OT, works bikes

[Ride]

Of topic stuff...

Remember back in the day when when the factories were works bike crazy, before the production rule? I wonder how much that production rule stifled advancements in off road bikes? I for one figured telescopic front forks would be long gone now. 15 years ago i figured we would all be on clean burning fuel injected turbo rotarys with fluid drive and active suspension that weighed 150 pounds. Now days it seems so formulated with everyone building a CRF. I find it a little frustrating even given as good as the current bikes are. Additionally as good as we think they are a mag did a test a while back and found the old Maico 490 is not to dissimilar from a modern 4st.

Rodger Decoster was quoted not long ago that that Suzuki works bike with the Ribi lever front suspension was still to this day the best front suspension he ever tried.

I used to LOVE looking through the pix in mags of the crazy works bike from all the manufacturers and the wild after market efforts like Mugen. I miss that stuff.

Duel exhaust, Ribi fork etc...

Article on the subject by the man himself...

http://www.dirtbikemagazine.com/archives.asp?var=read&id=21

Also found this cool site while looking for pix of that Suzuki...

http://www.mxworksbike.com/index.htm

[maru]

A wise man once said that championships are won with obsolete equipment. Having said that, telescoping front forks will be replaced just as soon as something works better. Guys with pocket protecters have been telling us how bad they are since before all the current racers were alive. Maybe they were wrong.

[Norman_Foley]

Works bikes were cool..... I guess Stefan Everts' aluminum framed YZ500F open class bike was last radical(sort off) works bike. It was nothing like the production bike or what the aluminum framed YZF later became. 500 class was still tops in Europe then, before it was demoted to MX3 and its own lesser series. No production rule in Europe or Japan, but bikes now are just prototypes for next years models with some cool handmade parts. The Italian company WRM, with the mostly carbon bike will have a World MX team this year, that should be interesting.

I remember reading in Trail Rider 30 years ago(New England Trail Rider in those days) that the telescoping fork and 2 stroke motors would be dead in a couple of years. BMW has been the leader in alternative front suspension for years and when they raced Dakar they used telescoping forks and their 2 most dirt focused bikes 650 X-cross and HP2 have telescoping forks. I guess that says a lot.

Norman

[tm_enduro]

I think offroad riders would probably fall over on the trail in a state of euphoria if we ever got a linkage (no stiction or binding) fork. As a physics / engineering type, I have waiting for that since I first saw it.

[Norman_Foley]

I think offroad riders would probably fall over on the trail in a state of euphoria if we ever got a linkage (no stiction or binding) fork. As a physics / engineering type, I have waiting for that since I first saw it.

Would a Greeves qualify?

[arod2000]

Those pictures are awesome. Thanks.

Timely discussion. I'm looking at buying an '04 Gas Gas 300 this weekend. When investigating the brand a little more I see that some of the technology in the bike is quite a bit older (while some is newer and even ahead of the rest). The older technology part really surprised me since most people that ride these bikes rave about them.

I guess the best technology at the right price wins. And to think blinkers are what put Husqvarna back on the map recently.

[Ride]

I think offroad riders would probably fall over on the trail in a state of euphoria if we ever got a linkage (no stiction or binding) fork. As a physics / engineering type, I have waiting for that since I first saw it.

I totally agree. The geometry of these linkage front ends can also be designed to be anti dive. Additionally using linkage eliminates binding under hard braking, like coming into corners hard and you can set them up to be as progressive as you want. I believe the idea has a lot of merit and is only being ignored because of customers perception, and convenience of existing tooling for the current setup. No one seems to want think outside of the box anymore. Hell, Yamaha "revolutionized" the 4 stroke and it completely changed the face of dirtbikes. I think similar revolutionizing of suspension and mass centralization would produce bigger gain than that.

I have thought for many years that the airbox needs to be where the tank is with a down draft carb and then stuff the gas tank right behind the forward tilted cylinder and right above the crankcase for a massive shift in mass centralization. Ever notice how a full tank verses a empty tank effects suspension and handling? this could be greatly minimized. Husabergs do this to some extent.

i was so disappointed when Cannondale had a clean sheet and built a heavy CRF with a reversed head

[Norman_Foley]

I guess it will take a big four company to do it and make it stick. I will say brake dive is bad in that the suspension locks up, but thought that the tightening up of the geometry was a benefit in tight woods turning.

[Dirtybill]

Would a Greeves qualify?

There's a guy in these parts that brings his out to classic/vintage events.

I wonder if he's the same guy I've seen on a Cotton??

Also saw a Nimbus in running order about a year ago. Think it's a Swedish bike?? Or Norweigan?

[thillsam]

I totally agree. The geometry of these linkage front ends can also be designed to be anti dive.

The Ribi front ends ARE anti dive, and furthermore the amount of brake-actuated anti-dive can be adjusted by some simple geometry changes...look at the pullrod the holds the brake plate on the Suzuki picture - see the adjustment holes? Most of the other Ribi front ends I have seen have similar means of adjusting brake-actuated dive resistance...

Speaking of anti-dive, how about the linkage that is actuated by the rear brake caliper on this one(look closely at the rocker above the rear swingarm):

The rocker midway up the swingarm turns a push around a bit of a corner there into a pull that squats the rear end(reduces wheel rate) during braking - very cool!

I have thought for many years that the airbox needs to be where the tank is with a down draft carb and then stuff the gas tank right behind the forward tilted cylinder and right above the crankcase for a massive shift in mass centralization. Ever notice how a full tank verses a empty tank effects suspension and handling? this could be greatly minimized. Husabergs do this to some extent.

