Jump to content
Sign in to follow this  

Question about Sprocket gearing ratios

Recommended Posts

Hey how's it going! First post here...

I just got my first dirtbike at 33 years old. I've owned motorcycles and quads before but never a dirtbike. Well, I got myself a brand new Yamaha 2015 TTR 230. I like it, but I'm not gonna lie...I'm a little upset that I didn't spend more money and get a 250. Oh well, it's definitely still a fun new toy. It'll be paid off in a year or 2, then maybe I'll consider upgrading. I really wish the shop allowed you to test drive before buying ;).

Anyway, it immediately became clear to me that I have to do the basic gearing, exhaust, and air filter mods as described here in this multi-part series:

http://www.off-road.com/dirtbike/project/project1554.html

In order to help others, I will be taking pictures and posting details about how exactly I did the mods. I know this information is already available, but it never hurts to have multiple sources to follow while searching the net. The least I can do is contribute by being one of those sources.

Anyway, this question is in regards specifically to the gearing mod...

Stock, the rear sprocket is 49T and the countershaft sprocket is 13T, yielding a ratio of 3.77.

In the mod, they tried changing the countershaft sprocket to a 14T and a 15T, and decided that the 15T was the way to go. This yields a ratio of 3.27 (they kept the rear at 49T).

The only problem with the 15T sprocket is that you can no longer put the cover back on. They say in the link that the countershaft sprocket cover is unnecessary, but I dunno...it seems to me that it's there for a reason.

I realized that you can get the same exact ratio (or very close) by simply switching the countershaft to a 14T and the rear to a 46T. This yields a ratio of 3.29. With the 14T sprocket, you can still get the cover on...so to me it makes sense to go with this combination of sprockets. Is there any reason why I shouldn't do this?

Forgive me if this is super basic stuff here...

My next question is...what if I even go SMALLER still on the rear. Maybe I could have some sort of combination like 14T and 42T, which yields a ratio of 3.0.

I understand that the higher the ratio, the more torque you get, but less top end...and vice-versa. The purpose of this particular mod, according to the link is to REDUCE the ratio, such that top-end power is INCREASED. Other questions about this mod have been asked, and the general consensus has been that there is still plenty of torque after doing this mod; it just gained the much-needed top-end.

So in short, my 2 basic questions are:

1.) Does is matter how the ratio of 3.27 is achieved, or should I just alter the front, countershaft sprocket size as per the link?

2.) Since the goal of the mod is to decrease the ratio from the stock 3.77 to close to 3.27....would it be a huge deal if I were to decrease even further to 3.0?

P.S. - I had to do it over again, i would've spent more money on a 250. The bike is not bad, but I know that it's not the beast that I will eventually want. Perhaps I will feel differently after doing the mods. I will be sure to keep you all posted though, so future TTR230 potential buyers can follow my posting to help them determine if it's what they are looking for or not.

Share this post


Link to post
Share on other sites

Hey thanks for the reply!

Your ratio would be doing the opposite of what they are doing in that linked mod though (increasing the ratio).

I was just wondering if anyone could help me understand if what I'm asking would work or not. Thanks a lot!

Share this post


Link to post
Share on other sites

 I lifted this sentence from the article you referenced.

 

"The cover on the countershaft is a complex deal,  with little bolts holding everything in place."

 

 Frankly, I wouldn't take their advice on anything!

 

 Some sprocket combinations may not allow proper chain adjustment, or may at least limit tire selection. A taller rear tire greatly improves traction and effectively raises gearing. 14x49 sprockets work well with a taller tire but I believe will require a longer chain.

 In general a large front sprocket is desirable and will last longer. And yes, the sprocket cover is there for a reason.

Share this post


Link to post
Share on other sites

I'm new to dirtbike riding...Actually, I'm new to doing my own mods like this, which is why I'm asking these questions that probably sound dumb...

 

I'm not new to riding in general though. I have a super fast LTR450 quad, and I have owned a couple motorcycles in the past. None of those ever gave me that "ugh, I should've got something bigger/more powerful" feeling so quickly as this bike did. That's why I started looking into mods right away.

 

One of the first things that everyone says to do to the TTR230 is "do the sprocket mod". They discuss the 14T vs. 15T front sproket in this thread here: http://www.thumpertalk.com/topic/954179-ttr-230-tuning/.

 

The guys in that thread seem to agree that the 15T is the way to go. So basically, that's what I shooting for (only I was trying to achieve the same thing by altering both the rear as well as the front). 

 

I think motovita answered what I was looking for. I'm just going to go with the 14T in the front so that I can still keep the cover on, and leave the rear alone for now. Then next step after that will be to uncork...

 

Thanks!

Edited by Irishman301

Share this post


Link to post
Share on other sites

Since a lot of people are still doin the 15T up front (which is a 15/49 combo)...I'm still just wondering if the same thing can be accomplished with a 14/46 combo? Just in case I do decide to gear down even more in the future.

I was unable to find the answer anywhere else.

Share this post


Link to post
Share on other sites

Anyone?

