R80/7 Refurb finished almost.

[jackonz]

Well after almost 2 years I have finally got the R80 back on the road, it has been a pleasant and at time frustrating adventure but the results have been worth it, am surprised by a few things first the brakes in that these are not as bad as I had feared, they are the ATE with the under tank master cylinder and everything was refurbished by me and new seals and pads, I paid attention to the correct set up of the twin calipers and spent extra on top of the line pads and it's all come good.
The motor is very pleasant and above 3000rpm there is no vibration at all, am still running standard ignition advance even though I have been advised that the Boyer electronic ignition should be full advance at 4000rpm as I wanted to compare the results first.

On the down side and am asking for advise here is the suspension, rear shocks are stuffed and am thinking Hagon as replacement's and am finding the front quits harsh as well, these still have the standard springs an am told progressive items are the way to go, here in NZ the speed limit is 100kph (62 MPH) max and is being enforced quite hard depending on where you live and our roads are quite bumpy.

So is the bike a disappointment? no not at all as it puts a smile on my face and compared to my other bike (F800 GS) is amazingly easy to work on and easier to get on and off as well, the GS is a bit top heavy for my liking so I think I will sell it.

See attached photo of the results of my efforts.

[melville]

Nice! I like the Hagons that I have on my RS.

Fork wise I think (but don't know for sure) that my bikes have stock springs and they seem fine, with the naked /6 being particularly splooshy. Where I have rebuilt the forks I have used BelRay 7 wt oil but I think I will try 5 wt on the R100/7 as I want that one to be cushier for me and my pillion.

[SteveD]

Looks great. That'll be a blast. The 800 motor is smooooth!

[Rob Frankham]

BMW forks are not known for being harsh...n rather the reverse. Try experimenting with the 'weight' of the fork fluid and make sure they aren't overfilled.

Rob

[barryh]

On the down side and am asking for advise here is the suspension, rear shocks are stuffed and am thinking Hagon as replacement's and am finding the front quits harsh as well, these still have the standard springs an am told progressive items are the way to go,

BMW spring rates did generally increase as the years went but in no case would an aftermarket spring have a lower rate than the stock items although BMW did do a HD spring which was stiffer. You should really be choosing a spring based on measured sag and possibly pre-loading the existing spring to get the required 1/3 laden sag. BMW springs are already sort of progressive in that they are dual rate. In use as long as they don't bottom out under provocation then they should be stiff enough. Oil level and viscosity are worth experimenting with.

[jackonz]

On the down side and am asking for advise here is the suspension, rear shocks are stuffed and am thinking Hagon as replacement's and am finding the front quits harsh as well, these still have the standard springs an am told progressive items are the way to go,

BMW spring rates did generally increase as the years went but in no case would an aftermarket spring have a lower rate than the stock items although BMW did do a HD spring which was stiffer. You should really be choosing a spring based on measured sag and possibly pre-loading the existing spring to get the required 1/3 laden sag. BMW springs are already sort of progressive in that they are dual rate. In use as long as they don't bottom out under provocation then they should be stiff enough. Oil level and viscosity are worth experimenting with.

Thank's Barry, I had real issues here in NZ obtaining fork oil and going through all the manuals I have on the bike no where is there a specification of what viscosity the original oil is, to add to it all the manufactures of fork oil seem to measure it different ways so its a guessing game.

[jackonz]

BMW forks are not known for being harsh...n rather the reverse. Try experimenting with the 'weight' of the fork fluid and make sure they aren't overfilled.

Rob

Hi Rob, no I complacently stripped them and fitted new seals rebound and compression bumpers and new rings in the damper tubes, then filled as per the manual and also measured the level in the forks again as per the manual, am suspecting one of two things fork oil is too heavy but I have no idea what the original oil spec is, or the previous owner had heaver springs fitted, he rode two up with full panniers and tank bag, can't ask him as his memory is not good these days unfortunately.
As for getting the original oil BMW NZ don't stock it and will take at least 13 weeks for it to arrive, so if anyone knows what it is I would be greatfull.

