Clutch tune to your desired performance sans new springs

[fe53series3]

I have learned that clutch grab point is intrinsic to achieving your desired performance.

On another thread, I recently attempted to achieve this, by adding roller weight, to activate front pulley grab earlier, so causing the clutch to grab earlier.

This worked, but by adding 2g to the roller weight, I only gained 200 RPM earlier clutch grab, while the raised gearing had a much greater effect.

The experiment was a success...... but I believe perhaps a 1g increase in roller weight, and an independent improvement of clutch grab would have been more desirable.

While I have received a very kind offer of another set of springs...... my scoot performance would still be governed by specific spring strength, which would put 'performance tuning' out of my control.
There had to be a better way......... and it came to me.

Adjusting clutch grab point, without changing the springs

(Work in progress - see further below for practical modifications to the theory)

This method works for both delayed launch, and earlier launch.
For delayed launch, it may be best to get close to your desired grab point first....... experimentation will show how much we can mod the shoes without changing the springs.

Preparation:
Remove the shoes, clean them up, weigh them, and take notes.

Establish A Datum Edge:
At the flung end of the shoe (opposite the pivot end)...... find two edges that can be measured from.

Mark Off:
At the thickest metal point on the clutch shoe (at the flung end), scribe a centre line at a point where the shoe can be drilled, leaving room for increased drill sizes, and or other holes....... and centre pop each shoe at the same position.

Objective:
Delayed clutch grab: By removing metal in stages, by increasing drill sizes, or by adding more drill holes..... the decrease in weight will cause the clutch shoe to fling out later.

This can be reversed by simply adding a self tapping screw, to return to the original weight.

The advantage of this method, is that the CVT performance can be infinitely tuned, instead of being restricted to 1000 RPM steps.

Earlier clutch grab: Again, drill a hole at the flung end of the shoe, only this time add a steel nut and bolt.
This additional weight will cause the shoes to fling out earlier, perhaps to take advantage of a low RPM power increase.

Not enough?
Drill a bigger hole, and fit a larger nut and bolt.

Notes:

A tacho is a must for this mod.
With the rear wheel off the ground, put your foot on the rear wheel, and slowly increase revs.
Note the clutch grip RPM.

Start small...... drill a small hole and weigh the difference.

The closer the mod is to the flung end of the shoe..... the greater the impact.
Therefore finer adjustments can be made at the centre of the shoe.

We can add or remove weight, entirely at our will, without any concern of cost, or postage delays.

We are totally in control of our tuning.
Nice!








 

[dan50]

Interesting tuning concept.
I have 1 scoot that I would like the clutch to engage earlier.

[humanshield]

Thinking outside the box again eh? Shame on you!

[oldgeek]

Excellent how to. Add some pictures if you can.

That was one of the first mods I ever tried on a CVT. I learned about doing it here a few years ago. Very effective, and cheap to try. I use a step bit to adjust the amount I remove. Good work!

[90GTVert]

A little more info on the subject here :
49ccscoot.proboards.com/thread/359/lightening-stock-clutch

[fe53series3]

On close inspection of the clutch shoes...... while there is ample room for metal removal, we have to choose carefully how and where we add weight.

The shoes themselves appear to be lead heavy, and we need to add more lead.
Sticky wheel weights are probably the best way forward, only the glue needs replacing with JB weld.... a high temp epoxy.

Here's the vid which shows how I did it:


 

[90GTVert]

One thing I would advise before anyone adds weight to a clutch is to test first in hot conditions. The clutch springs will fade with heat, sometimes quite a lot.

[filip]

I am a bit suspicious about adding weight to the clutch shoes. The clutch spins much more than the crank at top speed. It could be potentially dangerous if not done right.

On the other hand, stage6 uses a similar method with its torque control clutches.
Also, lighter shoes mean more clutch slip, and heavier shoes more grip.

[2stroked]

Instead of affixing wheel weights, wouldn't it be safer at least to melt the lead into holes drilled in the shoe? It would eliminate the possibility for the weight to fly off and either tear something up or God forbid hurt someone.

I have not attempted this mod yet, but thought about it early in my build. Drill the same diameter hole, at the same point in each shoe, and add the lead in equal amounts. Being a very soft metal lead melts at a relatively low temp. However it is toxic, so extreme caution should be taken while doing this. Added ventilation in your work area and a respirator mask would be advised.

If this would work, then there would be no limit for cvt tuning. Hmmmmmmm..... Possibilities...

[2TDave]

My S6 clutch has removable weights in the shoes.

[2stroked]

May 19, 2015 12:05:09 GMT -5 2TDave said:

My S6 clutch has removable weights in the shoes.

Kinds proved my theory for me...lol

I thought I had seen a clutch with a customizable weight and engagement point.

Or, don't do the lead, us lag bolts and jb weld. Just cut the point off, screw it in the pad, and then cut the rest off. Just a thought. Lead soukd be a tad more practical though.

[fe53series3]

Job done!
The clutch is back on the bike, and working

Here's what it looked like:





Slightly disappointing gain: the clutch now grabs at 4180 RPM....... a gain of 220 RPM.

To be honest, I suspected that the gain wouldn't be enormous, due to the weight being fairly close to the pivot point.

The shoes were 128g.

They are now 146.7g
18.7g added.

