From time to time either the small seal inside where the Tacho cable fits goes or the Cam shaft seal which comes through the Tacho drive goes.
1:Cable seal.
PITA to get out.Various methods have been used like small drills etc.Very dangerous as they can ruin the Tacho-drive.
Easy solution.
Remove cable.Spray and clean inside with Carb/Brake cleaner and cotton buds to dry out.Squeeze some Silicone RTV into hole and let dry for 15 mins.Insert cable.Add more RTV around cable if required.I like the Clear RTV for these jobs as it looks less messy especially when wiped off/cleaned up.Doesn't even have to be auto RTV.Bathroom Clear silicone works but Permatex is a great brand as is Hylomar.
USA Ebay Clear silicone RTV
http://www.ebay.com/sch/i.html?_from=R4 ... Categories
UK Ebay Clear silicone RTV.
http://www.ebay.co.uk/sch/i.html?_from= ... Categories
However better than above and more useful for many jobs get some,"Shoe Goo"( I've also used it to repair the splits in my Carb boots)
http://www.ebay.com/sch/i.html?_nkw=sho ... m270.l1313
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Tacho Seal.
Check parts fiche and you will need a Honda Parts supplier normally.
Part number 15 on here,
http://www.cmsnl.com/honda-cx500a-1980e ... t/E07.html
The spring side of these kids of seals Always goes towards the oil(Same as if you were doing the Rear case one or fork seals).
They are easy to fit once you have the Tacho drive off but the Tacho drive can be a PITA to get back into the engine unless you know the trick.Thanks to,"Cathy" on an Austrian forum there is an easy way once you have put the new seal in.
Put a 17mm Socket and wrench on the Crank shaft bolt as per setting tappets
http://www.pdsrecording.site90.com/cxgl ... XGLTappets
and turn the engine clockwise e.g as if your trying to tighten the crank bolt and press the Tacho-drive into the engine as you turn the crank.You should find the Tacho-drive moves into the engine if you use some force.