EFI opens up a lot of opportunities for this...up to now, almost every carburetor had to be gravity fed - the tank has to be above the carb. You could get around it with a pump, but few MXers had DC power for a pump...Not anymore with EFI - you have to have DC power for that, but I dont know why no one has taken advantage of this yet in the off-road world...

[thillsam]

More of a Honda works bike with Ribi front suspension variant:

[AJSB]

Portuguese AJP uses since day for a long long time in all models a carb with a "depression" pump...fuel tank is transparent and bellow seat...fake tank has air filter and a small battery in current PR4 125/200 Enduro range.

[Ride]

EFI opens up a lot of opportunities for this...up to now, almost every carburetor had to be gravity fed - the tank has to be above the carb. You could get around it with a pump, but few MXers had DC power for a pump...Not anymore with EFI - you have to have DC power for that, but I dont know why no one has taken advantage of this yet in the off-road world...

Actually there is a long standing and super simple solution for this that has been used a lot. A pulse activated diaphragm fuel pump. Simple, light, effective. i worked on a Yamaha Tri-Z 250 YZ powered three wheeler once, had the gas tank under the seat and one of those little diaphragm pumps about the size of a half dollar, worked perfect. And, Yamaha has had nice down draft carbs ever since the genesis 5 valve motor showed up about 20 years ago.

[Ride]

I'm more than half tempted to build one of these and try it. I have a design i have been playing with for years that takes this idea a step further and is supported more from the motor area than up to the current headstock area. This eliminates the high placed weight, the frame needed to rise up and the travel all the way back down to the front wheel. Basically the load is transferred back to the frame instead of up. I've been a bit of an alternative suspension freak for many years and have looked at every design out there. Anyone remember the RADD front end? Found some production on a Yamaha street bike and was used on some Honda Protos?

[thillsam]

I'm more than half tempted to build one of these and try it. I have a design i have been playing with for years that takes this idea a step further and is supported more from the motor area than up to the current headstock area. This eliminates the high placed weight, the frame needed to rise up and the travel all the way back down to the front wheel. Basically the load is transferred back to the frame instead of up. I've been a bit of an alternative suspension freak for many years and have looked at every design out there. Anyone remember the RADD front end? Found some production on a Yamaha street bike and was used on some Honda Protos?

Wheelpath is the ultimate bottom line in suspension. Damping rate and wheelrate within that wheelpath is next on the priority list. In the case of the front of a high-CG vehicle like a motorcycle with a standing rider on it, braking and acceleration behavior is next.

The RADD system has an arced wheelpath, the early stages of which moves the wheel FORWARD relative to the bike = bad for small bump compliance. The wheelpath needs to do the opposite - like the rear does on any modern bike - move back as it moves up("trails"), especially in the early part of the travel where square edged bumps are most likely to start the stroke of the suspension. RADD is fine for the street, but would never work very well in 95% of any offraod situation.

Remember the Yamaha BASS(Brake Activated Suspension System) that they implemented on the rear of dirt bike in the late ~80's? It halved compression valving on the rear during rear brake use, to try and get the rear end to pack a little further as the front end dove during braking - and maintain consistent steering geometry better. The bottom line is that it was an easy way to preserve steering geometry during braking.

They had a braking system on street bikes that ADDED a bunch of compression damping to the fork during braking, I can't remember what it was called but it did make for a much more positive braking feel...but the bike still dove as far if the braking stretch was long enough.

Ideally, in the dirt anyway, you'd want to add preload to the front end during braking(NOT spring rate/wheel rate as some might think). Mechanically, though, this is much more difficult to do in the response time window you have in an emergency or racing braking situation...it could be done with airsprings though...

[thillsam]

...A pulse activated diaphragm fuel pump. Simple, light, effective.

They used these on snowmobiles for a long time too, and also marine outboards and chainsaws...I always wondered why they never used them on motorcycles. If the diphragm was stood up vertiaclly, the g-loads of landings and such would not be a problem.

Of course these only work well with twostrokes, too...

[Flame]

Anybody got a photo of the old Sach's with the leading link front suspension? If so please post it.

I almost bought one of those in the late 60's. It was only a 125 though and is why I didn't buy it. I bought a 250 Montessa Scorpion instead.

I'd love to look at that Sachs again though.

[ss440gp]

Anybody got a photo of the old Sach's with the leading link front suspension? If so please post it.

I almost bought one of those in the late 60's. It was only a 125 though and is why I didn't buy it. I bought a 250 Montessa Scorpion instead.

I'd love to look at that Sachs again though.

Are you talking about a DKW? Didn't that have a Sachs Motor?

[tm_enduro]

If I recall correctly, when Honda picked up Roger DeCoster, he said that he would ride the Honda on one condition, that it have a Ribi front end, because it was the only way that he could ride with his injured shoulder. So Honda went out and bought the Ribi patents and then "went wild" with tricking it out. Sooooo, if we are to ever see it in production, it will be on a Honda.

There is alot of room for improvement in suspension once folks start playing with linkage (and can keep bearings tight). One only has to look at the mtn bike industry to see how much difference linkage makes. The four bar design licenced by Specialized to many other mfgs just plain works (it worth noting that I first saw this basic design on a Kawasaki in about 1975).

FYI, my 1992 Husaberg used a fuel pump to pump fuel from the lowboy tank to an upper reservior that gravity fed the carb. And yes, Husaberg still does a good job of mass centralization.

[jr50kid]

They used these on snowmobiles for a long time too, and also marine outboards and chainsaws...I always wondered why they never used them on motorcycles. If the diphragm was stood up vertiaclly, the g-loads of landings and such would not be a problem.

Of course these only work well with twostrokes, too...

My '72 Suzuki XR400 snowmobile had a nifty little diaphram fuel pump to supply from the tank in the rear of the sled....simple and worked great.

paul