15T gearbox sprocket on 350 SXF?

I'm nearly ready to try my 'supermoto' converted 350 SXF at a speed hill climb and the sprockets need changing to give suitable gearing. Some hills need significantly higher gearing than others and all need higher than MX. To give the greatest number of possible variations I like to have a choice of two gearbox sprockets and two or three rear sprockets. I got an additional 15T sprocket for it (14T original) but whilst the splines and offset are exactly right it looks as if there isn't enough clearance between the chain and the clutch slave cylinder to run it - at least with the Regina chain it has now - though I will be replacing that anyway as it is pretty worn. I'll run a HD non-o-ring RK as do on my other hill climbers as my local dealer always has them on the shelf and they work well for me.


The clutch  slave cylinder bears witness to have being worn by the chain already but I guess that may be due to being run at some time with a very slack chain. So can it be done?


No mention in the manual of alternate gearbox sprocket sizes and I can stock up on a range of rear sprockets but it is good sometimes to have the fine tuning option of a 15/4n combination to get the gearing perfect to hold one gear through a series of bends.


Despite playing with gearing calculators I just won't have a real feel for what I need to use until I give it its first run up Prescott hill on Saturday.

15T up front on a 350...HMMM


I did it on a 450 and it was difficult even with a 52 rear.


Supermoto wheels are smaller than MX wheels, if you go with a 14/44 you should be fine. Dont forget to reset your shocks for the new style of riding. As well as snag a supermoto filter kit from ktm...Also you will need a different chain and few more odds and ends...


Conversions look cheap but they be expensive!!!


Have fun



This will be used purely for speed hill climbs in the UK not supermoto as such. I run 15/40 or 39 at the longer hills on our tuned YZ450F which gives me 90 mph across the line at one of the courses with a reasonably long finish straight. Can't expect that from a 4T 350 but a genuine 80 ought to be possible.


I'd already decided on 14/44 as a starting point so it's good to hear that shouldn't be too far out with the 5.00x17 rear rim running a race wet. If it goes reasonably well I may get it lowered a couple of inches over the winter as we have done on the YZ450F and YZ250, but for now I'll just adjust the sag and damping.


This is my first venture in to the world of orange after a series of Yamahas what advantage is the supermoto filter kit?

The supermoto kit is a kn airfilter. I have it on my 450 And it screams all the time.

Silly fast

12-front, 50 rear. Let those titanium valves scream

12-front, 50 rear. Let those titanium valves scream


Ha! I did, but on the first run on 14/44 up  Shelsey Walsh I had a brain fart and thought I was on the four speed YZ450F so I hit the rev limiter at about 80 in 4th. My doesn't it bring action to a halt very abruptly. No bouncing off it. Perhaps because it's FI.

Definitely no need for a  15t front, though I may go down to a 42 rear for a couple of courses with longer straights.

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