The New And Improved Unofficial R65 Forum V2
General Category => General Announcements => Topic started by: steve hawkins on January 09, 2009, 07:36:36 AM
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Is there anyone here on this forum who has any direct experience of their R65 dropping a valve?
There is a myth that R65's are particularly prone to this type of failure, that is perpetuated by many, especially those with the larger capacity machines on Boxerworks - who tend to scoff at the smaller capacity machines for some reason.
But I cannot remember anyone mentioning that it happened to them on an R65 very recently.
Apparently, in days of yor, in a well publicised magazine test, some bike journo's managed to blow up an R65 by revving the knackers of it over a prolonged period of time. This occurance has been quoted many times since in various publications and on the internet. At the time the failure was blamed on the welded 2 piece valves that were fitted to all airhead models at the time and since the R65 valves are smaller - it stands to reason..... But does it all stack up?
I do seem to recall Joan's Blueberry dropping a valve on a long run some years ago? And I know Rob has had at least one engine......
I am in no doubt that R65s do fail in this way, but probably no more than larger brethren.....But it would be nice to be able to give more modern update on this?
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My 1982 R65 as over 90,000 miles on it. I have not had any valve problems at all. Just resently had a need to pull cylinders for a oil leak. In looking at the heads the valves still look great. Would not have a problem going farther with them. Before I pulled the cylinders I check complression both cyl's were 150 PSI. I also did a differetial test and had no leakage that way.
Don
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I think that part of the perpetuation of this web-theory is due to the fact that the R65/R45 standard valve stems were 7mm diameter, while the bigger bikes' were 8mm, and the thought was that the heat (particularly with the valve seats of the early 80s) would affect them before it would the larger diameter stems. So far (knock wood) I haven't had an issue or seen anyone I know of who has had this issue on any R65.
-Mike
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I just came from Boxerworks so I know what you're talking about. One of the articles mentioned the R80 having the problem too, though why it would and not the R100 is beyond me. I agree with your suspicion that the different writers are quoting each other. Mostly that isn't about the Boxerworks people picking on the R65 though. It's just that R90S always wants to pick on Funholiday.
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My original '79 engine did get destroyed. I never found out the cause, but the result was a connecting rod that looked like someone had grabbed the piston and twisted it until it broke. It was broken in two pieces. The lower piece flailed around inside the crankcase destroying everything it contacted. I don't know if it was the con-rod, but the camshaft was also broken. I wish I had kept the carcass for further study. This was around 1998, before I really got involved on the internet.
But both heads were still serviceable after the fact, AFAIR...
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I believe Joan had a valve let go in Blueberry...
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Someone here had a recent [past year or so] valve job and the ring grooves on the valve end were found to be extremely deformed. A precursor to the valve slipping out of its keeper ["dropping"] for some reason I think it was Sue, There were photos too. Someone have a look, gotta run right at the moment.
rich
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You are right, it was Sue's LRB - though the seats showed alot of nasty wear and the valves were starting to deform, they hadn't reached the failure stage, though the keepers were definitely getting thin. Here's the thread:
http://suraklyn.com/yabb/YaBB.pl?num=1200785184/30
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Just Blueberry for now, then. Sue caught hers in time. I changed mine out because the clearances wouldn't stay put, and they looked ok but Steve said they were starting to stretch. Next time I see him I'll ask him if valve problems are specific to R65s. Mine only had 60,000 miles.
I wonder how many times Chris in BC has had to do engine work on their R65, with high (can't remember how many) miles.
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I'll email Chris in BC Ed and ask. LRB had 87,000 miles on him when the keepers wore to knife edges. Remember Oak told me that we can expect things to need more attention after 80,000 to 85,000 miles on our BMWs. Some bikes make it farther; some less distance.
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What we need to do is to keep things in perspective, really.
I was reading an article in a classic bike magaizine on Triumph 750 parallel twin engines form the late 60/70/80s. The engine rebuilder was saying that if you are very careful with oil changes then a Triumph 750 engine can be made to last as much as 40,000 miles before it needs a full (top and bottom end) rebuild!
When you read things like that, and then think that even an R65 will usually make 80,000 or so before a little light top end work might be in order, then how can you say that the R65 has a reputation for dropping valves?
I pulled the heads on my 1979 R65 at 94000 miles - not because there was specific issue with the valves - and there was nothing obviously wrong with them on inspection - but to take advantage of an available post 81 heads (with extra 5bhp) with valves that had had the unleaded conversion on them. My original heads had a couple broken fins and a stripped exhaust thread. So I think I came out ahead.
Cheers for that.
Steve H
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Chris BC replies that he did the R65 heads at 225,000 km or that's 135K -140k miles. Clearances were starting to close up. He replaced the exhaust valves, seats and springs. They don't run their R65 hard like 80-90mph down a freeway all the time so he says they may get longer life out of the components. Same with me on that point. The higher revving engine with the lighter flywheel and nikasil cylinders seems happy to rev higher anyway he thinks. Chris says other than the slimmer valve stems pretty well everything else on our bikes is similar to the bigger bikes: clutch, gearbox, final drive, electrical. So no real need to carry on the myth! Everyone relax 8-)
I know that Chris's wife just received her 100,000 mile level award from the BMW MOA Long Distance Award program. :o
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Thanks, Sue. Now if we can get that guy from England (with over 400,000 miles on his first R65) to report in. I don't remember seeing a post from him in some time.
Steve, the bottom end (and tranny) on my Triumph were perfect at 80,000 miles, but I sure agree with those mileage intervals for the top end. I don't mean pistons/rings, just valves and guides. It's about $250 to get my Triumph head rebuilt, which I've had done about 3 times in the past 20 years.
