Broken Crankshaft?? WTH :/

[Ricky Gee]

I have a 1980 XS1100G for about 5 years now. I bought it in horrible shape. Got it running and rode it for about a year. Then C19 and life hit and it was parked for the last 3 years. I had other things to worry about.
I Got restless a month or so back and got it back on the road again. Big Smiles as i love the sound of the old school bikes with Kerker exhaust I took it out for its first good ride and few weekends ago. Bike ran great until it wasn't. Minding my own business, enjoy the warm spring day and she makes a odd sound, tried to die then just stopped. I coasted to a stop with the clutch in. Tried a restart and knew instantly we had a big problem. long story short. Once i got it back home and on the lift. Noticed the timing marks didn't match up. Thought timing chain. Nope, Broken crankshaft right next to the crank gear. Now i have been riding for over 50 years and have owned and repaired my share of bikes of all kinds. But i have never seen or heard of a bike braking a shaft. I already bought 2 other bikes and hope to build one good engine. Seems engine parts are not easy to find these days and if you do, they are used.

Is a broken crankshaft a issue with these bikes? the bike never made a sound outside of normal engine sounds. I heard no hard knock or bang when it let loose. I was just floored when I tore it down and saw the shaft busted. I might add. I don't hammer on the ole girl..

[DEEBS11]

I would imagine it had oil in it. Not sure what has happened here. Can you post some pictures? It's possible that the primary chain broke and that is what caused the crank shaft to break.

[skids]

It didn't get hydrolocked with too much fluid in the crankcase did it?

[Ricky Gee]

Just did a oil change, so that all good. Primary chain is there and in one piece, but it had more play than I thought it should. like maybe a 1/4 in of play.

Ill take a picture of it this evening. But the break is on the crank timing gear. I couldn't find or haven't found the specs on the primary chain to know if its good or not. Doesn't appear to have any sort of adjustment. I am about to the point of splitting the case halves. ill have a better look see when i get there.

the bike was running great. It just let loose..

rick

[DiverRay]

The cranks on these bikes do not break> RC engineering would run an engine all season on the drag strip and never split the cases. That being said, if you run them over 10K RPM the primary drive chain will let go, as the road racers in the EU have found out.

[DiverRay]

I should have a '78 crank in about a month. I'm working on one engine, and have one with a very bad transmission still in the frame. New chains are still available, but not cheap. I know as I'm replacing any part I can get in the engine I'm putting together. My plan is about 140HP with a turbo or super charger.

[Ricky Gee]

the primary chain didnt break, but it does have more slack than i think it should have..

i was no where near 10 grand. was only doing about 70 when it quit.

i have 2 spare engines both are 78-79 year model.. I'm hearing that they have a tad more HP than than the 80-81 did.

[DiverRay]

Yes they do, but you probably will not notice it. You may have had a P.O. who liked wheelies or something, and was about 300lbs. We never know what these poor bikes have been through.

[GNEPIG]

These are the heaviest inline 4 engines in the industry, never heard of one of these breaking a crank. Yours must have hit the ground real hard at one time or had a casting/ machining imperfection of some sort. A lot of other cool things to break on these bikes before the crank goes...

[DEEBS11]

Just did a oil change, so that all good. Primary chain is there and in one piece, but it had more play than I thought it should. like maybe a 1/4 in of play.

Ill take a picture of it this evening. But the break is on the crank timing gear. I couldn't find or haven't found the specs on the primary chain to know if its good or not. Doesn't appear to have any sort of adjustment. I am about to the point of splitting the case halves. ill have a better look see when i get there.

the bike was running great. It just let loose..

rick

This seems to be the only event that happened before the failure and should be taken into account. The crankshaft rides in plain bearings and glides on a thin film of oil pressure. If there was an abrupt lack of lubrication and the crank locked, the power of the pistons would continue to push. However, this usually results in a broken piston rod. You should look at the oil filter area of the engine. Perhaps you are the victim of Chinese maintenance parts.

[LAB3]

Then there's the things you either don't or can't see such as defects in the casting/forging process and heat treating. Either way it goes a broken crank is pretty a pretty dire thing to deal with.

[bikerphil]

Couple questions,

1. About how many miles on the engine?
2. What brand and what weight oil were you using?

[Larrym]

You should look at the oil filter area of the engine. Perhaps you are the victim of Chinese maintenance parts.

Oar? (O_o)

There is a right/wrong way to install the oil filter and springs/washers in the oil filter assembly. (O_O)

Do it WRONG and you can end up actually BLOCKING the flow of the ole SAE lubricament... (*´_ゝ｀)

[Prothec]

My XJ11 that I got as a basket case came with the cases split and crank missing. I got this bike from my father in law and the story goes he was riding it when the crank split, but limped home on 2 cylinders.
When I got a hold of it sometime around maybe 2010, the primary guide was chewed up and had broken links in the chain. It probably sat disassembled since ~1987. He believes a shop that did engine work dropped the crank and cracked it.

I don't think I have ever heard of a case of another broken crank on one of these bikes until now.