Anybody running a lockup clutch

[RacingJake]

Need the pros and cons of using a lockup clutch on my drag bike 8O

My best 60 ft time is 1.67, but normally I run in the mid 1.70's without bars. Will a lockup do better than that without bars?

Jake

 

[rosco15]

The lockup clutch allows you to dump the clutch on a dragbike in conjunction with a 2 step. You put in soft springs that allow the clutch to slip when you dump it. The arms on the lockup come in around the tree and cause the clutch to lockup and stop slipping. Mostly this is used on bikes with wheelie bars. There is one guy at our track that uses it on a bike with no bars. I have seen him stand it straight up once or twice.

The upside is better reaction times and more consistent 60' times. The downside is how hard it is on cranks, baskets, and the clutch parts. There is also alot of tuning and maintenance involved.

I would think on your bike you would be better off just using your left hand to regulate the slipping clutch. Your 60' is better than I can do on my streetbike. I would go the way of an air shifter.

Ryan
www.rccracing.com

 

[Paul]

I fitted a lock-up to mine because it was burning out clutches. Like a clutch per meeting, & that was a complete clutch - fibres & steels!
The steels used to warp like a crisp. I tried heavy springs, heavier springs, gorilla springs, spacers behind the springs - my left wrist used to hurt on the line! The guy who owned my local tuning shop used to tell me to fit a lock-up, but I was afraid of the price! Eventually he got me a pressure plate at the right price, & I made the rest myself.
I never bought another clutch plate again!
It was exactly the same to use as a normal clutch, except the faster it span the harder it gripped.
DON'T confuse with a slider clutch.
With a slider you just dial in your clutch settings, go to the line, rev the b-----ks out of it against the two step, let go the lever and it will feed the clutch in at your predetermined dial-in.

 

[Anonymous]

Biker66 in sweeden is running one on the street.

 

[RacingJake]

Thanks guys that what I needed to know.

I'm going to keep my OEM clutch assy with almost 280 runs it's still in great shape. Why fix something that is'nt broken.

Jake

 

[lecroy]

You may want to look at a slider. Still takes time to set one up.

 

[Anonymous]

:twisted: Trust me on this one. With your mods your clutch is toast..... :wink:

 

[Anonymous]

:twisted: Trust me on this one. With your mods your clutch is toast..... :wink:

Oops, hit the submit twice.
I run 1166cc, st.2 ported head with bigger valves, Oem cams( for now) RS36 and a VH supersport. Runs great but my left hand was about to look for another job every time i went riding. And I only street-ride my bike. As Scotty said about Biker66: He has it and after feeling his grip I went and bought one myself. The lock-up is great. But it requires different footpegs and a VH Sidewinder system touches a bolt on the clutch-cover. But the result is great. Smooth grip with std springs(still wheelies if you?re not careful) and no slip at all when you give it full throttle.

 

[RacingJake]

Well I'm not to sure what I'm going to do with the clutch now.

I did find some G4 cams and I'll just head to the track in a few months and see whats happens and go from there.

:roll: :roll: :roll:

 

[massakins]

Just to clarify what we're discussing here:

A lockup clutch typically describes a special plate with 5 or 6 fingers on it that various weights can be attached to for adjustment. It retains the stock clutch actuation, allows softer springs to be used and uses centrifugal force to "lock up" the clutch pack as the RPMs build. Very usable on the street and recommended with high powered engines. Cost is probably $250-350 for most models, I think. MRE is often credited with developing this.

A slider clutch describes a complete clutch hub/pressure plate assembly that has adjustable springs and weights. In general, the springs keep the plates from driving the bike until the weights overcome it. No clutch lever is needed with this setup (although it can be retrofitted) and different RPM engagement points can be tuned into it. Not recommended for street use or even for dragbikes that are ridden back to the pits under their own power following a run. Cost is near $1000+ for this, I think. MRE is also a supplier here, but others provide them as well.

These are not textbook definitions, but my understanding of the subject. Please improve on these definitions and explanations if knowledgable on them.

BTW, it's often argued that a lockup clutch increases its pressure as ground speed increases; I've often thought that it was related to engine speed since it was mounted on the transmission's input shaft; i.e. it clamps harder at the top RPM of each gear and eases up a bit with each shift as the RPMs drop, saving the wear and tear of a hard shock on the equipment. Thoughts?

 

[Anonymous]

massakins: Couldn?t agree with you more.

