Thinking the Unthinkable - Auto Clutch on a Competition Trials Bike

[Motobene]

I recently got past yet another prejudice: that auto clutches and trials bikes don't mix. I am now intrigued with the idea of converting my trials competition bike to the way all my other bikes have evolved: auto clutch, no clutch lever, no rear foot brake lever. Only throttle, one-finger hand brakes, and of course shifting. Very simple, easy, and I have found - for me anyway - superior in capability and the confidence that keep this old man going and competing well.

For top-level trials riders a manual clutch is a necessary, even as a big handful of throttle, spinning up the flywheels and releasing the clutch for big thrust impulses is necessary. Big jap-zaps, splatters, and even the 'yeeeuhhh! pulse-thrusting style many use. The French are especially strong in this clutch-slip culture and their event favor that culture:



The VAST majority of trials riders do not ride that way. My jap zaps and splatters are now small and don't need the big throttle mass clutch dumps. I'm not getting any younger and there is zero chance of me wanting to do the really big stuff again. It dawned on my at my last practice ride that the way I set up my off road bikes would definitely be an ADVANTAGE for me in trials. That is: The hydraulic clutch becomes the rear brake, there is no clutch lever or manual clutch of any kind, and gone is the entire foot brake. The only job for a foot is shifting, and feet are for dabbing without worry of loss of rear brake. My present battle is to stay calm and controlled and not fragment into spastic movements when too many situations and control movements overload old (or odd) brain. That's true even when on simple slopes:

TEMP - buffalodream

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But also true with logs, steps, drop-offs, etc.

My other bikes have:

• Brakes always available, instantly, all the time, no matter where the brake foot is (reduction in sphincter puckering)
• Clutch control that is steadier and easier to meter by throttle/rpm than I can with the combo of manual clutch and throttle
• A rear brake that works like a clutch and in the same timing as a clutch hop and pop up on things from a standstill

At the heart of the benefits of the controls simplification is an auto clutch that works right... as it should, engaging resiliently the instant you crack the throttle and behaving in the broad slip zone proportional to the amount of throttle, without hysteresis. Engine braking that is entirely normal when you chop the throttle, and a clutch that does not release until a touch above idle, and so well that you don't feel the transition.

I don't have a lot of videos to show every characteristic, but here's one that shows getting up a steep boondock trail. I'd never ridden it before, but knew that if I could not stand up all the way up that my Rekluse Radius CX EXP 3.0 would handle butt-weighted clutch slipping very well. Listen to the consistency.

240116 West Mesa 390 + Rusty 300 - buffalodream

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Back in 2019, before I went auto clutch and changed my controls, I was happy with the Beta's manual clutch after modifying it:

2019 Beta 390 RR-S - buffalodream

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But I was having issues stalling the bike, and bikes like it, in compromising places, and hurting myself. So I humbled myself and went auto clutch and had this day of discovery the summer of 2019:

2019 Beta 390 RR-S - buffalodream

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From then on this system proved itself over and over and is now three of my bikes, including the latest big beast 701.

I currently know of two approaches to attaining an auto clutch on a trials bike. One is to send EFM a whole clutch assembly and have him make a ball-ramp-style auto clutch. I have never ridden a bike with an EFM clutch so it's a blank. I spoke to the owner and he states he can make an auto clutch for ANY bike. That's a pretty bold promise, all things considered.

The major trials brands except Beta and Hontesa have gone away from the conventional helical compression springs clutches. My TRS, like GasGas, Sherco, and Veritigo all have the diaphragm style and are typically physically smaller. Fitting in the centrifugal hardware and still having enough fiber and metal plates might be an issue?

DIRT BIKES – EFM Auto Clutch – The Auto Clutch Expert

A well known product to me are the older ball-ramp Rekluse auto clutches and their newer EXP (expansion pack) versions. I have three 3.0 version clutches. Their latest 4.0 version has refinements and looks quite good.

I know Rekluse don't make a clutch kit for any trials bike, but any trials bike that uses the same clutch plates as other bikes Rekluse does have kits for would make it possible for me to custom my own kit, as Rekluse would have the critical EXP and plates to fit the basket and the hub. I wonder if the Beta trials bike might share plates geometry with the RR and RR-S? If so, and with normal slave cylinder, the Beta trials bike might also be a candidate.

