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R100RT to RS fairing swap

NMBeemer
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Re: R100RT to RS fairing swap

Post by NMBeemer »

srankin wrote:
Thu Nov 28, 2024 2:53 pm
A tricky issue, that could be as simple as the carbs not pulling off of idle at the same time. LOL, in the day when I had hearing in two ears, I could balance or synchronize carburetors by ear alone. Now I use a Twinmax sync unit.

Try adjusting cable pull off from idle and see if you spot anything. Changing the clip position on the needles to richer can really mess up fuel economy, with I have experienced no discernible increase in performance. The factory settings may be a tad towards the lean side but to be honest, I have been setting my carbs for 39 out of the 40 years I have had this bike. On my RS, the same. Of course the 84 R80RT and 78 R100RS euro bike are kind of like apples and oranges in performance. Both get along very well with fair milage. Or I should say the RS did til I totaled it. St.
Thank you for this.

On the cables: I did adjust them very carefully, so the tiniest bit of rotation of the grip (after taking up the small slack) moves the throttle levers at the same time. I also have a vacuum synch meter I had for my '67 MG Midget (when it was dual SUs), for balancing the idles precisely. But it's so even and smooth that I haven't done that. Idle mixture screws are both at 3/4 turn, which seems best for smooth idle.

On the diaphragms: I agree that these likely are not it. Also, I replaced both with new, so shouldn't be a mismatched issue.

As for the needles: okay, sounds good--thanks for the reassurance and saving me some work. 8-) I'm perhaps overly anxious about burning an exhaust valve due to over-lean running. But since your experience with this model running 40mm Bings is that they're set to run lean, and given that I'm at 5,000 to 6,000 ft. daily, it should be fine. Also, it does disappear when the bike warms up. So, what I'll do is try it on the road when the windshield is buttoned up (fasteners here in a just a few days), check the plugs and go from there.
1984 R100RS (converted from RT), 1971 Triumph Bonneville custom cafe, 1951 Harley Pan-Shovel

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srankin
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Re: R100RT to RS fairing swap

Post by srankin »

The issue regarding the diaphragm's was that the aftermarket or ones sold by EME were stiffer than those sold by BMW dealerships. Given the situation with parts these days, I cannot comment on one company's versus the others, for all I know, both are made at the same plant by the same company. The supposed stiffer ones supposedly have a tiny lag in acceleration. As I have not seen this in my limited experience I don't worry about it. Look, they are cheap and do wear out, maybe buy a set from a BMW parts source and try them. At least then there is more information on the issue out for us to see.

Once you get riding the bike, be sure to check the spark plugs for color to see how your mixture is doing. NGK gives a good source of how to read plugs on its website. Tan is the best color, white is too lean. Go from there with any change in jets or needle notches. What works for me is not the be all and absolute setting, just what works for me over the years. Good luck, St.
Owner of a 84, R80RT and 79 R100RT being stripped naked for summer, turned Into a frame up restoration,

NMBeemer
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Re: R100RT to RS fairing swap

Post by NMBeemer »

srankin wrote:
Fri Nov 29, 2024 4:00 pm
The issue regarding the diaphragm's was that the aftermarket or ones sold by EME were stiffer than those sold by BMW dealerships. Given the situation with parts these days, I cannot comment on one company's versus the others, for all I know, both are made at the same plant by the same company. The supposed stiffer ones supposedly have a tiny lag in acceleration. As I have not seen this in my limited experience I don't worry about it. Look, they are cheap and do wear out, maybe buy a set from a BMW parts source and try them. At least then there is more information on the issue out for us to see.

Once you get riding the bike, be sure to check the spark plugs for color to see how your mixture is doing. NGK gives a good source of how to read plugs on its website. Tan is the best color, white is too lean. Go from there with any change in jets or needle notches. What works for me is not the be all and absolute setting, just what works for me over the years. Good luck, St.
These were BMW diaphragms, and feel very supple. I have (at least) one more pair new in the box from the PO. So, I'm set for quite a while, I would think.

Yeah, for sure, I'll do the gross measure--the plug color check. I wish I had the motivation to weld up an insert pipe for my AFR gauge to be precise about it, but don't: too many projects going at once.

Anyway, I stupidly ordered some very nice and inexpensive bolts and nuts for the fairing, not noticing the origin was China (misleading advertisement from a US company), so dead in the water for... well, no idea how long. I could take it out today without the windshield in place but am a little worried that the copper rivets would be insufficient to hold things rigidly together and would start vibrating out in lieu of the windshield's additional support.

