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Fast_Frankenstein

Stiff throttle return spring

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Fast_Frankenstein

Hello Hive-mind! I've now gotten my project to the point that it's rideable (working on a full build topic shortly). I'm hoping that others have determined a solution to the stiff throttle return spring - especially noticeable with the R6 tube. TIA!  :)

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stickshift

I've never noticed the throttle return spring being heavy (I have a quicker turn throttle fitted also). It's actually a fairly light action.

Are those renthal grips you have fitted? I've used renthals on a few other bikes and they can be longer than the stock grips, causing friction on the bar end and or throttle housing, something to check.

It might also be worth checking the throttle cable friction if the cable's been re-routed.

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Triple Jim

As @stickshiftsaid, my 2020 has a very light return spring.  It's the lightest feeling of any of my motorcycles.  What year was yours made?

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blackout

I would confirm there is no binding in the cable and just leave it alone.  You want a good spring back for safety and control.   I never noticed any issues on my two bikes.   Your throttle should spring back quickly and smoothly. 

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Craig Mapstone
Upstate New York

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Fast_Frankenstein
On 6/3/2021 at 7:13 AM, blackout said:

I would confirm there is no binding in the cable and just leave it alone.  You want a good spring back for safety and control.   I never noticed any issues on my two bikes.   Your throttle should spring back quickly and smoothly. 

Compared with the throttle spring on my R1, this is stiffer, now that the R6 tube is installed (changing tube increases spring tension per degree of throttle rotation on a 1:1 basis). There is a softer return spring available for the R3, and I was looking for a similar solution for our FZ/MT. The cable routing is as stock, the grips are "Yamaha" brand, likely made by someone else, sold by Yamaha for the R6. There is no drag, and no interference from any other part of the system.  :)

 

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Fast_Frankenstein
On 6/3/2021 at 5:48 AM, Triple Jim said:

As @stickshiftsaid, my 2020 has a very light return spring.  It's the lightest feeling of any of my motorcycles.  What year was yours made?

Yes, the return spring is exceedingly light with the stock throttle tube - change the ratio, and you change the "effective" spring rate - 1/4 turn throttle is twice the effective rate/stiffness of 1/2 turn throttle. I've got a 2017, but the part is the same for all years. I'm hopeful of a simple fix from our group, or I will look to the R7 to see if the part was changed to cover the likely quicker throttle tube installed on that bike.

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M. Hausknecht

I have 1/4 turn throttle on my 07. I would characterize the return spring as "light" at the throttle. If yours isn't, either someone put in a heavier spring or there is something weird going on with one of the cables. Perhaps disconnect the cables at the throttle body and operate the throttle by hand, to see what it feels like. With only two throttlebodies to the R1's four, tough to imagine the throttle bearing harder to turn unless something is way wrong. 

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Triple Jim

In case there's any confusion, a stock MT-07 has a 1/4 turn throttle.

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Fast_Frankenstein
9 hours ago, Triple Jim said:

In case there's any confusion, a stock MT-07 has a 1/4 turn throttle.  I've read on this board that the R6 has a 1/6 turn throttle, but I haven't verified that.  With no other modifications this would result in feeling 1.5 times the return spring rate at the hand grip.  When modifying an R6 throttle tube with the ramp to give an MT-07 more grip rotation for a given throttle opening at the low end, the torque to rotate the grip will be less than stock off idle and something greater than that at the high end.  This assumes you can get the radius of the spiral you cut down to less than the stock MT-07 radius at the idle end of the ramp.

Triple Jim is correct - my statement indicated that taking a throttle from 1/2 turn to 1/4 doubles the rate. The MT/FZ is indeed a 1/4 turn (90 degree), my R1 (same as R6) uses a 60 degree tube. I am not modifying the tube, as the throttle works just fine as is, just a bit stiff. I'd hoped to find someone who had done a modification (back in the day Mikuni smoothbores could be modified for lighter action) to make the throttle action lighter. When I find an adequate solution, I'll be sure to post. :) 

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stickshift

Looks like you have an interesting build, I'm interested in seeing  more of it.

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