A tale of two (Ducati) Monsters

[jsudar]

I have the Monster almost fully assembled now. Still missing a few odds and ends. Which was the primary reason I’m assembling it— to see what’s missing.
After another month of riding my S4Rs and my Husaberg, and hanging around UMC for a track day, I think I’ve decided I want a super moto. But not just putting road tires and big brakes on my Husaberg. Really, I guess I want the Hypermotard Ducati should have built. Let’s be honest, if you’re aren’t actually racing super moto, a super moto is just an awesome hooligan bike. Need to pop over a curb or median? No problem. Have to blast up some stairs? No worries. Trying those things on a Hypermotard will probably not go well. The Hypermotard is just a street bike with a dirt bike riding position-which I like, but the Hypermotard only has like 40mm more travel in the fork than a Monster and the rear travel is about the same. Not a serious hooligan bike, but awesome in it’s weird category defying way.
Anyway, I want a Hypermotard that I can hit the giant speed bumps in my neighborhood at 40 and not even have to stand up (they’re a first/second gear affair on the S4Rs.)
Here’s the plan: Africa Twin front forks. These are perfect because they’re 230mm travel, so they won’t raise the front end sky high like a dirt bike fork would, but are nearly twice the travel of the stock Monster fork. They are set up for twin radial mount calipers and an off the shelf lower bearing will fit the fork and Ducati frame. Still need to machine a shim for the top though.
A bunch of math and AutoCAD tell me I should be able to extend the swingarm by 75mm and run a shock from a Ducati Desert Sled plus an adjustable pushrod to get me pretty close to 200mm of travel and the ride height I want.
Went to the Honda dealer today and pretended I actually wanted to buy an Africa Twin. Asked for a tape measure (which they had at the front desk!) and measured seat height so I wouldn’t look like a total weirdo and then went about taking a ton of fork measurements. Salesman asked if I was comparing against the BMW bikes. I told him yes to keep the questions to a minimum. But then I bought some new riding gloves so they didn’t feel like I was a complete waste of their time.
If my wife wasn’t forcing me to go to Hawaii for our 20th anniversary I would already be decimating the PayPal account. But I don’t want all my parts piling up on the front porch while I’m not riding motorcycles in Hawaii.

They only major issue I’m seeing will be my trail measurement. Dirt bike (and Africa Twin) forks have offset in the fork ends and triple clamps in order to get a high enough trail measurement with a 21” front wheel. Street bikes with their baby 17” wheels normally have no offset in the fork and only offset the triples because smaller wheels require less offset to get reasonable trail numbers.
They Africa Twin fork tubes will actually fit in the Ducati triple clamps (with some minor machining) but that netted like 65mm of offset and very low (unstable) trail number with a 17” wheel.
The stock Africa Twin triples have less offset than the Ducati triples but are designed for a 21” front wheel, so it’s still too much.
The only ways to increase trail are: less offset in the fork, slacker head angle or taller front wheel. I’m really hoping I can do this without cutting the headstock off to change the head angle. Although I have done that particular operation on a pedal bike, so it’s not out of the question. I may be machining new triples and hoping the turning radius doesn’t suffer too much ( forks hit the frame sooner with less offset). We’ll see.
Sorry for the long post. Too many thoughts.

 

[Gravy]

Supermoto is wicked fun. I spent a day a SoCal Supermoto around Thanksgiving.
If DRZsms weren't miserably slow on the actual road I'd have one.
That's kinda where I'm at with my Desert Sled. Just a little more dirt leaning.
I have some 17" supermoto wheels that I tried to put on my Husqvarna a while back and thought better of it. I'll take some pics.

 

[jsudar]

I changed my mind again and now I’m going with KTM 950 SM forks. I got fork tubes, axle and brake lines on eBay today. Still need to track down some triple clamps.
The downside of this is the SM fork only has 200mm travel. Feels kind of watered down from my original hope for 250mm of travel. But even the Africa Twin fork only had 230mm.

The upside is: dual radial caliper mounts and no offset in the fork lugs. And it cost less than the Honda fork.