Bummer, as it's a clear if cold sunny day--perfect for motorcycling...
1984 R100RS (converted from RT), 1971 Triumph Bonneville custom cafe, 1951 Harley Pan-Shovel

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Re: R100RT to RS fairing swap

Post by srankin »

I no longer have my RS in my garage, it is sitting at my friend's shop after I sold it to him for parts. I don't recall using the rivets for the windscreen but used nylon screws and nuts. The rivets are used on the RT fairing most particularly in the center two windscreen mounts to allow a metal plate behind the dash and out of sight to allow pivoting of the windscreen from full up to full down. This could not happen with screws and bolts. The rivets hold well as long as the holes they are riveted into place are not enlarged. St.
Owner of a 84, R80RT and 79 R100RT being stripped naked for summer, turned Into a frame up restoration,

NMBeemer
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Re: R100RT to RS fairing swap

Post by NMBeemer »

srankin wrote:
Sat Nov 30, 2024 1:39 pm
I no longer have my RS in my garage, it is sitting at my friend's shop after I sold it to him for parts. I don't recall using the rivets for the windscreen but used nylon screws and nuts. The rivets are used on the RT fairing most particularly in the center two windscreen mounts to allow a metal plate behind the dash and out of sight to allow pivoting of the windscreen from full up to full down. This could not happen with screws and bolts. The rivets hold well as long as the holes they are riveted into place are not enlarged. St.
Oh, cool--good to hear those copper hollow rivets are fairly secure. I don't think the holes were excessively enlarged. The upper fairing seems pretty darned solid with those 4 upper/mirror mount bolts cinched down tight.

Very well: I may take her out Monday (when the right-angle air hose chuck gets here) to see how she's running, and make sure that pre-warmup stumble is a non-issue.

Actually, it will be interesting to see where the air blast hits me without the windscreen in place--and then compare with after the installation. I've read threads on other forums where guys had trimmed theirs down (I don't want to go higher) to get their helmets fully into the air flow. One guy also said to try running it without the U-channel trim installed first, as evidently that deflects air slightly higher than just the molded-in lip...?

I must say that it looks sexier without the molding.
1984 R100RS (converted from RT), 1971 Triumph Bonneville custom cafe, 1951 Harley Pan-Shovel

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Re: R100RT to RS fairing swap

Post by NMBeemer »

All rightee then... the right-angle chuck got here, so I aired up the rear tire (deflated to get the rear wheel back on) and headed into Albuquerque to test the carbs.

Yup: the complete rebuild with throttle shaft O-rings, etc., plus the new intake 'manifolds,' did the trick--and the needle position feels perfect on the road. So, clearly the hesitation for a few moments after starting is merely this machine's cold-bloodedness. Unlike on the ride back from Wisconsin, there are zero flat spots, no bogging (even at 5,000~6,000 ft.). The only thing is I do need to break out the Uni-Syn and balance the idle speed screws so the vacuum is perfectly even at idle, as it's just a skosh uneven and I can't get it quite right by ear...

But the responsiveness and overtaking power suggest that the rings and valves are in great shape (I haven't done a compression or leak down test yet). The bike wanted to... just... go at highway speeds coming up I-25 from ABQ. I was frankly a little concerned coming back from WI but, clearly, the poorly adjusted valves, brittle 'manifolds,' and carbs were the issue.

More generally, re: the fairing conversion... oh, yeah, this was the right choice. First, the riding position is, for me, absolutely perfect for highway cruising (I've started a thread about a ride to The Very Large Array). Of course it's subjective, but I far prefer this posture to the bolt-upright RT bars: I experienced none of the crotch-bunching of my jeans that was driving my crazy on the 1,300-mile jaunt in October.

The steering is very light and responsive with that stunted Tyrannosaurus rex handlebar on the road, though I agree with reviewers that it's just a bit heavy in parking lots. But who cares? My regular 'short' ride is 20-something miles into ABQ, so this bike is precisely what I was looking for.

I would (again) plug the 'Beston' GT grips that I fitted after my experience on the Bonneville vibration factory. They are really comfortable, if you like the thicker-at-the-center profile.

Finally: it was 50 up here by the mountains and 55 in Albuquerque, but with the RS fairing I was able to use my unlined leather 'summer' gloves and just blue jeans (no thermals underneath). As you can see, I was without the windshield pending the fasteners arriving, but the protection from the ankles up to just below my collar bones was great, even so. Didn't get cold at all.

