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Thread: Lockup clutch spring pressures

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  1. #1
    Senior Member Fasthouse's Avatar
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    I know someone out there knows this from experience.


    I have a GS1150 basedcartire bike.


    It has the regular MTC lockup unit.


    With a 10X26 MT slick about how much spring pressure (at installed height) should I start out with How much weight on the arms


    It is a 1327 big valve motor. Super Comp combo


    If someone could help get me close it would save me a lot of grief!


    Thanks[img]smileys/smiley17.gif[/img]Edited by: Fasthouse

  2. #2
    Grand Squirrel
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    Jeff, If you are running 1150 primary gearing then around 220lbs of launch pressure and a maximum of 1.5 to 2 grams of weight on three fingers with the other 3 no added weight at all. This should get you started.


    If you are running the popular 750 primary ratio then start at 280lbs of spring pressure and about 3.5 grams of weight on 3 fingers only.


    This should be a good baseline to get you started.

  3. #3
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    are you refering to the actual clutch spring pressure , or the springs under the arms

  4. #4
    Senior Member Fasthouse's Avatar
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    I meant the actual total static spring pressure provided by the 6 clutch springs.


    That and the weight added to the arms for the lockup.


    I just dont want to spend the first weeks of the season stumbling for a baseline clutch setup. I can then make changes as I figure out what the bike wants.


    I have set these things up before but never on the big tire.


    I appreciate the help.





    Also, it does have the 1100/1150 ratio.


    The bike/rider will weigh about 610 lbs.Edited by: Fasthouse

  5. #5
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    I'm trying to learn this myself ,, last I worked on a lockup was an MRE back in 85 or so ,, I'm(trying)to help a friend with an MTC on a 210 hp Buell streetbike ,, lots to learn !

  6. #6
    Senior Member Fasthouse's Avatar
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    If I am planning on running nitrous, will I need more spring pressure/weight


    I just see a lot of lockup bikes that "slam" at the starting line. Its like they have a ton of spring pressure. Some even bog real bad.


    If your going to have that tight a clutch why bother with the lockup at all


    Or am I missing somethingEdited by: Fasthouse

  7. #7
    DaveDole
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    I.m running stock springs and 1 nut on each of the bolts in the arms.

  8. #8
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    Quote Originally Posted by Fasthouse





    If your going to have that tight a clutch why bother with the lockup at all


    I agree, You can get just about any clutch to lock up with stiff enough springs. The point of a lock up is to be able to lock up the clutch with softer springs so you wont bog or break the back tire loose on the launch.

  9. #9
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    Jeff: I have supplied a lot ofweak springs for guys wanting very little base in thier setup, let me know if you would like a set. The amount of weight will depend on your springs, its a balance between the two. TheProstockguys are masters at clutch tuneup and it seems that no two of them agree on exactly where to start as they all have combinations that work for them. Maybe GB3could give you a solid base line to start with.
    Your never too old to learn something stupid.

  10. #10

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    ... Some tires / suspension require a hit that almost bogs the engine. For thirty maybe thirtyfive years I and many crew guys have been hearing riders / drivers say "it did not feel like my best ET / sixty foot". This is because as the clutch snaps that last little bit of inertia out of the spinning crank mass it gives the tire the best "plant". I did not figure this out till about "87 when I was able to put incremental time slips together with data, but knew somewhat what the driver was saying since "74. The "feeling" is that the engine is too low and feels like it is taking forever to climb out; as opposed to somewhat driving through the tire and or clutch.

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