At present, I know the Montesa Cota could be a fit to existing Rekluse parts. The reason is the Cota clutch uses legacy clutch plates, a 22201- fiber plates and a 22321- steel plate. Rekluse makes an auto clutch for the CRF250F (22201-), so same EXP and fiber plates fit to the clutch basket, and they make one for the CRF450L and R (22321-), so same fit of the steel clutch plates to the hub. I was wrong about which models applied (see later post).

The most important requirement is the shape of the drive and driven plates and that determines the shape of the Rekluse expansion pack and their own thinner clutch plates.

The Cota is unfortunately weird in the use of a clutch-cover-based slave cylinder. That makes the clutch format 'bassackwards' at the pressure plate. Would that be an issue? Maybe not:

The CRFs have the clutch slave aspect (cam or hydraulic cylinder) on the left center case, thus 'forward-ackwards'

The CRF clutches are cable operated, which is strangely antique these days. Cable clutches make setting and holding Rekluse clutch-pack clearance at idle a bit more problematic.
I typically remove the cable and use only a threaded adjuster just upstream of the cam lever down at the engine. That gets rid of having the long elastic band (the cable) under constant tension,
from varying the clutch-pack clearance with steering degrees (which affects cable tension), and cable temperature, which also affects cable tension.

The Cota's clutch is hydraulic, which is good.

...so the clearance could be set by machining in a setscrew in the center of the cover to push on the slave cylinder piston backside.

That's how the Rekluse slave cylinder works:

Given I don't need anything hydraulic a simple setscrew would work in a Cota as I don't have to seal brake fluid or mineral oil.

I will talk to EFM about braving their auto clutch for my TRS.

Buy a cheap used Beta to try that angle with Rekluse?

I think I'd be more inclined to buy a NEW Cota just to do something new and work getting an EXP 4.0 to fit the HRC motor's clutch. Been gaining some interest in these heavy sleds anyway

 

[Motobene]

One of my options is stick with what I have, the TRS, and try to force an auto clutch into a ridiculously tight space. The chances of that even starting are near zero because the so-called 'diaphragm' (single-Belleville-spring) clutches are quite different than the clutches around which auto clutches have evolved. Belleville-spring clutches have have higher clamping force than helical coil springs clutches, allowing use of less than half the number of clutch plates. The brilliance of that design is clutch lever force is lower clutch lever force with respect to higher clamping force, and less pressure plate lift than helical springs clutches.

I recall in the `70 when I was deeply into rebuilding VW engines that there were two pressure plate designs available. The best one for feel, slip and pedal force was NOT the one that using helical compression springs. The HRC Montesa 6-helical-springs clutch is very good clutch, but I find all the helical-springs design are slightly, but noticeably, inferior. That the Montesa is a 4-stroke helps calm things, but once you experience a fine single-Belleville-spring clutch it's hard to un remember the experience.

One way I have often improved the clutch performance for most rider is to reduce the net clamping force by simply removing six springs out of conventional clutches. Less lever force and a wider slip zone. That's the 'modified' in the Beta 390 video in the first posting of this thread. You can hear in the video more elastic engagement and I've never had a reliability issue with a 6-to-4-springs clutch, even with a lot slipping technique used over many years.

Back to the problem adapting auto clutches to the single-Belleville-spring (part 14 below) clutches. They to 'too' compact!
For example the TRS (Xiu RDi-type) clutch:

This type of clutch reduces parts count and size, in part through manufacturing precision of a unitized steel clutch basket, primary, and kickstart gear. Traditional clutches have a cast aluminum basket swage riveted to a steel primary and kickstart gear for more runout and slop unless great care is taken in manufacturing. Aluminum clutch basket tangs can be stickier on release and end up with plate contact-wear areas. Rekluse uses very thin clutch plates. They dealt smartly with higher plate-basket contact stress via slip-in steel parts so plate-to-basket contact is steel-on-steel.

The biggest auto clutch implementation issue is there is no room for an EXP-type expanding pack, and it's harder to adapt a ball-ramp assembly on top of the clutch basket. Worst is the reduced plates count and space constraints would make auto clutch design a major program. I don't do those any more.

