Got Parts

[Curt Henry]

After almost 3 months I got a Nikasil cylinder and piston for the 92 R100GS, with the set of head I purchased in June, I have all the major parts I need to get the bike back on the road.

You do not see many R100 Nikasil cylinders on the market.

Here is a good read in ADVRider on dropped valves.

http://www.advrider.com/forums/showthread.php?t=609330

[Armaguidon13]

I've had the exact same "joke" with my G/S
Now the first think I buy with a new air head is BMW valves...

[gspd]

I think the probability of dropping a valve increases exponentially as the guide wears out and gets looser..
If the guide is loose, the valve doesn't slam squarely into the seat each time it closes.
I replace my guides BEFORE it starts to burn oil.
Exhaust guides always become loose enough to warrant replacing between 100,000 -160,000kms.

[enigmaT120]

Do you change them based on miles, or are there symptoms you look for besides smoke?

Edit: Distance, not miles. Sorry Mr. Metric.

[gspd]

Do you change them based on miles, or are there symptoms you look for besides smoke?

The inside of my valve covers and rocker area is as clean as the outside, looks brand new.
I clean it all spotlessly each time I check my valves (5000kms?)
When I start to see brown discoloration regularly re-occurring on the exhaust side,
I know the newness is gone and the end is slowly approaching.
If you catch them before they are shot, the valves and seats will just need a bit of lapping.
The guides are only around $20ea, no big deal.

The cost of refreshing a head greatly diminishes if you do it BEFORE the valves NEED replacing and the seats NEED re-cutting or replacing. (I do not cut valves, I replace them).

[Armaguidon13]

Broken valve at low city speed nothing to help me to understand a danger for the engine, no noise, nothing. This bike wasn't an oil burner