Any fork designed for 21” front wheels (like the Africa Twin) has offset in the fork lugs. After careful consideration, I would have had to decrease head angle by 3* AND go to a 10mm offset triple clamp to get the trail where I wanted it if I used the Africa Twin fork. I would have had machine my own triple clamps to get that little of an offset and then the fork legs would have contacted the frame too soon leaving me with a terrible turning radius.
To change the head angle by three degrees I would had to lower the back end of the bike a huge amount or cut the headtube off and reweld. Neither of those options sounded great.
The KTM SM fork will only require me to machine bearing adapters for the head tube and give me the trail I want with a 30mm offset triple and a 1* head angle change. Also it will actually only raise front of the bike 65-70mm which will be easier to match at the rear (both height and travel) without crazy swingarm mods.
Here’s that part that might be really awesome: most of the WP 48mm forks were pretty similar AFAIK. There’s a good chance I can remove the SM zero offset fork lugs and install them on a 300mm travel dirt bike fork. Then I’d have the trail I need with all the travel. It may be a trick to get the rebound adjusters to work, but I think it’s possible.
I’m going to try it out at 200mm and see how the bike rides. If that’s not enough for proper hooliganism, I’ll step up to dirt bike forks and rebuild the rear end to match.

 

[jsudar]

I don’t know if any cares, but this is the calculation for mechanical trail: (sin HA x R - total offset)/cos HA

HA is head angle
R is radius of front wheel
Total offset includes triples and fork lugs

My head angle will be 25*
Radius of a sport bike front wheel is 300mm
I’ll be using 30mm of offset

(sin25 x 300 - 30)/cos25 gives me 106.7mm of mechanical trail. Mechanical trail is measured perpendicular to the steering axis instead of along the ground (ground trail). Mechanical trail is the actual measurement of the lever acting on the steering system. A lot people measure ground trail (especially in the bicycle world) but it’s not really a useful number IMO, just slightly easier to calculate and draw.

 

[jsudar]

Couple updates: got exhaust head pipes from a Multistrada 620. The horizontal cylinder head pipe routes along the right side of the motor instead of underneath. This will net many more inches of ground clearance. Haven’t seen many Monster head pipes that aren’t scratched or smashed under motor.

Got the KTM SM forks. They are very much bigger than I had expected. 190mm longer than the stock Marzocchi forks. The uppers are only an inch shorter than the 300mm travel WP 48s on my Husaberg. This makes me think I can probably get more travel out of them. But they are so tall! Now I have to revisit my plans for the rear suspension.

I found some Ducati Hypermotard lower triples that will fit the 60mm WP forks with a very light bore job. Going to try a stock Monster upper triple. Need to bore 3.5 to 4mm out of it. More than I am very comfortable with. Kinda risky, but I haven’t seen a lot of upper triples breaking, so, um, YOLO? May end up machining my own upper if the stocker looks too sketchy after it’s bored out.

Also picked up a Multistrada 620 swingarm. Parts for the Ducati everyone hates can be found quite reasonably. It will get cut up and combined somehow with the stock Monster swingarm to make some Multiverse Monsterstrada Swingers swingarm. Probably have to weld a pineapple onto it somewhere.

 

[jsudar]

I picked up a Hypermotard lower triple on eBay. The steering stem is about 60mm longer than the Monster’s, however, other than length, they are identical. And no match for the 50 ton press. After I bore the fork clamp holes, I’ll press the Monster steering stem into the Hyper triple and all should be well. The steering stops are slightly different, but I think they’ll be okay. I also took the opportunity to upgrade from ball bearings in the headstock to tapered roller bearings. BTW: 1.5” rigid conduit is the perfect size to support the triple and receive the steering stem during removal

 

[jsudar]

Got the triples bored out. Then discovered the clamping areas on the forks are too far apart to work with the shorter Monster steering stem, so the Hypermotard stem went back in. Now, I’m going to machine a headstock extension piece that presses into the existing headstock and moves the upper bearing up 38mm. If it works well, it will probably get a fusion pass with the TIG. While it’s more work, it will raise the bars without having to go with big risers, so it’s not a bad thing. And most importantly, the forks will fit.
The KTM forks use a 30mm axle while the Ducati axle was 25mm. The front wheel had 25x47x12 bearings, but I was able to find some 30x47x12 bearings from an automotive air conditioning compressor that will drop right in. The new bearings have much smaller balls in them, but they are a double row bearing vs. the single row they replaced. I’m pretty sure they’re opposing angular contact bearings so they should handle the loading okay. If not, I’ll machine the hub out to fit 30x55x13 bearings. Or spend a million dollars on some Kineo spoked wheels.
Now, I’m just waiting on some material to turn a new bearing spacer thingy that sits in the hub between the bearings. Then I’ll spend an entire paycheck on some Brembo radial calipers and rotors and hope that spacing works out since the Ducati triples are slightly narrower than the KTM ones.

