R100 right side clack

[salty]

Thanks for the replies.
Let's travel to the past. When the bike first made the noise I had been in traffic for 30 mins and it was wafting heat at me for sure.. I wouldn't say overheating though - the heads have never felt red hot.
I put it on the side stand to open the gate, so it was idling for maybe 30 secs tops when it made the noise. BM motorcycles are bigtime airhead mechanics and I was surprised when they adjusted the valve with no explanation to how it could happen suddenly. When I rang Chris yesterday he suggested then that the valve might have pounded it's way out of the seat.

Tell you what - I'll pull it apart this weekend and tell you what I find.

Oh, and as a side note, I discovered the left carb mount loose and most likely sucking air which is a shame as probably why it ran so bad on the Hume sucking air and no doubt leaning mixture.

[ME 109]

Whatever you find Salty, when you get it fixed we can go and embarrass some sports bikes up in the hills.
I got another one just last sunday. I shouldn't do it really, probably soul destroying for the poor bastards.

[Airbear]

Yeah Jeff, it's a cruel activity. Those poor blokes on their 4 cylinder fuel-injected crotch rockets probably have to go and get their dignities repaired after failing to keep up with a 35 year old airhead.

[salty]

Here it is. Full destruction of valve seat. So, it started with a misdiagnosis.. I'm guessing the valve adjustment held it together. When I went to start it the slow valve movement probably caused the pieces to fall out and then have a party on the piston and head.
So. I guess I could try and find a 2nd hand cyl piston and a pair of heads... or I could save and get the 1100cc big bore kit from flatracer.. anyone tried that?

[ME 109]

That's a lot of crunching from one hit of the piston! Maybe there were two or three revolutions before it locked up?
I wonder if the seat was cracked but remained in place until you started it, and the 1/2 or however many pieces fell out, or whether the intact seat came out, got caught under the valve head and was broken up by the piston hitting the valve and seat? Can't see any damage on the piston crown opposite the exhaust valve so maybe the seat was already cracked and fell out as you say.
I haven't seen a broken seat before.
You may be able to salvage the head and barrel but I think the piston ring lands may have suffered as well as punching the piston crown out of round at the impact area.
Check the barrel for scores or a gouge, you might be lucky.

I think it's an expensive road to go down, the 1100 route. They haven't been around long enough to get good feedback, I don't think. Are you referring to the Edelweiss Motorsport parts? There's also the 1070 kit from Siebenrock.
A few options out there for upgrades, if you want to splash the cash. Our dollar won't help much at the moment.

Motobins have a barrel and piston kit for about 1,650 Au.

I wonder if the alloy housing on the end of the starter motor has cracked or if the bendix starter drive broke?
Maybe damage to the ring gear/flywheel teeth from the starter.

Spose you'd have the barrel off by now?

[salty]

After I saw the damage I put her back together for the day. I reckon the bits fell out = then when I did the jump starts it caused the main damage. Seems like the bore is ok because the piston just jammed there >> could only see hone marks.

Yeah I think I'll probably try to find matching barrels, pistons and a pair of heads.

I saw on gumtree a pair of heads from a 94 GS 1000. Will they fit?

[SteveD]

They'll fit, but will they be different? edit: see below. They won't fit, they are different.
Try The Fireman in Carrum Downs...he might have what you need?

[ME 109]

94 barrels won't fit without machining the bottom of the barrel, apparently. Or chamfering the edges of the engine case where the barrel spigot fits in. There's not a lot of material to remove but is it worth it......... I recently became the owner of some 92 barrels and pistons from ebay Germany but the bastards won't fit my 81. If the barrels were in tip top condition I'd consider machining them to suit, but I think I'll just on sell them and wait for earlier barrels or save up for a kit like the Motobins one I mentioned.
I'm not sure of what year the barrel base changed but i think it would be 85 with the introduction of the mono.
If your barrel isn't marked I'd look at using it again.

The head itself could be ok with that damage cleaned up and with a new seat, but my concern is that once seats start coming out and new oversize seats are put in, they can come out again if not done by an airhead expert. The broken seat may have been a replacement seat and the seat pocket may have been worked on.....who knows.
If you think the head is salvageable, you could send the pair to a 'guru' for appraisal. Several years ago I sent my heads to Hamish engineering in Perth for a rebuild. I've thrashed the shit out of them since then and put maybe 70-80,000 k's on them.
Second hand heads can be just as much of a gamble. Depends on whether you want to keep the bike for a few years. If you do, at this point I'd get the heads rebuilt and even send s/hand heads to be rebuilt.
I think the later heads 85> will fit 81 bikes ok.
Fix her up man, we can go sports bike hunting. The hills are lousy with them.

Edit, If you have good honing in otherwise unmarked barrels, I'd want to hang on to them.

[salty]

So I've located 93 barrels and heads from a GSPD, but guessing these won't fit. I'd probably still be keen on using the Pistons, but question is, will the late heads bolt onto the early barrels?

[ME 109]

So I've located 93 barrels and heads from a GSPD, but guessing these won't fit. I'd probably still be keen on using the Pistons, but question is, will the late heads bolt onto the early barrels?

I was told by an airhead mechanic that the later barrels won't fit circa 81. Unfortunately I don't have both types of barrel to view the difference.
I believe the head will fit although the rockers are different, which is ok. Later rockers used shims to set rocker axial play.
Check that piston really well for damage. Are you sure the barrel is toast?