More power for my new Airhead Hack? Please advise me.

Discussion in 'Airheads' started by Ace_Cafe_Rat, Aug 31, 2013.

  1. Ace_Cafe_Rat

    Ace_Cafe_Rat "Crazy Old Coot"

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    Greetings Adventurers,

    In a few short weeks I will take delivery on my long-awaited Airhead Hack. It is based on a 1984 "GS'd out" R80ST and a tricked-out M72 Sidecar from Dauntless Sidecars, with an oil cooler, leading-link fork, new monoshock, second front disc brake and a car-rear-tire conversion added by Lowell Neff Engineering. In addition to the GS tank, seat and luggage rack the previous owner installed he also put 1000cc nik. cylinders on the bike.

    I have owned a Perry Bushong built R100/7-based Airhead hack since 2008 so I know I will want more power for this new rig. This is primarily to avoid becoming a hood ornament on the Interstates I must endure to reach the fun/unpaved roads in The Four Corners states. But also for the long distance trips (3 Flags for example) that I aspire to. I have been researching power mods for Airheads online (including here @ ADV Rider) and have been very impressed @ the expertise of the Airhead Community here.

    So I am wondering if a 1070 Big Bore Kit might be the way to go? Probably do that along with dual-plug heads, larger valves, larger carbs and a less restrictive exhaust? Or would the strain of pulling the sidecar make a 1070cc kitted engine a grenade?

    Your words of counsel will be much appreciated.

    Ace Cafe Rat
    #1
  2. Houseoffubar

    Houseoffubar HoFmetalworks.com

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    Big CC's are the easiest, and most reliable way to make power.
    #2
  3. walkingbear

    walkingbear the road of life is full of twists and turns.

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    When he installed the 1000 cc pistons .. are they high compression pistons from the 70" or the flat head piston from the 80's?

    Changing to a high compression piston would add power.
    You need torque to pull a side car. I just changed out my R1150GS final drive to on from a R850 (37/11) plenty of power to pass and ride in the highway.
    Loss a few mpg but I have a adv tank

    I have a R100GS that had the top end ceramic coated. I'm running a R100S piston with R100 GS heads and 32 mm bings. Should have improve HP and better mph. Keeping the final drive the same.

    You could go to the 40 mm bings but I think you would lose your low end and mid range but you have your high end passing.
    #3
  4. Ace_Cafe_Rat

    Ace_Cafe_Rat "Crazy Old Coot"

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    Thank you both for your replies. It has been about three years since I purchased the bike so I'm afraid I cannot recall positively, but I believe the nikasil(?) cylinders did give a slight bump-up to the compression.

    I forgot to mention that another thing Neff Engineering did was to go to a lower ratio in the bike's FD...to one that is the same as the one in an R75/x...to think of it Perry's Sidecars did the same thing when building my R100/7-Ural rig back in 2008.

    Ace Cafe Rat
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  5. walkingbear

    walkingbear the road of life is full of twists and turns.

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    that would be a 37/11 great to get off the line but your top end is just about 85-90 pushing a tug. I would think your nikasil had the flat top piston which had less compression.
    #5
  6. Plaka

    Plaka Brevis illi vita est

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    Make a choice; do you want power and performance or do you want an airhead? If you're committed to the airhead you are working with 30 year old technology. It was a quieter and gentler time, the national speed limit was 55….

    If the R100 isn't getting it, your options are limited, mostly by your wallet. A stock R100, high compression, 38 mm exhaust will get about 70 HP.

    Starting with your R80: Spend $2700 for a Sibenrock 1070 kit, $1000 for some big valve R100 heads, a full valve job and dual plug drilling, 200 for some coils and $150 for gaskets and wires and you get about 7-8 more HP than the R100. (the Sibenrock kit advertises HP numbers in line with the R100 .1hp/cc). I bet you get more going with Moteren-Israels kit, they want you heads in their shop for work---gonna cost a lot more too. Anyway you're at 4,050 for maybe 78 HP (at the crank). THEN things start to get expensive.

    Go $450 for a pair of r100 nickasil jugs, $400 for new stock 9: 1 pistons, the same $1350 for the heads and etc. and you're at $2,200 for 70 HP. Its cost twice as much for only 8-9HP more!

    Rough general consensus is airheads top out at 90 HP…with enough money---and reliability and longevity are compromised.

    I looked at some of the DM series sidecars. They get coy with the specs. But looks like mild steel frames and cored 'glasswork. Heavy. 200# and an aerodynamic nightmare. The aeros will hurt you, exponentially, the faster you try to go. And you will suck fuel, so you have to carry more, your weight goes up further…

    If you bias your performance for off road work things may look better. If you can hold a steady 65MPH into a light wind you're good. Ride smart---your shadow always points to danger and the longer the shadow, the greater the danger. Conspicuity matters if you are depending on others seeing you for your safety. Kick back, but some Hendix on the 8 track and pound out the miles. The truckers will know all about you miles before they see you, everyone else will slow down to rubberneck the strange what-IS-that-thing.

    Here, you would do the R100 high compression dual plug conversion, then go with the low-first-long-fifth tranny mod, with a stock or slightly lower rear end.

    Nickasil by itself has little to do with power. Cools better so you can make a bit more heat.