So I'm back to the Hontesa being maybe the only viable bike to even try to pull off an auto clutch on a trials bike. Rekluse is my best bet for technically-sophisticated parts, but they may have zero interest in supporting me to one-off something, unless they are just curious. And these days my technical publishing has almost no reach , and Rekluse knows just what a hard sell 'different' is, and that reduces market share. Graham Jarvis, when asked about an auto clutches, replied, "Well, I've never certainly tried it and the extreme dump of the clutch is so important for that control... you lose a bit of control with it." Right....



Few will go big picture such as loss WITH gain and that's the end of it. Pfft! if that's true in the larger offroad bike market it will certainly be true in the dinky market that is trials!

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I tried to find decent videos on the EFM clutch to figure the design out. The first video isn't very good, but between that and the second showing some CAM software, I can take a good guess in how an EFM clutch works.





It's just another twist on the classic balls-ramps idea, like this older Rekluse, and the defunct Revloc:

What's different about the EFM is the expansion plate is affixed to the clutch hub (see the bolt circle fasteners around the outside). That allows EFM to ship a clutch whole and to assemble it on the tranny shaft whole. The hole in the center is access for the hub's washer and nut. The usual ramp-ball arrangement is used and the pressure plate, which floats free, or with some kind of spring resistance under the outer plate, presses against the clutch pack when the balls sling out. My guess is the stock clutch plates are used. I don't see hard coating of the aluminum parts and wonder about long-term wear issues at the ball-ramp interface with a line-contact around each ball's contact with upper and lower plates. Line contact means high pressure and high pressure plus vibration can translate to wear.

The modern Rekluse is the most sophisticated of the available auto clutches. The following video on the new EXP 4.0 clutch. It's marketing fluff but with enough tech detail to be credible.

They claim a more normal feeling to an override clutch on EXP 4.0 than 3.0, but I'm after the stark simplicity of hand brakes only with the rear hand brake uncluttered by another lever in that ergonomic space. The critical thing for me is how well and consistently and predictably an auto clutch slip-engages and has predictable engine braking then disengages unobtrusively.

 

[ZoomerP]

I look forward to seeing where you go with the idea. You may find Rekluse more agreeable than you think since some of the parts already appear to be on the shelf. With the help of the right person, maybe they can help you source the rest easier than you can by accessing their online catalog. It'd be neat if your investigation led to an addition to the Rekluse kit inventory.

 

[Nhuskys]

Almost 20 years ago, a few of us riding Italian Husky 2T bikes wanted to try an Auto Clutch. Rekluse had no interest in the application, but Gary at EFM went right to work build a clutch set up for us. Later I would use Rekluse in the Austrian Huskys I rode. I still believe EFM is a superior product to Rekluse.
I will add that I no longer run an Auto Clutch in my enduro bikes. Just my preference, not a good or bad thing. Good luck with your project.

 

[Motobene]

I had a nice long talk with Mike at Rekluse yesterday, and he is willing to support my project.

However, I found out more about this strange Honda part numbering system:

Honda motorcycle product codes meaning and how to decipher them - MotoFaction

Honda use a product code in their part numbers to show which motorcycle a part was first used on; here's a list, starting with those relevant to the Honda CX and GL family. Check it out!

motofaction.org

Rekluse does NOT make plates or EXP for MG3 = the Pro Link XR500 (steel plates) and KY2 = CBR400RR (fiber plates). Both are from legacy bikes, way back.
The other fiber plates are just the CBR plates with different friction material NN4 = Cota 4RT

The reply from Rekluse:

I wish I had better news but my guys aren’t confident we can help you out at this time. EFM may be the only option as of right now.

Sincerely,

Mike Campbell
Rider Support Manager/ Sales/ Tech

That leaves Gary at EFM. I sent an email full of tech info and left a message. We'll see what kind of response I get. IF he wants to go for it on an 'upside-down' type conventional clutch, I could buy all the clutch parts and send them to him. The assembly I get back could get dropped into a volunteer 4RT for testing. If it all pans out I'd consider the shiny new Cota to meet my controls goal, not just to have a Rekluse.

Or forget the project entirely. I already own three excellent trials bikes, all of which have the Xiu RDi-type clutches.

 

[FASTRacing]

Very interesting, I always learn something new reading your technical posts.
Thanks !!

 

[Motobene]

Almost 20 years ago, a few of us riding Italian Husky 2T bikes wanted to try an Auto Clutch. Rekluse had no interest in the application, but Gary at EFM went right to work build a clutch set up for us. Later I would use Rekluse in the Austrian Huskys I rode. I still believe EFM is a superior product to Rekluse.
I will add that I no longer run an Auto Clutch in my enduro bikes. Just my preference, not a good or bad thing. Good luck with your project.

