a 3 cylinder Triumph. I'll contact them however and get their opinion. Thanks!
 

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Have you tried APE? I've used them for all of my crank work with great results. You'll often be better off than before (balancing, tolerances, and such).
I used to work in an engine machine shop. If they make oversized bearing for that engine you can just have an engine shop regrind and polish the crank and recondition the rods... you need to have them all done not just the busted one. Will be A LOT cheaper than buying new parts.
That's part of the problem. There are no oversized bearings available. They have different size ones to account for conrod tolerance variations, but that's it. There's a big bold warning in the crank section of the service manual that states this fact and that if the journal is out of the service limit, then it must be replaced and cannot be resurfaced. Something about manufacturing materials and tolerances.
 

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A good machine shop can usually build up the material and grind it down to shape. I'd make some phone calls and see if that's a viable option.
 

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Falicon, APE, Marine Crankshaft, and others can do crankshaft work on motorcycle engines. If the crankshaft measurements show that something needs to be done about it, look 'em up and have a chat with them.

It may end up being cheaper to just get another engine, though. Last time I had to deal with a situation like this (customer bike), it was cheaper to ebay another engine and tear it down than repair the crankshaft.
 

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Falicon, APE, Marine Crankshaft, and others can do crankshaft work on motorcycle engines. If the crankshaft measurements show that something needs to be done about it, look 'em up and have a chat with them.

It may end up being cheaper to just get another engine, though. Last time I had to deal with a situation like this (customer bike), it was cheaper to ebay another engine and tear it down than repair the crankshaft.
Are they the only ones that do this kind of work? I am out of the states and need to repair mine, my problem is the shipping...it costs me almost 230$ only in shipping costs. Any help?
 

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Welding the journal and then normalizing the size can be done. This is not for just any good welder/crank grinder. Specialty crank shops (like GoFaster said) that regularly do stroker-cranks and such should be sought out. It takes very special equipment and prep - as well as proper cool down and straightening. In my area I use Crankshaft Craftsmen - which is South East Michigan.

Hope that helps with possibilities.
 
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