What are you trying to achieve? When you stated that you should've got the 250, me thinks that you want more power. If that's the case, then you want a higher ratio. The bike will "feel' like it has more power but the top speed will suffer. Stock gearing is 3.77:1. I you went with a 12t front, that would put you at 4.08. And you wouldn't have to modify the chain. I can't imagine, especially if you ride and ltr450, that you would want to go 3.27 or 3.0. That bikes a pig already IMHO  :)  Good luck

Share this post


Link to post
Share on other sites

You can acheive same the final drive ratio with various front/rear sprocket diameters (tooth count) combos.

It depends what can physicaly fit on the bike while also taking in consideration the chain's link count (length) to fit the diameter of the sprockets.

 

There are some issues with altering from the factory sizes,

 

Going to a smaller front sprocket is tougher on the chain as it must turn in a smaller radius,

in principal a smaller front sprocket also puts more wear on the swingarm's chain slider.

You loose ground clearance with a larger rear sprocket, it is more prone to get damaged.

Perhaps not as critical on a TTR trailbike, but changing the sprocket sizes alters the rear suspension's anti-squat geometry which affects rear tire traction under acceleration.

 

If a higher final drive ratio (lower numericaly, say your 3.27:1 ratio) is fitted,

there will be a point where the engine doesn't have enough torque to accelerate the bike.

 

On any MX dirtbike usually a 3 tooth rear sprocket change is quite noticeable, equal to about a 0.3:1 final ratio change.

With such a big change on an already entry level powered TT-R, any kind of tight trail / hill climb will be a challenge,

even if the engine could pull the bike to a higher top speed, the rest of the bike (brakes, suspension) isn't designed for it.

 

No matter how much you spend on modifications, it will never perform like a 250F motocrosser.

(may eventualy cost more in mods than to just buying a used 250F in good condition)

 

Perhaps not what you want to hear but I'd say keep it stock and enjoy riding it the way it is.

It will hold better resale value when you finaly figure out what bike is best suited for your usage and ready to change.

Remember that a high strung motocross race bike doesn't necessarely make for a great trail bike either, each usage as specific needs.

Edited by mlatour

Share this post


Link to post
Share on other sites

What are you trying to achieve? 

 

Through LOTS of reading and research, I have found that everyone that has owned a TTR230 and has regeared it, has changed the c/s sprocket from a 13T to either a 14T or 15T. The general consensus is that after modding in this manner, the bike feels as if it's geared the way it should be. Some resources that I've found which led me to this conclusion are:

 

http://www.off-road.com/dirtbike/project/project1554.html

 

and,

 

http://www.thumpertalk.com/topic/954179-ttr-230-tuning/

 

Also, if you search around the forums, the general consensus is that FOR THIS PARTICULAR BIKE, regearing in this manner is the way to go.

 

Yes, typically on dirt bikes, torque and acceleration are increased (low end) by gearing down (the opposite of what I'm trying to achieve here). HOWEVER, for this particular bike...the gears are so friggin short, that you never even get any use out of them with the stock 13/49 gear set up. Therefore, by GEARING UP, the gears are more 'spread out', and therefore you get a nicer feeling acceleration curve in 1st and 2nd gear. 

 

That, coupled with low-cost exhaust/jetting/airbox mods, you get a more powerful and better FEELING BIKE.

 

Banda from this forum explains it here:

 

http://www.thumpertalk.com/topic/954179-ttr-230-tuning/?p=10138948

 

Now, do I know if this is going to accomplish what I'm looking for? No, but according to all my reading about this bike...everyone says that 14T is better in the front, and a 15T is even BETTER STILL. However, with the 15T, there is still the issue that I mentioned in the OP of the cover not fitting back on. Therefore, I posted here asking if there was any downsides to using a 14/46 combo in order to try and achieve the same thing that a 15/49 combo will.

 

If and when I do buy a new bike, I'm going to do a bit more research, and make sure it's a big boy bike! I'm used to all of my motorcycles and quad just "feeling right" ever since the day I got them....and my motorcycles were arguably "slow" bikes (Kawasaki KZ440 and Kawasaki Vulcan 900). However, they just felt "right" to me...And by "right", I mean "fast enough" and geared properly.

 

This bike feels "restricted" to me...like something isn't quite right, and according to all of my reading and research, these specific mods apparently fix that. Do I expect it to become a 250cc 2-stroke? HELL NO! But, do I expect to get it running the way it should? Yes, absolutely!!

 

The bike is the perfect size for me, apparently "built like a tank", brand new, and covered under warranty for 5 years....and it is designed for trail riding, which is primarily what I will be doing with it. I believe that these particular mods will achieve exactly what I was looking for - Better breathing and "corrected" gearing.

 

I also bought the bike with the intention of learning how to work on dirt bikes :), so having a few mods to do gives me the perfect project!

 

So that's exactly what I'm trying to achieve...I was just unclear on some things regarding gearing, which is why I made the OP.

 

Share this post


Link to post
Share on other sites

I was comparing to a 250F, F commonly meaning a Four stroke in dirtbike lingo.

 

As per your other thread, a 415$ exhaust pipe isn't quite a low cost mod!

