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AMCQ46 wrote:would be interesting for a metallurgist to look at that to understand how it failed. looks like a stress crack (the flat dark grey surface) from the edge of the bearing wear mark that went through 70% of the journal then it it snapped the rest when it could take the load.

surprised and glad that the pistons didn't hit the valves, hope the new engine gets all the good bits and goes even stronger

In my head hitting first instead of second going into Park at Cadwell resulted in the stress and failure, it's on the clutch side. I went back to first instead of second several time over a couple of days. I'm guessing it couldn't take it.

Or this caused a crack which meant the flywheel side had enough movement for the flywheel and stator to touch and bind. This then snapped the crank.

Where would I find a metallurgist?

I work with a few metallurgists, if you take a few good close up photos of the surface, I will ask one for an opinion

freeridenick wrote: ↑Mon Oct 04, 2021 6:43 pm

AMCQ46 wrote:would be interesting for a metallurgist to look at that to understand how it failed. looks like a stress crack (the flat dark grey surface) from the edge of the bearing wear mark that went through 70% of the journal then it it snapped the rest when it could take the load.

surprised and glad that the pistons didn't hit the valves, hope the new engine gets all the good bits and goes even stronger

In my head hitting first instead of second going into Park at Cadwell resulted in the stress and failure, it's on the clutch side. I went back to first instead of second several time over a couple of days. I'm guessing it couldn't take it.

Or this caused a crack which meant the flywheel side had enough movement for the flywheel and stator to touch and bind. This then snapped the crank.

Where would I find a metallurgist?

You beat me to it. After seeing the photo of the crank I was going to ask you exactly when the crank let go.

Did a conrod big-end leave the crankshaft and damage the engine

Chris.

PS. Your thinking on how the crank ending up breaking sounds quite possible to me.

freeridenick wrote: ↑Mon Oct 04, 2021 6:30 pm Some JB Weld and it'll be fine, right?

holy shat nick thats ugly looking, but at least the rest looks good so thats a result

sirch345 wrote:
Did a conrod big-end leave the crankshaft and damage the engine

Nope. The clutch-side main bearing was heavily worn but complete. The front con-rod bearing is less worn but still toast, the rest look like they could be used again.

Only the flywheel side of the crank had any play so I think the fact nothing ending up inside the engine, and that it basically seized, has saved the pistons and valves.

freeridenick wrote: ↑Tue Oct 05, 2021 7:48 am

sirch345 wrote:
Did a conrod big-end leave the crankshaft and damage the engine

Nope. The clutch-side main bearing was heavily worn but complete. The front con-rod bearing is less worn but still toast, the rest look like they could be used again.

Only the flywheel side of the crank had any play so I think the fact nothing ending up inside the engine, and that it basically seized, has saved the pistons and valves.

I think you were very lucky not to have had anymore damage to the engine than you did, although having a crank go like that must have been a butt clenching moment

Chris.

freeridenick wrote: ↑Tue Oct 05, 2021 7:48 am

sirch345 wrote:
Did a conrod big-end leave the crankshaft and damage the engine

Nope. The clutch-side main bearing was heavily worn but complete. The front con-rod bearing is less worn but still toast, the rest look like they could be used again.

Only the flywheel side of the crank had any play so I think the fact nothing ending up inside the engine, and that it basically seized, has saved the pistons and valves.

Sad to see but know you're not alone (I went through it a few years back). I recommend you have a good look at the cases as mine had worn (leaving room for lateral play) and needed replacing (not hard to come by thankfully)

The cases are scrap and I think the pistons are too. Photos below and opinions very much appreciated. The wear on the bearing surfaces for the gudgeon pin are not bad but much worse on one side than the other - clutch side. The gudgeon pins have wear marks that can be felt with a finger nail. They can be replaced but I feel like the wear on the pistons would mean they'd move too much in replacement cases.

You might get away with the piston skirt marks but they would wear quicker than normal. I assume that the pin grooves are in the small end area rather than the piston journal area?
The other option for the pistons might be ptfe buttons or dlc coating in the skirt area.
I've never tried that myself, but apparently it lowers friction and heat transfer.

tony.mon wrote:You might get away with the piston skirt marks but they would wear quicker than normal. I assume that the pin grooves are in the small end area rather than the piston journal area?
The other option for the pistons might be ptfe buttons or dlc coating in the skirt area.
I've never tried that myself, but apparently it lowers friction and heat transfer.

Yes the grooves on the pins are from the small end. They'll obviously be replaced if I use the pistons again and I won't be using the con rods.

Now the stage 2 engine is out I've got a little ahead of myself and started to think about what to do with the rebuild. Given it's not going to be a track bike it opens up the options but I'm not sure which to choose. Input welcome

1) Full on race rep, eventually with ram air. Given this is and ex-race frame and now had 'Blade forks and race bodywork this was my first idea. But there are a few like this; Fabio's, Yeti's, GLRS's.
2) Semi-street sleeper. Basically the above but wrapped in stock bodywork. The trouble with this one is that the 'Blade forks and Mori exhaust are too obvious as mods.
3) Semi-naked special. I've still got the polished cases so a matt black frame/swingarm and satin black engine would look great. Flat bars on the 'blade forks and some sort of bodywork to hide the rads and it could look cool. Or it could look .

freeridenick wrote: ↑Wed Dec 08, 2021 3:48 pm Now the stage 2 engine is out I've got a little ahead of myself and started to think about what to do with the rebuild. Given it's not going to be a track bike it opens up the options but I'm not sure which to choose. Input welcome

1) Full on race rep, eventually with ram air. Given this is and ex-race frame and now had 'Blade forks and race bodywork this was my first idea. But there are a few like this; Fabio's, Yeti's, GLRS's.
2) Semi-street sleeper. Basically the above but wrapped in stock bodywork. The trouble with this one is that the 'Blade forks and Mori exhaust are too obvious as mods.
3) Semi-naked special. I've still got the polished cases so a matt black frame/swingarm and satin black engine would look great. Flat bars on the 'blade forks and some sort of bodywork to hide the rads and it could look cool. Or it could look .

What ever one that’ll get used the most . No point building it not to use . .

freeridenick wrote: ↑Wed Dec 08, 2021 3:48 pm Now the stage 2 engine is out I've got a little ahead of myself and started to think about what to do with the rebuild. Given it's not going to be a track bike it opens up the options but I'm not sure which to choose. Input welcome

1) Full on race rep, eventually with ram air. Given this is and ex-race frame and now had 'Blade forks and race bodywork this was my first idea. But there are a few like this; Fabio's, Yeti's, GLRS's.
2) Semi-street sleeper. Basically the above but wrapped in stock bodywork. The trouble with this one is that the 'Blade forks and Mori exhaust are too obvious as mods.
3) Semi-naked special. I've still got the polished cases so a matt black frame/swingarm and satin black engine would look great. Flat bars on the 'blade forks and some sort of bodywork to hide the rads and it could look cool. Or it could look .

I would go with the second option. Though I am a bit biased as even though I only have the junior version with my STG 1 I can say most folks don't even notice the SP2 front end or even the Akra cans, let alone the rest of the bits you can see.....

Option 2.

A wolf in sheep's clothing

As Hawk says, most Herbert's wouldn't even know what Moriwaki is. Paint everything black and then you'll be really under the radar.

option 3 but put a rad up under the seat with some fans on it without the side rads most normans will have no idea what they are looking at