However, as Filip suggests...... the clutch grab should be more positive, when it bites.

I didn't give it a thorough testing...... it was late, cold, and I had shorts on
I primarily wanted to see it working, and check the grab point.
There may be some bedding in, but we'll look at that later.

Regarding comments:

I guess we'll find out if the springs fade at higher ambient temperatures of summer...... we are beginning to get hot days now.
I've obviously no experience of this, but with the recorded data that we have, this could be interesting.
It's cold at the moment, but I'll get a more solid grab reading, once I feel confident that the shoes have bedded in.

Re whether the mod is dangerous (presumably meaning potentially destructive).

My position on this is, that much of what we do, in performance modification, is dangerous.
How many people have fitted kit, and melted a hole in their piston (etc.)?

It helps to have an understanding of what one is doing.
I do have high temperature experience with JB Weld, and this knowledge gave me the confidence to use this as the bonding agent.
I have never used it with lead before....... but the key was that it 'wetted' the lead very nicely.
Therefore, as long as adequate surface prep is carried out, I cannot see the bond failing.

RE melting lead into the available hole (leading to the spring attachment point).
I certainly considered this...... and may well attempt this mod.
The problem was that, I needed to create a bung, to prevent the lead from running into the spring mount.
I also figured I would need to run a tap through the hole, to ensure that there was a mechanical key, as the molten lead will not wet to the alloy shoe.
I tried it.
I cut come 'flux cored solder' to length, and placed them on the inside curve...... then put the shoes in the oven.
At 200 C the flux and solder ran, but failed to 'wet' the shoe alloy......... it just ran to the middle of the curve in a globule.

So it would need a bung and a tapping operation.
This would work, but it was clear that it would not be enough........ which would anyway mean also bonding lead to the shoe as I have done.

I figured that I'd do the latter, and see what gains had been made.
Melting lead into the hole remains an option, so you were right to pick up on this....... maybe the next mod

Clearly there is also the option of drilling a second hole (as shown in the vid), to allow more lead to be added.
However, in my estimation, there would be little gain, as the clutch shoe alloy appears to be very heavy, so must have quite a high lead content.
Drilling out the alloy might offer significant advantage to the guys looking to lighten their shoes........ but for adding weight, the difference between removed alloy, and added lead, would not be so great.

Filling the hole that is already there..... yes.
But also, adding weight to the inside curve, looks like it will pay dividends (using the JB Weld method).

With the weight further towards the flung end, we'll gain more, with less weight.
However, it's looking like I'll max out at around 3.8k with current rollers at 11g.

The thing is..... I now, don't want 11g rollers...... because they raise the primary gearing.
The earlier that the clutch grabs, the more I will need lower gearing.
This means lighter weights......... which will cause the clutch grab point to rise 


But in reality..... that's absolutely fine.
The heavier clutch shoes provide an earlier clutch grab, and I can then lower the gearing, to take advantage of that change.
How good is that?

The additional 2g on the roller weights only modded the clutch grab by 200 RPM, yet it changed the gearing substantially.

I think, we are looking at a scenario, where with additional shoe weight, and 11g rollers, we might hit 3.8K grab.

Returning to 9g rollers, should put us at 4k grab........ effectively just on the powerband edge.
We'd gain our controlled launch, the bike and rider mass would already have momentum....... and the throttle could be whacked open, to gain maximum surge.

Hey.... we might even be able to go for 8.5g rollers, to lower the gearing even further, and maximise acceleration out of a junction, and still have low speed mobility, and total launch control.

This project definitely still has legs...... we're only in the early phases.
Shame that I'm gonna have to drill out all the work I did on raising the roller weight.
But it served it's purpose well.

My guess is that tomorrow I'm going to find that, even though the rpm grab drop is only 220 RPM...... the launch and post launch acceleration will be lacking.

Time to regain the lower gearing, and re-gain that acceleration








 













 

[90GTVert]

May 19, 2015 14:06:22 GMT -5 fe53series3 said:

Regarding comments:

I guess we'll find out if the springs fade at higher ambient temperatures of summer...... we are beginning to get hot days now.
I've obviously no experience of this, but with the recorded data that we have, this could be interesting.
It's cold at the moment, but I'll get a more solid grab reading, once I feel confident that the shoes have bedded in.

I should have been more clear. I meant when the CVT is not, not necessarily summer heat. The clutch will get very hot in most conditions. It will be worse when it's hot outside, but the clutch gets very hot even in cold weather (especially if no/minimal CVT venting is done and in stop and go traffic).

[90GTVert]

May 19, 2015 14:06:22 GMT -5 fe53series3 said:

Re whether the mod is dangerous (presumably meaning potentially destructive).

My position on this is, that much of what we do, in performance modification, is dangerous.
How many people have fitted kit, and melted a hole in their piston (etc.)?

When I think of danger and clutches I tend to think of the vid below more than just ruining parts. Ruining parts is absolutely part of tuning and learning. The likelihood of a catastrophic failure as shown is probably very slim, but it doesn't look like something I'd want to experience. Just didn't know if you'd seen this so I wanted to share as I think it's a good reminder of how much energy there is when you spin these things at a high rate of speed.

youtu.be/mXn6SuU_8Jw?t=1m2s

[2TDave]

Looks like they set that one up to explode. Lots of force and energy there!