CB900 Scrambler - Rally Approved!!

Re: CB900 Scrambler - Now with 150% more video!!

Pretty cool vid, shows proof of concept works as 500lbs bike on dirt is going to be hard work whatever you do.
The fact you did a lot of miles means it must be pretty easy to ride most of the time?
I'm guessing the last couple of minutes was an uphill section with some large (ish) waterbars?)
Thanks for posting
 
Re: CB900 Scrambler - Now with 150% more video!!

Parts in the mail!

Wile_E;21829600 said:
After much delay, XR650R front end is headed your way.

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Speaking of delay, what took so long? I was using my free cycle time to prep the sub-sonic swine for hare scramblin' on the 4th of July. Now that all that is wrapped up, I got everything sorted and stuffed into cardboard. It looks like someone might have hit something really hard with the front wheel, just sayin. :evil

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Re: CB900 Scrambler - Now with 150% more video!!

10 Days until Rally WV and the racing debut of the scrambler.

I have questions about steering stops below...if you have any knowledge please lend it.

I got the XR650R front end in the mail last Friday but I already had riding plans over the weekend so I did that instead. Saturday the 900 got the nod. A buddy and I went out to central Ohio near Tar Hollow and Zaleski state forest to do a bunch of gravel roads from a road enduro route sheet I had from a couple years back. In total it was little over 180 mile loop and weather was awesome. The bike ran flawlessly too.
Saturday I took the 450 out to Dayton Dirt Riders club for about 4 hours of technical hills and trails. Epic day but sweltering heat.

So last night I got the forks and triples out to do some dry fitting to decide if I'm crazy to modify a bike that already runs really well on back roads. The racer in me would regret not trying since I think it will allow the bike to handle rough stuff faster.

Here's the bike at the beginning of the night.
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Everything came apart with the tools in my tool pouch. I left the brakes and throttle hooked up. lazy ass.
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This was one of those nights when the beer is cold and things are going right.

Keep in mind that these bikes rolled off the assembly line 21 years apart and where "originally" designed to serve two very different roles. These Honda guys stick with what works.

The fuse panel/upper handlebar clamp/choke cable mount fits the cast upper mounts on the 650 perfectly.
The 650 upper also has a set of mount holes from stock odometer that I can use to mount the ignition switch and the trail tech instruments.
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The stem has the exact same measurements (as predicted). Threads are the same and the length/location is spot on.
The top bearing is an exact match.
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The 650 forks are set wider so I only lose a few degree of steering turn on each side despite the fatter fork diameter.
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This set-up didn't come with a master cylinder but I started digging through the parts bin from the CL/FT500 and I found a brand new nissin unit in black. As an added bonus the taller reservoir will be better than the stocker which was designed for bars with a down bend.
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So there's still work to do.

Have to fabricate a plate to mount the ignition and gauges.

The lower bearing on the 650 is shorter and has a smaller outside diameter. Since the shaft is the same size I'll try to transplant the stock one but if I destroy it I'll get a new one in the mail ASAP.

New steering stops are needed to keep the forks from mashing the tank. Should I have a wider stop welded to the head tube or have some aluminum blocks welded to the lower triple clamp?
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The ignition lock plate needs to be modified or removed. I'll probably just trim the top edge off for now. It's very thick steel so it won't suffer any real performance loss.
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Once these things are handled I'll get into the forks and decide how much to limit the travel and trim the springs.

Other stuff to do in the next 9 days.

I still need to fabricate the mounting brackets for the eye-to-eye rear shocks.
Need to figure out a front fender mount. This may be the trickiest part of the whole deal.
Also need to make some number plates and transfer my numbers over.

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I'm going to get back to work now.... ;)
 
Re: CB900 Scrambler - Now with 150% more video!!

Either weld blocks to lower yoke or just drill through and bolt some on
It's much easier to carry a yoke around than a motorcycle with no front end, plus, you could get some distortion of bearing 'cup' in frame
I would probably 'clearance' the tank (or get one that's already dented/damaged to modify)
If you can manage the extra height I would set rear shocks to keep bike lebvel. XR/XL springs will be too soft for CB900 so you'll probably get a lot of static sag?
Don't forget to fit camera and don't forget to turn it on when your racing ;)
 
Re: CB900 Scrambler - Now with 150% more video!!

I would consider drilling and taping the stops that are already on there, they look meaty enough, make a plate to fit and conutersink it and use countersunk bolts and thread lock. That way you can adjust it with different thickness plates.

What is the difference in the weight of your slimmed down 900 and the XR the forks came from. I bet your not more than 40-50lbs more.
 
Re: CB900 Scrambler - Now with 150% more video!!

XR650R with oversized fuel tank would be in the 300 pound range. It carries it high and feels heavier. We'll see how the spring rates turn out.

