I read a email from Jerry Branch (www.branchokeefe.com) in Bill Rooks book "How To Build A Harley Davidson Torque Monster". Jerry recommends (in the early twin cams 2000 plus) dropping the motor sprocket from a 25 tooth to a 24 tooth and change the trans pulley sprocket from a 32 tooth to a 30 tooth. He said the motorcycle will run 10 times better everywhere with this setup. I asked my local Harley mechanic and he said to change the motor sprocket from a 25 to 24 and leave it at that. He reckons if i change both sprockets as Jerry Branch recommended above, the difference won't be noticeable because that setup will counter each other. I'm a bit unsure now what to do. Shall i fit both sprockets or just the motor sprocket? FYI - My riding is like this......I like to cruise at highway speeds but i don't want to waste more then about 3 seconds to get there. So shall i fit both sprockets or just the motor sprocket? Can anyone help me with this? Thanks in advance.
If you want acceleration, reduce the drive pulley size a bit or increase the size of the driven pulley a bit, do both but sometimes it can be a bit too much. Why not change one of the gearbox or wheel pulleys instead of the motor ones. Reducing both or increasing both will have little if any effect.
Yeah my final drive is 3.15:1 at the moment. But by changing the motor sprocket down to a 24 tooth and the trans pulley sprocket down to a 30 tooth it should end up with: 36 divided by 24 = 1.50 and 70 divided by 30 = 2.333.
So 1.50 x 2.333 = 3.50:1. final drive.
I worked this out by this method:- Divide the number of teeth on your clutch sprocket by the number of teeth on your motor sprocket. This gives you your primary drive. Then divide the number of teeth on your wheel pulley by the number of teeth on your trans drive pulley. This gives you the secondary ratio. Then multiply your primary ratio and secondary ratio together, and you get your overall gear ratio.
So with that ratio of 3.50:1 that should get the RPM up and the back wheel spinning!
I knew it would throw the speedo out, but that was not a worry just yet.
But like i said earlier, my local Harley recommended that setup is a waste of time, to just change the motor sprocket down to a 24.
Since i have both the 24 tooth motor sprocket and 30 tooth trans pulley, i might throw them both on and see how it performs.
I'll keep you posted.
Cheers!
Just swapped the rear wheel 66 pulley for a 70 on mine and stopped the lugging in 6th, not a big change but it did the job, there was enough adjustment in the swing arm to not need to change the belt. Got speedo recalibrated when next tuned on the dyno. If you've already got a 30 front (think the standard front is a 32) and the standard number of teeth on the belt a bigger rear pulley might go in easy. Lower rear profile tyre helps a bit too. Just other options to consider.
Hey Hazyboy, I had an 01 twin cam Dyna I did 90,000k on & I used evo primary ratio had different amount of teeth on clutch hub not sure on the number right now, but the final ratio when your in 5th was 3.37 I think that's the best overall ratio, as no matter what anyone tell's you that ratio is easier on your motor easier on your bottom end & you will go faster in normal road conditions. I latter went to chain rear more for getting home from a race meet, than really needing to change. Like I enjoyed riding up Queensland to willowbank raceway from Sydney racing then riding home. Anyway when I changed to chain my ratio went to 3.42. Did not notice much but loved it still, and I was doing 120 mph 121 mph on a good air day (air quality on the day ) & that was in 4th gear at 7,200rpm in speed trap would pull clutch to slow down after that. Rev's did not hurt it but my valve train was not stock. If you have a hi comp motor the low gear ratio makes life easier.
