I stole the title from another Vital forum, but apparently, there is some talk about the new 300 SX having piston and/or build tolerance issues (piston to crank). I guess this isn't the first-time folks have experienced piston cracking/exploding bottom ends on these 300s. Fact or fiction, I don't know.
I do know that I called Lanston's Motorsports and talked to the Service Manager. His response was that his shop hasn't seen any such failures on the new 300s and therefore, in his opinion there is no issue. I asked if he had heard of any failures, and he said no. His advice was to simply ride the bike. If it blows up, then bring it in and they'll check it out. I thought that was rather short sighted advice, as we both agreed that if KTM didn't admit to a design/manufacturing/vendor issue, I'd end up paying the entire bill. I've literally NEVER blown up a bike in over 50 years of riding (unless you count the old D&G 125 Elsinore pistons that were modified and kept breaking off intake side piston skirts, lol).
I might tear it down and check the piston (I've got 5 hrs) or simply look down the intake. Any cracks or stress risers would be fairly obvious, but there's probably no spec for piston skirt to crank clearance. Some folks are taking a mm or two off the intake side skirt just to be safe, but I'd rather not mod anything that could cause KTM to reject a future fix (assuming they own up to some internal problem).
What's everyone's experience with this issue? Is it just a case of one or two bad apples or is it more pervasive (a reliability issue) and KTM simply hopes the owners assume it's their fault?
I'm leaning towards "just ride the thing" approach.
Ride it
There is a thread about it on KTMTALK, I checked mine and posted pictures in that thread. No evidence on mine, I’ve inspected the piston and borescope the piston/crank with the cyl on to check clearances and all looks well. I question if KTM was short on parts at some point and tossed some stuff in certain production runs that was maybe not up to par? Just thinking out loud. I also know older KTM 300 pistons did have longer skirts, they used to be 74-75mm. Mines 72.3mm, did they maybe toss some of the older stock in some? The 2023 piston is the same back to 2017. Idk.
It might not even be something KTM did. Maybe the piston supplier missed a machining step and didn't knock the edge off the piston. Maybe there was casting flash they usually remove, and it was missed due to a new/untrained worker. This is getting more common in many industries since Covid.
Shouldn't something like that be caught at ktm during assembly?
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So what is the resolution you wanted from the Manager? Are you going to pay him to pull the bike apart and inspect it? Because even if he finds a concern KTM most likely won't pay anything, until there is an actual failure...
A 1 or 2mm issue on a single part? Yeah it would be great if they could but how much do you want your bike or car to cost?
You mean the pic of the piston out of a new bike not ridden. That clearly has a casting flaw. In the tech help post. I had one I'd tear it down running good or not. Replace it with one I know is definitely good.
What I didn't want to hear was some evasive "hear no evil, see no evil" answer. These guys aren't dumb (I assume), they read and watch the same social media we all do and should be particularly aware of any stories about customers with virtually brand new bikes blowing up! If I were a SM, after reading any such story I'd be on the phone to KTM USA and get their position on the potential issue. If KTM told me to keep my mouth shut, I'm not sure ethically that I could. I certainly wouldn't "play dumb" as this guy did as it makes him and the dealership look like unaware fools.
Ride it and if it blows and we'll have something to check? Boy, that's real deep thinking and could be said about any failure. Just wait till it breaks? By then all the potential evidence will be in a million pieces and nobody learns (or is accountable) to anything except the owner. Maybe that's the strategy!
I've never made a warrantee type claim in my life as I never had a need and would fix/repair my own engines anyway. So, it's not a matter of money. It's about being treated like I'm some misinformed dummy, even if there's no problem.
This makes the most sense… I have 50hrs on my 300SX, pretty much all Mx sand riding, been wringing it’s neck ever since the 15 minute break in I gave her. I have more faith in Ktm”s warranty police’s than any Japanese company, based off prior experiences. I would have no problem relieving some of the pistons intake skirt for piece of mind. Probably easier than drilling exhaust bridge holes. I also take fine grit & remove any sharp edges on new pistons from skirts and around cut outs or windows… maybe someone from Vertex should chime in?
I got this rapid response from Wossner when I emailed them:
Thank you for contacting the Wossner North America team.
Regarding this application, Wossner KTM 300 2006-2023 / Husqvarna 300 2014-2023 / Gas Gas 300 2021-2023 – