Honda NX500 Dominator engine is clicking as typewriter. Help me !!!

[Zlatan2]

I own a 1988 Honda NX 500 Dominator. I have a problem with the engine clinking coming from the top of the engine head. I tried to eliminate the problem but without success. First I replaced the timing chain - it didn't help, then the camshaft and exhaust rocker that was worn - it didn't help, then the decompressor and the spring - it didn't help, the timing chain tensioner - it didn't help. Another expert advised me that it was a piston - I bought a new piston set and had the cylinder cut. That didn't help either. Does anyone here know what the real cause of this clinking is? Here is a link to the video of the started engine:



Thank you so much for any further help.

[hanspumpel]

First of all hello and welcome here.
Have you ever checked the intake manifold? The rubber thingy between carburettor and intake (which Honda calls an isolator)
If that has a small tear at the bottom it makes such a strange noise.
It scared me shitless when I had it and I too thought it came from the cylinder.
Otherwise I would not know after all you swapped about.
Good luck.

[Barniebutsch]

Hallo, willkommen hier im Forum.
Das Geräusch hört sich an wie ein loser bzw. lockerer Ventilsitzring. Im Zylinderkopf. Ventile ausbauen und nachsehen.

[DomiJo]

I guess you have already checked the valve clearance...?

When you had the cylinder head disassembled, did you check the valves and the valve seats? Unfortunately the head tends to crack between the hole for the spark plug and the valve seats sometimes (usually caused by overheating), causing the valve seat ring to drop and then - worst case - jamming the valve.

Welcome, nice bike and I envy you for your kickstarter!

Edit: Sorry, missed the previous post - basically the same

[Zlatan2]

The valves are after overhauls - unfortunately that didn't help either.
I rather suspect an automatic decompressor on the camshaft.

[Nergal]

Is the noise permanent? Or do you just hear it sometimes? With my Domi it happened more often - but not always. In 2014 I have changed many spare parts. Only a completely new camshaft brought about a remedy. It was probably the decompression mechanism.

Greetings

Wolf-Ingo

[DomiJo]

Next thing you might check is the valve clearance of the right exhaust valve. When you rotate the crankshaft in the uppermost position ("T"-mark in the small hole visible) you may already have engaged the autodeco, which slightly lifts the right exhaust valve. If you adjust the clearance in this position it will be too much.

To avoid this you have to rotate the crankshaft (counter-clockwise) until you hear a click and then stop immediately, should be just before "T".

[Zlatan2]

Is the noise permanent? Or do you just hear it sometimes? With my Domi it happened more often - but not always. In 2014 I have changed many spare parts. Only a completely new camshaft brought about a remedy. It was probably the decompression mechanism.

Greetings

Wolf-Ingo

The lower the engine speed, the more regular this knock. When the speed increases above 2000 rpm, knocking stops being heard. I replaced the camshaft and part of the decompressor, including the spring, with a new one. But no change.

[Zlatan2]

Next thing you might check is the valve clearance of the right exhaust valve. When you rotate the crankshaft in the uppermost position ("T"-mark in the small hole visible) you may already have engaged the autodeco, which slightly lifts the right exhaust valve. If you adjust the clearance in this position it will be too much.

To avoid this you have to rotate the crankshaft (counter-clockwise) until you hear a click and then stop immediately, should be just before "T".

I adjusted the exhaust valve together with the others whenever I had the T position set. First the decompressor clicked, then I set it to the T position and then set everything. Was that wrong? The exhaust valve at the decompressor must be set to a position where it sounds like a click - somewhere before the T position?

[Zlatan2]

Solved. I remove autodecompressor.

[kc85]

I hope, you already closed the oil feeding hole in the camshaft.

kc85

[Nergal]

[...] It was probably the decompression mechanism.

Solved. I remove autodecompressor.

Congratulations!