I'll be away a while so a summary of thinking so far on this project. I'll circle back to EFM after wandering off a bit on stories.

The first bike I rode with auto clutch had the ball-ramp-style Rekluse or Revloc, I don't remember. An early Beta, pre-Beta engine, a 520 KTM RFS. I thought it interesting, but weird. I rode a 250 2 stroke later with one. Same impression.

Then an Arkansas dualsport ride with a friend with an older Rekluse on a 520 RFS KTM. I'd ride behind, listening to the resilient response to throttle and marvel at the weird pulsing rooster tail coming off his MT Parelli trials-type rear tire. During that ride I was on my much modified KLX330 with two of the springs removed from the clutch. Fun, spunky bike. Manual clutch dumps, popping up in the air at the crests of large wave-like terrain. Aaeeeeupp! Aeeeeupp! ...was all in good fun. My son now has that KLX.

Then the dive into EXP 3.0 and learning experiences.

A friend acquired another friend's 2005 WR450F with ball-ramp Rekluse. Set up late to engage and early to release, the clutch made the bike a handful. My friend wanted to toss the auto clutch as it was akin to sticky throttle tube and cables and a mile of cable slack. "Gimme a chance to make this thing work." I then had to learn about the older Rekluse and fortunately the bike came with the instructions and original extra parts for adjustments. I was after no hysteresis, throttle to response, getting rid of the delayed engagement and early release. Success! A wonderful clutch resulted and I was able to convince my friend to 'go all the way' to hand brakes only, no foot brake, not override clutch lever. Last year during a dinner conversation on the complexity of the FCR carburetor his wife, misinterpreting tech detail as 'don't like it' offered, 'just go buy yourself a new bike!' Now what normal man would pass up permission for that over a 19-year-old bike? He passed.

The feel of that older Rekluse was more slip zone resiliency, as in just enough to enhance traction control. Back to EFM, Gary's clutches are likely more resilient, being also ball-ramp. The following arm-prosthesis-related video of an EFM on a WR250 demonstrates that - and being adjusted for too much slip. That clutch would burn up with sustained slipping, 1st gear, in challenging off road terrain under the throttle hand of a machine-oblivious rider. Too much resiliency can be adjusted out.




Back to a trials application. Given the extremes define the mean, the majority will assume losing manual control separate from the throttle is a bad thing. The extreme top riders would NOT want an auto clutch, period. Example, see Adam Raga's 'first practice' on a Sherco after he butt heads with his long-time business associate Jordi Tarres of TRS.



While we all respect the incredible skills of top rider and make them aspirational, only a few percent of all of us will ever touch such a level.

A theorem is a proposition of an event that can be demonstrated, in this case through testing. That's what I'm aiming for, and I hope to at least have the option to do so.

My theorem, as a vast majority rider, is that I will benefit in trials competition from a properly set up auto clutch AND the hand brakes only setup that has benefited me on all my other bikes. I don't have adoption resistance any longer, and know adoption resistance will kill general acceptance. I don't care. Call is this engineer's ars gratia artis

 

[ZoomerP]

At a base level, I see this as exchanging one form of manual friction control for another. As you've said, proper adjustment is the key.

Your comments about how top tier pro riders need different things from their bikes than the majority of riders remind me of discussions in the bicycling world. So often, bicyclists will choose what the pros use without considering that they're worlds apart in abilities and needs.

 

[Motobene]

At a base level, I see this as exchanging one form of manual friction control for another. As you've said, proper adjustment is the key.

Your comments about how top tier pro riders need different things from their bikes than the majority of riders remind me of discussions in the bicycling world. So often, bicyclists will choose what the pros use without considering that they're worlds apart in abilities and needs.

Hadn't thought of it that way, but you are right. An 'auto' clutch is still controlled manually, with the right wrist.

What's amazing about trials is there is very little difference between the bikes of top-level riders and what anyone can buy. What anyone can buy works at all levels. The only notable exception is the Honda Montesa Repsols used by just a few riders are tricked out, but the differences are puny compared to most motor sports.

