Clattery Tach Drive Gear?

[Guest]

Hi guys,

First post so forgive me if I noob anything up. I've been going step by step through the process of getting a 1977 GS550b roadworthy. Last weekend I pulled the valve cover, checked clearances and replaced shims, repacked the tach housing with new oil seal and new o-ring, and tightened it all back up. Engine sounds way better but has developed a new sound... "clackety, clackety, clackety" from the tach housing. I tried pulling the tach housing out to check that everything was oiled and oiled up the tach cable as well. If I bend the tach cable around a bit while the engine is running it affects the "clackety" which suggests that the connection between tach drive and cable is related to the noise. Perhaps the tach drive is loose despite a new OEM oil seal? If I remove the tach cable the noise persists. If I remove the tach drive the noise is gone.

Added: BTW, the tach gauge works just fine despite the noise. The needle does not bounce at all.

I read in a related thread someone suggested it could be that the gasket thickness is not right (I did not use an OEM valve cover gasket in this case) and the tach drive is not seating properly. There was no conclusion to that post other than someone suggesting to use an OEM gasket next time. Before I order a $20 gasket and pull the cover off again does anybody have another idea?

Thanks,

[JE550B]

May have solved the problem. For posterity I will describe below:

Pulled the tach housing from the valve cover again. When I pulled it out I noticed that the tach drive was backed out of the housing by about 1/8" (sorry, 3mm... We all love the metric system). I could push the drive back into the housing to close the gap but it was pretty easy for me to pull/push the drive rod in and out of the housing this 3mm. It felt like the lip of the oil seal inside was just flipping back and forth the limits of it's elasticity. When I was pushing the rod in and out I noticed that the sound of the drive gear hitting the aluminum housing was nearly identical to the noise I heard with the engine running. If that was the cause of the sound then I needed to check the oil seal and see if there was anything I could do that would prevent that 3mm of play.

Hearkening back to the bwringer tutorial I referenced while replacing the tach seal and o-ring I remembered the comment "The seal will end up seated almost flush with the inside of the fitting". When I originally read this I thought it meant that the seal would sit proud of the inside of the fitting a bit. But what if it should actually be seated slightly deeper into the fitting? I was afraid of killing my seal and needing another trip to the dealer but I found a socket head that was exactly the same diameter as the seal and tried tapping the seal in a bit further. Surprisingly, the seal ended up seated about 1-2mm below the surface of the inside of the fitting. When I slide the tach drive rod back into the housing I could no longer easily feel the 3mm play. I inserted the housing back into the valve cover and fired up the engine and the noise was gone!

A ride down to the beach and back will tell if the issue has been fixed permanently. I'll edit this reply later to confirm.

Added: Confirmed. Noise is gone! Oil seal was a super tight fit but give it a few stout raps with the right diameter punch (socket head in my case) and check that it is seated fully, slightly below the rim of the hole you are filling. Also, blew my aftermarket valve cover gasket on the test ride. OEM was a good suggestion from the related posts...