I'm liking the drill and tap idea more and more.
 
Re: CB900 Scrambler - Now with 150% more video!!

Did some more mock-up work on the front end last night. I decided to make a new stop to mount to the existing stop on the steering tube rather than modify the aluminum triples. One more nice thing about the honda engineering...the lower headlight mounting holes are the same distasnce apart.

The stock fender doesn't fit between the thicker lower shocks from the 650 so me hammering may be in order before I can even think about maching some mounts for it.

I'm trying to decide if I want to go full knobby on the back for the race or stick with the 50\50 tire...hoping I have time to try the knobby. The 50/50 tire may be better though since it has a taller, rounder profile. It tracks and slides nicely. The dirt tire may be more prone to grip strong and then break loose suddenly. The heavier bike may make that less noticable. If the logging rodes are wet/muddy or have deep gravel I think the knobby will win out.

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I put the shocks on and the forks/ front wheel to get and idea of static sag and ride height.

Here are a few different mockup pics....

It will ultimately look this but with a few inches of sag front and rear to level it out. It doesn't sit level on the jack.
Thw 650r top clamp brings the bars back and up a little more than an inch so it improves the feel big time. More dirt oriented position for sure.
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These are interesting...

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Can't wait to see the UPS box so I can wrap this up.
 
Re: CB900 Scrambler - Now with 150% more video!!

If you go full MX rear it would probably be sensible to get MX tyre for front as well.
Luckily, since almost all MX bikes now use 19" rears they are readily available pretty cheap (although 21" will roll better if its bumpy and cut through sloppy stuff to something solid as it's narrower
Going to look 'professional' if you turn up with multiple wheel/tyre combinations ;D 8)
 
Re: CB900 Scrambler - Now with 150% more video!!

The 650 front wheel is a 21. I have a front knobby that's about 90% that I'll be putting on. I'm hoping the dual pot caliper and braided line for the modern setup will be an improvement. The rotor is thinner but the same diameter and drilled. For the front I think the lighter wheel and caliper up front will be close to the same weight when the beefier forks are considered.

I'm going to pull the rear wheel from the CL/FT500 to see if it fits as a back-up. It's from an earlier CB and looks identical but we'll see. It's an aluminum rim which is cool just for less unsprung weight. I can't bum a spare wheel for the CB the way I could for the KTM so a backup would be nice if I start to lose a bearing or spokes or something....
 
Re: CB900 Scrambler - Now with 150% more video!!

I spent some time in the machine shop over the weekend.

I'm making something like this for my steering stops.
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My order for bearings and a brake line that I places last Tuesday hasn't shipped yet so I'm pretty pissed about that.

I found a local bearing shop with what I need. I should have done that in the first place. I can scavenge the other parts.

I'll finish the steering stop, dash and shock mounts after work tonight. Tie it all up tomorrow night and then do a shakedown on Wednesday.

Keep calm and carry on... 8)
 
Re: CB900 Scrambler - Now with 150% more video!!

shameless plug....

I got a NOM for bike of the month...Thanks Rich Ard

If you've enjoyed my hairbrained scrambler scheme I'd appreciate your vote.

LBC

...end of shamless plug...back to the garage....
 
Re: CB900 Scrambler - Now with 150% more video!!

nothing wrong with a shameless plug. Keep up the good work and heres hoping for success in in BOTM
 
Re: CB900 Scrambler - Now with 150% more video!!

Well, I'm out of time on the long travel CB suspension. :mad:

I did myself in by not jumping on the project a little quicker when the forks arrived. By the time I had my plan together I stalled waiting for parts that were needed to finish some of the fab work. It'd take the next two nights working late just to get it all together and I'm not about to race without testing the new setup.

So I'll be running the stock forks and I ordered some stock replacements for the totally busted rear shocks. Those should arrive tomorrow.

I'll finish the fork swap when I get back and can do it without cutting corners.

The steering stop turned out nice and I like the 21" front wheel for sure.

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3 Days to Rally WV
 
Re: CB900 Scrambler - Now with 150% more video!!

Its a shame but better to err on the side of safety. Especially out in the wilds
 
Re: CB900 Scrambler - Now with 150% more video!!

Here's one for Rich Ard! Pristine, baked-on, WV clay patina after 400 miles of RallyMoto. If a muddy "street' bike makes you squeamish look away.

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Ride report will follow when I get home.

Cheers...
 
Re: CB900 Scrambler - Now with 150% more video!!

I love this bike.
 
Re: CB900 Scrambler - Now with 150% more video!!

I can't wait for the video (you did take some?)
 
Re: CB900 Scrambler - Now with 150% more video!!

Now thats what I call riden (ridden) whatever
 
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