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Old 03-30-2014, 03:21 PM   #1
Jim K in PA OP
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Joined: Mar 2011
Location: Pocono Mountains, PA
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1975 R90S hack - "Olga"

Some of you may have seen my "Anyone know this setup" thread. Based on the great feedback from the crowd here, my wife and I pulled the trigger on the money gun and "Olga" is now ensconced comfortably in my barn here in northeastern PA. I'll summarize the details, post a few pictures, and outline a few areas of attention that I may need assistance with. This will be an ongoing thread for me to log my progress, successes, and failures as I delve into the world of sidecars.

A few pictures. The sellers pics are in the linked thread above, as are some shots on the trailer after getting home. A few more in the barn:







The rear suspension has been converted to a monoshock, with a nearly new YSS Z366TRL shock installed in November of 2012.



The rear suspension is VERY soft, in my opinion, and I am going to adjust the pre-load on the spring. I am also going to re-install it with the main body end at the frame instead of the swingarm. I believe it is upside down at the moment, and it has very little compression damping. Rebound adjustment is at max, and I think that is all the damping it is giving.

As seen in the other thread, it has a leading link front suspension, with a pair of Koni shocks with progressive rate springs. It is rather stiff, but seems to work well. I am not familiar with these shocks, but they both have these markings on the springs:



It also has a pair of non-BMW (at least non-ATE swing type) brake calipers on custom brackets. Anyone know what these are? The pads are in decent nick, but I should probably identify what pads are used and have a spare set on-hand. They stop the rig VERY well.



The first issue I came across is related to the front brake lines. It has a handlebar mounted front master cylinder, but I do not know what from. It does have a splitter, and the upper line from the master is being beaten up by the Avon faring.





When this rig was converted for hack duty, there was quite a lot of effort put into strengthening the stock R90S frame. There are diagonals in two key locations at the rear, as well as gussets on the forward side of the tubes at the swingarm mounts.







The original Dellorto carbs seem to need some attention, as it will not idle without the enrichers on nearly full for a VERY long time, and even then the idle is quite low. When at speed it hauls ass, but it tends to stall when coming to a stop. It also pops through the carbs once in a while, so I will check the valve clearances and the timing to make sure all is proper there.

I also need to check out the starter switch, starter relay, and wiring thereto, as it has a very intermittent starter. It cranks like crazy with the car battery conversion (battery in the cargo box), but it will just stop cranking for no apparent reason.

Well, that is enough for a first post in this thread, I think. I will be traveling this week (work), so may or may not post up after Tuesday, as I will be in Paris until Thursday.

Thanks for watching!
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1979 BMW R100T - Otto - Returned to the road - 5/12/11
1975 BMW R90S Hack - Olga - Olga's story - adopted 3/22/14
Viktor - Coming to a thread near you - eventually
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Old 03-30-2014, 03:38 PM   #2
davebig
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After looking at your other thread Olga has fallen into the perfect realtionship It'll be a good deal for both of you.DB
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Old 03-30-2014, 04:43 PM   #3
Poacher Bob
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Old 03-31-2014, 04:53 AM   #4
Carl Childers
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Dellorto carburetors are great for performance oriented machines but can be incredibly fiddley to dial in perfectly for every day use on more utilitarian machines, it's part science and part black magic to get them spot on. Consider putting yours on display in your shop and replacing them with a set of Bing's or Mikuni's for every day duty on Olga.

BTW great rig! You lucky dog.
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Old 03-31-2014, 04:57 AM   #5
Wolfgang55
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I see a future here

A near 40 yr old scoot is going to get an up lift. I like the hacks design.
Have any pictures of its inside ?

I am going to stay clued to your progress.
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Old 03-31-2014, 05:19 AM   #6
FR700
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Quote:
Originally Posted by Jim K in PA View Post


It also has a pair of non-BMW (at least non-ATE swing type) brake calipers on custom brackets. Anyone know what these are? The pads are in decent nick, but I should probably identify what pads are used and have a spare set on-hand. They stop the rig VERY well.



The first issue I came across is related to the front brake lines. It has a handlebar mounted front master cylinder, but I do not know what from. It does have a splitter, and the upper line from the master is being beaten up by the Avon faring.


Thanks for watching!



The calipers , appear, to be from a 1980's honda 750/4 that have had a visit from a grinder in order to clear the rim.

The pic of the master cylinder is too vague at that distance to identify. The splitter is standard Japanese fare and likely came from the donor bike that gave up the calipers.

CB 750 F rear caliper.



Front caliper.

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Old 03-31-2014, 05:56 AM   #7
Dan Alexander
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Old 03-31-2014, 07:55 AM   #8
Jim K in PA OP
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Carl - I am tempted to swap the Dells for Bings, but the masochist in me wants to try and make them work.

