Bike is converted to 520 chain, 14/39 from Economy. I always felt stock gearing was pretty adequate for hauling my 250 lbs around. Since re-doing the top end, Dave F, filters, spacers, reeds, and DG chambers, along with 520 conversion I don't feel that 6th gear is all that useful anymore. Was considering going up a tooth or two on the rear, but this setup doesn't have many miles and don't want to buy another chain.
Would a 13 tooth wear ok and give enough of a noticeable difference in performance? I know reducing the front is probably a big compromise if I step too far down. From what I figure a 13/39 is equal to a 14/42.
Isn't stock 15/39? If you go down to a 13 that's a huge jump from stock. Are you sure your jetting is right? Too rich or too lean will make it seem that way.
With your set up you should be around a 200 main. Maybe even as low as 190.
I'd go up on rear . 13 is small and will be rough on chain
Stock is 15/40 if memory serves. John at Economy Cycle recommended 15/39 and I went with that and am happy with it. I can cruise at 70 and the motor is happy.
If memory serves me right, the RD350 user manual recommends 6000 rpm as the limit for cruising over any extended time. 6000 rpm with 15/40 gives around 115 km/h (just over 70 mph)
A 13 tooth countershaft sprocket will drop the 6000. rpm speed down to around 100 km/h. Which is just too low IMHO.
Yep stock gearing was 15/40. John lists the 250/350 conversion as 14/39. He may have recommended the 15/39 combo, but I can't really remember what I bought anymore.
Joe, I am almost certain I running 190 mains, maybe 180. Honestly I plan on messing with jetting a little more this year and may have to adjust clip position. I think you may be onto something as it really pulled hard with 220's, but couldn't get it wide open without falling on it's face.
I won't mess with gearing for now. It may be that I was trying to cruise at too slow in top gear too.