Gearing change for more acceleration - Wrist Twisters
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post #1 of 15 Old 12-15-2018, 03:41 AM Thread Starter
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Gearing change for more acceleration

The chain was last changed on my 05 919 20k back. It may be due a replacement. And if so, this would be the time to consider changing the gearing. I made a change just to a -1 front sprocket on my recently sold FZ1 and the change in acceleration was immense.

I see that many apply a -1 and +2 F and R change.

I rarely use anywhere near the top end and 99.9% of my ride is commuting and urban skirmishes.

Should I move to the -1 and +2 sprocket change and if so what chain and sprocket set is for the best? Some lighter chains to change rotating mass which to my basic, crude understanding, will help the power surge ever more?

Yet the bigger, more pivotal question is...if I change the sprockets will the speedo then be misreading? ANd require a speedo healer to show the correct speed?

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post #2 of 15 Old 12-16-2018, 02:04 PM
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Yes, the speedo reads from the countershaft rotation speed, and any final gearing change will throw it off.

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post #3 of 15 Old 12-16-2018, 05:51 PM
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There have been a few members here that have done 15 : 45 from the stock 16 : 43, and almost all subsequently went to a lower ratio, especially if commuting any great distance.

Crunching the numbers: stock gearing at 110 KPH has the engine spinning ~4300 RPM, while the same speed with 15 : 45 will raise that to ~4800 RPM. It gets tiring fast if you have any distance to go. Of course it will be a hoot doing the "urban skirmish" thing, and in first gear it will be difficult to keep the front wheel anywhere near the ground, but you have to determine if the less comfortable commute is worth it. Additionally, the smaller the countershaft sprocket the quicker the chain will wear due to increased centripetal acceleration as the chain follows the smaller radius of the sprocket.

Unless you are on a race track fitting a lighter chain and rear sprocket will not make a significant difference in acceleration. It will, however, benefit rear suspension compliance by reducing unsprung weight.

A few alternatives at 110 KPH:
17 : 44 = 4140 RPM. Preferable for touring / long commute.
16 : 43 = 4300 RPM. Stock
16 : 44 = 4400 RPM.
16 : 45 = 4500 RPM.
15 : 43 = 4585 RPM.
16 : 46 = 4600 RPM.
16 : 47 = 4700 RPM.
15 : 45 = 4800 RPM.

If you want to feel what commuting with 15 : 45 feels like put it in fourth gear and cruise at 100 KPH.

All speeds are calculated. The speedometer reads roughly 10% higher than your actual speed. It's up to you if you want a speedohealer, but consider the fact that if the speedo reads significantly higher than you are actually going it may help you to keep your license. It's worth considering.

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If it has already been done, it is safe to assume it is possible to do it.
On the other hand, if it has not been done never assume it is impossible to do it.
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post #4 of 15 Old 12-16-2018, 06:15 PM Thread Starter
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I had gone a little berserk with the -1 and +2 suggestion. Given the difference I felt in the FZ with solely a change from the stock to
17/45 to 16/45, perhaps I could do the same with the 16/43 down to 15/43 or 16/45 (same effect?).

Would such a drop to 16/45 even out the speedo!?

perhaps I should stick with stock.

Yet now I found the age of the chain and sprockets, I am more eager to perhaps replace. They have done close to 20k and been on there since 2012.

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post #5 of 15 Old 12-16-2018, 07:31 PM
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What you describe will make the speedo off more, not less. Also the odometer is fairly accurate despite the speedo so any gearing change will make the odo off. I have run 17/43 & 17/44 & it adds up to a few miles per tank verses the bike ( a different box stock Honda) I ride with..

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post #6 of 15 Old 12-17-2018, 02:31 AM Thread Starter
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Presently my commute is 20-25 minutes with the speed limit between 40 and 70km/h. Pretty much 100% of my riding of late is done in this zone. I will probably have chance to launch a little further afield, but rarely, given my familial situation is vastly changed of late and less time for lone wolf adventures. Hence why I was thinking of the sprocket change.

I will have the paddock stand soon and can give the chain a decent clean with a grunge brush, and will see the condition a little more clearly. Still, it seems that 18000km is a time when some would change a set of sprockets and the chain? I will try get some decent photos after the scrub and clean.

No eagerness to change anything unless its near the end of its life of usefulness.

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post #7 of 15 Old 12-17-2018, 09:47 AM
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From my experience, having a shorter first gear makes it almost unusable. It's very jerky. I want to try the gearing change just because I want to do second gear power wheelies but outside of that I don't think it'll make you acellerate any faster as first gear with the 17/44 seems like the perfect gear to launch as it only barely lifts the wheel on power.

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post #8 of 15 Old 12-17-2018, 05:38 PM
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I'll just add a bit more.

Reduced rotating mass allows for a faster acceleration of said mass if the same amount of energy is applied.
Reducing the front sprocket teeth count in association with stock or more teeth at the back, reduces the effective number of driving teeth, reduces the angle of wrap at the driving sprocket, and alters the stress lines in the side plates around the driving teeth because of the revised chain geometry, and increases squat.

