You can buy a single ring piston for the 150 from the KTM Power Parts range, but it is very expensive. In fact very very! Anyway, we have raced mx with 125s since 2012 and only use the top ring. Vertex 125 piston is the same price in the UK whether it be single or twin. We change the pistons in both bikes every 15 hours and the ring generally at 8 hours. Spare ring from Vertex is around 20 GBP so makes sense. Hope this helps a bit with your query. Unfortunate that you can't race a 250 2T in MX2 - when the 4 bangers came out the FIM allowed 144cc as they made same BHP. Wow, that was then and this is now - 250Fs make so much power and torque it's difficult for even a top pilot on a 150 against an equally talented rider on a 4T . But who the f###k wants a 4T. Too easy a life lol. Bob

 

250Fs make so much power and torque it's difficult for even a top pilot on a 150 against an equally talented rider on a 4T

That's interesting. I was up against a guy at an Ashdown HnH a few years back on my 150. I was knackered and he kept getting past. But on every straight, even the relatively short ones, I completely destroyed his 250F on my 150. EXCF against XC, maybe that makes a difference.

I guess the SX motors make more power than an EXC/XC, but I'd think that would follow for 150 and 250F.

 

Yup only the top ring on a 2 ring piston. We've not had any problems. However, I don't think you'll really notice much difference using 2 ring piston in your 150. Our 125 motors are heavily modified for motocross. Have you had a ride on a new 250 sxf - they are real good.

 

I do all the mechanical work on the bikes and we do not have coffins filled with coins, so I am glad that my boy does not want to ride a 250sxf (I have done repairs on some of his mates ones and even w/o the hourly charge [that is discounted to his mates] the price for a top end rebuild is 3 x what a 2 stroke one costs for me to do. And we take pride in that we can beat the 250f bikes with a smaller 2 stoke! My boy had a ride with one, but came back telling me it was no fun... actually boring compared to piloting a 2 smoker!

 

@ktm808 we did feel the difference in the 125sx. So our first intention is to find out if there is a clear difference in the 150sx also. There is after all almost 50% difference in the drag between one and two rings... (some minor drag from the piston also)

 

My 150s are both enduro models on two ring pistons. I’m not after the absolute top power but I’m with papercup....150s punch well above their weight. When ridden for speed then it’s rare you get overtaken on a straight. If you do it’s usually a fast rider that does so as they carried more momentum onto the straight to start with. Small bore 2t can pretty much outbrake any 4t as well. 4t are easier to plod about on though I suppose. The maintenance cost of a 4t puts me right off.

Check out Josep Garcia smoking 4t bikes on this video.

I wish I could ride mine like that!

 

The 150s are real good bikes. However I bought young Bob a 150 Power Parts kit for open racing in the winter and he just plain didn't like it. As said a top mx rider on a 125/150 will be beaten by himself on a new 250F. How the difference in cc's compare in H & H or Enduro is beyond my knowledge as you well know Pindie lol Bob

 

Meant to say did you have a look at the 150 sxs piston in KTM Power Parts? It is very much like the VHM one with single ring and the blind lightening recesses. I'm not sure if it has the oilways for the small end bearing like the VHM (unlike plain Vertex) Bob

 

Never checked KTM Power Parts. @ktm808 You have a link? (when I search for "KTM Power Parts" I end up looking through all sorts of after market bits to all possible KTM bikes)

 

Oops, I'm presuming it's a 2016 on 150 you have? If so just look on your KTM dealers site . It's part no SXS161509071. KTM don't do it for the pre 16s - I should have asked bike's age. Bob

 

It is a 2013. I like that the stroke is longer than the later model 150sx that has same motor as the 125, only with a bigger piston. But part of the reason was also that we got her for 1/2 the price of a s/h 2017 we were looking at. And as my son just has become a senior rider it is now up to him to pay for hos own bikes. When we were riding Junior 125 we had a 2016 125sx and a 2012 125sx as backup bike. The 2016 was very unreliable and my son ended up finishing many meetings on the 2012. This was not all bad as he learned to squeeze the last little bit out of the 2012 and his cornering became the best part of his racing as he kept the throttle on and did most of his passing there. I sold the 2012 and my son never forgave me as he loved that bike. So when we came across the 2013 150sx it was the one he would always pic. The blurb is that she has just below 39Hp at a fraction over 11.000 revs. With some modification she should still be a very respectable weapon. Plus with the longer stroke there should be more bottom end compared to the later model ones.

 

Ah, well that's cleared that up about the piston. I'm surprised you found the 16 unreliable. That's a shame as I think they are a better bike than the pre 16s. But that's just me. We still have a low hour race 16 which my son no longer uses but won't part with. It has a heavily modified motor and is way quicker than a 150 but very little bottom end which he doesn't really need for mx. The 19 on bikes with the new everything are very good 125/150s. We've not done any mods to the new race bike, just XTrig triples, HGS pipe, BUD carbon silencer, 39mm PWK, cone forks and a Trax shock - real good bike. Your quite right young one should pay, wish I could do the same lol Bob

 

The 2016 was a s/h bike also. I have not had the funds to buy new bikes (single dad with 4 boys... even if 3 of them have now moved out). So might have something to do with the previous owner. But at one stage I started to seriously doubt my ability to fix bikes as a result of the ongoing issues...
A short list of some of the main issues we had with the 2016 125sx:

• Dead CDI
• Dead stator
• Broken gears in gearbox (KTM knew of this issue as it was after they had changed gear box parts supplier. The new supplier/manufacturer did not do the hardening of the gears to the required standard, so KTM went back to their earlier manufacturer. But there was never any admitting that this was the case, so every owner of bikes with issues ended up paying for KTM's poor decision)
• Electrical connectors struggling to handle water blaster (never had one issue with this in all our earlier KTM's!)

Add a handful of smaller issues and we got very tired of the bike (long nights in the workshop for me... and race meetings where the bike would not finish a race). But when she did run she was a rocket!!

 

Hi, yes I knew of the gear problem (to much lightening as well was main cause) but never affected our two 16s. Only problems we had were the new for 2016 rotors - the bikes were not revving out - pulled both off and found that the liners which are glued in had come adrift. One was still in one piece while the other broke into pieces and eventually cut through the stator wires. Tried a claim with KTM but no luck. Tried to glue the whole one in again but came adrift first rev. Koukasan wouldn't help either. Had to buy to new rotors and a stator (gulp) but other than that the bikes were real reliable and deffo fast Bob