Beta Riders Club Discussion Forum

I've got 165 hours on my bike now, no issues other than the head o-rings some time back. My question is how do I know if I need a new topend or not. I've never personally done a topend job myself. I did replace the o-rings myself though, so I may be able to wing it. I've talked with many different riding buddies and they all say something different. One says change it every 100 hours, another says 150 hours and lastly one riding buddy says he has 400 hours on his 08 KTM 300xcw and has never done a topend on it. He says the bike still runs good! I'm just a little confused and looking for some sound advice. I've seen some of the post about the different size pistons, but how do I know which I need to order for my bike?

Somewhat subjective depending on one's riding style. I'm an old hack that is rarely on the pipe - I did a top end on my 09 KTM 300 XCW at 200 hrs and piston and barrel looked fine. I did a tope end on my 13 300RR at 8ish hrs and piston and barrel looked brand new. However on both bikes the power valve needed to be dis assembled and cleaned.

The main reason I did the Beta top end (at 80 hrs) was because the previous owner had the head modded to the point where race gas was required, was a PITA (and $$) so I got a new head and did a top end job. Honestly, to ME, I didn't notice any performance difference, compression was comparable before n after and now I run pump gas. I'll think about another top end when I approach 300 hrs.

Beta specs really good pistons and rings in their engines, so the answer as to when to change out the top end is just before a skirt breaks and lunches the cylinder
Seriously though, how long do you you think you should get out of a set? We've had bikes with upwards of 160 hours on the pistons and compression was still good, but how far do you want to push your luck?

I'll be doing mine soon at 180 hrs. Still runs and looks great but you can't see metal fatigue. I am more than happy with this interval. Everything is going back stock, as I like the power as is. With the 250 that uses a cast piston I don't think I'd go that far though.

On my 2014 300rr I replaced the piston at about 160 hours.
I had an engineer measure the bore and old piston and there was very little wear.
I put a new Genuine piston in it and rode it to about 250 hours when I sold it. The bike was running just great.
Bike has been the least expensive bike Ive ever owned, so I replaced it with a 2016.

I had over 200 hours on my 2014 300RR before rebuild. Piston and cylinder still looked great. I just went up one letter on the piston. Steve sent me the OEM rebuild kit. I agree, this has been the least expensive bike I've ever owned. I've ridden the "you know what" out of mine. Only replacement parts are normal wear items. Chain, Sprockets, Wheel Bearings, Brake pads, and rotors.

Anyone running an aftermarket piston like Vertex, Pro-X, etc. and/or could share some thoughts or opinions on such?

I would recommend using the KTM 300 OEM Piston "B" Size.. this is a better piston than the Beta piston.. But the Beta piston is a good piston.. I have also used the Prox Beta piston.. it works well also.. But the OEM KTM piston is the best piston IMO

Kels wrote:I would recommend using the KTM 300 OEM Piston "B" Size.. this is a better piston than the Beta piston.. But the Beta piston is a good piston.. I have also used the Prox Beta piston.. it works well also.. But the OEM KTM piston is the best piston IMO

Not flaming, just wondering ... in your opinion, what makes the KTM OE Vertex piston better than the Beta OE Vertex piston?

twowheels wrote:

Kels wrote:I would recommend using the KTM 300 OEM Piston "B" Size.. this is a better piston than the Beta piston.. But the Beta piston is a good piston.. I have also used the Prox Beta piston.. it works well also.. But the OEM KTM piston is the best piston IMO

Not flaming, just wondering ... in your opinion, what makes the KTM OE Vertex piston better than the Beta OE Vertex piston?

And to add that the Beta 300 OE Vertex is forged. Don't know about KTM's.
Also the correct way is to measure the bore and then decide which size to use. On bikes with 100-130 hrs I've measured, the B would be too tight.