What IS extreme, however, is how seriously deep skill differences are. Every level up is a significant jump up and the distance between levels is extreme near the top. Pat Smage has long dominated US trials. He is an exceptionally skilled rider who can at time do the seeming impossible. But check out his experience going to Europe to attempt at indoor international events a few years back! In his words...



Here's him doing another French X-Trial... trying to survive it anyway. And just think. Video makes those obstacles look smaller than they are. When you hear Pat talk about having to swap bikes, you'll hear about the few changes he makes to ergonomics, a stiffer clutch spring... little things like that.



I participated in an exhibition show in the Pontiac Stadium at a Monster Truck event in the '90s. What an intense experience! Scared the crap out of me. And that like riding a tricycle on flat concrete compared to an international indoor.

 

[Motobene]

ELECTRIC BIKES AND EASIER CONTROLS VARIANCE
Electric bikes are moving us into more controls options. I had at times contemplated a EM electric trials bike so I could easily revise the controls to that of all my other bikes. A friend Dale Malasec now imports the Mecatechno Dragonfly, and if I were to buy an electric, that would be the bike I'd buy. A very good bike and the lightest trials bike ever!

All the latest competition electric trials bikes have a 'diaphragm-type' clutch option or only come that way because in trials at a higher levels thrusting with clutch dumps is considered a must - even if it isn't for the bulge of riders that make up the mid level. You can spin up the motor and dump the clutch on an electric same as on a liquid-fuel bike. It just sounds weird, as in whiney.



What I know about electric trials bikes is you can get by without the clutch just fine and liberate the left-hand space for the rear brake. Some models give you a choice of a regenerative rear brake in place of a clutch!

An aside: One could fit a Clake and go for both clutch a brake on one finger. I've tested one on a trials bike and they work... at the price of maybe wearing out the left arm muscles doing both. And the cross talk can be a bit weird. But again, throttle modulation can be enough. Take motocross and this Stark Varg with NO manual clutch, here winning an event with massive torque potential alone:



The rider retains his lifelong habit of a foot brake, his brain being long programmed for that. And the whole leg coming down on a foot brake can be useful to purposely break traction, slide into corners... change directions. Notice the blank where the clutch lever used to be. Weird looking, like something broke off :-0 I look at that a drool as a hand rear brake would be SO easy to achieve, directly, without a need for the intermediary auto clutch.

My adoption of electric get short circuited by practical reasons for off road and trials. I have two electric utility bikes (UBCO 4X4) that are great for what we use them for. In the other world the range problem with respect to recharge time come up and the battery cost remains ridiculous. Some day there will be quick-change batteries for all electric bikes, and we'll be able to afford multiple batteries. Not yet! And then there's the ridiculousness of having to return to camp while your liquid-fuel bike friends continue to ride while you, back at camp reading a book, burn more gasoline to recharge the battery with a generator than you would have burned continuing the ride with friends on a fuel burner.

REAR BRAKE STRENGTH DIFFERENCE
During my last ride on the Beta 390 I was having some fun sliding the rear wheel during direction changes, with one finger on the rear brake, which is normal as I keep one finger on both levers always as that is a long-ingrained habit from trials. Thus: milliseconds braking response with no thought to where the braking foot is. No more face-plant risk during panic hard braking so you won't die, and the the braking foot is off doing some other necessary thing, like dabbing.

The reason a hand rear brake is viable against the strength of a rear foot brake is the difference in hydraulic advantage of a hand master cylinder versus a foot master cylinder. The hydraulic advantage over the foot master cylinder is 1.7X for a 10mm clutch master cylinder piston and 2.1X for a 9mm clutch master cylinder. Of course one must factor in mechanical advantage of the long foot brake lever and how legs are huger than fingers, much less arms. My discovery of how potent a one-finger rear brake could be was when I converted the first bike, my KLR 685, and at the first stop sign skidded the rear wheel. What?

Now if a person wanted to purposefully lock up the rear wheel with a hand brake bike for off road riding or skidding on pavement, using two or three fingers on the lever will do that with a hand brake. A lot of riders are already programmed for multiple fingers on clutches and front brakes for more input force potential. The gripping with all fingers on-off-on-off on the controls is not good for control, as in a panic stop many riders will lose control locking up the rear brake because that's mostly what they use anyway, and in a panic it's the first available option. Think Harleyman 'lays it down' and goes under a semi. Or can't slow for a decreasing radius corner enough and whee! Through a barbed wire fence.

