Rear sprocket - plus 2 teeth

Alocinapap

New Member
Joined
Jun 25, 2021
Messages
6
Reaction score
3
Points
3
Location
London
Visit site
I am looking to increase acceleration on my bike. I have a few questions.

1 - will going up to a 48 tooth rear sprocket (plus two teeth) make much difference? Any one have any experience with this mod?

2 - I recently fitted a new chain so would that work with a slightly larger rear sprocket or would I need to change the chain? I have read that 2 teeth should be in the parameters of an original chain.

3 - how much will it throw out the speedo? plus or minus?

Thanks in advance.

Alocinapap
 

Gary in NJ

Junior Member
Site Supporter
Joined
May 6, 2014
Messages
1,964
Reaction score
1,908
Points
113
Location
Amoungst the Twisty Roads
Visit site
Where is your rear axle in the adjustment? That would determine whether you can go up two at the back, or down 1 on the front (which is about the same as going up three at the rear).

Going to a larger rear sprocket will bring the wheel forward by about 3/8 to 1/2”, whereas going down 1 on the front will send the axle about 1/4 rearward (maybe 3/16).
 

Alocinapap

New Member
Joined
Jun 25, 2021
Messages
6
Reaction score
3
Points
3
Location
London
Visit site
Thanks for the quick reply. It seems like I have enough space.

what kind of difference will two teeth make to acceleration?
 

Alocinapap

New Member
Joined
Jun 25, 2021
Messages
6
Reaction score
3
Points
3
Location
London
Visit site
So I fitted the sprocket. Certainly has more giddy-up. Will gently lift the front wheel on full throttle in first now. Speedo is out about 2-3 mpg at 30 so not too bad. Overall happy with the change.
 

jaffabaffa

Site Supporter
Joined
Aug 27, 2021
Messages
34
Reaction score
24
Points
8
Location
Andijk
Visit site
I just ordered a +2 rear sprocket AND a -1 front sprocket, which should be equal to going +5 in the rear only. Very curious for the results...
 

7UPyours

Junior Member
Joined
Apr 20, 2011
Messages
691
Reaction score
10
Points
18
Location
Rockland, MA
Visit site
Is there a DID kit that offers the 48 tooth in back for our bikes or do you have to buy all parts separate? I am only seeing the 530 16/46
 

Chris6R

New Member
Joined
Aug 23, 2023
Messages
1
Reaction score
0
Points
1
Location
77590
Visit site
Noticeable. What will also be noticeable is the cruising rpm going up 4.3%. So at 60 mph you'll go from 4,950 to 5,170 rpm
All right I'm going to go ahead and tell you off of what you're saying that modification would cause then my bike definitely got an issue it's a 2009 FZ6R what I'm running into I literally actually did the math I checked my speed on GPS with my phone on two different apps I'll say real quick they read the same and then whenever I would pass the little police signs that read your speed out that was showing the same as the GPS and at 47 58 69 mph on the speedometer I'm actually only doing 41 51 61 at respectively 4k 5k and 6k (and I do mean within 50 RPMs) what I found out doing the math at lower speeds just about at 5 mph the speedometer shows off by over by .6 The only thing noticeable to me that has been done towards the bike is it has a two brothers possibly just a slip-on exhaust or maybe a full system and I just don't know what it's supposed to look like if it is full system but also the power commander that they would sell with it The front sprocket is a 16 currently and the rear is a 47 but I can say when I check throttle response I am limited to 87% if it is governed I'm going to hate somebody that I can't even determine who it was but you would be doing me a great help that way I don't have to spend additional money to attempt the switch to a front sprocket with 15 and a rear with 42 but I do want anybody that knows what that would do to the motorcycle please let me know I'm not very keen to the trial by error in case it matters if I'm over the shift point for any certain gear and I decrease the throttle by half or more and hold the clutch just so the tire doesn't lock I can get damn near about a two and a half foot flame out the exhaust and if I drive at normal speed and the next gear down from normal it would just sit there and sound like you're firing a CO2 powered airsoft rifle I say that so you can actually look it up and hear what I'm talking about it's very similar on the other thing that I have done outside of factory is the rear tire is currently at a 170/70/17R I can also say that no this could tell you something about transmission if I let off throttle and hold the clutch at any gear it does take a good while to slow itself down I don't hear anything binding or other issues anywhere if you have any ideas tips for tricks please let me know I appreciate you reading my overly long comment thanks and I hope you all thanks keep up with young as well as mine has with me
 

Gary in NJ

Junior Member
Site Supporter
Joined
May 6, 2014
Messages
1,964
Reaction score
1,908
Points
113
Location
Amoungst the Twisty Roads
Visit site
^^^
I agree, I spent so much time trying to understand the sentence structure that I gave up thinking about the problem. Flaming exhaust...CO2 rifles...Two Bros exhaust...what does any of this have to do with the gear ratio of the final drive?
 

TownsendsFJR1300

2007 FZ6
Site Supporter
Joined
Feb 7, 2009
Messages
12,516
Reaction score
1,157
Points
113
Location
Cape Coral, Florida, USA
Visit site
Plus 1 to both above.. Paragraphs help the reader as well.

If your throttle is only 87%, and has the European version, de-tuned, below is a pic of the throttle plate which can be modded for full throttle:



Slow to return to idle is a sign of being too lean.

.
 

Gary in NJ

Junior Member
Site Supporter
Joined
May 6, 2014
Messages
1,964
Reaction score
1,908
Points
113
Location
Amoungst the Twisty Roads
Visit site
OK...I broke out my calculator on this run-on question.

Changing the rear sprocket from a 46 to a 47 tooth sprocket changes the FDR from 6.0876 to 6.2199; a change of -2%.
Here is the big one - going from the stock 180/55 rear to the 170/70 rear changes the speedo error by an additional 6% - but in the opposite direction, so there is a net change of 4%. What's all of this mean? A stock FZ shows 4,954 rpm @ 60 mph. With the sprocket change and tire change 60 mph happens at 4,759 rpm. But our speedo's are geared off the transmission, so when the speedo indicates 60, you are actually going 62.5 - and that doesn't account for the error that was built into the system by Yamaha - which some estimate @ 5%. With all of that said, based on the information provided, your speedo should only be off by 1%.

I'm not sure if I answered your question, only because I didn't understand it.
 

theJackal

New Member
Joined
Dec 6, 2023
Messages
5
Reaction score
0
Points
1
Location
Lodi
Visit site
To be honest I am done with top speed. Looking forward to more acceleration. 48 tooth sprocket is ordered.
You should just do the 520 conversion while your at it. Stock chain and sprockets are 530. Going to a 520 will give you even more acceleration.
 

theJackal

New Member
Joined
Dec 6, 2023
Messages
5
Reaction score
0
Points
1
Location
Lodi
Visit site
Incorrect. Chain brand highly dictates strength and longevity. So, running a 520 did evr7 or rk gxw chain..which is rated for street use up to 1000cc - high reving engines, is perfectly safe and recommended if you're trying to get more out of you bike..and essentially increasing mpg. I've been running these setups for years with zero issues and extra free'd up engine power. Works great!
 
Top