I'm a fan of 18/48 sprockets. Riding at 70/75mph with a 17 front makes me a little edgy. I prefer to go a little faster than traffic so most things happen in front of me, not coming from behind.
I honestly did not remember what I had installed back in 1993. I make a run down I69 near Fort Wayne now and then and speed limit is 70 and traffic runs 80, 17/48 is pretty buzzy at 80 LOL. Have not been up to 80 on the 18/48 yet but it should be better. I usually run 60 in a 55 and it is interesting how your brain gets wired to a given engine RPM and for the first few rides I'd look down and see I was going 62 not 60 :-).
I wouldn't mind trying a 19 front but none avail right now.
Bill
I have the 17, 18, and 19T countersprockets for mine, using them according to what I am/was doing.
The 19T usually requires that you have added some torque to the engine, either in the form of an overbore (even 1st oversize is enough) or by porting the heads on the post-3/72 K2 engines (and later, up to K5). It drops the top speed (with Vetter) to about 105, but it feels like a real Overdrive, with the engine purring like it loves it at 80-90 MPH. The highest [speedo-indicated] top speed comes on most of the K2/4 bikes with the 17T front sprocket (all these use 48T rear) while feeling more 'buzzy', and for heavy in-town commuting is my first choice. The 18T came out in the K2 in response to Honda's customer feedback talking about the 'noise behind fairings' that came mostly from the Vetter's incredible impact and sales in those days, which for the first time brought ALL the engine's mechanical noises right to the rider's face: at the then-new 55 MPH speed limit this put the engine at 3950 RPM, just below the 'on-cam' low-end response, so it felt sluggish and required a downshift (or two) for passing. This noise-abatement agenda caused the locked-down rocker shafts to happen (and NOT due to 'broken shafts' as claimed so often in Internet trash articles) and the change in cylinder fin supports from the little pins to the wide casting bosses (in the K4), all to stop radiated noises.
If you go to the 19T, some MUST DO things are:
1. Trim 2mm off the tip of each sprocket tooth (I also trim 1mm off each 18T tooth). This both mimics Honda's specially-made sprockets of this era to quiet and extend chain life, and makes the chain last MUCH longer thru better lubing (see my book for the details).
2. Cut away the rubber on the sprocket cover's stabilizer post. The tips of the non-Honda 18T sprocket will have already ground off about 1-2mm of this rubber, so you will have a built-in guide as to where to cut: remove it all the way to the support post, or the sprocket will do it, loudly! The Honda 18T countersprocket just barely kissed this rubber block.
3. Get the countersprocket(s) with the thicker reinforced inner body. The cheap ones often come with a washer (or two) to space the sprockets correctly with the rear one, but the narrower sprockets also wear the countershaft. Get the wider (thicker) one to mitigate this action.