 

[1969honda]

Mmmm you said Kineo. Used to have a '69 cb350 with a nt650 SSSA, triumph eccentric and a custom axle collar to accept a vfr400 wheel. Always thought It look killer on some Kineo rims if I won the lottery.

 

[Gravy]

I've got a 21" and 18" KTM wheelset.
Probably could split them up.

 

[jsudar]

I've got a 21" and 18" KTM wheelset.
Probably could split them up.

Thank you, but I’m pretty committed to my 17s at this point.

 

[Gravy]

I've got a set of KTM (fitment) spoked 17" DNA racing Supermoto wheels and with brand new tires I'll likely never use

 

[jsudar]

Got a 30mm hub bearing spacer made. Stock Ducati on the right, new one on the left. Now my Ducati wheel goes in the KTM fork.
Also have the beginnings of my headstock extension. It took a $95 piece of 4140 steel to make that. Crazy thing was, they wanted $107 for plain carbon steel in the same dimensions.

 

[jsudar]

Headstock extension is all done. Got my dual rotors installed and checked all my caliper measurements. Had to make a custom axle spacer to center the wheel. 90% sure the calipers will bolt right up, but it’s a $250 gamble on a pair of used Brembos. But I already have a pile of “no longer useful” parts from eBay, so whatever. It’s only money. I’ll just make more. This weekend I’ll get the extension pressed in and a bracket fabbed up to attach that sexy Acerbis fender.

 

[jsudar]

Just waiting on some gold Brembo calipers to arrive from Italy and the front end is pretty much finished. Then on to the rear end…

 

[rholbrook]

Are you turning this into a full time adventure bike?

 

[jsudar]

No, it’s more of a hooligan commuter bike. I work at the mouth of Provo canyon and live near the mouth of AF canyon, so Alpine loop and Cascade Springs are often parts of the ride home. I just want something with a more upright riding position than my S4Rs, but still sporty and with enough suspension travel to get over a curb or something. And I like building weird stuff.
It’s not dirt oriented at all. I thought about making a Dirty Monster, but it’s just too heavy. For the kind of off-road riding I do, I often feel like my 275 lb Husaberg is too heavy. Makes me want another two stroke.

 

[jsudar]

Got some fancy gold Brembo calipers shipped in from Italy. Turned some spacers on the lathe to get them pinching the rotor in the right spot. Have no idea what bike they came from. I only knew the 100mm bolt spacing and 30mm offset were what I needed. Hopefully, there’s not a ton of Brembo front brake pads to choose from when it’s time to get new pads. The banjo bolts fit nicely with the KTM brake hoses, so that was a plus. Also, got the headlamp assembly on there. It’s too small for my taste. I made have to make some Kydex shrouds or something to make it larger. Already planning on some custom formed Kydex fork guards.

 

[jsudar]

Currently, I have an air cooled 620 cc with a five speed transmission for this bike. It makes 63 HP. That does not sound like fun. My other Ducati makes twice the horsepower.

I have a six speed gear stack that I *think* will fit in the case, but I won’t know until try. And since I’ll have to split the case, it only makes sense to put in 88mm high compression pistons and cylinders and new rods while I have it apart. That would make it a 750cc. And probably get me 75 HP and cost $1500. At least. Then there’s dyno tuning….

I’ve found a running bike with a 1000cc air cooled motor that should drop right in. 38k miles. The air cooled liter bikes made 85-90 HP. It’s $3k for the whole bike. That’s a big up front investment as opposed to buying parts for the rebuild over a few months. The 1000 is also a larger, heavier motor than the 620/750.

Neither of these will make the kind of power my liquid cooled engine does, but the air cooled engines have their charm too.

What would you do? Big cc motor swap or build the smaller, lighter motor?

 

[Corban_White]

Option c, just drop in the 5 speed engine and ride. . Once you aren't having fun doing that, then worry about upgrades.

 

[Gravy]

I think a monster based anything needs a round headlight. The new 2021+ with the drl ring could be found on eBay. Or just a strong 7" or 8" LED.

That halogen polisport unit sucks. I had it on a YZ I made street legal. It was like a candle in a mason jar.

I'd run what you have for a minute and see if you want more motor first? Gearing makes a difference too if you never plan to run it 100+ mph down the freeway just delete a tooth up front or add 3 or 4 in the rear and enjoy.