    Bigger carbs will hurt your lower and midrange. Build the motor to have good torque there then use your gearing to keep it near the torque band on the highway.

    The exhaust doesn't have some big cork in it that you can pull out and get all sorts of performance. I have a very high flow exhaust. It is good for a little---very little. A 2--->1 system will give you a bit better scavenging if it's built right. Maybe half a HP there. Going to 40 MM is also good for something. Last time I talked to the Epco guy he had built some custom stainless 2--->1 sidecar exhausts. They run up the left. Makes it easy to change your oil too. The big gain is in weight savings. Shave 40 LBs right there. Look good.

    Getting it lighter will help a lot with climbing hills and passes, and off road. Get 150 lbs off and you get it back near the merely bloated R80g/s. Between the bike, chair, your carry on luggage and your waistline, there are many opportunities. Most of it costs money: light batteries, special tools, etc. --except the waistline where you can save money on food.

    Keep an eye on the aeros at speed, particularly parasite drag.
    #6
  7. DaveBall

    DaveBall Long timer

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    What Plaka said - :D

    Putting a sidecar on an Airhead is a great idea, if you are not looking at high speed touring. The two just don't work well.

    If you want to be able to do high speeds with a sidecar, you have to make a lot more horsepower and torque. You will need a much more modern engine, frame, etc. Or, just install a VW engine and hop it up. I have seen some done that can cruise at very high speeds, but I wouldn't want to do it. High power in an Airhead rubber cow frame attached to a heavy sidecar is just asking for trouble.
    #7
  8. Ace_Cafe_Rat

    Ace_Cafe_Rat "Crazy Old Coot"

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    Plaka,

    Wow! I REALLY appreciate you taking the time to share so much experience and knowledge with this relatively noob Airhead owner. Cold counsel is the most valuable and the hardest to obtain. Thank you for yours. You have saved me a boatload of money and time trying to make an Airhead engine into something it was never intended to be. Dang it! :-)

    Ace Cafe Rat
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  9. Ace_Cafe_Rat

    Ace_Cafe_Rat "Crazy Old Coot"

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    Thanks! Those are all good points. Dang it.

    I wonder if a carb Oilhead engine would even fit in the R80ST's frame? I think have seen a pic of one in this web forum that IIRC was fitted into what appeared to be a /2 frame.:ear

    Ace Cafe Rat
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  10. walkingbear

    walkingbear the road of life is full of twists and turns.

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    Kind of wonder what is your vision for this R80/100ST/GS

    Are you going to reinforce the frame?
    #10
  11. Ace_Cafe_Rat

    Ace_Cafe_Rat "Crazy Old Coot"

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    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/showthread.php?308-R1150-2-Old-meets-New

    All Advice is Welcome!

    Ace Cafe Rat
    #11
  12. R100LT

    R100LT Chasing 11

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    Don't give up so quickly ... We like spending other people's money
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  13. walkingbear

    walkingbear the road of life is full of twists and turns.

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    think about a R1100GS or R850 R .. pretty reliable and will easily pull that car. The R850 has a 37/11 rear drive. I just mounted the same drive to my R1150gs. It pulls nicely



    You can take a R1100GS and put carbs on them and take the abs out.
    Now you have a nice ride
    #13
  14. supershaft

    supershaft because I can

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    More CC's than 980? The factory stopped there for MANY good reasons!

    Did your 800cc heads have the combustion chamber enlarged? Did it get the 'kit' Siebenrock pistons for such an occasion?

    You already have the best clutch/flywheel setup, now you need a 336 and some 38mm Dellorto carbs. That's your biggest, completely reliable, way more low rpm pulling power torque getters for the money. I would probably raise CR and dual plug at the same time for even more all good from all revs. Clean up the ports some and 44mm intake valves would help too. All of those modes are just as reliable as stock but with way more low, mid and high rpm power.

    38mm Dells or Mikuni's will get you way more low end than 32mm Bings AND way more top end. Compared to 32mm Bings? Bigger carbs will HELP your low rpm performance! That is except for 40mm Bings.

    3.37:1 FD? you should still be able to pull 115mph IF you modify it to get more power.

    I wouldn't run a 1070 kit. 980 is a big as that engine can handle long term.

    I wouldn't follow the typical advise of looking for some big port/valve heads. The small port heads breath better IMO and can easily get the same 44mm intakes of a big port/valve head. The best of two worlds in a lot of eyes. They just aren't as googleable.
    #14
  15. supershaft

    supershaft because I can

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    :huh

    You can google a whole lot of this misinformation. It's like a rash all over the idiotnet but that doesn't make a lot of it right.
    #15
  16. JimX

    JimX .. .

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    So what final drive do you have? What size is your rear tire?
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  17. Ace_Cafe_Rat

    Ace_Cafe_Rat "Crazy Old Coot"

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    :rofl You're nuthin' but a band of scoundrels the lot of ya!

    :D

    Ace Cafe Rat
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  18. Ace_Cafe_Rat

    Ace_Cafe_Rat "Crazy Old Coot"

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    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.

    Ace Cafe Rat
    #18
  19. JimX

    JimX .. .

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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.
    #19
  20. Plaka

    Plaka Brevis illi vita est

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    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.
    #20