Finding a Weaker Carb Return Spring

[sam000lee]

I've decided that the return spring for my carb rack is too strong. After a few hours of riding, my wrist gets really sore. In a certain sense, it affects "performance" since it's harder to flick the throttle open. I've ridden cross country on this bike and so it's not a matter of just "riding more to build up muscle" - after 6 weeks riding ~200 miles/day, my wrist still ached at the end of each day. On my GS450 and GS550, the throttle feels great - easy to pull and snaps back quickly. On the GS750, it snaps back quickly but is noticeably more difficult to pull.

Are there any known drop in replacements? Sadly, the one from my GS550 is much shorter or I would have just plopped an extra I have in.

[Nessism]

What about a throttle friction device?

[sam000lee]

Hmm interesting - Wouldn't that make it harder to open the throttle, needing to overcome both the spring and friction force? It would make for easier cruising.

[Grimly]

Suzuki probably erred a bit on the strong side just to be careful with their design. On the older carbs the return springs tend to be stronger than you'd think preferable, but there's a good reason for that.
Having said that, I fitted a pair of lighter springs in the VM34s on my XS, with no bad results. There's no pull-shut cable on those either, so I'm entirely dependent on a free linkage, working spring and quick kill-button reactions in the event of a stuck throttle.
Have at it, and just be wary of the downside.

[dorkburger]

I use one of those cramp busters that attaches to the grip. It works well. Cheap enough to try before going thru the headache of messing with springs.

[salty_monk]

I messed around with springs on the 78 1000 (probably the same as yours). At anything noticeably less than stock it doesn't snap shut as it should....

[Steve]

I use one of those cramp busters that attaches to the grip. It works well. Cheap enough to try before going thru the headache of messing with springs.

If it were <my> bike, I would not care how much the headache would cost,
I would find a spring LONG before using one of those evil devices.

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[Cipher]

Or you could use a more appropriate technique to grip the throttle grip.
ON long trips I use my thumb and index in a light wrap around the tube housing while applying pressure onto the tube with the palm.

Plenty of friction and very little effort. and alterable in a split second.

I get the feeling you are on task constantly and there is no way a hand wrist forearm can do that for hours.
While the factory spring grip etc are a constant the anatomy of the rider is variable.

Its akin to telling a person to fret a guitar in a way that hurts them when they may be able to do it differently than accepted normality. Differently but no less effectively.

[John Park]

I messed around with springs on the 78 1000 (probably the same as yours). At anything noticeably less than stock it doesn't snap shut as it should....

I'm not sure of the physics involved, but I tried modifying the spring on a 78 750 and a 79 850 and found that when you run high enough rpm the suction would actually stick the slide to the bore or suck it open somehow and not want to return. This is downright terrifying. There isn't the same effect with the butterflies of a CV carb so the springs can be softer.

Yes, you can reduce the spring effort a bit, but it's a dangerous game. Everything will seem fine until you hit the wrong wrist/rev combo. Hopefully nothing else important is going on when you discover that.

I don't think that it's the rotation stiffness that is fatiguing so much as the constant grip tension required for traction. Stock grips aren't bad in that regard, but slippery gloves are useless. I have a pair that I rub beeswax on regularly just to get enough grip that my arm pressure will hold the throttle without constant squeezing.

Best of luck.

[RichDesmond]

Back in the dim times, before CV carbs became ubiquitous, I’d see an ad in the back of every bike mag for a device called Twist-Assist, or something close to that. Might be worth searching eBay or other vintage bike forums for one.

[Steve]

Back in the dim times, before CV carbs became ubiquitous, I’d see an ad in the back of every bike mag for a device called Twist-Assist, or something close to that. Might be worth searching eBay or other vintage bike forums for one.

Yep, "Twist Assist" is correct, I had those on my first few bikes.

It was a tube with an internal spring that would slide into the right side of the handlebar and expand to lock in place. There was a threaded stud on the end of the spring that would stick through the end of the rubber grip. By winding some counter-pressure on the spring and squeezing the end of the grip, it would counteract the spring on the carbs.

It could be adjusted to perfectly balance the carb spring, which would require you to manually move the grip in both directions. You could also over-adjust it so it would ADD throttle when you let go. Yeah, you could also add spring resistance if you needed to add some muscle tone to your right wrist.

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[RichDesmond]

Yep, "Twist Assist" is correct, I had those on my first few bikes.

It was a tube with an internal spring that would slide into the right side of the handlebar and expand to lock in place. There was a threaded stud on the end of the spring that would stick through the end of the rubber grip. By winding some counter-pressure on the spring and squeezing the end of the grip, it would counteract the spring on the carbs.

It could be adjusted to perfectly balance the carb spring, which would require you to manually move the grip in both directions. You could also over-adjust it so it would ADD throttle when you let go. Yeah, you could also add spring resistance if you needed to add some muscle tone to your right wrist.

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And the big advantage of that system is that if you close the throttle the full force of the stock spring is pushing the slide down, unlike if you fit a weaker return spring to the carb.

[Gorminrider]

You could increase the diameter of the grip. This will increase leverage turning AND holding....and your hand will not need to clench as far so fewer wrinkles of your hand or gloves might increase "grip versus pressure.."
possibly mock this idea up with some handy materials (wrapped leather, foam wrapped with grippy hockeystick tape and go round the block) before you buy stuff

If you find that WOT too slow, you MIGHT try increasing diameter at just one place or two places on the grip...under a knuckle...this is merely an idea.

Grips with raised longitudinal bars in the moulding might also help.

[Steve]

https://buyee.jp/rakuten/detail/auc-pretty%3A10004640

Not sure about anyone else, but I'm REALLY hesitant to buy something I can't read.

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[Cipher]

Not sure about anyone else, but I'm REALLY hesitant to buy something I can't read.

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Google translate is quite the awesome thing. It just came out 15-20 years ago.

☆ Made by PRETTY RACING ☆ ○ The contents of the exhibition are hollow aluminum throttle + 3 throttle spacers SET ○ Compatible models = GS400 (all year) / Sanpachi (all year) / 400 Zarigoki / ○ Safe and secure one-piece structure aluminum throttle ○ Throttle Because the finish of the inner surface is beautiful, the accelerator slides smoothly and smooth accelerator work is realized ○ The inner surface of the throttle has a straight structure ○ The big difference between 01 and 02 is that the size and height of the stopper are different and 02 is larger This will prevent the throttle from spinning. 〇 The throttle spacer will be a spacer to fill the looseness between the throttle and the switch box in the switch box, and you will not have to worry about interference with the grip with an external spacer. * Please purchase separately as it is not required for the GS400 early model switch box. ○ We recommend those who can maintain the installation or install it at a motorcycle shop.