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Old 09-02-2013, 02:55 PM   #16
JimX
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Originally Posted by Ace_Cafe_Rat View Post
The overarching goal is to have a rig capable of taking me anywhere in the Southwest and back again. Since moving from Madison, WI back in early 2003 to the Greater ABQ area in NM I have learned the joy of the unpaved roads. Unfortunately to reach most of them I have to endure miles of Interstate Highways with as Speed Limit of 75 MPH...which means most folks are going 80 MPH at least. On its best day my current R100/7-Ural sidecar sidecar will go 80 MPH on the flat desert floor, but it greatly prefers 65 MPH. I figure the R80ST-DMC rig with its current 1000cc jugs will be no faster. I was after a rig that was faster than a Ural sidehack rig and I have that I am sure.

Lowell Neff Engineering has already modified-strenghted the swingarm to fit a car tire on the bike and installed a new heavier monoshock. But IIRC all of the Airhead frames are rather "flexible" so adding some addition power will probably reveal the need for additional bracing. Especially if I fit an Oilhead engine in it. Like this one someone created http://www.bmwra.org/forum/showthrea...-Old-meets-New

All Advice is Welcome!

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So what final drive do you have? What size is your rear tire?
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Old 09-02-2013, 04:52 PM   #17
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Old 09-02-2013, 04:59 PM   #18
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So what final drive do you have? What size is your rear tire?
Neff Engineering fitted the FD ratio from an R75/x since it has to tug a big sidecar plus camping gear, extra fuel, personal kit, etc..

The car rear tire is going to be a 15" one. I'm not sure what the net ratio comes out to be. I'm going to look it up and be back with that info.

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Old 09-02-2013, 06:37 PM   #19
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Most R75's had the 3:20 ratio. With a 15" car tire conversion the overall ratio will be approx. 10% lower (compared to an 18" tire). A stock R100 with hack will pull that fairly easily. Depending on the chair weight, and aero factors, an R100 in decent tune will pull a 3:09 or a 3:00 with that rear tire.

Any higher than that, and you won't be happy. If you are at altitude, into a headwind, climbing, with a full load and passenger, you will be downshifting........


Modified engines? I have no experience.
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Old 09-02-2013, 07:40 PM   #20
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Originally Posted by Ace_Cafe_Rat View Post
The overarching goal is to have a rig capable of taking me anywhere in the Southwest and back again. Since moving from Madison, WI back in early 2003 to the Greater ABQ area in NM I have learned the joy of the unpaved roads. Unfortunately to reach most of them I have to endure miles of Interstate Highways with as Speed Limit of 75 MPH...which means most folks are going 80 MPH at least. On its best day my current R100/7-Ural sidecar sidecar will go 85 MPH on the flat desert floor, but it greatly prefers 65 MPH. I figure the R80ST-DMC rig with its current 1000cc jugs will be no faster. I was after a rig that was faster than a Ural sidehack rig and I have that I am sure.

Lowell Neff Engineering has already modified-strenghted the swingarm to fit a car tire on the bike and installed a new heavier monoshock. But IIRC all of the Airhead frames are rather "flexible" so adding some addition power will probably reveal the need for additional bracing. Especially if I fit an Oilhead engine in it. Like this one someone created http://www.bmwra.org/forum/showthrea...-Old-meets-New

All Advice is Welcome!

Ace Cafe Rat
Methinks you're leaving a few things out.

Rip the injection off an oilhead motor and you don't get it back to the simple engine you know, but you do kill the power. That's where it's coming from. You also get away from resources that can help you keep it running. Owning anything unique has downsides: you need to be unusually self reliant.

You seem set on it doing 80+ mph, consistently, on the interstates. Have you ever toured an open bike all day long at those speeds? You get beat up. At the end of the day your over-the-road speed is just the same as if you were running 65---that is, 50 to 55 mph. I've done the Taos to Co. Springs run a few times at a steady 90 on an open /5. Didn't get home any sooner than the crowd running 65. you need more and longer breaks. When you want to make time, not stopping is the way to do it.

I've ridden from mid Maine to Denver at exactly 55, on the the interstates. Some very long days but otherwise not a big deal. I needed maximum mileage. It worked.

If you want to pull lots of speed and make time, just use a secondary engine---like the one under the hood of an F150 with the hack on a trailer.

