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Old 05-10-2013, 12:18 AM   #1
lagfish OP
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Joined: May 2013
Location: Ann Arbor, MI
Oddometer: 22
R90/6 scrambler build

Hi All ,
Last year I acquired a 1974 R90/6 with 70k miles on it for my second bike and rode it almost everyday for 6 months. Even though I really enjoyed the bike and there weren't' any issues with it, it's not in the best condition. The frame has rust spots on it which I've painted with a brush but looks like crap when you look close, the engine is full of grime from the leaking seals, the seat cover had several cracks in it, and the paint on the tank is cracking around the filling hole because the gasket is shot.

I wanted something nicer, unique to my personal tastes, but still keeping the classic style of the R90/6 that I fell in love with. I don't really enjoy the cafe look and think that it has been overdone. I like the scrambler look and would have some practical uses for the dual sport tires since I plan to do some trips off the beaten path. The goal was to make it into a classic GS. I do have pretty good fabrication skills, so I will be doing most of the modifications myself. It will save some money, plus I think the more you put into it the more you will "know" your bike and love riding it.

I made some sketches on paper then photoshopped the following for my build concept:


I will be doing a complete frame-off resto-mod with the following major things:

-Snowflake alloy front and rear wheels (was too lazy to photoshop the rear wheel) from an R100
-Dual front brakes with ATE calipers. Since a /6 right fork slider with mounts for the brake caliper is pretty rare, I will be buying another left fork slider and modifying it to take a caliper on the right side. I will keep the master cylinder under the tank but modify it so it has two outputs for the dual caliipers
-Shortened subframe to give it a sportier look. I will fabricate another frame (sub-subframe) that will bolt onto the sub-frame. The sub-subframe will have aluminum side bags attached to it.
-Custom seat and cover
-New paint on tank
-Scrambler type handlebars and newer controls
-Powdercoat fork sliders, wheels, frame, and sub-frame.
-Raised front fender from an R100, chopped rear fender from undecided yet
-custom headers or at least new mufflers
-/5 headlamp (expensive!!) or new and much smaller speedometer

I think it's a pretty ambitious project, but I'm young and don't have a family so I'm pretty motivated and have lots of time to work on it. Hopefully you guys can provide some encouragement as well.

Wish me luck!

lagfish screwed with this post 05-10-2013 at 12:45 AM
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Old 05-10-2013, 12:32 AM   #2
lagfish OP
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Night #1

First an introduction to my workspace. It's a corner of a storage unit that I've rented. For shelving, I've stacked some cinder blocks and used OSB for the shelves. I think it was less than $20 for materials. While I would like to have a nice garage to work in for this restoration, I don't think it's necessary and you've got to work with what you've got.

Here is a photo showing my little corner and the bike with a large tank I picked up. It's a lot more dented than I anticipated, so I will probably just sell it and get another one that's not as dented. I also took the carbs, cylindes/heads, and oil pan off on a previous day.


Here's what the bike looked like by the end of the night.


One thing I anticipate that will be a major PITA will be reconnecting all the wires back tightly into the headlamp.

Next time the engine will come out and the frames, front end, and wheels will be separated. I hope you guys will enjoy this build!
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Old 05-10-2013, 12:56 AM   #3
Houseoffubar
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Looks like a good candidate! Be sure to seal up that crankcase, before you get debris in it!
Have fun

BTW, check out Elite-less's build. He built two beautiful bikes in a space smaller than what you are working with.
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Old 05-10-2013, 11:56 AM   #4
apt13
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can't wait to see the progress!
i assume you've seen the last few CRD bikes? They have this look you are after nailed down pretty good. might be nice for the extra inspiration if you haven't seen them.

http://www.caferacerdreams.com.es/mo...-r100-7-crd-27

http://www.caferacerdreams.com.es/mo...-the-challenge

http://www.caferacerdreams.com.es/mo...d-17-ruby-ring
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Old 05-10-2013, 04:46 PM   #5
lagfish OP
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Quote:
Originally Posted by apt13 View Post
can't wait to see the progress!
i assume you've seen the last few CRD bikes? They have this look you are after nailed down pretty good. might be nice for the extra inspiration if you haven't seen them.