Really hope it lives up to your expectations.

 

Better check if your '5 year warranty' is still valid once anything as been modified (pipe, airbox)

 

GENERAL EXCLUSIONS
from this warranty shall include any failures caused by:
a. Competition or racing use.
b. Installation of parts or accessories that are not qualitatively equivalent to genuine Yamaha parts.
c. Abnormal strain, neglect, or abuse.
d. Lack of proper maintenance.
e. Accident or collision damage.
f. Modification to original parts.
g. Damage due to improper transportation.
 
Anyway good luck with your project, next summer I'm hoping to start a CRF or TT-R 230F trail bike project myself to compliment my current YZ125 track bike
but know very well ahead of time the performance limitations of such a bike and not to set my expectations too high (or spend like crazy trying...)
Edited by mlatour

Share this post


Link to post
Share on other sites

 

I was comparing to a 250F, F commonly meaning a Four stroke in dirtbike lingo.

 

As per your other thread, a 415$ exhaust pipe isn't quite a low cost mod!

Really hope it lives up to your expectations.

 

Better check if your '5 year warranty' is still valid once anything as been modified (pipe, airbox)

 

GENERAL EXCLUSIONS
from this warranty shall include any failures caused by:
a. Competition or racing use.
b. Installation of parts or accessories that are not qualitatively equivalent to genuine Yamaha parts.
c. Abnormal strain, neglect, or abuse.
d. Lack of proper maintenance.
e. Accident or collision damage.
f. Modification to original parts.
g. Damage due to improper transportation.
 
Anyway good luck with your project, next summer I'm hoping to start a CRF or TT-R 230F trail bike project myself to compliment my current YZ125 track bike
but know very well ahead of time the performance limitations of such a bike and not to set my expectations too high (or spend like crazy trying...)

 

 

Thanks bud! 

 

I replied to the thread before I saw your reply. I was actually just referring to a "super fast and powerful bike" in general (which I know this bike will never be).

 

I do expect to make it ride better though. I decided to go with the aftermarket exhaust so I can keep my old one in tact. The "cheap exhaust mod" that I was talking about was the removing stock baffle and drilling the spark arrestor. But I want a nice sound, yet still not obnoxious, and of course the power gain so I decided to go aftermarket. Also, I decided to go full system vs. just a slip-on because I liked the extra weight reduction and shape/size of the header...Of course the header probably won't have a major impact on the overall performance of the bike, but I still figured that since aftermarket exhausts are still upwards over $200, I might as well just spend a little more and get the header as well.

 

But ya, if you just want to make it breathe better a rejet/drilling will probably achieve the same power output as the full aftermarket system. However, it's my new toy and I want it to sound badass, yet not obnoxiously loud, and be faster, while still being able to keep my old exhaust undrilled. Other then maybe bark busters, I don't plan on doing any other mods to the bike. If the exhaust and regearing don't give me what I'm looking for, then oh well. However, I suspect that it will!

 

As for the warranty...All mods that I do can be undone (stock jets, replace old exhaust, put snorkel back into airbox). The only thing that can't be undone is the cap over the mixture screw in the carb, which has the cap that needs to be drilled. I called the dealer, and they said that exhaust and rejetting won't void the warranty anyway. Worst case scenario...they lied, and the warranty gets voided. Oh well, at least I have a cooler bike then when I first bought it!

Edited by Irishman301

Share this post


Link to post
Share on other sites

Put on the 14t and ride it. If you want more you can regear the rear. It will not hurt anything. You can also use YZ rear sprockets if you replace the bolts with the YZ countersunk bolts. Much easier to find YZ sorockets than TTr.

Share this post


Link to post
Share on other sites

Nice! Thanks for the tip about the YZ sprockets and the confirmation that altering the rear won't make a difference if I do decide to do it. Thanks!

Share this post


Link to post
Share on other sites

Through LOTS of reading and research, I have found that everyone that has owned a TTR230 and has regeared it, has changed the c/s sprocket from a 13T to either a 14T or 15T.

 

 WRONG!

  I prefer a 13 tooth front sprocket for trail riding, I only switch to a 14T for dual sport riding. I think that with 15/49 gearing the bike would be nearly useless on trails.

Share this post


Link to post
Share on other sites

Well...only one way to find out!

I will definitely be keeping everyone posted. This is all fun new experimenting for me.

Share this post


Link to post
Share on other sites

On my 2 cr-250s I prefer to run 13-51 combo, bearing that in mind that ratio suites me fine for the tight twisty trails in Texas, lots of land and mx parks have closed, so its all I got for now.

hay mate wondering if i could get some advice in laymens terms i will explain what iv got id like some sugestions

02 cr250r

fmf fatty

fmf shorty

boyseen rad valve

39mm keihin karb

brand new cylinder

woosner forged piston

all these mods have made my bike go stupidly quick

iv a 14 tooth on front

a 48 tooth on rear

now my issue is im in and out of 2nd and 3rd way to much and every gear im either wheel standing or sliding with not much in between is this somthing i can sort out with gear ratios or somthing iv goto live with any advice would b good chers

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...