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Discussion Starter · #1 · (Edited)
Hi! I recently decided that I should modify my bike, to get better performance out of it. Right now I get about 95km/h of speed, but I'd like to go up to 110km/h, at least. I've heard some things about a needle shim mod , and I'm wondering if this could be done for the TW125? I'd also like to know ways of improving the general handling and speed of the bike. It's a great bike, it really is, especially at low speeds and in offroad conditions, but I'd like a bit more speed. If you have any advice on what parts to get, how to install them and so on forth, I'd really appreciate your help. I can not do this on my own...
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honestly mate your going down the wrong route.

Ive also got the tw125 and the more power thing will cost alot and not give alot either.

My advice is put a performance exhaust on, re jet to suit, get a high flow filter, a dam good service and then change the sprokets to suit but remember what you gain low you will loose top end and so on.

The speeds your getting currently are about 5mph lower than mine, engine work to achieve what you want is simply not necessary. the above service on its own with sprockets will get you around where i am.

I got mine to be reliable (i only ride off road) if i want more performance ill just get a DRZ400.

Hope this helps.
 

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Thanks for the reply! Do you know how to re-jet it? I'm pretty new to this stuff...
yes, visit Procycle usa website they have all the parts you need, I say they have them, they only deal with the TW200 so you will need to find out if the parts will fit yours. all frame parts are the same with a small amount of modifacation i can tell you that

here is the link to the web site, ive took you straight to the page you will need.

Yamaha TW200 Parts and Performance - ProCycle

Again id just service it and do the sprockets to achieve what you want, As a rule of thumb as far as modification goes the more performance the less reliable.
 

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Discussion Starter · #6 ·
Well, I just had it serviced, and the last gear is pretty much un-usable right now(it doesn't have the power to keep going, so it slows down instead)... thanks again!
 

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Well, I just had it serviced, and the last gear is pretty much un-usable right now(it doesn't have the power to keep going, so it slows down instead)... thanks again!
Also, is there a step by step for re-jetting it? I have no idea which parts to use, and how to properly install them :(
ok in all honesty its not an easy thing to do but i honestly think your looking in the wrong place! a simple sprocket change will give you your top end.

Your carb is tuned to the standard exhaust by yamaha, if you change this set up you need to get it tuned in and basically this is what jetting is.

I have put some vids below but again i think its a waste of time.

you say its been serviced if you've had the following... oil change, oil filter change, air filter change, new spark plug and valves gaps checked then yes your right its been serviced if you have not had ALL of those then its not a major service.

how many teeth has your front and rear sprockets got? count them and we will be able to solve your issue. also whats the year and milage on your bike? what psi are you running in the tyres? all could be relivent to your issue



 

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Discussion Starter · #9 ·
It's a 2006/07 model, It's barely driven, i think maybe 20 000km. The service was full, I can assure you that, those guys have worked with this same model a lot. It has got the standard sprocket combination and the psi is adjusted to what the manual says. Can't remember what that is though.
 

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It's a 2006/07 model, It's barely driven, i think maybe 20 000km. The service was full, I can assure you that, those guys have worked with this same model a lot. It has got the standard sprocket combination and the psi is adjusted to what the manual says. Can't remember what that is though.
In that case just change the sprokets and your sorted mate. a nice cheep and simple job to solve your issue
 

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Discussion Starter · #11 ·
Really? It's just a bit of a weird solution since its not able to run well on the fifth gear right now... getting smaller rear sprockets would just make it worse? No?
 

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I would count the teeth on both sprockets and verify that it is stock or not. The way you describe the problem, it sounds like they are already to small, so I would go bigger, easiest is just to change the rear. I don't know what stock size is on a 125, on the 200's, it is 14/50.
 

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Discussion Starter · #13 ·
Well at the moment, I'm running a replica of the original one, a 50 tooth rear one and (i think) a 14 in the front. I'll try out the sprocket change, maybe that'll work. I'll post updates!
 

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The 125 is the same tooth count out of the factory as the 200.

Go bigger on the back, it will solve the issue as your gearing will be lower giving you theoretically more torque to get 5th gear working.

Gearing is an important part of an engine, long gears = high top speed slow acceleration. Short gears = low top speed high acceleration.

What you have to realise with gearing is there is no such thing as a win win situation, you will always loose one eliment.

The factory setting again theoretically speaking is a happy medium.

Just to make it clear in extreme circumstances, put a massive 70 tooth sprocket on the back will mean short gears lots of power low down but a poor Top end.

A small sprocket on the rear would give a slow acceleration and a high top speed but the problem with this comes another factor... The engine bhp. Go to small on the back your bike may well be capable of 100mph but it would never get close as the power is not there to do this.

Your issue is you have not got the power to use 5th hence going up a few teeth on the back, this will make 5th usable in turn making your top speed go up.

I run 52 on the back.

Post pics off the bike and don't solve the problem an disappear, forums like this work best when you feed back the results.

Hope this helps you
 

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Discussion Starter · #15 ·
The 125 is the same tooth count out of the factory as the 200.

Go bigger on the back, it will solve the issue as your gearing will be lower giving you theoretically more torque to get 5th gear working.

Gearing is an important part of an engine, long gears = high top speed slow acceleration. Short gears = low top speed high acceleration.

What you have to realise with gearing is there is no such thing as a win win situation, you will always loose one eliment.

The factory setting again theoretically speaking is a happy medium.

Just to make it clear in extreme circumstances, put a massive 70 tooth sprocket on the back will mean short gears lots of power low down but a poor Top end.

A small sprocket on the rear would give a slow acceleration and a high top speed but the problem with this comes another factor... The engine bhp. Go to small on the back your bike may well be capable of 100mph but it would never get close as the power is not there to do this.

Your issue is you have not got the power to use 5th hence going up a few teeth on the back, this will make 5th usable in turn making your top speed go up.

I run 52 on the back.

Post pics off the bike and don't solve the problem an disappear, forums like this work best when you feed back the results.

Hope this helps you
Tanks, I'll see what I come up with, will be posting results!
 

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Discussion Starter · #16 ·
Hey everyone! Just finished adding and adjusting this: Yamaha TW125 TW 125 Trail Way 6 Sigma Custom Carburetor Carb Stage 1 3 Jet Kit | eBay and it seems to be having a significant amount of more power now, not sure yet though, since all we have here is ice and I'm restricted to a pair of non-winter tires. I made a whole compilation of images, thinking of posting them all here and editing them to become an some sort of how to/what I did thing. Thoughts? I'm going to post the pictures either way, but I was wondering what you people think.
- Happy TW 125 owner :D
 
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