One way trials riders can tell when join a group of strangers at an off road ride is who exactly is not a trials rider. It's pretty much instant watching the use of the hands and with rider position. I have to force myself to to use more than one finger on hand levers, and to not stand up the instant things get sketchy!

 

[ZoomerP]

Hadn't thought of it that way, but you are right. An 'auto' clutch is still controlled manually, with the right wrist.

Do you find yourself dabbing the brakes while staying on the throttle? I know dragging a brake isn't the same as feathering a clutch, but that'd be another method of moderation possible with an auto-clutch.

Those international grade obstacles are no joke. The skill and confidence required to size up things like that and know how to make the bike reach those heights is impressive.

I don't doubt that full manual clutch control makes some techniques easier (or even possible). I know I'm never going to be attempting those. As long as I can loft the front to clear an occasional log, an auto-clutch should work for me.

 

[smdub]

Oh, where do I begin...
I come from the mtb side of things and I've run the brakes euro/moto style w/ the front brake on the right ever since college (I was riding street bikes at the time.) I'm 50 now. Picked up dirt bikes much later in life. I can't use a foot brake for squat. So, I converted most of my gas bikes to Clake. That include my 2019 Sherco trials bike (that I barely ride anymore.) Clake kicks butt! I typ don't have a stalling problem so I've never looked into auto clutches.

I have several electric dirt bikes now too. The LHRB is awesome. Going back and forth between those, the mtbs, and Clake is seamless.

So where am I going with this? Late last year a local old fellow (and friend) was selling his trials bike that he used to use for technical trail riding. 2014 Beta Evo 200. It had sat for a while so wasn't running. It had an EFM autoclutch in it just about the time he stopped riding it. I was intrigued just to play with it. Anyway, the bike just sat not selling. Condition was scaring everyone away. But it was taunting me. So against my better judgement I eventually asked him what his lowest price would be and he made me a killer deal. I cleaned it all up and got it running pretty quick.

So what is it like to ride a trials bike w/ EFM clutch? WEIRD
I still haven't ridden it more than just around my yard. I'll note I think the engagement rpm is a little too high. I don't know how to adjust it and an email to EFM went unanswered. I'm mechanically inclined so I'll open it up and figure out how to do it myself. The engagement doesn't seem to be as consistent as the Rekluses I've briefly test ridden but its not horrible. But the whole 'riding very slow' thing is very difficult when you can't reliably slip the clutch. I have to use the real clutch lever, rev it past the engagement rpm, then slip it to do the whole balance/ultra-slow thing. Just riding around isn't a problem. But it is definitely NOT like an electric bike, gas w/ a Clake, or even a regular gas bike. It is its own beast to learn - which I don't think will be a good thing.

My hope is that I can setup the EFM to grab just above idle. Basically just to provide anti-stall. Then a clutch slip slow/balance would still feel natural. He had the long-ride seat kit on it, so if I can get it working more predictably it would be a good technical enduro bike or one beginners can ride around the farm.

FWIW, My buddy who owns the farm w/ all the technical stuff we ride had major surgery last fall so we haven't had a chance to get the Beta out and play w/ it on real trails. Looks like he will be better by spring so I can finally tinker w/ it some more.

In summary, even though I can blame it now on an adjustment/setup I'm still not convinced an autoclutch on a trials bike is a good idea. Woods bike? yes. But trials you spend a lot of time just off-idle riding slow/balancing even if not doing a jap-zap (I can't do any of that stuff.) You still need to use the clutch lever then and the auto-clutch is one more thing that adds some unpredictability right at a moment when you can't afford it. MAYBE if you can set it up to be more predictable just off-idle it would be ok? But even then there is that little delay to lockup adding some unpredictability. So maybe take my unexpected discoveries into account before you go down a long and expensive experiment. FWIW, Electric bikes are WAY better and I'd look at that if you want a real solution.

 

[Motobene]

smdub you hit right on my major concerns regarding hysteresis in the response. Disconnecting throttle response to clutch response increases brain cpu load. The forearm amputee vid with WR250 and your report with the Beta point to engagement that is too late and too resilient on both.

Rekluse 'gets it' in their EXP-based standard setup and adjustment recommendations. Immediate start to engagement when cracking the throttle with slight resilience up to full hookup in the clutch.

