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-   -   Sportster dual-sport adventure bike (http://www.advrider.com/forums/showthread.php?t=855692)

dpetersak 01-14-2013 09:01 PM

Sportster dual-sport adventure bike
 
After roaming Mexico and Central America over the summer on a rented KLR 650, I came to realize that a dual-sport bike is the way to go. What this meant is that I needed a new bike, but I have been and still am extremely happy with the Harley Davidson line-up. Specifically, I hate to give up the reliability and power of the Evolution engine. My current hog has well over 100 thousand miles and I've never even had to add oil, and many Harley riders scoff that they are not even broken in until over 200 thousand. But the lightness and handling of the KLR continued to haunt me, something I could never experience on my 800 pound bagger. I could look for a used Buell Ulysses, but I really do not like the looks of that bike, even if I could find one. This is when I decided I would build my own dual-sport bike, using a Sportster 1200 Evolution engine.

What I learned is, Harley won't sell the straight engine unless I swap one from an existing bike. But after looking for an engine or engine/frame combo, I learned that low-mileage sportsters are not very expensive, and there were quite a few on the Alaskan craigslist. I think this is because many first time riders realized (after buying a new bike) that biking in Alaska is not quite the same as the lower-48. The season is short and cold, the roads are rough and few, and Sportsters just aren't all that comfortable. So, I bought a 2006 Sporty, with 5700 miles, and the rubber-mount 1200 Evolution, for $4800. Let the build begin. :D

<a href="http://akulsp01.smugmug.com/Motorcycles/Sportster-Build/27242605_QsJxjX#!i=2288974227&k=RmCCXVW&lb=1&s=A" title="Photo & Video Sharing by SmugMug"><img src="http://akulsp01.smugmug.com/Motorcycles/Sportster-Build/i-RmCCXVW/0/M/2012_0419AB-M.jpg" title="Photo & Video Sharing by SmugMug" alt="Photo & Video Sharing by SmugMug"></a>

dpetersak 01-15-2013 06:31 PM

step one
 
The first thing I needed to do was 'correct' the geometry of the bike-- the footpegs are too far forward, the handlebars are too far back, the front end is too high, the back end is too low. While some people prefer that laid back chopper style, handling is severely compromised. I also needed to get the frame up off the ground, 5 inches of ground clearance is not near enough.

Starting with the front end, I had three options: improve the stock suspension, go with an after market suspension, or fit a dirt bike or dual sport suspension to the Sportster frame. Improving the stock suspension would require progressive springs, new valves, and a fork brace. But this would cost around $500 and serve only to change a poor suspension to a fair suspension. I would still be stuck with 39 mm forks that are prone to flexing, and have less than 5 inches of travel-- not much for a dual sport bike. Aftermarket options did not change this and cost a couple of thousand more. A pair of chromed, upside down forks may look good, but are no good on a dual sport bike. This left option three.

I knew the triple clamp from a KTM had the same stem length as Harley, and the outside diameter of the KTM bearing race was the same also, so I bought a KTM triple clamp off ebay to experiment with.

http://akulsp01.smugmug.com/Motorcyc...2_0930AH-M.jpg

The bearings fit perfectly and the only thing I had to do was reem out the steering neck a sixteenth of an inch to fit the KTM shaft. Turning radius is reduced because the bottom clamp hits the frame, but I have a few ideas on how to correct this later.

dpetersak 01-15-2013 06:56 PM

forks
 
I paid $250 through ebay for 48 mm WP forks off a 2005 KTM EXC. A local shop in Anchorage went through them, replacing the bushings, and adding Race-Tech valves and springs set for the weight of rider and bike. He also cut 2 inches from the springs to lower the forks so I could eliminate the chopper effect of the Sportster's geometry. The difference in physical size between the WP forks and stock Showa forks is impressive, plus I have dampening and rebound adjustments on the forks, something I could never have on the Showa forks, and an infinite amount of settings with the Race Tech valves. Even with shortening the springs, I still have just under 10 inches of travel.

http://akulsp01.smugmug.com/Motorcyc...2_0930AF-M.jpg

dpetersak 01-15-2013 07:31 PM

footpeg placement
 
Because the stock footpegs are too high to be comfortable for a 6' 1" rider, and they are too far forward, I needed to find the ideal placement. I wanted them back in more of a cafe style, and since I was adding at least three inches to the ground clearance, I could afford to lower them without worrying about dragging a peg when cornering. But I didn't want to mount the footpegs to the engine. I specifically went with a rubber mount frame because I did not want to feel the vibration. Also, I did not want to risk damaging the sidecovers or block if I were to lay it down. The frame rail is tucked in under the primary case about 5 inches, so I needed away to move the footpeg mounts out this far from the frame. To accomplish this I heated and bent 1 inch tubing into mini crash bars and welded the footpeg mounts to these. I used the stock mount holes in the front and the passenger mount holes in the rear.

http://akulsp01.smugmug.com/Motorcyc...2_0907AC-M.jpg

http://akulsp01.smugmug.com/Motorcyc...2_0930AD-M.jpg

http://akulsp01.smugmug.com/Motorcyc...2_0930AC-M.jpg

dpetersak 01-15-2013 07:52 PM

rear suspension
 
With the height of the front suspension now set with the shortened WP forks, I experimented with the rear to determine where I needed to be to level out the frame. The swingarm here is set at 16 inches. Now to find a 16 " shock which as much stroke as possible.

http://akulsp01.smugmug.com/Motorcyc...2_0423AA-M.jpg

This however created a new problem. The farther down I moved the swingarm, the looser the belt became. The stock shocks on a Sportster only have about an inch of travel, not enough to significantly affect belt tension. I needed a way to take up the slack but not impede the travel. I also hated to give up the belt and go with a chain and tensioner. The belt is another one of those things on a Harley I never have to worry about or mess with. I still have the original belt on my '87 with over 100 thousand miles on it, and half of that was pulling a sidecar. I don't plan on doing any gear jamming, trail riding, so I don't feel the need to go with a chain. I want a bike that can handle the the frontier roads of Alaska and the Yukon, such as the 800 mile haul road above the Arctic Circle to Deadhorse. Ebay came to my rescue again where I found an idler pulley from a 2003 Buell Firebolt. I welded a bracket to the frame and it fit perfectly. Belt tension is now constant regardless of the position of the swingarm.

http://akulsp01.smugmug.com/Motorcyc...2_0930AJ-M.jpg

JimmyTheHog 01-15-2013 07:58 PM

Nice start! Looking forward to this.

Can you elaborate on the 1/16" ream of the steering neck? I put a KTM triple clamp and bearings on my 03 and didnt have to ream the neck at all. Maybe the 06 neck is different? I did have to increase the hole diameter of the top dust cover to fit the KTM steering stem though.

dpetersak 01-15-2013 08:25 PM

shifter controls
 
For my shifter, I stumbled across a photo of a Baha Sportster, and was immediately impressed with the simple design.

http://akulsp01.smugmug.com/Motorcyc...sporty-L-M.jpg

I searched ebay in vain for a stock shifter lever off of anything that would work, but finally gave up and made my own from a length of 3/16th inch flat stock. I welded a bracket with a pivot bolt to the front of the kickstand bracket. I then cut down the stock shifter lever used with mid-control peg positioning and used the original rod from the stock forward control pegs, but cut it way down. Works great! I still need to paint it though.

http://akulsp01.smugmug.com/Motorcyc..._0930AAA-M.jpg

http://akulsp01.smugmug.com/Motorcyc...2_0930AK-M.jpg

dpetersak 01-15-2013 08:30 PM

Jim,

I actually had to use a honing stone on a drill to open up the inside-- not much though, maybe 1/32" all around, the same amount as the lip on the shaft where the top bearing sits. It must be one of the changes between the rubber-mount and the hard-mount frames.

Dave

dpetersak 01-15-2013 08:57 PM

exhaust
 
Even though I will be raising the frame 3+ inches, I still couldn't have the exhaust hanging so low without interfering with my footpeg mounts and idler pulley for the the drive belt. The exhaust had to come up, so I went with the Vance and Hines Tracker. I was blown away with how much lighter this exhaust is when compared to the stock system. On the newer Sportsters, Harley hid the crossover tube next to the frame rail and behind the mufflers. This thing is massive, though. I must have shaved-off 20 pounds just with the new exhaust.

http://akulsp01.smugmug.com/Motorcyc...2_0417AB-M.jpg

The blocks of wood got old real quick. I was soon on my way to Sears (yes we have Sears in Alaska :-) ) to buy a motorcycle jack.

http://akulsp01.smugmug.com/Motorcyc...2_0930AA-M.jpg

This crossover tube weighs almost 10 pounds by itself. This is after I cut off the mounting bracket to use it for a brake pedal mount.

The only modification I to make to accommodate the new exhaust was to cut off the plastic air scoop thing from the stock air cleaner housing.

http://akulsp01.smugmug.com/Motorcyc...2_0417AG-M.jpg

kellymac530 01-16-2013 08:41 AM

Dpete,
Nice project. I love it when someone knows what they intend to use a bike for and build to that concept. You can really get what you want that way and not what some factory thinks you want. :clap

Not to criticize your work at all, your fab skills look excellent, but have you thought about your peg mounts possibly putting alot of leverage on just the flat stock mounting tabs?

