Sputhe Positrac arrived today [pics]
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Road Warrior
Joined: Dec 2008
Posts: 1,530
Likes: 1
From: Upstate, SC
I just got off the phone with Jeff at Sputhe Engineering. The new front bracket with an offset mounts so that the offset is away from the frame. Thus the correct orientation is to the left. He also said the way to mount this is one bolt at a time to prevent the engine dropping like it did when I tried to install the TT. The True-Track folks really do need to pull those "instructions" that were done by some magazine that say to remove all the isolator bolts at the same time. That is a recipe for disaster, even if you've got the engine supported by a jack.
Will be installing this later today (hopefully).
Will be installing this later today (hopefully).
Road Warrior
Joined: Jan 2007
Posts: 1,276
Likes: 8
From: Minneapolis Area, MN
...The use of either a front or rear stabilizer makes lateral flex of the motor mount a non-issue because it allows for absolutely fixed lateral positioning of the drivetrain and swingarm assembly. With either a front or rear stabilizer installed, the drivetrain and swingarm can no longer move laterally no matter what the condition of the motor mounts...
Think of it like this. The stock setup with 1 link atop the engine acts as a pivot point for the engine. Any side load against the rear wheel (as in leaning over in a corner) will result in the swingarm acting as a lever forcing the engine to pivot about the top motor mount. The amount of this pivot is only limited by the condition of the 2 motor mounts.
If you were to hold the frame ridigdy and push the rear wheel right, the swingarm would end up pivoting the engine about the top link; the rear of the engine would move right, and the front of the engine would move left.
If you place a link on just the front motor mount to resist this left or right movement at the front of the motor, the rear of the motor is still allowed to move. The rear motor mount is still allowed to flex as much as it did before. The drivetrain and swingarm can still move laterally no matter what the condition of the motor mounts. This absolutely does not fix lateral positioning of the drivetrain and swingarm assembly.
You will definitely feel a tightening up of the bike. And as you've said, it will probably be just fine for your riding style.
Keep us posted.
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Road Warrior
Joined: Dec 2008
Posts: 1,530
Likes: 1
From: Upstate, SC
Thread Starter
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Road Warrior
Joined: Dec 2008
Posts: 1,530
Likes: 1
From: Upstate, SC
Road Warrior
Joined: Jan 2007
Posts: 1,276
Likes: 8
From: Minneapolis Area, MN
With the original top link only, the engine was free to rotate in any direction about a point, the top link, only limited by the flex of the motor mounts.
With the addition of another link, the engine movement is more defined as it can only revolve about a line, an imaginary axis drawn between the two links, as well as rock within the frame, now limited by the flex of the motor mount without the link. The flex of the remaining naked motor mount allows the rear wheel to move laterally (albeit in more of a controlled circular path about the axis defined by these two links).
Adding the third link limits engine movement to a single plane defined by the three links. The only movement allowed is a rocking motion about that plane.
Cruiser
Joined: May 2007
Posts: 198
Likes: 0
From: Colorado Sprgs, CO
Sorry man, but that is not how it works out. The only way that would work is if the top link were actually an axle running down through the center of the motor. Then limiting the lateral movement on either side of the axle would limit movement on the other side (like a fat kid one one side of a teeter totter and a skinny kid on the other). But this is not the case here, all you've done is changed the engine's pivot from a point to a line.
With the original top link only, the engine was free to rotate in any direction about a point, the top link, only limited by the flex of the motor mounts.
With the addition of another link, the engine movement is more defined as it can only revolve about a line, an imaginary axis drawn between the two links, as well as rock within the frame, now limited by the flex of the motor mount without the link. The flex of the remaining naked motor mount allows the rear wheel to move laterally (albeit in more of a controlled circular path about the axis defined by these two links).
Adding the third link limits engine movement to a single plane defined by the three links. The only movement allowed is a rocking motion about that plane.
With the original top link only, the engine was free to rotate in any direction about a point, the top link, only limited by the flex of the motor mounts.
With the addition of another link, the engine movement is more defined as it can only revolve about a line, an imaginary axis drawn between the two links, as well as rock within the frame, now limited by the flex of the motor mount without the link. The flex of the remaining naked motor mount allows the rear wheel to move laterally (albeit in more of a controlled circular path about the axis defined by these two links).
Adding the third link limits engine movement to a single plane defined by the three links. The only movement allowed is a rocking motion about that plane.
Road Captain
Joined: Mar 2008
Posts: 646
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Road Warrior
Joined: Dec 2008
Posts: 1,530
Likes: 1
From: Upstate, SC
Would you not agree that the amount of deflection is greatly reduced with the addition of the front stabilizer because now for the drivetrain to pivot around an axis defined by the top and front stabilizer the rear mount not only must deflect on the horizontal, it also has to compress on the vertical? The construction and design of the isolator itself is designed to prevent just this sort of deformation.