exhaust valve life?-R80G/S

**merlin** · #1 29 May 2003

a question for the high mileage guys and gals
how many miles has your original valves done?
are they good for 100,000 miles if the cylinder compression is good ?
do the later >81on 8mm dia stem valves drop the heads like the earlier bikes?
thanks

**Grant Johnson** · #2 29 May 2003

At 80,000 miles on my 86 G/S my valves only needed a slight grind - everything looked very good. Haven't heard of any problems with later valves.

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Grant Johnson

Seek, and ye shall find.
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One world, Two wheels.
www.HorizonsUnlimited.com

**Bill Shockley** · #3 6 Jun 2003

My 1983 R80ST has the same motor as the G/S. My son has a 1983 G/S. Both of us had worn out valves at around 75K miles. Mine got very bad and would not hold a setting for 2K miles and would go dead tight on exhaust. The bike would refuse to idle until I reset them. The cure was new OEM valves and seats done by a professional. All the R80 motors of that vintage are notorious for valve recession. If you go to the Airheads web site there are several tech articles on the subject. Be warned to replace both the valves and seats together and the best advice is to stay out of the aftermarket for parts. Exspect to spend around $500USD to have the work done. Sorry, but the bike is worth it if you have problems. Bill

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**merlin** · #4 1 Jul 2003

thanks Grant and Bill for your replies,
my G/S is an '86 ,like Grant's ,with the hard lead free valve seats so in "theory "i would not expect it to have valve /seat problems at ~65000 miles
compression is good @130lbs/",engine is nice and quiet,but my exhaust tappet valve clearance had tightened up from .008"to .005"
do the post '81 bm's drop valves -wreck engines like the early models?
do the valves stems stretch ?
i guess it's heads off for a properlook?:-(

**ChrisK** · #5 4 Jul 2003

Hi, the problem with the early BM valves is that they are welded and after a while the heads drop off.I had this happen on a 1981 R100RT at about 76,000 miles, though by it's condition that could well have been 176,000. Not heard of a problem with the later bikes, post 86 with lead free seats but valves don't cost much and if I had a high miler and was off somewhere remote I'd change them any way.

**merlin** · #6 24 Jul 2003

what did we find?
the exhaust valves very worn and the seats worn and lipped,
new valves/guides seats recut....the heads may not drop of the valves now, but thanks
too unleaded petrol new valves are still a service requirement .!!!

**Roboyobo** · #7 1 Aug 2003

I just had an exhaust valve "burn out" on a 60,000 mile '93 R100GS-PD. Before then it was running a bit rough, and had started using more petrol (below 40mpg). The valve had an interesting green plastic like deposit on the underside.

The valve was replaced and the seat reground by a BMW dealer. They also suggested that i use a petrol additive designed for leaded heads, as they suspect that the 2-valve unleaded models may still have problems. It's now running very well, starting without choke, idling correctly, and using less petrol (46mpg).

I am cosidering getting the remaining valves overhauled soon.

Rob