http://www.caferacerdreams.com.es/mo...-r100-7-crd-27

http://www.caferacerdreams.com.es/mo...-the-challenge

http://www.caferacerdreams.com.es/mo...d-17-ruby-ring
Thanks!
I have in fact seen the CRD bikes, and was the base for my photoshopped image. The one thing I wanted to change about their scramblers was that I think the typical flat scrambler seat does not work well with the large BMW tanks. There is a large step going up from the seat to the tank and looks weird to me. Maybe changing it to a curved seat doesn't make a true scrambler, but I am just trying to build the bike that looks the best to me!
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Old 05-13-2013, 11:26 PM   #6
lagfish OP
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Night #2

Couldn't work on the bike over the weekend because I sprained my neck. But today I made some good progress. I was able to take the swing arm, subframe, and loosen the front end with the tools I modified:

BTW, the two large nuts that keep the front end in place were probably the tightest non-seized nuts I've ever encountered.


Here's what she looked like by the end of the night:



Next time the engine will come off.

Are there any simple things I should fix/replace now that I got the engine and transmission apart? The engine was running fine, and the transmission seemed ok, aside from the fact that it would slip into neutral sometimes between gears. The engine has ~75kmiles on it.
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Old 05-14-2013, 07:51 AM   #7
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While the cylinders and heads are off, I would likely have the heads done (all new valves, new exhaust guides, new springs). If the seats are the originals, I would have them replaced with hard seats if they look like they are recessing.

I would likely re-use the cylinders but have them honed. First oversize rings and file them down to .010" end gap and re-use the pistons.

I wouldn't mess with the transmission unless you feel really strongly about it. If you decide to do the transmission, I'd replace all the bearings, the shifter pawl spring and all the seals.

Just an opinion.
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Old 05-14-2013, 09:54 AM   #8
Roach Carver
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Looking good!

I am sure you know that those rims have a certain value being Lester mags? You could sell/ trade those for parts if you were so inclined
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Old 05-14-2013, 02:09 PM   #9
SERE Nate
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Looking forward to watching this build.
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Old 05-14-2013, 05:18 PM   #10
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Given a choice I wouldn't go for snowflake wheels on a scrambler if you are actually going to use it on dirt roads. I've destroyed 2 sets of these just from small (fist size) rocks on dirt roads. This includes a 4" long split in a front rim.
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Old 05-14-2013, 06:09 PM   #11
lagfish OP
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Quote:
Originally Posted by Rockman View Post
Given a choice I wouldn't go for snowflake wheels on a scrambler if you are actually going to use it on dirt roads. I've destroyed 2 sets of these just from small (fist size) rocks on dirt roads. This includes a 4" long split in a front rim.
My original plan was to use them because I though they looked really cool. But the more I looked at it the more they didn't look right on a scrambler. I think they draw too much attention to the wheels/tires, which already look pretty busy because of the knobby tires. I guess from a practical view, spoked wheels are also better. BTW, does anyone have a pair of spoked wheels they want to sell / trade for Lesters?
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Old 05-14-2013, 06:14 PM   #12
lagfish OP
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Quote:
Originally Posted by Pokie View Post
While the cylinders and heads are off, I would likely have the heads done (all new valves, new exhaust guides, new springs). If the seats are the originals, I would have them replaced with hard seats if they look like they are recessing.

I would likely re-use the cylinders but have them honed. First oversize rings and file them down to .010" end gap and re-use the pistons.

I wouldn't mess with the transmission unless you feel really strongly about it. If you decide to do the transmission, I'd replace all the bearings, the shifter pawl spring and all the seals.

Just an opinion.
Gotcha. Is it recommended practice to use oversize rings with a standard size cylinder? When I was making a model sized engine, I machined the rings so that they are the exact same diameter as the cylinder, then split and spread them so that they provide a circumferential sealing force on the cylinder but once they are inside the cylinder there is pretty much an even pressure all the way around the rings.
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Old 05-21-2013, 12:15 AM   #13
lagfish OP
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Third night

I managed to get the engine, wheels, and forks off today. I've also been taking apart and cleaning the carbs.

