1975 BMW R90/6 - Rocinante

Rider52 said:
I wonder if that carb is just worn out. Back when I actively restored antique motorcycles it was not uncommon.
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Well... I had thought of that, I guess it's possible. The thing only has 42k miles though and I know these are known to last a long time. The thing did sit w/ slowly decaying gasoline in the tank and carbs for over 30 years and what I cleaned out can be seen in earlier pix on here. The petcocks were really destroyed so it's possible the inside of this carb is as well, however I did a really thorough go-through on the things the other day and it all looked surprisingly good. I can't tell if the float valve seat is bad, but I did manage to do a good cleanup of it and from what I can see looks ok. I think I've seen replacement seats available but I'm pretty sure that's not something I can do myself, is it????
 
ridesolo said:
Well... I had thought of that, I guess it's possible. The thing only has 42k miles though and I know these are known to last a long time. The thing did sit w/ slowly decaying gasoline in the tank and carbs for over 30 years and what I cleaned out can be seen in earlier pix on here. The petcocks were really destroyed so it's possible the inside of this carb is as well, however I did a really thorough go-through on the things the other day and it all looked surprisingly good. I can't tell if the float valve seat is bad, but I did manage to do a good cleanup of it and from what I can see looks ok. I think I've seen replacement seats available but I'm pretty sure that's not something I can do myself, is it????
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I don't have any experience with the the later Bing carbs. The last one I worked on still had a slide and was on a two smoker. I did a search for Bing carb seat replacement. Seems like one of the common complaints is gas puking out of the overflow. The seat looks cheap enough to try replacement especially when compared to the cost of a replacement carb.
 
Rider52 said:
I don't have any experience with the the later Bing carbs. The last one I worked on still had a slide and was on a two smoker. I did a search for Bing carb seat replacement. Seems like one of the common complaints is gas puking out of the overflow. The seat looks cheap enough to try replacement especially when compared to the cost of a replacement carb.
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I was just doing some research on that and, unfortunately it looks like the later 40mm Bings have a seat that can be changed but there doesn't seem to be one available for the 32mm carbs like mine. I can see why. The seat in the 32mm carb is up at the top of a cylindrical hole in the aluminum carb body and that hole is where the body of the needle goes up and down. On the 40mm carb that cylindrical hole for the needle is actually part of the entire seat which presses into the carb body. Also, as I think about it if there were a problem w/ the seat it would be more likely that I'd have a problem w/ too much fuel rather than not enough.

What I've decided to do is attempt to be as precise as possible and use a caliper to get the height of the tab on the float and test it. Then as necessary measure each succeeding change and test so that each adjustment is absolutely minimal until it's right. There has to be a happy medium in there somewhere. If I had access to a 3D printer I'd attempt to print a transparent float bowl so I can see what's happening in there. EME has a set of two available but I'm not going to spend $99 to get them.
 
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Progress? Not exactly. I got in a set of new float needles. In the pix below you can see the new vs. the old. (Top one is the old, bottom is new.)

BMWR90236.jpeg


So, I put the new one into the troublesome left carb w/ no changes to the float and there was no change. Decided to switch the floats. Now the left carb (w/ the float from the right carb) drips fuel from the overflow but the cylinder does run. The right side, however, now pukes fuel out the overflow! OK... time to gather patience again, and start over. (My previously thought-to-be "endless" reserve of patience is about to go on life support!)

On other issues: The front wheel is back over at the local Cycle Tech shop; hope they'll get the slow leak fixed, I've only put six miles on the damn thing! I pick that up tomorrow.

AND the last time I put it onto the center stand I got this:

BMWR90237.jpeg


Frankly this old girl is really starting to get my goat. :mad: Anybody know where I could trade it for a tricked out Grom of Ruckus? ;)
 
LOL. I feel that. Some days you just wonder when all the little crap will stop happening and just be finished.
 
ridesolo said:
Frankly this old girl is really starting to get my goat. :mad: Anybody know where I could trade it for a tricked out Grom of Ruckus? ;)
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Ok, thoughts of a Ruckus are extreme, nice utilitarian platform, but 50cc? Nah,,,
 
Some day when this thing is running great you’ll look back at the frustrating bits and chuckle


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adventurco said:
Some day when this thing is running great you’ll look back at the frustrating bits and chuckle
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Well, it's running but I'm not chuckling... yet.

Today, though it's a bit closer to a girlish giggle!
 
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BMWR90238.jpeg


So, the news today is that I went for a successful 30 mile ride!

