Plug oiling up

[Jinks]

The spark plug on no1on my '81 gs 850 is oiling up, I suspect the guide stem seal, how do I test ?.

[Brendan W]

Exhaust would be the most likely?
If you remove the header from #1, get the plugs out and turn the motor over from the ignition pick up side you should be able to get a view of the valve head and stem.

[zed1015]

Leave the bike stood overnight then inspect the valves via the inlet and exhaust ports for evidence of oil and also view down the plug hole into the cylinder..
The exhaust is usually easier to spot as the burnt oil build up shows as excess carbon and a wet guide .
The inlet gets washed by the inlet charge.
Also plug fouling on first start when stood overnight and puffs of smoke from the exhaust on start up and acceleration are a big indicator.
You will need to replace them all .

[Suzukian]

A lot of motorcycles do not run exhaust valve stem seals, as there is not suction there. Some do, but a lot don't. If your bike has them, replaced them when worm, if they don't, without a ring to hold them in, they won't stay in place. I guess if you were putting in new valve guides, it would be easy enough to make a grove and snap a Vitron seal, but some of these valves require the tiny bit of oil that gets down there for lubrication. On the intake side, the gasoline lubricates the valve stem.

[bitzz]

If the bike puts out white smoke on heavy deceleration (engine braking) you probably need valve seals

[Rob S.]

There is a style of plug (wire thin) that resists fouling in oil. Rode my Z1 like that for quite some time.