Honda CRF1000L Africa Twin Forum

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-   -   Lightening the clutch (https://www.africatwinforum.com/forum/177-engine-technical-discussion/35981-lightening-clutch.html)

Mastercore 08-22-2019 01:28 PM

Lightening the clutch
 
2 Attachment(s)
Hey Guys,
I had a work wrist injury back in April (just a sprain in the left wrist I thought) and made it worse about 6 weeks ago off-roading. Did it when I picked up the bike after a down.
MRI shows a torn ligament in the wrist. ****. And right in the middle of the riding season.
I can ride the bike but I have pain and I cannot ride for long.

Have been wondering if I can lighten the clutch a bit to make riding a little easier on the wrist.
Being handy guy, I put myself to the task and thought I would share my experience here.

This is what it looks like stock
https://www.africatwinforum.com/foru...=49927&thumb=1

And this is what it looks like with the first mockup of the mod
https://www.africatwinforum.com/foru...=49925&thumb=1

Testing:

The spring is just something I found lying around in the workshop so had to make do. It is a little long and a little stiff for the job
Length I can mod, and if I take out some of the length, it may lose some of its stiffness as well.
The 6mm threaded rod on the right I left so I can play with the tension in testing
I modded a short stud that holds the other end of the spring is just hanging off the edge of the clutch activator arm. It hangs on there with the spring tension only.

Results:

With full tension in the spring. i.e. I tightened the adjusting bolt all the way. Till the spring hook hit the plate. The clutch seemed to still not slip noticeably at low speed. I tried jerking the throttle open and closed at low speed to see if I could detect any slipping. Seemed all fine.
Then I took in on an open road, this is where I think I detected a bit of slip. 100kmh in 6th, then knocking it back to 5th and opening it full up. I think I noticed some slip in the clutch for a short time, then when changing up to 6th on full throttle at about 130, again seemed to slip somewhat.

Next test:
I want to move the plate on the right on to the other side of the locking bolt (on the cable housing) to give it some more room for adjustability and then test again. I want to be able to tighten this till there is noticeable slip in the clutch, then be able to dial it back.

Result in the clutch feel.
At the full adjustablity, where I felt the clutch may have slipped a bit at high speed gear changes on full throttle, the clutch was very noticeably lighter. Without measuring it with a spring scale, I would guess about 50% lighter.

If anyone is interested in this mod, I will keep documenting this project here.
Would love to hear of anyone else who has tried this or other things to lighten the clutch.

Back to my wrist exercises. Doc recons it will take 3 months to get over this injury. Just in time for winter again. Aaaggrrrr

VFMoore 08-22-2019 04:17 PM

Try a magura hydraulic clutch. It cut the pull weight in half on a friends bike.

Mastercore 08-23-2019 03:45 AM

Quote:

Originally Posted by VFMoore (Post 310683)
Try a magura hydraulic clutch. It cut the pull weight in half on a friends bike.

I did a lot of research into alternative clutch setups.
But I am not one that throws money at each problem by default.

I am the do it yourself fix guy and enjoyed this project far more than a shopping expedition online
The set what you see here in about 15 min. The post took more time!

HerrDeacon 08-23-2019 06:09 AM

Very ingenious, I love seeing projects like this. Hope it helps out and enables you to keep riding until its better.

RayCollington 08-23-2019 05:50 PM

I would be concerned what effect the constant spring pressure might have on the clutch life and if any high torque situations could result in slippage.

Mastercore 08-30-2019 04:23 AM

1 Attachment(s)
Quote:

Originally Posted by RayCollington (Post 310741)
I would be concerned what effect the constant spring pressure might have on the clutch life and if any high torque situations could result in slippage.

I am with you on this. It was the reason I built this prototype the way I did.
There is a 6mm threaded rod connecting the spring. I can count the tightening nut turns to gauge the relative tension of the assisting spring.
I tweaked the design so that I can tighten it till it opens the clutch, or loosen it till it has no tension at all on the system.



This is what my testing of different setting has yielded:

- At low RPM I find that the adding more tension to the spring is tolerated. I cannot notice any slippage even if I jerk the throttle open and closed in first and second gears. The reactions between accelerating and decelerating is sharp and crisp. It is the same as with no spring tension at all.
At a functional tension for this low RPM range, the clutch is significantly lighter than stock. My guess is >50% lighter.

