Knackered Crankshaft on Honda cb 125 t! Help!

[kimarie]

My 18 year old son bought a Honda cb 125 t which had a rebuilt engine 3 months ago. He was told to run the engine in for 500 miles at no more than 40 MPH which he did. He's had a couple of small problems but the other day whilst riding it it made a couple of loud bangs and then an awful metallic grinding noise. He's stripped it down and the crankshaft is knackered (polite phrase!! ) What now?? Sell it as spares or repair?? One online company is quoting approximately £650 for the part. He's devistated as he saved hard since Christmas and now looks like he's gonna lose money
Any advice would very much appreciated.
Kim

[Frost]

Don't buy new parts online, they will always cost far more than they are worth. Either get the part off ebay or get an engine off ebay. Most engines tend to fail at the top rather than the bottom, so he can buy a non running engine and get the crank out of that.

I'm very surprised that the crank on it went, if you don't mind me asking, how do you know for definate it's the crank thats gone? How do you know that it's not gone due to oil starvation or also knackered the top end?

Pictures are always very useful.

[kimarie]

Hi, thanks for your advice. I'm just going by what my son has said. He's a mechanic (cars, just qualified) but has colleagues who are heavily into bikes. Your point about oil starvation is interesting as it was leaking oil and he'd just got a new seal for it. Don't know if he'd fitted it or not or if that could have caused it?? Not a mechanic myself so not sure about the top end damage?? i'll try and get some piccies and more info when he gets home.

[Frost]

The top of the engine is where most of the high speed parts are and where most of the friction takes place. Little bikes tend to use oil quite quickly and a leak won't help matters. If the crank has gone i would suspect a lack of oil which would cause a lot of damage to the top (cam lobes and camshaft seats). So if he's not looked at these its worth doing so before buying parts to fix what might only be 1 of the problems.

A friend ran his RV125 out of oil and knackered it. He got an engine out of a bike that had been stolen and burned out. The electrics were gone and the engine was a horrible colour, but it worked. He swapped the electrics over and repainted the engine, end result was a fully working bike after spending £150, much cheaper than buying parts etc.

[kimarie]

Think you might be onto something!? The bike's engine has been totally taken apart but not sure if other components are damaged. Will speak to him when he get's in and find out exactly what's what!
Any ideas what other engines would be compatible in this bike? There doesn't appear to be many cb 125 t's around on ebay.