Wolfgang - I will take some more detailed pictures of the cargo box when I get back home. It is a simple box, with no interior fit up other than the battery box.

FR700 - those calipers sure look similar, which hopefully makes finding parts (seals, pistons, pads, etc.) a simple task. The wheels are 15 inchers, so I am not surprised they got a haircut.
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Jim K in PA
1979 BMW R100T - Otto - Returned to the road - 5/12/11
1975 BMW R90S Hack - Olga - Olga's story - adopted 3/22/14
Viktor - Coming to a thread near you - eventually
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Old 03-31-2014, 10:07 AM   #9
NitroMax
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Great looking hack, love the big tank and the Avon fairing !
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Old 04-06-2014, 04:35 PM   #10
Jim K in PA OP
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Rear suspension adressed

Thanks for the kinds words.

I was traveling for work this past week (to Paris and back from Philly, in three days - ugh) so did not have much time to do anything until Saturday afternoon. I decided to pull the tank and seat, and swap that rear shock around. As I mentioned above, the rear suspension would sag substantially when I plunked my 175# arse in the seat, and there did not appear to be any compression damping. Rebound damping was marginal and that was with the adjuster maxed.

I removed the shock and before I swapped it end for end, I put it in the vice and added some pre-load to the spring. The collar was run up about 0.25" past where I found it. I re-installed it with the body at the frame end, and I had to rotate it 180 degrees to clear the center tube.

The result? Immediate and substantial improvement. Initial sag is now minimal; compression damping has returned; and I had to back the rebound adjustment way back from max (at ~50% now).

I did not have a chance to ride it today, as I got my '79 out of storage and rode that for a good portion of this afternoon. I took a ride with my son also, as he is a new rider and we are getting familiar with the bike and riding (he is on a 2002 Buell P3).

Well, that was a worthwhile effort, and cost nothing to accomplish the upgrade!
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Jim K in PA
1979 BMW R100T - Otto - Returned to the road - 5/12/11
1975 BMW R90S Hack - Olga - Olga's story - adopted 3/22/14
Viktor - Coming to a thread near you - eventually
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Old 04-06-2014, 05:18 PM   #11
Dan Alexander
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Funny someone who owned this and seemed to know bikes would install the shock upside down.
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Beemers Past and Present: 74 R90S, 77 R100RS, 85 K100RS, 2x 87 K100RS, 96 R1100GS (getting hacked), 99 R1100S, 2002 R1150GS, 2005 F650 Dakar
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Old 04-06-2014, 05:23 PM   #12
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Not that unusual Dan, mine came with it upside down and I see another long term member here with the same bike and shock who's is the same
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Old 04-06-2014, 05:48 PM   #13
Strong Bad
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Back in the mid 70's in Motocross and Offroad, running the rear shocks "up-side-down" was common practice just prior to the lay the top of the shock forward craz, all of which was prior to Mono shocks of course.

BTW, it is a VERY cool rig and it appears that it truly deserves to be brought back to life!
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Old 04-07-2014, 04:59 AM   #14
Dan Alexander
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Really?

If it didn't work properly and had no rebound damping what the heck was the reason

And totally agree on the cool factor.
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Beemers Past and Present: 74 R90S, 77 R100RS, 85 K100RS, 2x 87 K100RS, 96 R1100GS (getting hacked), 99 R1100S, 2002 R1150GS, 2005 F650 Dakar
Plus the occasional Triumph, BSA, Yamaha, Honda, Suzuki and KTM but who's counting
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Old 04-07-2014, 06:25 AM   #15
Jim K in PA OP
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I will not cast any aspersions toward the P.O. or anyone else regarding the orientation of THIS particular shock, since the P.O. accidentally mounted it upside down and told me so when I went to look at the bike before purchase. He was quite clear that the vendor of the shock told him it was upside down when shown a picture of the installation. Since the rig was only ridden about 600 miles since November of 2012, I doubt the orientation of the shock was something that he considered a priority. He has 5 other sidecar rigs, plus about as many solo bikes.

I have seen twin shock airheads with expensive Ohlins shocks mounted upside down. Clearly the owners are trying to either follow a fad or impart some sort of "inside knowledge" about the hot setup for suspensions.
however, adding un-sprung weight does NOT improve the suspension dynamics of any vehicle.

The YSS as I have it mounted now has moved the heavier end of the shock to the frame, but I doubt that will make any real difference in the dynamics of the rear suspension. Allowing the ports to control oil flow and perform damping certainly will!
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1979 BMW R100T - Otto - Returned to the road - 5/12/11
1975 BMW R90S Hack - Olga - Olga's story - adopted 3/22/14
Viktor - Coming to a thread near you - eventually
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