Videos (linked to youtube)
Illustrations of crankshaft.
Images from the disassembly of the engine.
I was ridning my motorcycle when suddenly a harsh noise appeard from the engine/Gerabox area. I was able to ride the bike but as the noise got worse I decided to stay after some kilometer. Further more. The guys behind me noticed excessive smoke coming out from the Crankcase. The noise had the same frequency stroke as the engine rpm. And was like metal hitting metal. Not by far a noise you would regard in any way driveable.
I. Valves, lifters, rods cylinder heads looked ok. No debree.
2.The pistons rods and crankshaft looked ok. No significant play in crankshaft (axial or radial) The crank turned without problem.
3. When removing the gearbox i noticed wear on the cluth Rod - It has lathed somehow in a distance of 40 mm. Just in front och the oil seal of the rod.
I decided to dismantle the engine at home for further inspection.
Further inspection at home
First I dismantled the heads and found that the right cylinder exhaust valve guide has separeted from the cylinder head (!) I would guess the engine restorer (Sweden) used a guide with too small dimension.
At this time I was pretty sure i found the problem. so i cleaned and reassembled the engine with my spare cylinder heads.
Reassembling the engine went smooth except for the simple task to mount the clutch rod. I used the same rod as it still was usable and put the other clutch parts in the center of the gear box. I had problem to fit them, but after a while all parts seemed to find their right position so I finally could mount the clutch shaft.
As not seen on the video I had some issues to get the engine firing. But when it fired a harse noise reappeard again instantly. (click here for video) Im not sure it was the same noise but at that time I just wanted to give it all up.
After some hours of therapy, I started to dismantle the engine for the third time. I regret not trying to start the engine and try to relocate the noise by using the clutch. A guess is the noise came from area from were the engine andgearbox meets.
I did some more tests on the work bench.
A: Gearbox: I put a drill in the outgoing shaft at low speed to simulate rotation: No problem at all. Easy to shift; 1-4 and reverse. I inspected the primary shaft (clutch side) for wear. Looked ok. No metal debree in oil. No outside wear on the secondary shaft
B: Alternator: Nothing to say here really. Its a denso 500W with an adaptor and gear. Sits tight and with no play
C: Engine: I inspected the gears between Cranckshaft and Camshaft. No wear just smooth rotation and a slight noise whenthe cylinders still were mounted (Click here for video) When dismantling the Camshaft its bearing was tight to the shaft, with no play in any direction. The camshaft itself looked fine without any significant coulors/shadins and no deformation on its cams. The end cup in bronze or brass looked fine and seemed to fit tight.
Again i was looking at the crankshaft. As I have really trouble to get the flywheel off from the crankshaft, (Probably I need to heat up the flywheel to some 200 degrees and then use a heavier machine från a tool shop to separate it) I just could do another optical inspection from outside the crankcase. No noise when turning the rods. No noise or axial play on the rods. (Click here for video). The only thing that I can suggest could to be a problem - is the play on the shaft itself (Click here for video)
No noise no metal debree and somehow it should almost be the wrong path to go - to dismantle the crankshaft - as I dont se or notice anything wrong at all.
I checked the connecting rod bushings for the piston bolts: While the left bushing seems ok the right bushing has too much clearence. The piston rod slides too easy, as the brass bushing seems to be a little worn. (I try to rug it a little or do I need to change the bushing?)
Update: I did go along and removed the flywheel. Unfortunately the gear on the flywheel is hard to dismantle But I be back.
The harse noice - as from the video ... Where does it come from?
Your guess is better than mine. I have really no clue.