Well done Rob Valdez

[steve hawkins]

107 on the thread reply counter for your question on flywheel lightening......on Boxerworks.

Did it help?

Interesting reading.....

Cheers

[Rob Valdez 79 R65]

I never could have done it without the incessant bickering of my beloved fellow posters...  

 


But yes, I have decided to lighten it.

I swear, those big cc boys have their heads where the sun don't shine, sometimes...

[steve hawkins]

I'd love to be a fly on the wall if/when they all meet in person!

I had my flywheel balanced with the clutch etc, when I had mine done.

I did not remove that much as it was going to get expensive.  Certainly not to the level of some of the pictures I have seen.  I should have taken a picture of mine - but it was not really that impressive and I am sure someone would have piped up that I should have gone the extra mile.....Law of diminishing returns, etc.

However, I did feel it, I fancy, when I rode the bike.  On pick-up and slowing down.

I was pleased.  Still not ridden a post 81 r65, so I have no comparison.  

My 1982 R100, was not that impressive either with its light flywheel and extra power.  I was expecting a massive difference between my R65 and the R100 - but I just did not feel it.  All I can feel is the greater weight of the R100, and its less than sparkling handling.  But perhaps its just the one I got

R100 - Swing arm is back on, although the drive shaft is not yet connected, and the subframe and shocks will be back on this week.  Then I will have a rolling chassis again and can move it about a bit.  things have been a bit slow in the cold weather

[Semper Gumby]

When I have to go get the Main Seal, I will probably have the fly wheel and clutch balanced together but not lightned.  I have heard that the bike has to be tuned to run for a lightened flywheel.  I rather like the "tune" of my R65 as it is.  So be it!   8-)

[steve hawkins]

No it does not have to be tuned.  All you are doing is closing the gap in weight between the heavy flywheel R65 (pre 81) and the light flywheel R65 (post 81).  Not that the heavy R65 flywheel is as heavy as the long stroke R60/75/80/90/100 flywheels - I am led to believe.  The pre 81 flywheel is unique - correct me if I am wrong Rob.  Not sure what the weight difference is though.

You are reducing the inertia of the flywheel, which will allow the engine spin up a little quicker, but also allow the engine to slow a little quicker.  

I used to have the feeling of still being driven into the corners, even though my throttle was closed, as the engine was still spinning.  Yes, I was not driving the R65 particularly well, approaching the corners a little bit hot, but then I built my bike to 'hoon around' in the the twisty's, rather than tour.

The post 81 R65 was not tuned for its lighter flywheel, although it is more powerful that the pre 81.  However I do have a set of post 81 heads on my pre 81 bike - which should have given me 5bhp over the pre 81.

Rob - did you get the Valeo starter with your new engine?  It is significantly lighter that the bosch - and along with nikail bores and pastic airbox, Robs bike will be a good deal lighter than it was.  Most of the weight difference between the pre and post 81 R65's is in the engine and ancilleries.

Rob will have to give us an insight on how his new engine compares with his old one, and how he likes his bike with its weight loss.

Cheers

Steve

[Rob Valdez 79 R65]

No it does not have to be tuned.  All you are doing is closing the gap in weight between the heavy flywheel R65 (pre 81) and the light flywheel R65 (post 81).  Not that the heavy R65 flywheel is as heavy as the long stroke R60/75/80/90/100 flywheels - I am led to believe.  The pre 81 flywheel is unique - correct me if I am wrong Rob.  Not sure what the weight difference is though.

There is a difference, but I am not sure what it is.  I seem to remember the magazines attributing the R65's improved shifting to the lighter flywheel (in '79) as well as the linked shifter mechanism.

Rob - did you get the Valeo starter with your new engine?  It is significantly lighter that the bosch - and along with nikail bores and pastic airbox, Robs bike will be a good deal lighter than it was.  Most of the weight difference between the pre and post 81 R65's is in the engine and ancilleries.

The engine was stripped clean, save for the flywheel (thank God!!!) and the alternator rotor - apparently they couldn't figure that one out.  It was apparent these folks hadn't worked on too many BMW's before.  No starter, no front or starter covers, no airbox (I prefer the look of the clam-shell, thank you).

But that is OK.  This is the 2nd swap I have had to do to this bike.  The original engine died of terminal con-rod twist-in-half.  That engine was wasted!

Rob will have to give us an insight on how his new engine compares with his old one, and how he likes his bike with its weight loss.
Cheers
Steve

I'll do my best.  Spring is a long way away.

[Ed Miller]

But that is OK.  This is the 2nd swap I have had to do to this bike.  The original engine died of terminal con-rod twist-in-half.  That engine was wasted!

Huh?  What kind of turbo did you install, to do that?  

[Rob Valdez 79 R65]

I wish I had saved some of the pieces, or at least taken pictures.  This was around 1993 - pre-digital (makes everything so easy compared to film), an pre-internet, so I wasn't thinking of sharing the memories with anyone.

No turbo - but there was one time (that day? too long ago) that I had it out in the woods.  The "road" I was on kept getting more densely overgrown that off into the woods seemed the quicker route to the "other end".  I finally came to a fallen tree that was too big to cross.  I went to a point where I thought it was low enough, and I managed to get the front wheel over, but then I got stuck.  I shut off the gas and laid it over on it's side, thinking I could just pivot it over the tree.  Well, as the rear went to the good side, the front went back where I didn't want to be.  

