Hey guys, I'm not really all that knowledgeable in the area of chains and sprockets. I'm fairly confident that my '03 F4i does not have a factory tooth-count which I believe is 16 up front and 46 in the rear. I've ridden a friends F4i and my bike seems to pull MUCH harder than his does. Much more than different maintenance practices/abuse between two different owners should be able to account for. Also, my speedometer seems to be off. I've calculated that it displays roughly 125% of my actual speed. When the speed limit is 40mph, I accelerate to about 50mph and am moving just fine with the rest of traffic. And on I-94 here in Michigan, nearly every driver cruises at 80mph consistently and by the time my speedo is displaying 100mph I seem to be keeping a fair pace. I'm assuming all of those things are related (slow speedo and above-average torque to the rear wheel). It's going to be time for me to get a new chain and sprocket set soon. The adjustment of the tension brackets on the rear tire are almost maxed out, and sprocket teeth are looking worn. The rear sprocket has "521A-49" stamped into it (I don't know what that means) and the master link has "520 GXW" etched into it (also don't know what that means). I guess what I'm really asking is, should I buy a set of OEM spec parts or should I replace the sprockets and chain with something of the same tooth-count?
Also, what does it mean when somebody mentions a "520 chain?" I see that a lot.

Thanks in advance for any and all responses/attempts to impart wisdom.

 

You are running a +3 rear, and who knows what up front with a lighter, smaller 520 chain. Your bike will do exactly what its doing with that combo. If you like it, stick with it and get a speedo healer. If not, go back to stock and your speedo will work. Gearing Commander: Motorcycle Speed, RPM, Chain & Sprockets Calculator will have the answers to other combos. check it out!

 

Yes, OEM for the F4i = 16/46 steel sprockets & 525 chain size (RK & D.I.D are OEM chains).

A popular mod is going -1/+2 for quicker acceleration. Yours could be this, etc. Sounds like you're running a 520 conversion - most likely w/ aluminum sprockets.

When you run anything other than OEM sized sprockets, your speedo will be off (odo too). You'll need a speedo-healer for it to be correct.

For street use, I'd suggest going w/ steel sprockets & 525 chain. They will last longer & wear better. You can still go -1/+2 if you desire the quicker acceleration...or you can go back to stock size of 16/46 (no need for speedo healer if you go back to OEM size).

Check out Sprocket Center for deals on kits.

 

Thanks guys, that was quicker than I expected. I did a little math and under the assumption that the new sprocket ratio has the speedo ever by exactly 125% (pure approximation) I've calculated that the front sprocket has 12.782 teeth (13 maybe?). I suppose I could just go count them. But the rear is definitely aluminum, and I never thought about electronic correction for the speedometer before, thanks for that. That may be the route I take.

 

Did you decide what direction you are going to take with the sprockets? If you like the way the bike feels you need to keep the set-up you have. Going back to stock will give you higher top end but how often do you need to go 160mph?? The speedo healer gizmo sounds like a good thing though.

I just checked out that Sprocket Center site and it seems pretty good. Good luck.

 

Yeah, I decided I'm going keep the tooth ratios I currently have. I've estimated my top speed is "only" about 125-135 which is of no concern to me. I know the current power and torque characteristics like the back of my hand and rely on its familiarity to keep the rest of my riding in check. I'll be getting the speed healer sometime in the future for sure though