I was contacted by Garry of EFM and it was clear he did not read my email in detail. A phone call when I get back should get things answered. He has a relative competing in trials so he gets the sport. But like everyone, his design will be influence by the philosophy of approach.

I don't know EFM in detail yet, but typically if you want sooner and less resilient engagement, clamping force relative to rpm must go up. Don't know the diameter of the bearing balls, but do know increasing their density to tungsten carbide, in some proportion of them mixed in, will make the engagement happen sooner and come on harder.

 

[Madmx]

My atv tire swamp bike (minibike) uses an auto clutch. Engine tune and gearing is everything. Many riders with similar setups have ditched wrist throttles. Tire slip and clutch grab can be very interesting with a 3.5 psi atv tire and a 5lb flywheel. I use the brake as much as the throttle to control the clutch.

I have one finger trigger throttles on a few builds..works great! I can yank the heck out the handle bars at any angle without affecting the throttle.

 

[Motobene]

Do you find yourself dabbing the brakes while staying on the throttle? I know dragging a brake isn't the same as feathering a clutch....

I never was partial to rear brake dragging for traction or to 'stabilizing a turn.' For me, that's been a job for the throttle/clutch, which is why any auto clutch must slip predictably.

If snow and ice driving a car or truck, I have done throttle and brake at the same time for traction... easy for me because I have been a two feet driver.

 

[Motobene]

Madmx, I've never heard of a 1-finger trigger throttle. Like the attached?

 

[Madmx]

I use a short bicycle brake lever. It works great

 

[Motobene]

This project must be set aside a while, as I lost three weeks to an international trip and now two more weeks to my first Covid infection, which has been nasty.
Getting away, then getting sick, does reset the perspective!

The first conclusion? Not now. Too busy. I will still have that talk with Gary of EFM to see about just how widely his design can be adapted to either basic clutch design and if his design can engage quickly with a less-wide zone of resiliency. Right now it's hard to talk without coughing so it may be a few more days.

Second conclusion: Consider an electric bike as it changes the way a trials bike hooks up at slow forward progress. Auto clutches are a way to get around the stall problem with the fuel bangers, while freeing up the left-hand ergonomic space for a direct rear brake. Electrics don't stall so the need for an auto clutch is elminimated.

My current electric fav is the Mecatechno Dragonfly, which I bekieve to be the best currently-available eBike. The importer, Dale Malasec is a long time friend, so support won't be an issue:

Electrics can be finely metered at creeping speed without using the excellent diaphragm clutch. In this scenario I'd leave the capability of the diaphragm clutch in place and make that master cylinder secondary and hanging down. Not so easy to use byt still possible to use. Then the primary left-hand ergonomic space would go to a direct rear brake and all the foot brake crap will get tossed.

If I can compete well at my level just with throttle control, that would be it. Dump the clutch only when rarely needed!

One of the Clakes could combo the functions, but I'm pretty strict on rear brake only on a 'clutch' lever as I use the rear brake like a clutch lever.

This is a rare, quality made, expensive bike! Danny Butler's take on riding a 2023 in competition:

 

[Nhuskys]

An odd aside, related to hand controls.... about Bart Markel the great AMA National Champion in the old Grand National Series. In the old days it was a combined series of flat track and road racing. Bart was first most a flat tracker and was used to just a clutch lever on the left handlebar. For dirt track TT and road racing they would run a front brake. Bart couldn't wrap his head around having a lever on the right handlebar, so he would run both clutch and front brake on the left side. It's about making it work for you....

 

[Motobene]

Making it work for me has always been a battle between capable complexity and stark simplicity. Anyone can clutter a bike up with crap.

For me the balance between the two finally met when I got over my trials rider prejudice against auto clutches, and realized a direct hydraulic hand rear brake is no different than a direct hydraulic hand front brake.
Since going that way on the non trials bikes it's revolutionized my rider experience. Control and confidence is up and reaction time is down.

On my trials bikes my reaction time and control are normal. The left foot brake made that possible. What I'm after now is better than normal, by doing what I have done with non-trials bikes on a trials bike. Hand brakes only would definitely be better than normal! That I night be able to do that on a Mecatecno without doing anything but plumbing the rear brake direct to the left hand is pretty intriguing. Having a second, out-of-the-way lever on the left hand is added clutter, but given I could ignore it almost always is a pretty interesting idea.