Not looking good; Piston and exhaust valve have made contact. Not removed the valve yet as I don't have a spring compressor although you'd hardly know it had hit but I assume it is bent or shoved into the head. Barrel looks OK but it was difficult to get the pin out of the piston and the bronze bush in the con rod came with it. Hard to see if the rod is bent but it looks like it might be. Head/valves; Rod; The picture actually makes it look more bent (forwards) than it appears in life, probably due to the wide angle iphone camera but I fear it may be very slightly bent...
Oh Sh*t................Valve has got tight and stayed open IMO. These engines should be pretty much bullet proof, so I can only think it was unleaded petrol that has caused a valve to stick from heat unless oil wasn't getting to the valve stem. The con-rod appears to be twisted slightly (the small end seems to have turned clockwise in the pictures)......... The big ends are accessed from below when the sump is off, so I would change the shells as well if you change the con-rods........use STP or Wynns painted on with a brush to keep the shells in place..........it also helps when you first fire it up again. It's a real shame because the burn on the exhaust valve is spot-on. Make sure you replace all the bloody O rings on the barrel / head studs when rebuilding.
It looks it although the picture does distort it slightly due to the 'fish-eye' perspective and the lens being offset to the left but I'm fearing the worst and assuming that it is, and the bush being loose can't be good. Never seen a piston pin so tight in the piston, had to extract it with a big nut/bolt and socket as a spacer which tells me the whole assembly has bent/squashed forwards a little. Funny because other than the idle it ran OK and only marginally down on power with no loud noises other than a slight tappety sound (may have been the piston/valve 'kissing'?) On the plus side the barrel looks fine, cross-hatching still there and no scratches or scrapes.
Shit Shit Shit The only thing I haven't come across from Al's advice is replacing the head studs. I've rebuilt 2 of these (well not that exact engine a LM1000 & a Sporti) and never done that. That said I'd at least check them for straightness and if one is out of kilter replace the lot, given the fault that's occurred. I agree that trying to tell damage like that from a photo is nigh well impossible due to optical distortion. I would also renew the big end bolts and nuts, again I know a few who haven't and their bikes run fine but its not one you want to really leave to chance. Real pity your not in Jockland or near Al both of us would have loved to help. Take a copy of Ropers Engine rebuild I posted that's a really good guide on how to take apart put together these engines, although they are simple. Depending on your pocket it may be time to consider Carillo rods, Wiseco pistons and some tuning, just a thought and also while your at it put on a decent chain tensioner for the timing chain and get Al's triplex chain (I had never heard of them, so shows what I know). Bit of a hit to the pocket but its a great bike Good Luck John
Gutsibits have a few complete engines.........might be cheaper in the long run either for swapping over or for robbing parts from it.
Piston broke... Well not any more; Cleaned up nicely, honed the gudgeon pin hole and it all looks good, rings and bore are OK so it's now just valve and maybe the con-rod, still can't get a definitive measurement to show it's bent and it did run OK and at a good pace for at least 15 miles which you would expect to have gouged the barrel if it was bent...
Test fitted the piston with the barrel tightened down and it looks OK, goes up and down smoothly;. Doesn't seem to be tilted in the cylinder...
Yes, fully expecting the guide and seat to be NG but it would be nice if I didn't need to change the con-rod as everything else is just re-assembly of what I've taken apart, I'd rather not be grunting with the rods under the bike unless I have to...
Don't forget to buy some 'lead additive', unless you intend having the heads and valves converted for unleaded.........
Well..........unless the OP or the previous owner has got a faulty feeler gauge (ie, about 1/2" thick) it has to be valves getting tight in the guides...... ......so that can only mean some effect of unleaded petrol or oil not getting through..... I would be surprised if it was the latter, because the pump is pretty powerful on these engines, so sludge in the oilways shouldn't get a chance to build up. But if this has all happened at the top end with no evidence elsewhere, then I think new valves, valve springs, pushrods and cam followers is the way to go. I ran mine for 1000s of miles and regularly redlined it and maintained high speeds for long distances. The only think I ever discovered when I decided to strip the engine down (and that only happened because I broke a seized inlet manifold stud/bolt in one head).....was that the cam followers (correct name 'tappets') were seriously pitted.
Perhaps it's lack of use that has caused this to happen. No engine likes to be sat idle for too long.
I have doubts about that Fig........I think it is unleaded......... An old acquaintance from when we had TR4s (I sold mine; he kept his)....ran his vehicle very carefully on unleaded for a few weeks........seemed AOK...... ....then he took it to France and it packed up because of really badly burned valves and valve seats...
