DR650 Cafe. Scratch Built Amelioration

[Hurco550]

Well, per the norm, a Hurco550 project has "changed directions" while still in its infant stages. The original plan, for over a year, was to build "this" project, but with another 1996+ dr650 lump like what I built my bobber around. I searched for a good while for one, but prices had gone a bit wonky and I thought it was out of reach. That's when I stumbled upon the XL500 lump at Mid Ohio and decided that it would take the place of a DR650 unit.....

That was until New Years Eve Eve, when @john83 shared with our group chat a local to him Marketplace listing for a 1998 dr650 engine for $400. A few messages with the seller, and John went and collected the engine for me on New Years Eve. Then, as a bonus, the engine came with an FCR39MX carb (which is the same as I put on my stock 05 as well as the bobber. Its easy to wrap up almost the entire purchase price up in the carb itself.) It also came with a CDI, a harness (which I will hack mostly just for the CDI plug) and then a bunch of other stock dr650 parts that I will likely flip to offset the cost a bit.

And the pile sitting safely in Johns Garage until I can make a trek to Georgia to collect it.

 

[ridesolo]

Looks good. Guess the XL lump goes into something else, huh?

Curious; are you planning to design and fab a swing arm and suspension to go w/ the frame or are you going to design the frame around an existing swinger?

 

[Hurco550]

Looks good. Guess the XL lump goes into something else, huh?

Curious; are you planning to design and fab a swing arm and suspension to go w/ the frame or are you going to design the frame around an existing swinger?

Yeah, of course I am already stewing on other uses for the XL lump

I haven't decided on a swingarm yet. A big part of me is thinking about trying to adapt a swingarm from a KTM 390 duke. They are a neat trellis cast aluminum piece, and use a simple, non linkage type shock setup. Plus, I have a friend local (ish) that has a complete bike that I could copy dimensions from. They are also pretty cheap on the used market.

 

[ridesolo]

I haven't decided on a swingarm yet. A big part of me is thinking about trying to adapt a swingarm from a KTM 390 duke. They are a neat trellis cast aluminum piece, and use a simple, non linkage type shock setup. Plus, I have a friend local (ish) that has a complete bike that I could copy dimensions from. They are also pretty cheap on the used market.

Makes sense, there's lots of goodness there: Quality brand donor, great looking, simple suspension, avalability, fender already figgured out, and availability of replacement parts.

 

[Hurco550]

Makes sense, there's lots of goodness there: Quality brand donor, great looking, simple suspension, avalability, fender already figgured out, and availability of replacement parts.

My original plan was to build a simple chromoly swingarm with a yamaha tz style design. I may still go that route as well...

 

[ridesolo]

Lots of options for sure. That look is is pretty nice, too. To me that sub frame support is especially appealing and that blue ain't bad either.

 

[Maritime]

Nice score on the DR stuff!

 

[Hurco550]

Still playing around on this thing a bit. I went ahead and bought a KTM duke390 swingarm off of ebay to give a try. I am going to do a bit more drawing up and figuring, but its almost 3" longer than what I had originally drawn up and figured, and Im a bit concerned that it is going to throw all of the proportions off. It is a neat piece of engineering though..

 

[ridesolo]

You're right, that's a pretty nice looking piece of metal. I'm not any kind of expert on proportions, not really an expert on much of anything for that matter, but I'd think one advantage of having a little longer length, overall, on the thing is that you might be able to go w/ a longer fuel tank on it which might help to achieve the GP bike look. A longer wheelbase will give you a better, less choppy ride which might also help to keep it less squirrely in the handling department. (?)

 

[irk miller]

Looks like the Duke's wheelbase is 2" longer, but still only 54". She'll appreciate a little more length.

 

[Hurco550]

You're right, that's a pretty nice looking piece of metal. I'm not any kind of expert on proportions, not really an expert on much of anything for that matter, but I'd think one advantage of having a little longer length, overall, on the thing is that you might be able to go w/ a longer fuel tank on it which might help to achieve the GP bike look. A longer wheelbase will give you a better, less choppy ride which might also help to keep it less squirrely in the handling department. (?)

Looks like the Duke's wheelbase is 2" longer, but still only 54". She'll appreciate a little more length.

I think its a bit of a mix of alot of things, but part of this thing comes from riding dads buell, mixed with riding the bobber. I want something very compact that might be a bit twitchy for doing rowdy stuff with lots of torque. Though the style will be more cafe, the intended use will be more closely related to what youd go do on a street legal supermoto bike.

I shouldve paid more attention to the full pick of the 390 duke. The engine is set so far foward and down, both directions farther than I want to go on this build.

 

[ridesolo]

OK, I understand what you are saying. There's a pretty fine line there when you're talking two to three inches but I can see where there could be great differences in how it handles. I suppose the ultimate way to go would be to create the cradle you want and then make your own basic swing arms in different lengths or perhaps some kind of "adjustable" working swinger and then test bed everything until you get just what you want. Sounds like lots of time, work, and expense but the end result would probably give you a remarkably good rider.

 

[doc_rot]

Supermotos typically have a longer wheel base, less rake, and more trail than sport bikes. 690 SMC R is 57.9”. 450 SMR is 57.8”

Buell has some strange mojo going on that might be hard to duplicate beyond rake/trail/wheelbase. 52” wheelbase is extremely short - the KTM RC250GP is 52.7

 

[Hurco550]

Supermotos typically have a longer wheel base, less rake, and more trail than sport bikes. 690 SMC R is 57.9”. 450 SMR is 57.8”

Buell has some strange mojo going on that might be hard to duplicate beyond rake/trail/wheelbase. 52” wheelbase is extremely short - the KTM RC250GP is 52.7

My current cad drawing has me at 24.5 deg rake, 3.73" trail and a 53" wheelbase (theoretically with the adjusters all the way foward/ shortest). This includes a drawn pivot to axle dimension of 19.5" where the same dimension on the KTM swinger is 22.5". The dr650 motor is fairly compact as far as engines go, or at least I should say the transmission is fairly compact. Im likely going to try a tz inspired cantilever monoshock setup. For a cafe inspired style ive always thought that the length of the monoshock swingarm just kills it. Ive yet to see what I would call a well proportioned "cafe" style 96+ dr650 and I think much of it is due to the length of the swingarm and wheelbase combined.

 

[doc_rot]

I agree with you on the look of the longer arm - I only mentioned those other lengths because you said the intended use is a "street legal supermoto". Its interesting how supermotos are typically associated with quick nimble bikes yet their geometry is fairly relaxed and much longer than sport bikes. Clearly there is more going on than rake/trail/wheelbase alone to make a bike nimble. Obviously this has to do with the light weight nature of a supermoto but I suspect this due in part to mass centralization and a well proportioned center of gravity.

Regardless, the sketch of the dimensions is looking great. I like the frame style - moto martin-esque

 

[irk miller]

I agree with you on the look of the longer arm - I only mentioned those other lengths because you said the intended use is a "street legal supermoto". Its interesting how supermotos are typically associated with quick nimble bikes yet their geometry is fairly relaxed and much longer than sport bikes. Clearly there is more going on than rake/trail/wheelbase alone to make a bike nimble. Obviously this has to do with the light weight nature of a supermoto but I suspect this due in part to mass centralization and a well proportioned center of gravity.

Regardless, the sketch of the dimensions is looking great. I like the frame style - moto martin-esque

The wheel/tire combo is a really big factor coupled with dirt bike suspension. There's a shit ton of rubber surface area managing only about 270 - 300 lbs, depending on the bike and combined with a dirt bike suspension the COG really sits on the axles in the twisties. Makes for really stable carving. It is so easy to stay within the limits of grip even when you're completely laying down. The low end power delivery of an offroad thumper seems to just add to the handling.

 

[Hurco550]

I wish in all the talk I had just gone back and found these pictures to more clearly show what I am going for. This was a mockup of my old RD350 project (which of course @irk miller finished off in a fantastic fashion) These are more or less the proportions and style that I'm roughly shooting for. Funny enough these are the forks that I'm using, though they made a rip FROM Georgia, TO Ohio, BACK to Georgia and then once again BACK to Ohio haha Irk has these supermoto wheels on his FT500 as well. I digress.

I sourced another set of supermoto wheels. One is a complete front wheel that is from a CRF450 and the rear is a bare hoop that I will lace to a spare dr650 hub that I have, which should make swingarm fabrication pretty straight forward. Also, on the general wheelbase topic, the AC RD 350's have a wheelbase of 52", though the rake is 27 deg. which I will steepen up to the 24.5 deg when I build the frame.

 

[Hurco550]

Hey, what's one more pivot in the grand scheme of things...

This project got back burnered, moved and so on for the sake of the old 49 ford truck and some house projects etc, and at the end of the day, building another frame from scratch is just out of my scope of probability at this moment in my life. I'll still do another one someday, but just not right now.

I've seen a few vintage style supermoto builds out of 96+ dr650's, and a couple by Parr moto really caught my eye.

Both are amazing builds, but the top one along with this one below both use a Suzuki ts250 tank, which seems to suit the frame about as well as an old tank can..

Over the last few years of messing with and owning several 96+ dr650's, I've amassed a good number of parts and bits, and I'm planning to build this with a budget and using as much on hand stuff as possible. I picked up a set of 05 rmz450 usd forks that I never got around to mounting to my 05 before selling. I have a sm front wheel from a crf450 with a 320mm rotor that I'll adapt to the forks. The frame came from a scrap pile, and the bottom end that was in it is currently powering the bobber. I have a friend in Vermont that is going to "sell" me the bike *cough *cough and that'll take care of the title part. I already had my sherif friend run the Vin to make sure it was on the up and up...

I hacked off the subframe and did a bit of mocking up.

I'm down south this weekend, and plan to stop by @john83 place to pick up the motor that I had previously mentioned in this thread, and @Kanticoy is hooking me up with a spare tank that he had tried on his bobber build. Fingers crossed for a quick build and braps to be had sooner than later...

 

[Maritime]

Nice! Say Hi to John and Kiley for me. I so hope to get down that way this summer/fall!

 

[ridesolo]

Watching and will ride along.