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Perhaps the guy was touting for business.
I would be disappointed with a full rebuild at those sort of mileages. Not that I am currently doing them, but I do tend to keep my bikes for a looong time.
My had the r65 for 8 years...
Cheers Ed
Sue,
That puts a different perspective on your failure - much higher mileage than first thought. And it was definately valve seat issues.
Thanks
Steve H
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Sign of impending Exhaust valve failure is the valve clearences closing up. Normally they should not much "move" at all over a normal 4.5-5000 mile service interval. But if the exhaust valves are tighning up .001-.002 every 1000 miles or so you are heading for trouble. I had my heads overhauled at about 70,000 miles and while the intake valves were just fine, the exhaust valves were "sharp enough to shave by".
Now they are nice and quiet!
So sayeth Nathan at Boxerworks.
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So the concensus is that most of these occurances are caused by valve seat issues and not the valves themselves.
Once the valve has been undermined by the recession of the seat - it is only then that we are seeing failures or potential failures.
I feel it is a good idea to pull your heads at a certain mileage to be sure. But where do we draw the line? 60, 70, 80, 90 thousand?
Or do we just say - watch out for closing up of the exhaust valve and leave it at that?
What do you think?
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I think that more frequent/rapid closing up of the valve lash is a pretty good indicator - either of valve seat wear and/or wear at the keeper end and/or plastic deformation of the valve itself. I don't think that the engine would just drop a valve without some indicators appearing first. They key thing is to do regular maintenance checks so that it can be detected in time. I also think running the valve lash at or a bit above BMW spec is best for longevity. Running the clearances as low as some of the guys on B-works I personally think is a recipe for a repair bill. I've gotten too tired of wading through all the BS on B-works lately to even bother posting there anymore.
:(
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I wouldn't have pulled my heads if not for the valve clearances changing. (The leaking push rod seals weren't sufficient motivation by themselves!) The right intake actually kept opening up, don't know what that was about. Like nhmaf, I think watching the clearances is a good diagnostic tool. I wish Joan would let us know how recently she had checked Blueberry's valve clearances, and if they were giving any hint.
Unfortunately something like what happened to Rob (throwing a rod) probably doesn't give any warning.
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I seem to remember reading somewhere that the valves are actually "two-piece" with the head and stem being different metallurgies. Although this is apparently common practice it seemed there was something about the thinner valve stems on the R65 engine that possibly made them more prone to failure at the mating point.
This is what snowbum has to say about BMW exhaust valves in general, he makes no mention of R65 valves:
"The BMW exhaust valve is a TWO-piece, inertia welded, and pricey, but VERY good quality and performance. It is VERY rare for a BMW two-piece exhaust valve to come apart in service...contrary to rumors pushed by other makers of valves."
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That is the point Justin - the R65 has what I feel is an undeserved reputation for dropping valves and the explanation often given was 7mm stem. When it seems not to be that common - or at least no worse than other boxers of a similar age/mileage.
As with all other boxers, only when some other malady, like valve seat recession or excessive wear of the valve guides or keepers, is a factor on some high mileage machines does there seem to be a problem. And we all must remember that the mileages we are talking about, most other bike manufacturers of aircoooled engines could only dream about.
It is an explanation put forward in the early days - that could easily be a 'damage limitation brush off' from the manufacturer. Which, at the time, was replacing 19 inch cast front wheels at a significant cost. This is purely conjecture of course. ;)
It 'weak valve theory' also only affected a certain time period of early production - but the whole range from 1979 onwards is often implicated. It also affected R80's and R100s as well.
It could be an RPM thing also - an R100 will be doing less RPM for a given speed than an R65 on the open road - a worn R100 engine might get away with it for longer as it is not being worked as hard.
It could be that most R65's are not used in the same way as R100s anyway which will also fog the issue. Although there is plenty of overlap - i.e there are plenty of long disance tourers/comuters on R65s as well as those R80/100s?
It has to be said I get really peeved when I hear this from someone who has had little or no experience of the model(R65) and is just repeating, inaccurately in most cases, what he/she has heard or read about weak valves - implying that the R65 is a model to avoid and that any R80/100 would be a better choice - when it is obviously not the case.
I have both. I find the chassis of the R65 are far more competent package that that on the larger models - it handles better - or at least my R65 does! Is it the forks? The swb? lower ride height? Or all three? I find the R65 engine more than adequate for my purposes.
Cheers
Steve H
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YOUR R65 is considerably lighter than an R100, from the looks of it. Do you have any way to weigh it? I bet it's a blast to ride. I think lighter bikes are more fun, unless it's really windy. I don't remember what the weight difference is between a stock R65 and R100. My R65 is all the touring/commuting bike I need.
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I doubt if there is a lot in it. It is essentially the same drive train for an R65 or an R100.
At least when comparing like for like agewise. The big lumps will be similar weights - the only difference being the wieght of the longer barrels and bigger pistons.
And the battery and fuel tank. A post 81 bike will be lighter that a pre 81 though. That much is for sure.
The rest of it is detail. Forks might be lighter? I do not even know if the spoked wheeels are lighter than the cast ones!
Cheers
Steve H
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So the concensus is that most of these occurances are caused by valve seat issues and not the valves themselves.
Once the valve has been undermined by the recession of the seat - it is only then that we are seeing failures or potential failures.
I feel it is a good idea to pull your heads at a certain mileage to be sure. But where do we draw the line? 60, 70, 80, 90 thousand?
Or do we just say - watch out for closing up of the exhaust valve and leave it at that?
What do you think?
The exhaust valve was wearing thin. The seats were just cut to fit the new valves when they were installed.
Yes! Watch for closing valve clearences. Your mileage may vary.