I'll report back when the windshield is affixed--first without the edge treatment. R&R'd the tank and rear cowl roundels, so all I need to do re: interim aesthetics is polish those mufflers...

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1984 R100RS (converted from RT), 1971 Triumph Bonneville custom cafe, 1951 Harley Pan-Shovel

NMBeemer
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Re: R100RT to RS fairing swap

Post by NMBeemer »

The paint is so-so on the used fairing, and of course isn't an exact match for the no. 573 RT's OEM shade. I won't touch it for a while, as it looks fine for my daily commuter and there's no rust on the tank. And in NM, won't be for decades.

However, I saw that Duplicolor sells rattle cans of Silver Mica Metallic, a Toyota/Lexus color (see image) that I think would look fantastic with the lines of the RS fairing.

Another choice if I wanted to stick with German paint, is VW silver reflex metallic (2nd pic). Actually, it's a bit less gray and lighter, so might be more in line with a departure from the OEM gray, which is too leaden for me.

Either way, with a good-quality, fuel-resistant clear coat, it would be an inexpensive way to have a really cool-looking custom RS.

Screenshot 2024-12-02 at 5.28.07 PM.png
VW Silver reflex metallic.png
1984 R100RS (converted from RT), 1971 Triumph Bonneville custom cafe, 1951 Harley Pan-Shovel

NMBeemer
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Re: R100RT to RS fairing swap

Post by NMBeemer »

For those unfamiliar with a Uni-Syn, here's a photo. They cost $23 on Scamazon.

Use is dead simple. Just warm up your bike and get the idle speed and mixture roughly where you want them. Then, without the air box snorkels in place, hold the Uni-Syn against the carb's throat. Adjust its center plate until the bike is j-u-s-t unaffected by the Uni-Syn being in place (often it's correct out-of-the-box).

Note that the little red float will move along its clear tube and hover. Dial the idle speed screw out until the engine speed falters, then back in until it stabilizes. Put a piece of masking tape to mark where the 'float' hovers--unless it's on one of the index marks.

Move to the other side, adjust the screw until the 'float' is in the same position.. and you're done.

I should say that you can also use the unit to determine very precise throttle-opening when adjusting the cables, too, if like me you have to wear magnifiers to peer at the levers on the carb. Not anymore!

Uni-syn.png
1984 R100RS (converted from RT), 1971 Triumph Bonneville custom cafe, 1951 Harley Pan-Shovel

NMBeemer
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Re: R100RT to RS fairing swap

Post by NMBeemer »

I'm not a believer in fate, but this is weird...

The PO found the extra keys for the bike and mailed them to me--along with two (?) of these key fobs.

Reverse says 'BMW' but depicted on the medallions? An RS.

So, one could say that the bike was meant to be an RS, all along...

IMG_4484.jpeg
1984 R100RS (converted from RT), 1971 Triumph Bonneville custom cafe, 1951 Harley Pan-Shovel

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Re: R100RT to RS fairing swap

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One of the reasons I bought this particular $1,500 bike was the stainless exhaust. Many people don't realize that, in addition to not rusting as readily as chromed mild steel, you can sand and polish stainless to remove bluing and scratches, cooked on oil and rubber from the soles of boots--all of which these mufflers suffer from.

Here are before and after pics of the L/H muffler.

I began at 800 wet but should have started with 600 or even 400, as I didn't quite get all the scratches out. Anyway, went up to 2,500 wet before hitting it with Eastwood's stainless buffing compound, followed by jeweler's rouge... looks pretty good.

I will do the R/H muffler when rebuilding the rear master next week, and will do the headers next oil change--when it'll also get a new oil pan gasket and exhaust sealing doughnuts to stop the (minor but irritating) leak on the R/H side.

One thing to note: I hadn't used stainless polish before, but you really have to heat up the buffing compound, as compared to the usual Tripoli formulation used on aluminum. That is, you kind of burnish it into the surface of the stainless (it turns into a fairly hard black film), then must use quite a bit more pressure and go slower to remove the polish. But the results are fairly impressive, as you can see. (Use a new wheel on the buffer, so you don't mix the differing formulations.)

The headers are far worse in every way, so I'm anticipating having to start all the way down at 120 or even 100 grit--which means a two-day job (my hands get too tired if I try a dozen levels of sanding before moving straight to the buffer wheel). We'll see whether I can resurrect them next year when I do the next oil change service!



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1984 R100RS (converted from RT), 1971 Triumph Bonneville custom cafe, 1951 Harley Pan-Shovel

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