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1390 Gearing

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#21 · (Edited)
R0man said:
KTM blamed the 16x40 gearing for the Cruise Control issues that I have been having on my Gen 3 SDR. No details have been provided, though. While this has not been stated in the service manual, it seems to have been KTM's concern.
Click to expand...
I have/had 16/40 on my Gen 3 1290, with no issues, actually made the quick shifter slicker. But yesterday i brought a new 17 tooth and fitted it. No test run as yet, readying the bike for a November 2 week trip in NZ's South Island........Ok took bike out yesterday in the pouring rain, everything working, quick shifter and cruise control.
 
Discussion starter · #22 ·
Installed the 17/40 combo with a new DID ZVM-X chain at 114 links. Unfortunately I hamfisted (over torqued) the rivet tool on the masterlink which split the end of one of the roller pins....doh! Probably would've worked fine but I'm not taking a chance and have the chain come apart and destroy the engine case and/or clutch slave cylinder.

Sadly I only had a 520 spare and a search of all local shops came up empty so had to order new masterlink (bought two!) online. Didn't get to ride this weekend...bummer! Hopefully they arrive before the weekend.

Insert face-palm here.

Jeers
 
#23 ·
Lowrance said:
Installed the 17/40 combo with a new DID ZVM-X chain at 114 links. Unfortunately I hamfisted (over torqued) the rivet tool on the masterlink which split the end of one of the roller pins....doh! Probably would've worked fine but I'm not taking a chance and have the chain come apart and destroy the engine case and/or clutch slave cylinder.

Sadly I only had a 520 spare and a search of all local shops came up empty so had to order new masterlink (bought two!) online. Didn't get to ride this weekend...bummer! Hopefully they arrive before the weekend.

Insert face-palm here.

Jeers
Click to expand...
I see Acosta broke his chain while racing Moto GP, and Binder broke one in practice. Best not take a chance.
 
Discussion starter · #24 · (Edited)
I saw that as well!! And, he flipped off the bike like it was KTM's fault....and not DID, Regina or?? Apparently they lost 3 over the weekend! Must've gotten a bad batch from which ever chain supplier they use....or they have an incompetent chain riveter.....doh!

I still can't get my head wrapped around a 520 holding up to the torture those bikes put out!
 
Discussion starter · #25 ·
I kinda screwed up. I modified too many things at once and lost my way a bit.

I installed 17/40/114 gearing. Due to my hamfisted torquing effort I didn't get to ride the bike with just the gearing change. I also installed the OFT Stage 1 map as the tuner came in last weekend. First ride with both mods was today. I have to say, if you like ferocious acceleration (I mean really FEROCIOUS), this is the setup for you. Substantially more violent than the 16/38/112 gearing (with stock ECU mapping) I had installed on my last ride...which if you read the post, you'll recall I stated was a huge gain in acceleration over stock gearing (with some fairly minor short comings). With effectively a one tooth step taller final drive ratio and OFT S1 map, the bike has gained a massive step in acceleration which points to the OFT S1 tune being something really special.

Another thing I noticed is that for the tight twisty bumpy roads I'm riding, the extra length in the swing (due to the 114 link chain) may not be the best chassis geo change. Bike didn't do anything evil but I got a sense of slightly less feedback for traction under hard acceleration. This probably wouldn't be an issue on smooth roads or a track but I noticed it nonetheless. May have been the extra leverage ratio on the spring making it slightly softer in rate creating some vagueness at the tire, don't know but (at least where I ride) I think I prefer the 112 link chain. A one step stiffer spring might sort the issue but not prepared to go down that path....just yet anyway. It didn't really slow me down at all but more feedback is always welcome! Another possibility is a slightly more forward weight bias (shifting more of the bike/rider weight from the rear to the front).

So next logical step is to revert back to stock gearing (17/38/112). If nothing else, it'll allow me to test the OFT S1 tune on it's own which I'm sure Stic is waiting for (teaser, pretty sure it's going to be really good).

Cheers

-John
 
#26 ·
^^^ I would presume 17/40/114 would give a similar wheelbase as 17/38/112. With the 112 link chain and 17/40 the concentric adjuster is right forward, a 114 chain puts it somewhere in the middle with those sprockets. But a 114 with 17/38 might put the concentric adjuster at its furtherest out position.
 
Discussion starter · #27 · (Edited)
Yep, 17/40/114 is just under 8mm longer than a 17/38/112 combination. That is a pretty sizeable change. I base these #s of Eric's eccentric ride height charts on his website. Very useful tool!
 
Discussion starter · #28 ·
So, plan was to go back to stock gearing (17/38/112) to evaluate the OFT Stage 1 tune on it's own merits. However, I really wanted to try the 39t rear sprocket before removing the 114 link chain. The 17/39 combo is good, really good from a balancing acceleration/RPM compromise. Problem is it makes the swing arm even longer reducing effective spring rate even more. Heavier spring rate would definitely be required if one were to stick with this combination.

So what has all of this experimentation taught me? KTM's choice of 17/38/112 is probably the best combination for the riding I do. If you're on track, the longer swingarm from a 114 link chain will offer slightly more stability but the ability to accelerate harder with shorter gearing is the real bennifit. If your looking to get every ounce of performance out of the bike on track this would be the path I'd choose.

With the OFT S1 tune, the 1390 accelerates so much better that a shorter gearing choice has proven to be unnecessary, at least for me on road (a dedicated track bike would be a different story). The Spark Ti pipe has arrived so another step in performance with the OFT S2 is expected which would make a shorter gearing combination needed even less.

Don't know if this excersise was helpful to anyone other than me and my curiosity but there it is. Obviously if you own a 1290, it's a different story. The bike with its taller 5th and 6th gears definitely bennifits from shorter gearing but the 1390, not so much.....IMHO of course.

Cheers

-John
 
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