Life expectancy of original valves/valve guides

[bcgilligan]

This previous April, I was prepared to spend some time and $$ on the old 1991 R100GS. I believe it is common practice to rebuild Airhead top ends somewhere around 100,000 miles. The BMW mechanic ran a 'warm' compression test as I watched. Both cylinders on this old gal, at 110,000 miles, showed approx 140psi.

We decided to let her go for another low mileage season on the original valves and valve guides. I spent a few hundred $$ with the shop to replace the timing chain and tensioner, and to do complete carb rebuilds.

It's nearing the end of the season, and the GS now shows nearly 116,000 miles (she shares riding duties with a 2003 Triumph Bonneville). I took the bike on a ride from Cleveland around Lake Superior in July, and she averaged a little better than 40mpg, and used less than a pint of oil over the 2000+ mile ride. As long as I don't park the bike on the sidestand for extended periods, startups are smoke-free (probably indicates worn valve guides?). When I adjusted valves yesterday, the exhausts had tightened up, but only slightly ,,,, they were both at .007, instead of .008. Intakes were spot on. And this was the first time in 20,000 miles or more that I had to do anything but check them.

Since I'm not riding the GS 15-20k miles per year, I may take it season by season on the top end refresh.

Bob

[rocketman]

140 ? wow that's good, my 78 at 160K is now showing around 90 each side! But she still runs great though just not as peppy as before so this winter she's getting a top end job and new bearing on the big end. I'll either hunt up some low mileage replacement heads, and jugs in my mechanic's old shop its a veritable treasure trove of airhead parts last time i looked he had at least 20 sets lying around not counting the 20 more or less complete bikes he has, so finding a set of 1000 cc jugs heads should be easy. Then just do the big end bearings and rings. Then I can have the old ones reworked at my leisure and still have the airhead running over the winter, since its rare that we get more than a few days in a row that I can't ride.

RM

[AntonLargiader]

I bet that when you finally see the condition of the valves and seats, you'll be amazed that the bike ran at all. I pulled the heads off my GS with about 125k miles (estimated) on them and it was just a horrible situation as far as wear goes, on the guides, exhaust valves and exhaust seats. I didn't have time to work on it so I buttoned it back up. Bike runs OK...

[108625]

I believe by the time your '91 was built they pretty much had valve recession under control. It was the early unleaded fuel engines that had the most trouble, like my '81. Between the improved metallurgy and milder tuning that moved the powerband a little lower in the RPM range, it makes sense they should last longer.
I would suggest inspecting your heads and valves this winter, and making an educated judgement call. There are enough threads here about how to look for signs of valve recession, (see "valve clearance trouble" for the most recent).
If you've kept your exhaust valves regularly adjusted, towards the widest clearance specified (which keeps them seated longer, allowing the head to draw away more heat from the valve), they could still be in good shape, regardless of what your odometer indicates.
Really, it's guys like you who are finding out these parts last, for the benefit of everyone else with the same year bike and fewer miles.

Bob

[Polarbear]

My '78 R100/7 I bought new and now at 330000 miles, still has the original valves, timing chain and high compression! Believe it? I find it quite amazing, but its true here on mine. BMW should probably contact me for a look see at this one:). I had some valve adjusting years on this bike, but found a few years ago a gas additive for "valves" that completely stopped the valve adjust to maybe once a year at best. I think I must have an exceptional engine here, beyond my description and its a very strong runner that I ride several times a week still:). I did a 10000 mile loop on her in '06 to the Vermont National Rally. This engine has always used oil from new, but minor consumption at half a quart every 1000 miles or so. I have had so many BMW's now and find the older R100/7 my prise and joy, for obvious reasons. Its treated me very well:). Happy Trails, Randy"Polarbear":usa

[rocketman]

I bet that when you finally see the condition of the valves and seats, you'll be amazed that the bike ran at all. I pulled the heads off my GS with about 125k miles (estimated) on them and it was just a horrible situation as far as wear goes, on the guides, exhaust valves and exhaust seats. I didn't have time to work on it so I buttoned it back up. Bike runs OK...

Hell, I'm amazed that I still run, much less the bike! But whatever I find is OK I'll get her all fixed up in time, I'm pretty much expecting having to do a complete top end replacement.

RM

[sumran]

1991 is a new one in this neighborhood.:whistle Read your post a few times. I did not see anything that would make me take it apart. Compression is good, valve adjustment is normal. Smoke after being on side stand is normal on these bikes. It sounds like it is still running well. I would keep riding.

[amiles]

[QUOTE=Polarbear; I had some valve adjusting years on this bike, but found a few years ago a gas additive for "valves" that completely stopped the valve adjust to maybe once a year at best. Randy"Polarbear":usa[/QUOTE] Mucho snipped

So Randy, What is the magic elixir?

[Polarbear]

CD2, a super concentrated LEAD "substitute", for adding to unleaded gas. Replaces lead protection, reduces exhaust emmsions and works on old Airheads like mine:). A 32 fluid oz. bottle goes forever, up to 320 gallons of treatment. Half oz. treats 5 gallons, 1 ounce for 10 gallons and so on. I put in a half ounce every tankful and I have NO valve issues, since I started using this stuff on my 330000 mile Airhead motor. I've been using it for maybe 50000 miles now:) and and maybe one or two valve adjusts in that time. GOOD. Made in USA...www.cd-2products.com . I have found it sold at my local auto parts store, Kragen Auto Parts. Randy:thumb

[20774]

I've been using ValvTect VT-6000. I can't buy it locally anymore...I used to get it at West Marine which sold the product for old marine engines. I have to order it on-line now. Been working fine for me.

http://www.valvtect.com/products04.asp

[osbornk]

As long as it runs good, leave it alone. You won't gain anything by doing it early.