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My 1600 tracks straight, but the left pull has been reported enough times to be considered a legitimate concern. I think, however, it is a geometry problem, not one of physics.
I agree that it isn't due to being a shaft drive. If it were, I think it would affect all bikes about the same amount. Mine will drift left, but not even noticeable with one hand (or even a finger) on the bars. Some bikes are really bad, others almost nothing, some don't drift at all. It must be something about assembly rather than a design flaw - unless the flaw in the design is that it can be assembled out of spec somehow.
 

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For some 290,000kms on different K16s I’ve had the left pull when running PR3GTs and PR4GTs. Last year I fitted Angel GTIIs and the bike ran straight and true, but it coincided with new front wheel bearings. 13,500kms still running straight, another set of Angel GTII fitted and no left pull for another 14,000kms.

Last week I put on a new set of R5GTs and guess what: a left pull is back, albeit not uncomfortable so far with 1,000kms on the tyres but it is definitely back to colour my riding.

Grrrrr.......
 

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Here's an interesting tidbit I'd like to share. My 2018 B had a slight drift to the left since brand new. When I blew the motor up at 40K and had it replaced the left drift wasn't present anymore. Here's the difference: I've watched a few detailed videos on how the K1600 bikes are assembled. When the motor comes down the assembly line it's mounted securely to a motorized platform and when it gets to the station where they attach the frame the assembly worker starts putting the bolts in one at a time torquing them down completely. There are no temporary alignment pins and no shoulder bolts used, just regular bolts. Now from a machinist point of view that's a poor assembly technique. A regular bolt has a ton of slop in it and you can see as the assembly worker adds more bolts he has to bump the frame holes into alignment with the first bolt already torqued down. That will create a twist in the frame and 10 thousandths worth of twist at the engine mount can easily translate into a 1/4 inch at the front axle 3 feet away. So here's the difference: When they installed the new motor in my bike it was sitting on it's tires and they lifted the motor up into the frame from the bottom. They started all the bolts by hand and after that proceeded to tighten them down to the proper torque. By doing that the motor sat in the frame and found it's proper alignment through gravity with no influence applied and frame didn't get tweaked. My new 2019 GT also has a left drift so I'm going to make a request to the dealership repair shop to take my bike and loosen all the engine mount bolts and let the motor hang freely then step torque them in a sequence that would be side to side to the proper torque and we'll see if that cures the drift.........................................................
 

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I’ve already posted my 2 cents worth, however...
New tyres and screen and mine is so straight and true I can sit on the back seat and hold the handrails and just let cruise control take over.
On my last ride me and one of the guy on an R100RR had a little contest steering hands free along a gently turning road. We went for quite a few kms... He won, more out of boredom that any steering geometry concerns ;)
 

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I’ve already posted my 2 cents worth, however...
New tyres and screen and mine is so straight and true I can sit on the back seat and hold the handrails and just let cruise control take over.
On my last ride me and one of the guy on an R100RR had a little contest steering hands free along a gently turning road. We went for quite a few kms... He won, more out of boredom that any steering geometry concerns ;)
I wish that was the case with the new GT.
 

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Here's an interesting tidbit I'd like to share. My 2018 B had a slight drift to the left since brand new. When I blew the motor up at 40K and had it replaced the left drift wasn't present anymore. Here's the difference: I've watched a few detailed videos on how the K1600 bikes are assembled. When the motor comes down the assembly line it's mounted securely to a motorized platform and when it gets to the station where they attach the frame the assembly worker starts putting the bolts in one at a time torquing them down completely. There are no temporary alignment pins and no shoulder bolts used, just regular bolts. Now from a machinist point of view that's a poor assembly technique. A regular bolt has a ton of slop in it and you can see as the assembly worker adds more bolts he has to bump the frame holes into alignment with the first bolt already torqued down. That will create a twist in the frame and 10 thousandths worth of twist at the engine mount can easily translate into a 1/4 inch at the front axle 3 feet away. So here's the difference: When they installed the new motor in my bike it was sitting on it's tires and they lifted the motor up into the frame from the bottom. They started all the bolts by hand and after that proceeded to tighten them down to the proper torque. By doing that the motor sat in the frame and found it's proper alignment through gravity with no influence applied and frame didn't get tweaked. My new 2019 GT also has a left drift so I'm going to make a request to the dealership repair shop to take my bike and loosen all the engine mount bolts and let the motor hang freely then step torque them in a sequence that would be side to side to the proper torque and we'll see if that cures the drift.........................................................
I might just do that myself.
 

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I had all the engine bolts loosened and re-torqued in sequence and the verdict is: it still drifts to the left but not as bad. Instead of having to shift my butt to the right all I have to do is hang my right knee out. And life goes on ...................:)
 

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I had all the engine bolts loosened and re-torqued in sequence and the verdict is: it still drifts to the left but not as bad. Instead of having to shift my butt to the right all I have to do is hang my right knee out. And life goes on ...................:)
If it has an effect, perhaps there is a different sequence that will have a greater effect.
 

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I had all the engine bolts loosened and re-torqued in sequence and the verdict is: it still drifts to the left but not as bad. Instead of having to shift my butt to the right all I have to do is hang my right knee out. And life goes on ...................:)
Or maybe once the bike was assembled at factory and strain was induced on the frame, over the course of time, heat cycles, pot holes, gravity and other elements, some of the "tweak" on the frame became permanent. Loosening the bolts and re-torquing them simply did not bring the parts to proper alignment.
 

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Or maybe once the bike was assembled at factory and strain was induced on the frame, over the course of time, heat cycles, pot holes, gravity and other elements, some of the "tweak" on the frame became permanent. Loosening the bolts and re-torquing them simply did not bring the parts to proper alignment.
There was 2K on the bike when I had it done.
 
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