I played that game for at least 1/2 hour.  That might have starved the left side enough to cause a problem.  But I was quite close to home when the engine blew, so who knows?

Another thing, carry water when you go off-roading by yourself!

[Altritter]

Steve Hawkins wrote:  <<  between the heavy flywheel R65 (pre 81) and the light flywheel R65 (post 81). >>

Steve, I hate to pick nits, but where does that leave us who have 1981s? Heavy or light?    :-/

One of the joys(?) of having a 1981 is the uncertainty regarding exactly what I have. I've read that BMW made major changes to the R65 in '81 (and I know some of them), but there seem to have been other significant ones in later years. I often feel that I don't know what I don't know.

Something I keep in a very safe place at home for my airhead VW is a slightly wacky book by John Muir (the VW wrench-head, not the conservationist),  How to Keep Your Volkswagen Alive — A Manual of Step by Step Procedures for the Compleat Idiot. In the back of the book is a chapter titled "Mechanic's Information and Data," containing separate year-by-year lists of major changes for Types I (Bug), II (Van), III (Fastback/Squareback/Notchback), and IV (Models 411 and 412). I realize that Noemi Berry and others have tried, and that there are partial lists all around the Internet, but I think there are still informational gaps. (Sigh)

[Ed Miller]

Mine was made in November '80, so it's a pretty early '81 model and has the light flywheel.  A clutch carrier, actually, as it's so light it probably has no real flywheel effect.

[Rob Valdez 79 R65]

Yes Altritter - do not worry, you have the lightest "flywheel" produced for twin-shock airheads.  I know nothing about monos.  But I doubt they went back to a heavy flywheel.

[not-so-fast-ed]

I'm sure you're right on the Mono's, Rob.
I have nothing to compare with, but when I removed my transmission I was surprised by the thickness (lack of actually) of my flywheel.  Ed M has coined the correct phrase in "clutch carrier".

[steve hawkins]

There are many little indicators to tell the difference between a pre and post 81 R65 (LS aside) without resorting to inspecting the clutch carrier/flywheel.

Round brake master cylinder reservoir - 1979/80
Rectangular brake master cylinder reservoir - 1981

Original aluminium airbox - 1970/80
Black rectangular airbox - 1981

Airbox mounted choke lever - 1979/80
Handlebar mounted choke lever - 1981

ATE brakes - 1979/80
Brembo front brakes - 1981 (although ATEs were used till they ran outs o some early 81 bikes have ATE's).

Smooth Light Twin pull throttle - 1979/80
Horrible stiff single pull throttle with splitter - 1981

Rounded smooth final drive housing - 1979/80
External ribbed final drive housing - 1981

30lbs lighter? - 1981 light flywheel, nicasil bores, valeo starter, bigger valve heads.

Any more?

I often seen bikes which have parts that are mixed and matched, my own included, and in the UK, I have regularly seen pre 81's advertised as post 81's - which is a bit naughty :-/

However my 1979 R65, has a later rectangular master cylinder mounted on an earlier twin pull throttle, no airbox, no choke levers, and later brembo's.  It still has the heavyish flywheel, and the older style final drive, but if any bike were to confuse the expert, it would probably be the one!

Steve H

[Rob Valdez 79 R65]

The only reason (that I know of) that I want a rectangular brake reservoir is so I can mount G/S brush guards properly.

[trolle]

The differences between the pre '80 and the post '80 (80-85). The post '85 is quite another motorcycle

Main nozzle pre 140 to post 145
Inlet valve pre 38 to post 40
Interference pipes pre 1 post 2
Engine weight post -2.5 kgs
Clearance between cylinder and piston post 1/100 mm (less than pre) diminishing the rattle of the piston against the cylinder walls
Flywheel post  40%  less weight
Engine housing post reinforced with changed oil ducts demanding a bigger oil pan, oil pan constructed to hinder oilstarvation in extreme situations (like tilting the bike to get it over a tree trunk :-) )
Ignition pre points post electronic Bosch
Top speed pre 177 kmph (110 mph) post 181 kmph (112 mph)
HP pre 45 post 50
Weight with full tank pre ? post 204
Rear wheel fork transverse tube diameter pre 40 mm post 45 mm
Distance between transverse tube bearing and rear wheel bearing post +10 mm
Access to battery is easier on the post '80
Foot rests mounted differently to exclude vibrations
Choker placed at handlebar
Clutch pressure needed at handle pre 85 Newton post 50 Newton
Economy pre 5.5 l per 100 km (2.34 gallons (US) per 100 miles post 6,1 l per 100 km (2.55 gallons per 100 miles)

Pro

Quick and lively engine
Excellent handling
Good sitting position

et cons

Much valve noise
Vibrations around 4500 rpm
Mediocre brakes

All these informations are taken from an article in the German "Motorrad" 21/1980 on the "new" r65

The conclusion of the article:

"The BMW engineers have thus concentrated on enhancing the model. This motorcycle which is more safe driving straight, livelier in handling and whose engine is quicker now really deserves what the former head of development said when asked why the pre '80 r65 only had 45 HP: "It suffices."

From 1982 onwards the r65 was delivered with two discs on the front as far as I know, but this is not verified.

greetings from a grey and relatively warm north 40F