 

[rosco15]

The lockup works off the rear tire speed. The greater the rpm of the rear tire the greater the pressure applied by the arms. So the faster you are going the more the lockup comes in. Take a look at my video section for a good example. The bike in the example seems to fall off as the bike gets out near the tree. The white bike is a basically a stock gs1150 motor. He launches by dumping the clutch on a 2-step at like 7grand. I think he only runs three or four springs. This allows the bike to slip the clutch as it leaves the line. Right around the tree as the tire speed increases the lockup comes in and actually starts to bog the motor. In the video it looks like the bike shifts side to side. He fixed it by taking some of the weight off the arms. The lockup was coming in too early and too hard. Save the video to the hard drive and then play it. If the download is real slow just stop it and come back in a few days when not so many people are trying to download from the site. Yahoo doesn't give me very much bandwith, but it's part of my dsl service.

PS. I dont see why you would need a lockup on a street bike. If a busa and zx-12's can do it with 160 or so horsepower. And the 12 has a cable clutch.

www.rccracing.com
My GS1100, Prostar, and Dragracing video's
Prostar at Norwalk 2003
al#2

 

[Anonymous]

The lockup works off the rear tire speed.

This cannot be correct. The clutch speed is directly linked to the engine RPM by the primary gears, but variably linked to the rear tire by which gear you are in. The lockup effect can only be related to engine rpm because of this. This is the way you want it, too. As massakins noted, it lets up a bit after shifts and also it ALWAYS bites harder as revs climb, regardless of what gear you are in. The engine makes the same peak torque in 2nd gear as it does in 5th (although road speed is very different), so you want your clutch to be linked to the engine rpm no matter what gear you are in.


Mark

 

[rosco15]

I think of a lockup as rear wheel speed related because of launching the bike in first gear from a dead stop. The lock-up is RPM related after getting the bike moving. Once the lockup is spinning fast enough it stays at the same primary ratio no matter the gear. The lockup engages as the rear tire moves in first gear, and as the clutch locks, it acts like a regular heavy duty clutch for the rest of the gears.

Sorry when I think lockup, for tuning purposes, I only think about the first 60? and not the rest. As long as it doesn't shift too hard.

 

[Paul]

The lockup works off the rear tire speed.

This cannot be correct. The clutch speed is directly linked to the engine RPM by the primary gears, but variably linked to the rear tire by which gear you are in. The lockup effect can only be related to engine rpm because of this. This is the way you want it, too. As massakins noted, it lets up a bit after shifts and also it ALWAYS bites harder as revs climb, regardless of what gear you are in. The engine makes the same peak torque in 2nd gear as it does in 5th (although road speed is very different), so you want your clutch to be linked to the engine rpm no matter what gear you are in.


Mark

It is correct
The lock-up plate is fixed to the clutch centre. The clutch centre is fixed to the gearbox. The gearbox is fixed to the rear wheel. The engine is fixed to the clutch outer. The clutch is a variable speed drive. When the rear wheel starts to rotate the clutch centre starts to rotate, and the lock-up begins to take effect.
So rosco is right.
You have to ride one to know how it operates.

 

[Anonymous]

The lockup engages harder with increased rpm on the primary shaft in the gearbox, not wheel rpm. Remember that you have 5 gears, at least my bike. The clutch can slip a little when launching, but as soon as the inner hub start to rotate, the lockup will go to work no matter wich gear or speed. Totally engine RPM related after launching. Enough said... :wink:

 

[GER144]

I love my lock-up! No problems yet either, but I am still messing with it. I have a 1428cc, car-tire (26x10-15") Katana, 76" wheelbase. I ordered a snowflake lock-up from MTC. I bolted it in exactly the way it came, and with new-stock springs, my first pass on the bike netted a 1.28 60ft. and a 9.01et. After messing around with tire pressures, launch rpm, and I tried some different springs, I now run 1.25 60fts., and the et is now 8.85 at around 150+ mph. I also run the RBD quick-access cover, and highly recommend it to anyone. I'll be trying some new things with it this year too, as I hopefully will be making some more power!

 

[RacingJake]

Ok I'm going to buy a lockup and some wheelie bars. I like what you guys can do with them.

 

[cbxchris]

I`ve used them both slider and lockup. The slider is much more complicated and much better when correctly adjusted. The lockup is easily adjusted. Good rule of thumb is try stock springs and one nut on each arm then go from there. I ran 2 nuts with a ten inch car tire and mid 4 second 1/8 mile bike. The slider is so much easier on trannies it is worth the investment and time for drag racing only. Plus you get to go with a switch and not a lever on the handle bar which usually results in better reaction times and also you have both hands completely around the hand grips instead of one holding a clutch lever. Ever seen what happens when one hand comes off....its not pretty.