If you want a modern powerful engine, then get one. But you have to leave it a modern powerful engine and wrap your head around getting into the 21st century and learning the thing. I've been debating the same thing. The only appeal of an airhead off road is I don't need to learn a new bike. Otherwise they suck. The KLR has more power, a more efficient drive train, will ride a tighter trail, costs less, etc, etc right out of the box. The beemer is a better head trip and amusing to screw with; HPN this Moorspeed that and ya better reinforce the frame so it doesn't fall apart. Meanwhile the KLR people went camping. Different trips. I know the airhead very well, so that's a powerful attraction, and if I wanted to ride open country, fire roads and the like, I'd go for it. And I still might. But if I learned the KLR I'd have a lot more capacity for a lot less money. (Or maybe a transalp). As an aside, I ran into a guy recently who had ditched his KTM in favor of a Honda. he wanted to go riding, not screw with changing 3 oil filters and getting a second mortgage to pay for it. I didn't know they had multiple filters. Dead deal right there.)

If you want to play in the shop and try to build the "ideal" rig you can spend completely unlimited time doing that. If you want to go riding, you can take what you have and ride the piss out of it. My best trips I had anything but the "ideal" rig---or gear. I wanted to go so I went.

Ran into a young guy in CO a long time ago. He was spending the summer touring the country. He had some sort of moped/scooter thing, sagging to the floorboards under duffles and back packs. He said his top speed was around 35. He'd been riding the backroads, on the shoulder. So far he'd made it to CO from back east somewhere and had half the summer left. Was having a blast.

Couple of years ago I ran into an old guy in a gas station in Ventura. Mid 70's and riding a maxi-scooter. he also was spending the summer touring the ciountry. Little luggage, moteling it. Said he used to ride Harleys (his skills said he learned on the scooter he had) but because of a back injury he couldn't swing his leg over a regular bike, so he got the scooter. Again, from back east somewhere and had made it to California with half the summer. I was headed north up 1 so invited him along. Turns out he's running 55-60 to my 90-100. After loosing him a couple times I figured I see what king of mileage the RS could get if I wanted it to. it was a little dicy on the 8 lane stuff at that speed but there is almost 75 miles of 40mph road in the middle of that run. Very, very pretty and extremely dangerous. 40 means 40 and you don't screw around. By the time we got through that he was pretty pale---terrified of gravel and all the turnouts were gravel. We stop for a nice lunch and then on to the mellow stretch up to San Francisco---except it was afternoon and the onshore winds were blowing his scooter around. he stays at 40 a lot. I get him through the city and across the bridge---difficult navigating and a guide is really nice, then lost him in the winds at the headlands. I think he peeled off at a string of motels I knoew about. I rode another 80 or so home, after dark on very hairy road across the delta. I usually like to be across that will plenty of light. Just another adventure. upshot tho', you don't gotta go fast.
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Old 09-03-2013, 06:39 AM   #21
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I would get the Mikuni carburetor kit. I think that is a 36mm carb. Don't over carburate, it will hurt low end power.

Dual plug. Minimum of 9.5:1 compression. (actually would want 9.5 exactly)

336 cam or something more special from the few sources. I don't have much experience with cams but if I was doing what you want to do I would learn real fast. The only real power made is with a cam shaft.

Anything more than this and it won't be an Airhead anymore.
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Old 09-03-2013, 06:58 AM   #22
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I would get the Mikuni carburetor kit. I think that is a 36mm carb. Don't over carburate, it will hurt low end power.

Dual plug. Minimum of 9.5:1 compression. (actually would want 9.5 exactly)

336 cam or something more special from the few sources. I don't have much experience with cams but if I was doing what you want to do I would learn real fast. The only real power made is with a cam shaft.

Anything more than this and it won't be an Airhead anymore.
Unfortunately the power the cam makes is on the high end, not the low. The Bing has it over the Mikuni for mileage. How much juice you wanna carry? The Mikuni is more responsive, the Bing takes more abuse, is simpler to service, eats up crappy gas...
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Old 09-03-2013, 07:15 AM   #23
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Originally Posted by JimX View Post
Most R75's had the 3:20 ratio. With a 15" car tire conversion the overall ratio will be approx. 10% lower (compared to an 18" tire). A stock R100 with hack will pull that fairly easily. Depending on the chair weight, and aero factors, an R100 in decent tune will pull a 3:09 or a 3:00 with that rear tire. Any higher than that, and you won't be happy. If you are at altitude, into a headwind, climbing, with a full load and passenger, you will be downshifting... Modified engines? I have no experience.
According to Lowell of Neff Design Engineering http://neffdesign.org tells me that the FD Ratio works out to 3.54.

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Old 09-03-2013, 07:30 AM   #24
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Originally Posted by Ace_Cafe_Rat View Post
According to Lowell of Neff Design Engineering http://neffdesign.org tells me that the FD Ratio works out to 3.54.

