Before you read this, get up to speed reading parts one and two.
Part 1 • Part 2
Shortly after the 2nd part of the article came out (about an hour) I got a phone call from a good friend and multi class champion racer Andy Baumbach, he told me, “Your 60’ is still high, you need a multi-stage, it is more adjustable.”
Multi-stage lock ups / clutches
Multi-stage set-ups operate in much the same way as a single-stage, although they have more adjustability. What makes the multi-stage different from the single is the fact it has the ability to attach springs to the centrifugal arms as well as by adding weights to them for a greater range of tuning.
This allows you to better apply the power as you are coming out of the hole. On bikes that have multiple stages of boost or nitrous progressions this is an incredible benefit. Take a Pro Street Turbo bike for example, it leaves on 5 -7 lbs. of boost, once it gets out 100’ it ramps up to 15 lbs. by the 1/8th it is probably going to be at full boost. This also applies to a Pro Street nitrous bike when they ramp up the nitrous shot. With a multi-stage you can adjust for each of these increases in power.
Engine or Rear wheel driven multi-stage
There are two forms of multi-stage set-ups, either engine driven or rear wheel driven. The top part of the hat of an engine driven multi-stage is attached directly to the basket and no bolts are used to attach the pressure plate to the hub. In a rear wheel application the unit is attached to the hub just like on a single-stage set-up.
I’ll give you a scenario and you determine whether an engine driven or rear wheel driven set up would be best for you:
You throw the clutch at the line, the tire hooks up hard and you feel the engine start to drive through the clutch.
1. With a rear wheel driven lock up the tire is planted and does not come up to speed to engage the centrifugal arms as the lock-up is attached to the hub and not the basket. As a result you continue to burn through the clutch, your only hope of saving the clutch is to either let out of it, or hope the rear wheel eventually moves fast enough to engage the arms.
2. With an engine driven lock up the basket is being driven regardless of what the rear tire is doing, as it drives through the clutch the rpms are going up and the centrifugal arms start to lock up the pressure plate and eventually get you moving down the track. In this instance you would have to make some adjustments so you do not do this again, although you may still have a clutch left and you more than likely were able to get down the track.
How a multi-stage works in more depth
Hays Machine Works supplied me with their Pro Street Convertible Multi-stage for this article. In the multi-stage mode I am about to describe, it works in the same fashion as other engine driven multi-stages. But, it does have a significantly different feature than its competitors I will discuss later.
An engine driven unit is made up of two pieces, the top hat and the pressure plate. In between these two pieces is your first level of engagement, the static spring pressure. With the Hays unit an assortment of different springs are sent with it.
Because the top hat is attached to the clutch basket and the static springs are in between it and the pressure plate, this forces the pressure plate downwards on the clutch pack. (In my instance on the Track Pac fibers and steels I am testing.) With this set-up alone you would blow right through the clutch pack on launch as the static pressure is not enough to keep the pack compressed.
This is where the next line of tuning comes in to play. There are six centrifugal arms on the top hat that apply pressure to the buttons on the pressure plate as you build rpms. As mentioned earlier, there are holes in the arms you can attach different spring configurations to; this provides more range as to when pressure is applied. Along with attaching the springs in different configurations, you can also use different weight springs, going one step further you still have the option of adding or removing washers to each of the arms.
You need to determine how far you want to go and how anal you are when fine tuning your bike. The multi-stage is definitely designed for those of us suffering from OCD.
We are not talking about the “gut grenade” hamburgers here or the pitch Ted Williams thought was the best pitch of all time.
The slider is a feature the makes the Hay Machine Works Pro Street Convertible Multi-stage unique in the market. It can be a single-stage, a multi-stage, a slider or a multi-stage slider. You are basically getting 4 potential setups for the money.
Have you ever noticed bikes in the staging lanes that have no clutch handle or a rider at the line that has his hand off the clutch handle while he is still in gear? They can do this because they have a slider clutch. The slider is rpm activated and does not come on until the rpms hit a pre-determined point.
The way this is accomplished with the Hays product is instead of placing the static springs in between the top hat and the pressure plate the springs are put on top of the top hat. Studs are supplied with the kit to screw into the pressure plate allowing them to come up through the springs on the top hat. Nuts are applied to the top of the studs applying pressure to the springs, in turn pulling the pressure plate up off of the clutch pack. The opposite of what happens in multi-stage lock up mode.
In this arrangement the centrifugal arms are solely responsible for moving the pressure plate down on the clutch pack. As in the multi-stage set-up engagement is determined by the weights and springs you use on the centrifugal arms.
The advantage to this setup is that all you have to do is turn the throttle wide open at the hit. Just like riding a scooter… albeit a fast one.
A few more things to consider
- Air gap
When setting up these types of systems you need to be mindful of your air gap. To find what your clutch stack should be all you have to do is measure from the bottom plate of the hub to the outside edge of the clutch basket. This is your total stack height, just subtract the air gap you are trying to achieve from that and you will know what stack height you need to run. Check with the manufacturer to find the optimal gap.
- Clutch Cover
You are going to need a clutch cover for a multi-stage. The factory one will not cover it. MPS supplied me with a cast one although there are some pretty nice billet ones out there if your wallet is deep enough. Check to make sure you have clearance with the cover you are using to make sure everything is free, especially the centrifugal arms.
At the track
The bucking is gone, the engine dying as soon as I release the clutch at low rpm is gone and the bike is launching once again without my having to perform spur of the moment cloud inspections.
Most importantly… This one of the most incredible performance pieces of equipment I have ever put on my bike. (Mark Doucette’s transmission is another one.) It is simple to set up and you do not need a degree in engineering to work with it. I literally throw the clutch at the hit. The bike launches smooth, at first it feels so soft you wonder if you are going to have a decent 60’, then you look at your ticket and you just had a 1.54 60’ when it felt like a 1.8. And this was with the base set up Tim gave me right out of the box.
I was only running the 1/8th and ran back to back 5.9 passes 4 times in a row. I actually thought I was on a wheelie bar bike. I have not been on it enough to make changes and only leave at 6K, I know I can leave harder now. I can tell I do need to make minor changes because the front wheel starts to lift as I go to wide open throttle from the initial hit. As it is, I am going to leave it alone until I get used to it then start to experiment.
Being an ET racer I am not worried about posting big numbers, but if you were this would be another avenue to take to them.
The whole day I could not stop myself from smiling like a kid in grade school who just got the best tricycle at recess. It is amazing I actually ran the bike all these years trying to finesse the clutch to be consistent when all I had to do was put a Pro Street Convertible Clutch in.
I am still smiling.
See ya at the track…
- Paul Cavanaugh
Tim Hays for supplying the entire clutch set-up to review and explain in detail, Brock Davidson for his information, product and technical critique, Doug Ray for prompting me to write the article, Brian Livengood because he helps with everything, Dan Rudd at MPS for supplying the clutch cover, Mark Paquette for giving me some pointers on tuning a multi-stage, Don Chavous for his astute observations at the line and Andy Baumbach for his support in trying to get me to run an 8 second pass.