Early model Tacho with Over-rev warning LED

[Tony Smith]

I promised a couple of days ago to post a picture of a R65 Tach with a warning light - unfortunately I have forgotten which thread the discussion was in - hopefully those interested will find this.
 
As I understand it, the original R^% Tach incorporated an orange LED to tell you that you had just over-revved. My wife's R65/80 had one fitted when new and I seem to recall that the LED did come on, but was only visible at night anyway. The original Tach was crunched in 1994 when I pranged her bike....Anyway, int he process of gathering bits to rebuild the 1985 R65 i bought a couple of Tachs and one of them proved to be an early model.

Here it is in all its glory.


Picture deleted by admin for being excessivly large for the site, please resize and check size after posting .

[Lucky_Lou]

My 79 has the rev light........... Steve Hawkins is an expert on this subject..
Lou

[montmil]

Dude. The Photo Nazis are on your case.

[smiley=dankk2.gif] Forum Moderators!

[Tony Smith]

Picture deleted by admin for being excessivly large for the site, please resize and check size after posting .

Again, whoops - I thought it was under the 3meg limit in the rules. But never mind. Here's a direct link

http://tinyurl.com/orv2tlz

[steve hawkins]

I think the story goes something like this,  Or at least this is my view:

"Back in the day, when the bike was first released they gave one to some 'bike journalists' for an extended test. As the R65 was perceived and marketed as a higher, more freely revving, sportier model, the journalists proceeded to rag it down the autobahn (speed limit free freeway, only to be found in the Father Land) for an excessive amount of time at max revs.  It eventually dropped a valve."

This is where some of the perceived R65 reliability issues originally stemmed from (there is a pun in there, when you read on).

BMW had changed the valve construction to two piece, friction welded on the stem, (?) items that proved to be less than perfect (probably a quality control issue) especially when ragged at high rpm for extended periods...However this construction method for valves was used across the range with R80s and R100s.  However the unreliability was 'all R65' as it was the new model, even though the new larger models still suffered from the same issue.  Some people will insist that since the valves on the larger models were bigger, they were less prone to failure.  I would suggest that if you have a weakness in the valve stem through a poor weld - the stem is gonna fail sooner rather than later - whatever the valve stem size.  Many got away with it, a few did not.  But don't get this premature valve failure mixed up with recommended top end refresh intervals.

BMW fitted an 'rev light' at this time.  I am not sure it was fitted to stop people from over-revving the engine as a result of the above test debacle, by giving them a time to change indication, or whether it was dropped to stop people hanging on the those high revs for extended periods, as "it must be okay as the rev-light is not on".  Whatever, the light disappeared before 1979 was out.

There was also the issue with the spring in the gearbox which appeared at the same time, again it was a problem that 'only the R65' suffered from, as the new model, although the gearboxes are shared across the entire range (?)

Add this to the fact that the R65, as a lower and entry level model, it was looked down upon by many, especially in the US of A (Boxerworks)where bigger is always better, as a bike for girls and those that are not so long in the leg.  When, in fact, it deserved better.

I have now seen the light in the flesh, but it was not until lucky_Lou showed me his!

People may correct my errors if they wish.

Rev. Light

[Ed Miller]

At what rpms did the light come on?

[Lucky_Lou]

At what rpms did the light come on?

Ed 8000 rpm .... nice description Steve

[montmil]

Return of the Rev. Light!

The TrailTech Vapor digital instruments I have installed on the '81 R65 and '78 R100S have a "Shift" and "Rev Limit" programmable feature.

Both bikes are programed for the yellow "Shift" lamp to pop at 4K revs. The "Rev. Light" is set for 7K. With the bikes in sport mode, I frequently go beyond 4K but do hold the engines to the 7K limit. I find those lamps to be quite helpful and they are severe bright in daylight, too.

BTW, the '83 R65 rocks an Acewell. Same features, just more $. Looks cool.

[Julio A.]

Wow, that was a great story! I also have people telling me that the r65 was a bike made for girls, mostly people with r100's though.

Now that you mentioned it, all of the r65's that I encounter in the Philippines are ridden by girls.

[steve hawkins]

Julio, my advice to ride with the R100s and let them know that you can keep up in all situations on the road.  And then pass them.   With the R65 BMW improved the handling over the larger models and gave the bike 'enough' power in a revier package to market it with mild sporting pretentions - even the 79 model.

As far as revs are concerned, to get the maximum speed out of an R65 you need to stay in the lower gears for longer and only change up to top when you get there.  You will not pull max rpm in 5th anyway.  So 5th should be your safety net?  (Discuss)

That said I would have thought it would have all been over by the time you got to 8000rpm.  But I do not have a torque curve graph in front of me, or a rev counter in fact, so I do by feel.

Perhaps someone has a graph to put up...

Rev. light

[steve hawkins]

Here is a power/torque curve from a R65 1981:

http://www.bmbikes.co.uk/photos/specphotos/1981%20r65%20power%20graphs.jpg

It shows that the show is over before 8000 rpm, in fact it would seem that 7000rpm is probably closer to the mark, torque has peaked and bhp/kw is about to.....But the tail off is not as abrupt as it might be?

Rev. light

[Julio A.]

What you told me is exactly what I do!!

The old timers give me advice on when and how to shift up or down. The general consensus was to shift before even reaching 5.5k and shift down before dropping below 3k.

I told them it felt wrong and shifting before 6k felt the bike was just about to build up momentum then abruptly cutting it. My expaination would always be quckly intterrupted by you're over-revving the bike or a down right you're wrong statement.

Sometimes I realize they are just underestimating their own bikes. These airheads can give out so much more than they think.

Oh, and don't worry, I could definitely keep up with r100's. It is with thse newer oilheads and hexheads I just won't try passing.  

[steve hawkins]

But remember this is an old push rod engine and you will get only so much out of it.  Even in R65 guise there is only so much revs it will give you.  Many a prospective racer has over-revved one with usually fatal results (for the engine).

I have an R100 as well, and can appreciate the lazy low down torque.  But I still like my R65.

Rev. light