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[rayivers]

The 27.5" diameter knobby on my '14 FX dirt conversion reduced acceleration so I installed a 71T sprocket, using the stock 12T front sprocket and a 113 link chain.  I'm very happy with the results, but if you need a super-low ratio like this I'd go with an 11T front sprocket (info below) and the 65T chain-kit rear sprocket instead, which is much cheaper and probably easier too.  My motor was recently replaced under warranty, so I didn't want to go that route this time.  I also wouldn't go larger than 69 or 70T on back, to keep a reasonable amount of chain-guide clearance / adjustment range and an even number of links.   UPDATE: Check out this thread for the most recent chain-drive upgrades.

REAR: Sprocket Specialists did up a massive hard-anodized ('Titan Tough') 520 sprocket with the ultra-light option.  They based it on their 981 pattern for the '03 - '07 KTM 85 SX (132mm diameter M8 4-bolt circle, 110mm center hole dia.).  This pattern appears the same for all '13 and later Zeros.  UPDATE: The Titan Tough finish was a waste of money; everything else wore out first, so now I have a very expensive sprocket with tons of life left in it that I can't use with a new chain & F sprocket.

http://sprocketspecialists.com/product/ktm-85-sx-rear-motorcycle-sprocket-yrs-03-07-sku-981/

The 71T, 65T, and 49T (KTM) sprockets:



On the bike - note the tight fit to the chain guide:




FRONT: The Martin 50BS11HT-1 11T sprocket (hardened teeth, 1" wide, 1" finished bore w/.25" keyway & 2 setscrews, #50 / 530 chain, teeth .334" wide) can be ground down to .227" tooth width for 520 MC chain, or used as-is with #50 / 530 chain & rear sprocket.  The pic below shows it after initial machining, w/12T sprocket from the Zero chain kit on the right; later I'll have the 'step' removed.  UPDATE: I ended up using a Martin 10T sprocket instead (50BS10HT-1), which is a wicked torque beast.




If you're changing both sprockets you may want to use 530 chain, especially for the higher-powered Zeros. You won't need to machine the front sprocket, and the rear will be the same except for tooth width.  Sprocket Specialists can do this, and most anything, within reason.  The chain guide inner liner may need widening.

I also found a cool online chain calculator, which was quite accurate for this job:

https://www.rbracing-rsr.com/chainlength.html

The bike's really coming along. It feels like a crisp-running auto-clutch CR500 stuck in 3rd.



Ray

[McRat]

So for technical dirt riding, you'd recommend the 11/71 combination?

[rayivers]

No, sorry - I should have specified  11/65  (using the chain kit's 65T sprocket) to use, as it's the same ratio as the 12/71 combination that's performing so well now.  Unfortunately, a 71T sprocket is just too big for the FX swingarm setup; mine fits (barely), but I wouldn't recommend it.

If I keep the chain, next time I'll probably go with an  11/66  530 setup.  I haven't given up on the belt, though.  I'm currently working on a guide/guard setup using a heavy-duty tensioner / idler multi-roller setup, which will control belt snap and shield the belt from most foreign objects while allowing it to handle whatever small stuff gets though without breaking.

Ray

[steven_first]

I have a stock 2015 FX.  Can you quantify the difference between the stock belt drive top speeds and acceleration compared to the sprocket ratios you have tried?  Is there a safe chain setup to get you down to say 70MPH max with higher acceleration?

[rayivers]

Can you quantify the difference between the stock belt drive top speeds and acceleration compared to the sprocket ratios you have tried?

Sure - there isn't any.   Right now, both my FX's accelerate at about the same rate and have roughly the same top speed despite the bigger rear tire on the dirt bike.  This was my goal for the sprocket change, and I feel it was a success.  The belt-drive bike still seems to accelerate a bit harder, but the difference is minimal now - maybe it's the belt, or maybe the 2.8's controller has a different throttle curve programmed in, I don't know.

How fast does your bike go now?  I've only had my 2.8  up to 65 mph (at which point it was still accelerating very slowly) and it seemed like there might a little more left above that on a level surface.  The 5.7 was still accelerating medium-hard at 70mph, but I ran out of road that time and haven't run two batteries in it since.

Regarding your idea about a 70mph top speed with more acceleration on a '15 5.7 - I suppose this could be done using 12/67 or 12/68 sprockets with all the accompanying noise and increased maintenance, but it's really too bad we're forced into hardware solutions instead of just a minor tweak of the controller torque curve.  I'm going to try the Zero app next week in the hopes that reducing top speed may add a little more torque below that and/or improve throttle response, but I doubt it will.

Ray

[steven_first]

My stock 2015 FX 5.7 well hit 85MPH in 5-6 seconds with almost no loss of torque.  I have not tried running my bike on one battery yet.  I am guessing I need to take the termination block out from under my seat and install it into the empty battery slot.

[rayivers]

85mph sounds about right from the other posts I've read here, and certainly more than fast enough for the riding I do.  Hopefully I'll see the day when my bike will do that on one battery...  It's really nice to have the option to use one or two, it was a major selling point for me.  You might want to try one battery sometime, just for grins - the range will be halved, obviously, but the other effects (low-speed acceleration, handling, etc.) may not be what you'd expect.

Yes, the plug fits into the unused battery port on the frame - I was told it's basically a jumper to tell the MBB? that two batteries are installed.  Mine was tie-wrapped from the factory, but now I use a slightly-modified Bikemaster 86mm exhaust spring to hold it in (I drilled a small hole in the vertical LH Formex wiring cover between the battery ports for one end of the spring, the other uses the 'earring hole' in the rubber plug cover). The spring is barely under tension, but the plug doesn't budge at all.

