A forum for owners of Yamaha TTR250 trail and enduro bikes!

Michael TTR250 · Veteran Member

Advice on sprocket size

KentJ · Veteran Member

I've got the North American Blue model so I'm not sure if my experience is applicable to you, but I'm currently running a 48 tooth rear and switch between a 13 and 14 tooth front sprocket.

The 13/48 setup is what I use in the woods with lots of steep hills, single track etc. The 14/48 is better for wider terrain or faster trails where I keep the speed up. It doesn't seem like much of a difference on paper but does actually make a difference on the trail. The 14 tooth actually let's me ride faster too, as I can hold 1st or 2nd gear longer on hills instead of having to shift around. the 14/18 setup will let me do nearly 120kmh on the highway (wide open).

The difference between the two ratios is slightly less than 10% (3.69:1 vs 3.43:1). If you're looking at 14/44 (3.14:1) and 14/47 (3.36:1) it might make enough of a difference in the trail that you'll be happy. You can keep the 47 tooth on the back and throw on a 13 tooth if it isn't low enough, that should make it crawl like a tractor.

If the bike had more torque I could probably get by with taller gearing all the time, but we can't all justify owning KTMs...

-Kent

matador · Veteran Member

it's all a bit subjective but from what I have found - here goes. standard 14-44 is too high. I have used 13-44 = ok for flat trails/ road. The thing to remember is the TTR likes to rev a bit, so if you have a few road miles it's ok to go lower. My son's TTR is 13-47 and covers most and runs ok at say 55 mph on the road. I went for 14-52 as I could vary the front from 13-14-15 easily for different rides, I run it at 14-52 which gives the same ratio as my son at 13-47.

The only problem I found with a 52 on the back is the back of the chain guide needs to be lowered, no probs if you are into engineering.

as a rule of thumb 1T on the front is the same as 3T on the back. You could run 13/14 on the front with a 47 on the back.

Be careful with front sprockets - see my post, as 'Talon' sprockets are thicker than others and will cause bad chain vibration - which won't run in after a bit, I had to surface mine down to run ok.

Good luck

Cubber · Super Guru

I run the same as you, Matador.

14 gearbox and 52 rear - and I lowered the chain guide to suit.

There's been lots of discussion on this site and many others regarding ideal sprocket set ups.

No two sites agree and no two people agree wholly. It's like chalk and cheese because there is no ideal that suits all applications. disbelief

To help the knowledgeable novice choose, this site offers an easy calculator - it's a lot cheaper than buying a cuddy load of sprockets. biggrin

Martyn

Michael TTR250 · Veteran Member

Thanks guys,

So if I am reading this correctly if I went 13-47 like matador's son I should not have any problems or need any chain guide lowering, but if I wanted a bit more I could go 13/14 on the front and 49/52 on the back but will need to make some chain guide adjustments... Is the chain guide lowering difficult Cubber?

Thanks, Michael

Cubber · Super Guru

Not at all, Michael.

To make the adjustment means taking off (ideally) the chain guard and elongating either the fixing holes in the lugs on the arm or elongating the fixing holes on the guard - indicated A.

I used a small round file (shown) and made the lugs and the guard holes slotted and lowered the whole guard by about 5mm.

The chain will still tend to rub but not enough to wear through as if it wasn't done.

Martyn

Michael TTR250 · Veteran Member

Ok, thanks Martyn appreciate the advice (and the picture, very helpful) that seems easy enough.

Cheers, Michael

matador · Veteran Member

Michael TTR250 wrote:
Thanks guys,

So if I am reading this correctly if I went 13-47 like matador's son I should not have any problems or need any chain guide lowering, but if I wanted a bit more I could go 13/14 on the front and 49/52 on the back but will need to make some chain guide adjustments... Is the chain guide lowering difficult Cubber?

Thanks, Michael

Yep 13/47 is possibly the best setup, and you can still go up to 14 on the front if you want to. I went for 52 on the back - ok to be honest because it looks cool, and I could go lower by using a 13 with it, but after testing on trails I doubt if I need to go for that lower option. Either way it's trying to get the chain length so you can use a range of front sprockets

Only problem with my son - trying to keep up with him biggrin

I need to show a picture of how I made a lowering bracket as although easy, descriptions are not easy.