The PO broke the top part of the idle jet off, leaving the threaded part inside the carb. I am trying to tap a left handed thread into it and remove it by turning a left hand thread socket cap into what's left of the jet. The jet also seemed to be seized, which is probably how it broke in the first place.



I've also been reworking the original concept. I think I like this look more:



The more I look at the original concept, the more the large tank seems to dominate the bike too much. It looks almost like a streetfighter with the short seat and large hump for a tank.

This rear suspension configuration will allow me to use a short modern rear shock and give a very progressive spring rate. The total travel will be something like 5" - while not really comparable to modern adventure / offroad bikes, it's about the same as the original R90/6.
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Old 05-22-2013, 12:43 PM   #14
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Quote:
Originally Posted by lagfish View Post
My original plan was to use them because I though they looked really cool. But the more I looked at it the more they didn't look right on a scrambler. I think they draw too much attention to the wheels/tires, which already look pretty busy because of the knobby tires. I guess from a practical view, spoked wheels are also better. BTW, does anyone have a pair of spoked wheels they want to sell / trade for Lesters?
I actually have a 74 r75/6 with spoke wheels. Shipping both ways could be prohibitive though. The spoke wheels are available on ebay. If you think of a price you would take for them (no tires needed) PM me.
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Old 05-23-2013, 08:40 AM   #15
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hey man:
i have a r75 that was rebuilt/customized by Untitled Motorcycles last year. since i am living overseas without any real tools, workshop, or help... and since i am not that experienced with working on my bike, i decided to have them do the cosmetic upgrades and initial tuning. Now i have the bike with me here in Italy, and it is rad. The bike is not running right now, and i am trying to figure it out, but that is another story...

I am stoked to see you taking this on, and the CRD-style scrambler is a great inspiration. I respect you for digging into the bike, and customizing it to make it yours.

If I could give you a couple of points of advice that i learned on my build... it might help you...

First, i love the custom seat, being a little thicker near the tank. my custom seat is similiar, but when i am actually sitting on mine and the seat is compressed, the front part comes up and there is a gap between the seat and the tank. it is kind of a bummer, and when i get some money, i want to make a new seat-pan or something to help combat this. So, try to craft a seat so that doesnt happen.

Second, Untitled builds their motos with a /5 style headlight, but it is a repro... much cheaper, and then the original speedo fits inside with a simple hoseclamp. i siliconed mine in for a better fit. but, it is an elegant solution that does not involve buying some super expensive headlight bucket. it does mean that you need to change the wiring and simplify everything, similiar to what all the euro builders are doing. I have no idea HOW to actually do that, but i can say that it works well on mine, and inside the headlight bucket there are only a minimal of wires and fuses... like 4 or something. its nice. HOWEVER, if i had it all to do again, i would use either http://jvb-moto.com/rocknroll/?page_id=30 a headlight shroud from JVB. i have seen them in person and they look INCREDIBLE. check out the fotos... or, i would think about a r80GS headlight assembly with tach, ignition, and clock... http://www.stephenbottcher.net/BMW/gs1.jpg i think that would be pretty rad on a scrambler.

Third, i have a close fitting hugger rear fender... and it is a pain in the ass. looks great, but kinda sucks. Basically, run a high fender like you have in your renderings, but make it go all the way to the swing-arm to keep dirt, rocks, water, etc from blasing your battery. Making sure the rear tire (especially if it is a knobby) clears the shorter subframe is pretty important at full compression of the rear shock.

i really like the battery remounted lower in the place of the centerstand. you dont have a centerstand then... but whatever.

Also, consider going with some slightly longer-than-stock rear shox. i got stock length, but wish i got some longer for quicker turn-in. i think the bike turns in slower also because of running Dunlop K70 tires. It might be even more exaggerated with knobbies. You can measure your shock length, but i believe stock is 13.5 inches. I have talked with works performance, and they can make any shock length you want, but from my research a 14" or 14.25 would be good. Too long, though, and you run into drive-shaft problems.

anyway, just food for thought. Good luck with the build!

rob
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