Ray

[Burton]

  They based it on their 981 pattern for the '03 - '07 KTM 85 SX (130mm diameter M8 4-bolt circle, 110mm center hole dia.).  This pattern appears the same for all '13 and later Zeros; maybe MX / DS / XU / S / SR owners can confirm this?

Just went to the bike and measured (didn't remove rear tire) 110mm hole but 132mm diameter for bolt holes center to center. I have confirmed this by measuring ~93.3 from center to center on the shortest distance between two bolts.

SQRT((132^2)/2) = 93.338

2013 S ZF11.4

Worth noting the part number 30-05090 from zero for the 2014FX has the title 65T 520 SPROCKET 132MM BOLT CIR

[rayivers]

Burton,

Wow, good catch - thanks!  The JT diagram below shows the same thing - don't know how 130mm got in there, probably from a quick early measurement or something.  I updated my post, hopefully no one had problems because of it.



Ray

[Burton]

Now to figure out sprocket sizes

I am running 25 : 98 right now which would be 12 : 47
I had ordered a 28 front pulley for when I streamlined the bike which would bump me to 3.5 or 13 : 46
Stock 28: 132 would be 12 : 57

12 size front based off your other 11 model number given
https://www.mrosupply.com/sprockets/finished-bore/262573_50bs12-1_martin-sprocket/

13 size
https://www.mrosupply.com/sprockets/finished-bore/262587_50bs13-1_martin-sprocket/


Anyone convert to chain on a 2013+ S / DS ... no mounting point for a chain guard I can find on the swing arm :/

[rayivers]

Is it common for road bikes to have chain guides?  The Yamaha R1s haven't had them for at least the last 10 years, but I don't know if that's typical.

The FX uses a well-made formed bracket supporting both sides of the guide and welded to the side & bottom of the swingarm. This is great, but in my opinion a simple drilled aluminum plate of the proper thickness, mounted to the swingarm tube with thread-forming screws and JB Weld, would hold the guide & bolts just as well in anything short of a crowbar-on-the-road event, in which case all bets are off anyway.  This should be fairly easy to do on the S or DS, and also to undo later on if needed, with a little touch-up work afterwards.

A side note which may or may not be relevant in this case: I doubt the Zero chain guide will pass 530 chain.  It's a tight fit even with HD 520.

Ray

[Burton]

Don't have one on my ninja 250 either but was just checking

What about chain slack ... on my ninja it is between 35 & 45mm ... I have seen a SV650 with less if I recall.

I think I am going to go the chain route .... wonder if my dealer is going to be upset I am going to have to cancel my sprocket / belt order ....

Poor Harlan has a message on his system for an inquiry to buy belts >_<

How much louder is the chain over the belt and do you still get the awesome motor noise at lower speeds?
What does it sound like when you regen?

Anything else I need to know about chains on an electric bike?

[rayivers]

My chain slack varies greatly with wheel position - I think now it goes from 20mm to 50mm or something.  Next time the wheel's off I'm going to true the sprocket trying for a uniform 25mm or so, hopefully that will help.  OMG, I hope the belted bike doesn't vary this much...

Speaking of which, the changing slack adds a cyclical variation to the chain noise that I find especially irritating.  The chain's quite loud, especially at speed - way louder than the motor, which I can only identify below 10 mph or so.  It's like a giant zipper being pulled at 100 ft/sec.   If anything, it sounds even louder during regen.

Ray

[Burton]

Hmm ... don't think I would like hearing more noise than the motor up to 45 which is where the wind noise kicks in.

When I tested belt tension last it was uniform all the way round. I did this because I thought I should check it like I check my chain slack and adjust at the least slack location.

Maybe if I change my belt yearly I can avoid going to a chain ... I put on 13-16k a year on average. Let me go find someone with an electric on youtube with a chain and listen to it :/

UPDATE: Screw it ... going to order the sprockets for my current gearing in 530 ... wonder what size chain I need :/
May as well try it given it isn't too expensive to swap back.

Second update: Talked to Harlan and Terry ... the SR's break belts on 25 fronts. Harlan recommended 132 30 ratio and 30 being stock on new SR's ... so going to get three belts (one extra put on bike ziptied out of way) and new pulleys.

Ratio will be 4.0 and it was 3.9 so no big change.

[rayivers]

If there's any way at all you can, I'd use a belt.  On my ICE bikes the chain noise just sort of blended in with the other racket, but on the Zero it's an in-your-face pitch-shifting screech that's impossible to ignore above 40mph, for me anyway.  Maybe an O-ring chain is quieter, I don't know.

Ray

UPDATE: After living with the chain for over 2 years now - and especially after replacing the 12/71 setup with 10/65 sprockets, which sound completely different & are way quieter - I've revised my opinion.  On the street I can't hear it much below 15mph, and a big part of the 'screech' mentioned above turned out to be motor noise (which is mostly masked by wind noise at higher speeds anyway). In the dirt, I don't notice it at all.  I also don't think it affects the smooth feel of the bike much, but since my bike has non-DOT knobbies (which are also super-noisy on the street) it never feels smooth on hard surfaces anyway.  With the huge torque increase of the 10/65 setup and complete freedom from worry, I won't be returning to belt unless something changes drastically in belt & sprocket availability / parting strength.