Carbon Fouling

[Anthony Liss]

During the resurection process of this T120V I've encountered corbon fouling.  I noticed this on the old plugs so the problem existed when the bike was last run in '94.  After changing plugs to NGKs I adjusted the carbs, ie increased air mixture and balanced them to no avail.  I notice a fair amount of oil seaping under the points, is there a seal in there that needs replaceing or is it normal to get oil in there to keep things lubricated?  I don't think I'm getting a strong spark so I'm wondering if I should look to the condenser, coils wires or what.  Is there a way to bench test these components?  The wires look good.  The bike starts and runs well until the carbon builds and she starts to miss.  Maybe this is pointing to a carborator re-build.  Any advice would be welcome.

[TBS]

There is an oil seal behind the points, so you will need a contact breaker cam extractor tool and a pilot for the contact breaker oil seal when replacing the timing cover. I would automatically replace both crankshaft and points oil seals, they are both the same part number. VERY IMPORTANT replace them the way they came out, which should be crankshaft metal spring inwards, towards cover (so you can't see it), points seal, metal spring towards engine (so you can't see it from the points)
Regarding carbon this is due to running rich, that is caused by modern day fuels, so I would check your throttle valve cutaway and go up 1/2 to 1 size eg number 3 to 3.5 or 4.
Sparks, I would check all terminals and rough up with emery. Make sure you have good earths, this is most important for lights and sparks.

[Anthony]

I suspect the rings might be gummed up on the left side causing blow by which is showing black on the plugs.  I'm seeing smoke out the left pipe but not the right.  Is it possible to do a ring job without tearing the head apart to get at them?  How simple can I make this job or is this not the proper attitude to approach this situation?  Running the bike tonight without the points cover on I didn't see much oil seeping in like before.  Is it possible for the rings to free them selves up through usage?  Wishful thinking I suppose.  As for the carborator cut outs how does one know which size they are to start with?  I didn't see any no. on them when I had them apart for cleaning.

[TBS]

I would replace all the seals throughout the engine as they would have become brittle with age and non use. The smoke you refer to could well be condensation, however the only way to check whether your compression is reasonable is to get the engine to running temperature and do a compression test. Only then can you suspect worn bore, rings, or valve seating problem. Throttle valve numbers are situated on the underside of the valve, and are individually stamped with a single number. Discount the MB and 928 number, it's the single number on it's own which shows the size..
Hugh
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