Switching front and rear sprocket.

[Jtarnowski6]

Would it be a bad idea to switch around my front sprocket to the rear and vise versa?
Want to experiment with gear ratios but I can’t find anything on how that would affect the performance, and whether or not it would destroy the bike.
-78 Yamaha xs650

 

[jpdevol]

I guess the short answer is Yes (bad idea): the sprockets won't bolt-up interchangeably. The stock gearing is 17 teeth countershaft (front) and 34 rear. That's generally good all-around gearing. You can find 16 and 18 tooth front sprockets and rear sprockets starting around 30 teeth on up. Most of us find the stock gearing to be a little low for highway speeds and many here run 32 and 33 rear sprockets with a 17 front. I have one bike that I run 17/30, but it has a 750 kit and an 8-plate clutch.

 

[Kevin Werner]

As you go up in teeth on the front and down on teeth on the rear you lose torque multiplication and hence, performance. But , heh, an XS is not about peak performance but more about power delivery and broadband response. A stockish motor is ok with up one on the front or down 2 on the rear. I was 40 pounds lighter last time I rode one with that combo.

 

[toglhot]

I think this guy might be taking the piss!

 

[AUTOMAN]

Bot/Troll
U took the bait

 

[Jtarnowski6]

I guess the short answer is Yes (bad idea): the sprockets won't bolt-up interchangeably. The stock gearing is 17 teeth countershaft (front) and 34 rear. That's generally good all-around gearing. You can find 16 and 18 tooth front sprockets and rear sprockets starting around 30 teeth on up. Most of us find the stock gearing to be a little low for highway speeds and many here run 32 and 33 rear sprockets with a 17 front. I have one bike that I run 17/30, but it has a 750 kit and an 8-plate clutch.

Thanks for your input

 

[Steve C]

So, if you over came the engineering issues and made suitable adapters and swapped the front and rear sprockets it would be surprising if the bike would even get rolling in 1st gear without stalling the engine as the gearing would be so high.
One tooth up or down on the front sprocket and 3 teeth up or down on the rear sprocket has a significate effect on performance.
I would start small and avoid an irreversible modification just to 'see what would happen'