clunking sound under acceleration

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My factory Trixie Combat can cause a fork top out clunk by on off throttle snaps but its obvious from forks and only once not repeated if staying on throttle. Can also get same top out clunk lifting bike hard up by handling bars like to load in trailer or clear something to park. Sometimes its road lumps or limbs or roots crossed. Might be fun to try to audio record it after wrapping up microphone to shield air blast static. Most noise I get from Trixie right now that's tractor like is the head light rattling in shell as missing a few retaining clips i ain't attended to yet. Temporary solution is clear packing tap to hold steadier. Got to replace gaiters and speedo lens so waiting to do it all at once.
 
Bent exhaust push rod, hard to see by turning but the wear marks give it away. head gasket leaking caused the white smoke, re torque would have fixed that, it was due.
 
ugh if these Commandos weren't so cute there be a bounty on em. Now must determine what bent the exht valve, something got under the seat or something hit its head, so look close at chamber-piston surfaces and back into carb slides. Carbon coke could hang up stem in guide but that don't bend it till a piston strikes it or clashes with intake valve. Over rev'd missed shifts are known to do this, so hits rising piston.
 
Or fitting/torquing down the head without using elastic bands to ex. studs trick, flashlight to see all 4 are truly seated in rocker ball ends ?
 
I had what I called a "Tappety sound" coming from the engine when it was under load, I checked the valve clearances which were fine, checked the exhaust headers, they were tight, searched round the head with a stethoscope(could hear it slightly at Idle) and could not pin point the noise. As I was doing this I noticed the R/H exhaust had started to smoke, a few blips of the throttle confirmed all was not well.
Head and Barrells off revealed pistons slapping about in the bore, (My mind must have been somewhere else when I built the engine up) so a +20 rebore and new pistons have cleared the noise away.
New inlet valve stem seals, Thackery washers replaced with soild spacers fitted during the rebuild and I'm now in the process of the running in phase.
I hope this is not your problem but it sound awfully familiar!!!
 
Problem finally solved, I did not realise that the bike had not been run in, apparantly I overheated the pistons leaving material on the bore and then they shrunk, this was causing the clanking sound, so I obtained a second hand set of barrels had them rebored, new EMGO pistons not sure of the brand of rings, cam followers re grind and by now I am getting good at pulling the head off etc so 6 hours later all done and gently running in along with re torque regime, I have done 100 miles and the bike is running and sounding lovely and idling at nicely at 650rpm.
 
Congrates on filling us in on unexpected reason for clunking only on acceleration and a salute to stealing the time to dig in process and replace. My 6 hr jobs like that usually take at least 18.
 
I have to say, I really appreciate you posting your fault diagnosis. It is really helpful and considerate. So often we get great support from forum members in trying to isolate a problem but when we work it out, we move on to the next thing. I'm guilty of this but thanks to you, we know EXACTLY what was the symptom, cause and solution.
Thanks heaps
DKT
 
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