Disaster With 390 Engine

Took part in my first Vintage Hare Scramble event yesterday at Ashby Motoparc here in the UK, a 3 hr event, split into two 1.5 hour sessions, and all was going really well for the first hour or so. The 390 was running perfectly and I was really enjoying the variety of the terrain on the 4.5 mile circuit.

Unfortunately on lap 7 I was on the fastest part of the course when there was a sudden loud crack and the engine locked up solid. Looking down I could that gearbox oil was pouring from the bottom of the engine!

After taking the clutch cover off it soon became clear what had happened. The nuts on the back of the clutch basket had worked themselves loose and at least one had dropped off with disastrous results. The clutch cover has a large crack and split but even worse, the left engine case has a large hole where the kickstart shaft inserts into the case. So the engine now needs a full rebuild with replacement cases and clutch, plus who knows what else we will find when it is fully taken down.

Oh well, that's racing as they say...

It's even worse than I thought. The bottom end is completely solid. I think that one of the nuts from the back of the clutch has gone between the gear on the crank and the clutch primary gear and damaged probably the main bearing, which in turn has then failed and locked it up. The barrel and piston are fine, but the crank is solid, so I am not looking forward to stripping this one down to inspect the damage. Might need a crank as well.

Sorry to hear about that. I bet you will own stock in Loctite when the new engine goes together. PM Huskydoggg about parts, I bet he can fix you up!

There is a set of 1980 390cc cases on " a popular internet auction site " right now . There are some other parts also but I don't remember seeing a crank .

That's a shame.
I hope my nice new basket does not go the same way. I have made sure it is loctited and torqued as per the manual. Lovely new hard anodised basket too.
Just had to put a new r/h end on my crank as well. The old one was 3 thou out of true (bent !)