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Preparing a KTM SX 150 for enduro riding

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I just bought a used KTM SX 150 for my 15 years old son.  He wants to go riding with me in the woods and trails (and maybe some enduro racing) but it was virtually impossible to find a 125/150 cc "enduro" used bike for him (well yes, but, a new the Husky TE 125 for 7,000 US$ plus...too much money!).

Anyway, I bought a used KTM SX 150 and my project is to adapt it as much as possible for trail/enduro riding.  I was thinking to re-gear it from 14/50 to 13/52 (thus increasing the gear ratio from 3.57 to 4, almost half turn) to increase the bottom-end.  Then I plan putting a flywheel weight (8 oz) on the rotor.  The idea is to make a much more friendly engine for long rides.

I may modify the front suspension, but I really don't know what to do there as "suspension" always has been a sort of "black science" to me.

I would be very grateful for your comments and tell me if in your opinion I am on the right path and if possible, give me some guidance on what to do with the front suspension.

Thank you!

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Fly wheel weights make small bores too sluggish IMO. 

 

 

All I did to mine was put a bike tank on it, rad guards, hand guards, link guard and one tooth on the rear. 

 

Emperor Racing out of BC makes great guards, and will the weak Canadian dollar it's a steal for you southerners! ;)

 

 

With suspension, have it valved for his weight. I run stocker with the clickers three softer in the front and one softer in the rear.


Checkpoint Offroad out of MN does great woods work. 

Edited by BoxcarWilly
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I am over 50 and now exclusively use 125s for both hare scramble racing and trail riding. There is only one thing you really need to address, and that is suspension. Get a reputable tuner to re valve it for your son's weight, speed, and riding conditions. Then add hand guards and any other protection appropriate for your area, and you are good to go.

I have found that stock gearing works pretty well on most 125s as measured by lap times. Some folks gear too low IMO and end up doing a lot of extra shifting. The clutch is your friend.

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I bought my hand guards for my 150sx from my KTM dealer. There not so bike specific, more bar specific.

I also race mine in xcountry races, just added an IMS tank. I dont feel it needs much more.

Let him ride it and see what he needs to make him comfortable on it and put in some seat time.

I put a 9oz weight on my 200, and it was about right, I don't want a weight on my 150, but if you go that route maybe a 6oz to not over do it.

Also I tried going up two teeth on the rear and it took a lot of top speed away out in the open, so I went back to stock gearing.

Edited by orangeone

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I just bought a used KTM SX 150 for my 15 years old son.  He wants to go riding with me in the woods and trails (and maybe some enduro racing) but it was virtually impossible to find a 125/150 cc "enduro" used bike for him (well yes, but, a new the Husky TE 125 for 7,000 US$ plus...too much money!).

Anyway, I bought a used KTM SX 150 and my project is to adapt it as much as possible for trail/enduro riding.  I was thinking to re-gear it from 14/50 to 13/52 (thus increasing the gear ratio from 3.57 to 4, almost half turn) to increase the bottom-end.  Then I plan putting a flywheel weight (8 oz) on the rotor.  The idea is to make a much more friendly engine for long rides.

I may modify the front suspension, but I really don't know what to do there as "suspension" always has been a sort of "black science" to me.

I would be very grateful for your comments and tell me if in your opinion I am on the right path and if possible, give me some guidance on what to do with the front suspension.

Thank you!

I changed the gearing on my 150sx to 13/51. Made a big difference for me.

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Enduro Engineering will sell you anything you need for that bike.

I added radiator guards,hand guards,skid plate.

A turbo ring from REP suspension and had the same guy revalve the bike for woods work.

It was recommended not to add any flywheel weight and I did not. Raced it all year and am very happy.

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