1979 Gearing Suggestions?

[Ed Townsend]

I'm running, I believe, stock 1979 sprockets and 630 chain. Since the chain's relatively new and the countershaft sprocket's in good shape, I'd like to reduce the highway rev's (about 4200 at 60mph for instance) with a replacement rear sprocket. Any suggestions on number of teeth and a supplier? The chain still has plenty of adjustment - it'd be nice not to have to remove links but I'd appreciate some advice. Thanks.

[Mike Barone #123]

hi ed



going out on a techno limb here...but i think the calc below will tell you the reduction in rpm e a c h tooth off the back sprocket will have



i am doing this for a stock 80 since i dont know what the teeth counts are on your 79........so just plug your numbers in



80 stock front sprocket = 18

80 stock rear sprocket = 42



1 tooth divided by 42 teeth = 2.38% which will be the reduction in revs for each tooth you take off your rear sprocket



now.....take your actually revs at 60mph



...then reduce this in increments of 2.38% until you get the rpm at 60mph you want



...then buy the rear sprocket from cbx performance, tims or cbxman



hope this is accurate and helps





mike

[xneric]

Ed, it's a direct ratio. For instance, if you want to reduce your revs 10%, you have reduce the number of teeth of your rear sprocket by 10% or as close as you can get it. Example: A 40 tooth sprocket will reduce revs by 10% from a 44 tooth sprocket. Call Bob Franzke of CBX Performance, cbxperformance.com. I'm sure he can help you out. Eric