[barryh]

The original BMW fork oil was extremely thin. The nearest I was able to actually buy was the Motul 5W Here's how it compares with some other fork oils It's best to make comparisons at 40 Deg C which is nearer the actual operating temperature of the oil.

Fork oils.PNG (12.75 KiB) Viewed 1467 times

[Rob Frankham]

BMW forks are not known for being harsh...n rather the reverse. Try experimenting with the 'weight' of the fork fluid and make sure they aren't overfilled.

Rob

Hi Rob, no I complacently stripped them and fitted new seals rebound and compression bumpers and new rings in the damper tubes, then filled as per the manual and also measured the level in the forks again as per the manual, am suspecting one of two things fork oil is too heavy but I have no idea what the original oil spec is, or the previous owner had heaver springs fitted, he rode two up with full panniers and tank bag, can't ask him as his memory is not good these days unfortunately.
As for getting the original oil BMW NZ don't stock it and will take at least 13 weeks for it to arrive, so if anyone knows what it is I would be greatfull.

It's worth remembering that the SAE 'weight' of fork oil is not a good measure of how it will perform in use. Back in the day, BMW didn't produce their own oils and they issued a list of suitable oils from various oil manufacturers. Very few of these quited SAE ratings and those that were quoted varied in 'weight' between SAE 5 and 10. Needless to say, very few if any of these oils are available these days. My best advice would be to pick a make of oil and fill with some at - say - SAE 7.5. Ride the bike and see how it goes. If the ride still seems to harsh, swap to SAE 5 from the same manufacturer. If it is too soft, go to SAE 10. By sticking to one manufacturer, you can be pretty sure that SAE5 will be lighter than SAE 7.5 and SAE 7.5 will be lighter than SAE 10. If you swap manufacturers you can't.

The opnly other thing that hasn't been mentioned (and excuse me if I'm teaching grandma) is to check the fork alignment. If they're even slightly out of line, the result will be a harsh ride.

Rob

[jackonz]

BMW forks are not known for being harsh...n rather the reverse. Try experimenting with the 'weight' of the fork fluid and make sure they aren't overfilled.

Rob

Hi Rob, no I complacently stripped them and fitted new seals rebound and compression bumpers and new rings in the damper tubes, then filled as per the manual and also measured the level in the forks again as per the manual, am suspecting one of two things fork oil is too heavy but I have no idea what the original oil spec is, or the previous owner had heaver springs fitted, he rode two up with full panniers and tank bag, can't ask him as his memory is not good these days unfortunately.
As for getting the original oil BMW NZ don't stock it and will take at least 13 weeks for it to arrive, so if anyone knows what it is I would be greatfull.

It's worth remembering that the SAE 'weight' of fork oil is not a good measure of how it will perform in use. Back in the day, BMW didn't produce their own oils and they issued a list of suitable oils from various oil manufacturers. Very few of these quited SAE ratings and those that were quoted varied in 'weight' between SAE 5 and 10. Needless to say, very few if any of these oils are available these days. My best advice would be to pick a make of oil and fill with some at - say - SAE 7.5. Ride the bike and see how it goes. If the ride still seems to harsh, swap to SAE 5 from the same manufacturer. If it is too soft, go to SAE 10. By sticking to one manufacturer, you can be pretty sure that SAE5 will be lighter than SAE 7.5 and SAE 7.5 will be lighter than SAE 10. If you swap manufacturers you can't.

The opnly other thing that hasn't been mentioned (and excuse me if I'm teaching grandma) is to check the fork alignment. If they're even slightly out of line, the result will be a harsh ride.

Rob

Hi Rob,

Agreed and that is the plan going forward, there is only one brand of fork oil in NZ that I can get that has more than one weight of oil available, this is all down to us being a small population and therefore a small market to sell to but has the advantage here in the south island of fewer vehicles on the road.

As for fork alignment yes it was one of the things i paid close attention to during the rebuild and spent a few hours getting it just so.

Do you have a preference for brand of rear shock absorber by chance?

Phil