My old HF with Os 28. Its currently running a 18T CB (just fits), 100 k centre diff, for some speed runs and got 96 k/hr (60mp/hr). I have another old HF i use for parts. Ive had the HF for aprox 3 yrs. </p>

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I did another few runs today with the 18T and only got 92k/hr. That sounds more realistic. 96k/hr didnt sound correct. The 18T CB is slightly to tight on the mesh and the os doesnt seem to like to push that gearing. 17 T CB is perfect for the speed runs, still revs out nicely. I have switched back to a 14T as its back to the track for a bash.
I did hit a post hard today at high speed and didnt break anything, go old hellfire go.