Is it DONE? There are still a few little issues that'll require some attention but it runs and rides very well. Since @Hurco550 switched over to Mikuni carbs on his airhead I borrowed his Bings and threw them on there. After a couple of required "fiddles" it now runs and rides like it's supposed to and will even sit and wiggle away at a civilized idle speed. I was concerned about the fog of oil smoke but it's gone after the ride so it must have been getting the new rings seated and got the assembly lube burned off.

What's left? I still want to try and get my carbs working like they are supposed to or at least finally find out why the left one was being so difficult. If I can get them sorted out I can get Levi's back to him. Also I've got to dig into the "dash" lights. Strange, when I got it, about the only electrical stuff on it that I could get to work was the lights on the clocks and the Oil, Gen, & Neutral lights. After lots of messing and frustration I figured out the bad headlight relay and the odd-ball headlight sub-harness and now everything is working well EXCEPT the "dash" lights! That's a project for another day. I'd like to get a nicer fit between the head pipes and mufflers. That'll require taking the mufflers off and working w/ a Dremel and maybe some files to get them to slide together more securely. Even though these mufflers are hand-made they look great and are very quiet.

The old girl runs along just as nice as can be, very civilized and lots of go. The suspension is a bit stiff but it handles well and has a very civilized and stable ride. I like the seating position in relation to the handlebars, mirrors, and fairing and I was very pleased to get in close to 20 miles before right-hand-numbness started to set in. I'm still keeping eyes open for a solo seat... someday!

Is it FINISHED? No! But I can comfortably call it done... for now.

 
I got a 40 mile ride in today and it seems to be settling in very well. It's been starting right up w/ no choke and settles down to an appropriate idle w/ minimal warm-up. There's still a little smoke at first but it seems to clear up quickly; typical old airhead, I'm told. The ride is very pleasant and I think I could spend hours on it comfortably puttering around the local country roads.

On another note, I acquired a GoPro camera the other day so I'm looking forward to vids of mile after mile of travel between fields of corn and soy beans. I know, you can't wait, right? I don't have a chest harness for it, what is practical for mounting? Helmet mount? Fairing mount? Is wind noise a problem w/ either of those?

I also found an original Krauser windscreen for the S fairing that I'm looking forward to getting and mounting. It's taller and will offer a bit more protection but also fits in with my attempt to outfit the machine w/ period correct goodies. AND I was really happy to get it cheap, cheap, cheap through one of the Re-Psycle auctions. (Pictures as soon as I pick it up from @Hurco550.)

Still have some tinkering to do that I will get to next month after the flurry of travel home to PA (50th anniversary HS graduation reunion :eek:) and medical appointments between now and the end of the month.

BMWR90240.jpeg
 
That's a great looking scoot man.. it looks like it could soak up the miles for sure
 
In my attempt to carefully farkle this old beast to the "vintage survivor" look I'm going for, I found a vintage Krauser S windshield. It's not perfect but will be improved w/ some plastic polish work. The practical coverage seems pretty good and provides a larger rider envelope. I've taken the Krauser exhaust heat shields in for a powder coat job and if they come out looking good they'll go on as well.

BMWR90244.jpeg
 
I forgot to post this here a while back.

I got tired of trying to turn the thing around in the shop so I started looking for different methods and after lots of research, thoughts of trying to build something, and more research I settled on one of these:

BMWR90245.jpeg


I'm impressed with the build quality and it went together fairly easily alone though an extra set of hands would have made it easier. It's well-thought-out and fairly easy to use. Each end has a rotating part that functions as a ramp and a brake at the same time. It's only 1.5" off the floor so it isn't difficult to push or ride onto.

BMWR90246.jpeg


I would have liked to be able to use the center stand but the main rail isn't wide enough. I think if I had skills as a fabricator and welder I'd try to come up w/ a modification to allow that. It's relatively stable there even on the side stand but I decided I'd feel more comfortable if I could have it held more securely so I mounted a removable wheel stop I had picked up.

BMWR90248.jpg


And then added some heavy duty mounts for ratchet straps. Unfortunately the material I had on hand wasn't rigid enough to make it steady enough for my satisfaction but @Hurco550 may be able to help me find something better.

BMWR90247.jpg


BMWR90247.jpg


It doesn't roll quite as easily as I'd like it to, most likely because of my rubber conveyor belt flooring, but I've gotten that figured out. It sure is nice to be able to roll it off to the side so I have more available floor space for other projects. When I want to ride I've got the front wheel pointed toward the door so I can just ride out. While the engine is warming up I roll the dolly around and set the ramp/brake so I can just ride on when I get back.

For about $120US it's a pretty good device for an old guy to move his nearly 500# bike around the shop.
 
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