I played the spring tension all the way till I could feel the slip when doing this. The clutch is feathery light and I could play it even with my pinky. But this is a useless setting because at any higher speed, there is significant slip.

- At the other end of the spectrum, I can make the clutch slip even at relative low tension setting. This would be in an overtaking case. Say 80kph (45mph) and knocking it back to 5th and opening up to overtake. In 5th it still feels OK, but in the upchange back to 6th on an open throttle, there is a second or so of slip till the bike catches up.
I guess this is due to the higher HP and torque at the higher RPMs. (see image)

Because of the way this prototype is setup, I can easily adjust with an 8mm wrench.

Current conclusions:
- I have no idea yet on the effect this is having on longevity of the clutch, but I am sure it is wearing it out faster than without the mod. (obvious)
- If I detect no clutch slip, then it does not necessarily mean there is no slipping, but I am assuming it to be minimal and probably nothing to worry about.
- I have yet to do a temp test of the clutch cover, aside from using my hand which is not very scientific. At least it is not burning the skin off!
- I am also working with the assumption that motorcycle clutches are not overly difficult to replace and not very expensive.
- I am wondering about shortening the spring and bridging the gap with a fixed section to magnify the spring effect and see how it changes the behaviour.
- Using a compression spring setup may yield better results, but would require a different setup all together. Maybe if I am bored one day.
- I have used it with a pillion (a realistic simulation of a packed bike I'd say). There was a difference but it was not as large as I imagined. That surprised me.

How I can see it being used:
- I would imagine that dropping the tension right off for highway or mainly tarmac riding
- Rise the tension for off-road conditions. Especially long days off-road where the wrist may get tired and painful.



I will be doing an off-road tour around Sardinia, Italy in about a month so will have a good chance to test.
This is the real test for me will be the off-road, because road use is not the problem for me. The wrist is slowly getting better, but it is the 8h off-road riding, day after day, that will really be the test of this device.


I am a furniture designer and I can imagine a fully developed product. It would be a simple bolt on thing, which even a novice mech could install. It would be adjustable from zero to full slipping, and could be a useful add on for cable clutched bike that are a bit heavy on clutch tension (BMW GS800 for example), or female riders who find the clutch work a bit much for their left forearms.

n.b. I done some off-road tours with the africa before my injury, and did not even think of this idea.
This innovation is born basically from my ill timed injury i.e. right at the start of the riding season here in Europe.

ProCycle 08-30-2019 01:03 PM

I'd be very concerned with severely shortening the life of whatever the AT uses as a release bearing.

Mastercore 08-30-2019 01:08 PM

Interesting, will look into this.
Thanks for your input

ProCycle 08-30-2019 02:04 PM

Quote:

Originally Posted by Mastercore (Post 311193)
Interesting, will look into this.
Thanks for your input

Yeah, release bearings are sized for momentary intermittent duty. Spinning with pressure on it for long periods would very likely overwork it.
Usually referred to as a throwout bearing it's a pretty common failure in the automotive world. Folks get a bad habit of sitting in traffic in gear with the clutch pedal depressed or driving around with their foot on the pedal and that toasts the bearing.

I looked at the parts breakdown and didn't actually see a separate bearing. It may be that Honda only sells it integral with the pressure plate.

I like experiment you are doing but I would strongly consider traveling with spares and tools to replace the release bearing if it fails far from home.

Mastercore 08-31-2019 05:11 AM

Thanks @ProCycle
I have been looking at the workshop manual to get a better idea of the mechanics of this connection.
I understand pretty well what part you are talking about. it is the part that connects the rotating pressure plate to the stationary "actuator arm" (the best words I could think of)
The manual is a little light on what exactly is going on here because it concentrates on assembly and disassembly.

My intended use of this mod was to increase the assisting pressure of the spring mainly when I am off-road.
I imagined from the start that this mod would increase the wear of some parts inside, but I assumed the cost was bearable considering it meant I could keep riding and I not impede my recovery.



Has anyone out there got good pics of a clutch change operation on the AT. In particular, how and what is actually in contact with the clutch pressure plate to activate it?


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