The backfires and popping from the exhaust were down to timing, there was an electronic ignition in it that gave up so I went back to points, did static timing and that seems to have cured those woes. The backfire through the carb was down to me rushing and pure stupidity! Also, theres a new exhaust with gaskets after going onto it but now that its had a few heat cycles I'll tighten everything up again.
You had mentioned that before and to be fair I got sidetracked with timing and clearances ect. I'm going to lift the lid and inspect that next because it sounds like you could be on the money with that plate as the noise is there with the fan belt off.
Being that you think that the rattle is between the fan and the carb, if you remove the top cover of the fan shroud you should see a deflector-plate over the top of the fan that guides a certain amount of 'cooling' air over the cylinder head----check that this isn't loose.
Ive been subconsciously following this thread out of curiosity. And i think you might be onto something.
Delighted to hear that the source of your rattle has been found, but I cannot take all the credit----Dave (Toshi) also suggested that the cause was the deflector plate. Just goes to prove, eventually the combined brain of the Forum will sort these obscure problems.Hobbler was bang on, the deflector plate came out, looks to me that over time due to fatigue it cracked the whole way across.
Fan looks to be intact so I don't think anything fell in and got chewed up and bounced around.
Going to look at the spare 600 engine I have and see what condition it's in and do a transplant. Think it has a dynamo though
We're going in....
Sorry Toshi and thanks! Didn't mean to not include you!
Instead of going through the problems of getting the new 'deflector' welded in (on one side only) why not get captive nuts welded on the INSIDE of all 4 of the securing lugs (of the deflector), bolt it in on the normal 'bolt-on'side, then drill 2 holes in the shroud on the side that the deflector plate is normally welded to, and bolt in that side as well.
To be honest the way it fatigued I don't think there is a way of nutting and bolting it in, the backside that is welded is intact and still there so at least there is a solid surface to butt weld to, the receiver closest to the block that takes a nut on the alternator side also broke, I have this to I'll see if this too can be welded. I think a welding job is the only way forward until I can secure the correct housing
Just a thought, timing chain rattle?
On the plate, on the bolted side there is a reciever nut closest to the engine, that had snapped away. All the damage was confined to the rear section. I got the whole lot spot welded today, they didn't go too mental with the tig as the metal used isn't super and they were afraid they'd just blow holes through it.