I was thinking maybe a verticle brace going up to a tab you could add on the frame behind the motor. On the left side {shifter side} it looks pretty simple, you could even make it removable if there was a service interference. The right side may be a bit tighter, but I think you could sneak something up behind the exhaust.

I am just thinking that if you put much weight on the pegs when you cross train tracks or a rough spot, I know you do not plan on heavy off road but standing may still be needed at times or even just putting extra weight on them, then the leverage on the 5" wide mount bars and then the even wider pegs put alot of torque on the bolts and tabs.

The spot right at about the rear bend on the bars and run it up to the frame even just a few inches will really add some strength.

I hope the idea does not offend, just wanting to help.

boatpuller 01-16-2013 08:48 AM

Wonderfully informative thread. Thank you for it and please keep it coming.

Most who have ADVed a Sportster use a pre-rubber mount model. Like you, I prefer the rubber mounting for long distance touring, and am planning a similar build soon.

dpetersak 01-16-2013 10:51 AM

Kellymac,

You've read my mind. The strength of the footpeg mounts is something that is gnawing at me. Now that you noticed it also, I think I will devise a way to support them further. The mounting tads are 1/4 inch steel, so I don't think they will bend, and the point where the tube butts to the tab, I made the tube double thick, but I still worry about it tweaking elsewhere. I can support the left side easy enough from underneath, but the right side has the brake pedal and idler pulley in the way. I will have to ponder it some more. Thanks for the input.

Dave

kellymac530 01-16-2013 01:55 PM

I am not there looking at your bike or your set up so I can not tell you how to bolster the strength. I just know that the first way I would look at would be a hanger running up to the frame somewhere. Running under may not give you the support you may need, think triangulation for strength.

Trust me, 1/4" thick steel can easily bend with a bit of leverage and some force...5" out + pegs = leverage...150+ man pounds {205 for me} = force...pretty easy bending possibilty.

I think of how any dirt bike frame supports it pegs, verticle frame with almost flush mounts right on it.

I had a few bikes back in the day that were a round bar under the frame and stuck only 1-1/2" or so past the frame mount and I bent those easily.

Glad I did not offend with the observation. :freaky

dpetersak 01-17-2013 09:23 PM

brake pedal
 
I worked on the brake pedal tonight, trying to get spacers and bolt lengths matched. This is one section of the building puzzle that fit together almost as if it were designed that way. I cut off the mounting bracket for the exhaust crossover tube, which bolts to the transmission housing and nests around the transmission sprocket. There was just enough of the bracket hanging below the side cover for me to drill and weld a 9/16 " bolt for the brake pedal to pivot on.

http://akulsp01.smugmug.com/Motorcyc...2_1003AA-M.jpg

http://akulsp01.smugmug.com/Motorcyc...2_1003AB-M.jpg

I found a brake pedal on ebay from a 96 Honda 1100 that had the perfect length and angled away from the bike the perfect distance. When I attached the master cylinder to the brake pedal, the bolt hole on it lined up perfectly with the 3/8" bolt on the side cover. All I had to do then was cut out a piece of 1/4" aluminum plate to mount the other bolt to and to reach the other side cover bolt. A slight bend of the brake line and it all lines up. :1drink

http://akulsp01.smugmug.com/Motorcyc...2_1003AC-M.jpg

http://akulsp01.smugmug.com/Motorcyc...2_1003AE-M.jpg

http://akulsp01.smugmug.com/Motorcyc...2_1003AH-M.jpg

I love it when a plan comes together.:clap

dpetersak 01-21-2013 10:30 AM

The KTM front wheel cost me $100 on ebay, and I'll stick with the stock rim. The new oversized supermoto disc came in this week. This thing should give me plenty of stopping power.

http://akulsp01.smugmug.com/Motorcyc...2_0930AI-M.jpg

The weight difference between the stock Harley wheel and the KTM wheel is significant. The Harley wheel is 9 pounds heavier and that is without taking the axles into consideration. Harley has a solid steel axle and KTM uses a hollow aluminum. Since the KTM front end can handle sailing through the air on a motocross course, I think it will be plenty tough enough. The wet weight of the Sportster is roughly 575# and my goal is to get below 475#. With another 9# gone, I'm well on my way, and that's 9 pounds of unsprung weight.

http://akulsp01.smugmug.com/Motorcyc...2_1005AD-M.jpg


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