Ace Cafe Rat
OK...you have a 3.20 on there. If you have a monolever rear end, your choices are more limited than the twin shock type. There was a 3.0 final drive on the late RS models. With a 15" tire. that works out to 3.30. Should be fine with a good running motor (unless you have driving lights the size of dinner plates, a 200 lb. Great Dane, etc.).
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Old 09-03-2013, 07:36 AM   #25
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...You seem set on it doing 80+ mph, consistently, on the interstates. Have you ever toured an open bike all day long at those speeds? You get beat up...
Not at all friend Plaka!

My current R100/+Ural sidehack and I are both much happier just truckin' along @ 55-60 MPH. Usually I "shunpike" as much as possible. For example to go from the Greater ABQ Area to Taos on my current rig I plan my route to use as much of Pre-1937 Route 66 as possible and get on I-25 only when I have to. It works pretty well until we get the dreaded escarpment of La Bajada there we MUST ascend a steep incline on I-25 because there is no alternative route. If I am going the posted speed limit of 75 MPH in 5th gear at the start of La Bajada I am going 50-55 MPH in 4th gear by the time we get to the top and I am getting flipped off by cabrons in white pickups as they blast past me.

I just want to my new rig to be able to do a bit better in those sorts of circumstances. So I am not looking to do the impossible, I only want to increase my top end enough to be safer in such instances.

ThanX agin' for your thoughts.

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Ace_Cafe_Rat screwed with this post 09-03-2013 at 10:13 AM Reason: Fixed typos.
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Old 09-03-2013, 07:41 AM   #26
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Originally Posted by disston View Post
I would get the Mikuni carburetor kit. I think that is a 36mm carb. Don't over carburate, it will hurt low end power.

Dual plug. Minimum of 9.5:1 compression. (actually would want 9.5 exactly)

336 cam or something more special from the few sources. I don't have much experience with cams but if I was doing what you want to do I would learn real fast. The only real power made is with a cam shaft.

Anything more than this and it won't be an Airhead anymore.
That and stay with small port heads. It will have good power right off idle and be reliable. Mess with rear ends for more tuning.
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Old 09-03-2013, 07:48 AM   #27
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OK...you have a 3.20 on there. If you have a monolever rear end, your choices are more limited than the twin shock type. There was a 3.0 final drive on the late RS models. With a 15" tire. that works out to 3.30. Should be fine with a good running motor (unless you have driving lights the size of dinner plates, a 200 lb. Great Dane, etc.).
Thanks! The driving lights are about the size of saucers.

Alas the 200 lbs. of Tibetan Mastiffs we own will stay in the rig only until the engine is started and then you will not see them for the dust.

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Old 09-03-2013, 07:51 AM   #28
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That and stay with small port heads. It will have good power right off idle and be reliable. Mess with rear ends for more tuning.
I checked in the email-trail of the purchase of the R80ST and here is some additional info I mined:

The heads are stock R80ST heads
The PO was able to run 87 Octane gas after installing the 1000cc kit.

That says to me stock compression 1000cc jugs. Am I right?

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Old 09-03-2013, 08:26 AM   #29
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I'm not an Airhead expert by any means, but I know a lot of things about a lot of things. I've learned, through wasting tons of money, sweat, tears, frustration and antacids that sometimes the more expensive option is cheaper.

I'd sit down and really crunch some numbers, because I wonder how close in price you'd be to a more modern GS rig once you drop serious loot trying to make this into something it's just not (and shouldn't be - different strokes and all that!).

I love my Beemer, but the engine produced 70 horsepower new and the frame was designed 45 years ago. I can make it go faster and handle better, but I'll never play hide-and-seek in the canyons with a new GSXR750. Just the wrong tool for the job.
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Old 09-03-2013, 08:31 AM   #30
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Originally Posted by Ace_Cafe_Rat View Post
I checked in the email-trail of the purchase of the R80ST and here is some additional info I mined:

The heads are stock R80ST heads
The PO was able to run 87 Octane gas after installing the 1000cc kit.

That says to me stock compression 1000cc jugs. Am I right?

Ace Cafe Rat
There were several "stock" compressions. I would say you have the lower one, 8.?:1. But you effectively loose some compression at high altitude. At any rate, if you dual plug you can go 9.5 without any issues. I'm running regular (85?)

It would be really good to know whose "kit" that is. You may not be able to drop any pistons in it. but you could still shave the head. See if the barrels are marked A, B or C at the base.

Try looking more anti-social. I go for somewhere between seriously crazy and frankly psychotic. It's fairly easy, the Sheeple (and the flip-you-off cowards are definitely that) are well TV conditioned to certain costumes. Lots of black leather, well beat up. loud pipes help. I back it up with a large caliber automatic tho'--and I'm skillful with it. I've never needed it, but it changes your stance in a subtle way...
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