So my friend picked up an 01 F4i (Silver/Black) bone stock except for front flush mount signals. As I rode his bike, I didn't feel the same thrill as I do with my bike. The bike did not pick up as quick as mine, especially the low-end. I had noticed that my rear sprocket/chain did not look like his at all. So I assumed that perhaps the previous owner had changed the gearing. I look at the rear sprocket and the gearing is the same 46. So I thought, maybe a 520 conversion? Nope, the chain had an engraving that said 525. So I thought maybe the front sprocket was changed. Checked that out, nope, stock front sprocket.

So here's where I would like some input:
1) The first thing is, my bike has an Akrapovic slip-on. I noticed the midpipe is a lot smaller than stock F4i. I already knew that the pipe would increase the power, but could JUST the slip-on have such an increase in low-end power and overall performance?
2) The rear sprocket and chain on my bike is not OEM for sure. The rear sprocket resembles that of a Vortex sprocket, but I couldn't find any insignia. Could the lightened mass of the aftermarket chain and rear sprocket affect the performance gains I'm feeling between my bike and a stock F4i?

Any comments would be appreciated. Sorry if these are "dumb questions" but I'd like some input is all

 

Maintenance items like plugs, filters, stuff may have had something to do with it, plus normal variations in how a motor runs, injector flow, fuel pump pressure, but the lower rotating mass may have been a component too.

My guess is that you maintain your bike and run it fairly hard, bikes/cars/boats need a little abuse now and then, it keeps them fast.

 

Thanks for the reply. It does make sense. Maybe my motor is just stronger in general, and yes, I generally run the engine hard. Otherwise, I feel it'd be a waste of the bike

 

there are two types of weight on a bike, sprung weight and unsprung weight. sprung weight is anything the shock or forkssupport, frame, body, engine, etc... unsprung weight includes wheels, sprockets, chain, rotors, etc... decreasing the unsprung weight enables the bike to spool up quicker, giving youquicker acceleration offthe start. your smaller chain and sprocket gives this effect, you may also have a aluminum sprocket, while the stock would be steel(heavier). not sure if that's why, just thought i'd give you that info.

 

I just put an Akrapovic on my stock '05 and I don't notice any difference in performance other than a slightly louder exhaust note. I doubt that you could explain the difference on the basis of the exhause

 

Isn't the stock exhaust alot heavier than the slip-ons

 

i put exhaust and all it did was make a diif note no power i have yoshamira exhaust and still no power i did a tune up plugs wirs oil ect. and felt faster and stronger he needs a tune up. and check the valves !

 

Thanks for all the input! The unsprung weight makes a lot of sense and I'm thinking that and a combination of a better maintained motor makes the difference.

 

Yeah the exhaust doesn't add a very noticeable amount of power, but it adds just a little and a lot of noise

And as for the weight of the stock muffler vs. an aftermarket......that difference wouldn't make the bike THAT much quicker....it's probably a 3pound(?) difference