Some have gone to 15 tooth fronts, and I don't recollect hearing of any related failures.
I would never go less than 16 for a 5x0 pitch chain on a motorcycle.
Personally I use a 16:45, noting I am at 3500 ft altitude and have matched peak and runout power to be coincident with the aerodynamic limit of the bike at the reduced power due to altitude.

IF you were to try a 15/45 and use it as you say you want to, I'd be looking for a 02/03 shock and spring, otherwise your 04 spring will be seeing your shock bottom out and be on the snubber way too much, and not just in 1st gear.

When it does come time to get a new chain, go with good 520 and sprockets.
AFAM is great stuff as far as sprockets are concerned.
I have an AFAM aluminum rear.
I couldn't get a AFAM 16 tooth front when I did my kit 11 years ago.
So I got a Renthal instead.
My recollection is the smallest front that AFAM had at the time was a 17.
I still have the same chain and sprockets on the bike.
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post #9 of 15 Old 12-17-2018, 11:20 PM
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Quote:
Originally Posted by thegutterpoet View Post
Yet now I found the age of the chain and sprockets, I am more eager to perhaps replace. They have done close to 20k and been on there since 2012.
Don't rush into it, it all depends on condition rather than age and mileage. I have 39,000km on a 520 17/44 set I got from LDH across the pond - Maryland Mike is doing even better with his...

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post #10 of 15 Old 12-18-2018, 05:04 AM
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So far, in 5 years of riding a 919, I have never found the acceleration "lacking." What would you do with more besides get into more trouble?

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post #11 of 15 Old 12-18-2018, 03:07 PM Thread Starter
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More an enquiry than surefooted eagerness and echoes of grasping at the ghost of my beastly FZ1...I figured it was worth researching given the age of the chain and sprockets and possibility that they are due for replacement. Will know more on that score once I have given them a good clean. I have seen that many people actually change the gearing in the opposite direction to give more comfortable cruising and more accurate speedo. I am happy with the launch and will be ever more so when I have my new Angel Gts to replace these hideous T30 evos which have been like walking on eels in any rain and even quite slippery in the dry if accelerating on a small covering of dust or debris...worst tyres I ever rode on.

LDH seems to have equipped many a 919 owner with satisfying parts on this score!

I will check back and repose my question towards condition of the chain and sprockets. Rather than moving towards maniacal boy racer (yet again) as I peek curiously at 40!

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post #12 of 15 Old 12-18-2018, 03:32 PM
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Quote:
Originally Posted by thegutterpoet View Post
More an enquiry than surefooted eagerness and echoes of grasping at the ghost of my beastly FZ1...I figured it was worth researching given the age of the chain and sprockets and possibility that they are due for replacement. Will know more on that score once I have given them a good clean. I have seen that many people actually change the gearing in the opposite direction to give more comfortable cruising and more accurate speedo. I am happy with the launch and will be ever more so when I have my new Angel Gts to replace these hideous T30 evos which have been like walking on eels in any rain and even quite slippery in the dry if accelerating on a small covering of dust or debris...worst tyres I ever rode on.

LDH seems to have equipped many a 919 owner with satisfying parts on this score!

I will check back and repose my question towards condition of the chain and sprockets. Rather than moving towards maniacal boy racer (yet again) as I peek curiously at 40!
Yes, there's many a happy WT'er on well priced, top shelf 17/44 520 kits from LDH.

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post #13 of 15 Old 12-18-2018, 05:06 PM Thread Starter
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Definitely no need with my current and ongoing usage of the bike to focus more on comfortable long commute, so will avoid the 17/44 kit for now. Though if the chain and sprockets overly worn then I will certainly be seeking ideas for replacements in the stock 16:43 ratio. I like the punchiness of the 919, it feels like a boxer jabbing its way through the traffic in the city and then roaring from the lights when the road opens up before me...have yet to head out into the sticks for a decent ride since purchasing in March. Work and family commitments.

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post #14 of 15 Old 12-29-2018, 06:38 PM
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I put on a 15T with a 43T a little while back, and I've been happy with the results,
all my riding is around tight twisty mountain roads, although when they need replacing,
I'll most likely get a 16T x 45T with a 520 chain.
When I bought the bike I had new tyres, chains and sprockets fitted, but they trimmed the chain
so the rear axle was hard up towards the swing arm, so I couldn't fit a 45T rear without extra links,
and as the chain already had several K k's on it, I didn't want to try and find the extra links somewhere.
If I was only commuting I would't have done this.
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post #15 of 15 Old 12-30-2018, 12:01 PM
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I got my new sprockets and chain in spring 2018. I picked 16/42 gearing and I am happy with it. Bike has less vibrations when on expressway and 2-3% loss of torque is not too bad. I am in 3rd or 4th gear most of the time when on twisties and bike is still sharp enough. Seems like speedometer is more accurate with this setup but counts miles quicker lol. My fuel reserve light used to come on around 160 miles after filling up my gas tank, now it is around 170.
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