Modern Vespa

Hello everyone,
I have a vespa 200 gt engine overhauled, everything cleaned with cleaner and ultrasonic, then new crankshaft from Malossi installed, new piston rings, the piston and cylinder are old but the hollow grinding still looks very good after 40 k kilometers, the piston is properly installed with arrow down, the piston over the cilinder at TDC I have measured is at 0.2mm without lower gasket, the inlet valves were slightly leaking, I have ground them and checked with the gasoline and compressed air, I have also replaced the valve wedges and valve stem seals. The springs were also installed correctly.

Timing adjusted according to the markings.

I have turned the engine a few times by hand, the timing is correct, the crankshaft can only be turned with slight force but has no axial play.

When I start the engine, it rattles, the more gas, the faster as if something is beating, I have checked with the endoscope and see nothing on the piston, no impacts, the valves go in and out cleanly.

Most of the noise comes from the cylinder head, the cylinder has compression and starts very well and runs at idle without stopping, uphill it pulls quite well.

The cylinder and cylinder head are original, nothing has been machined here.

I have a 0.3mm head gasket, the bottom gasket is taken from the Piaggio set.

Could it be that the cylinder touches the cylinder head slightly by a hundredth at top dead center when it is working.

Would be very grateful if someone could give me some advice.

Nevermind.

I don't know, the mark on the alternator and on the cam was aligned. Malossi ships the crankshaft with his own sprocket, maybe is it here the fault.

I changed the chain tensioner and removed the sparkplug and checked with the endoscope when the piston reaches the TDC (best way to find the TDC on every machine) and checked the timing, it was 1 theet wrong. I corrected it, now seems to be gone.

Now it starts better, it doesn't rattle and i needed to adjust the idle screw, rev was to high), Compression is also here.

On the Piston i don't see any damage, so i think it doesn't have damaged something.

Does some one know why it rattles when it's one theeth off the timing?

I'm glad you sorted it out!

Is it possible the valve was just touching the piston to cause the rattling? Are you sure there was no contact?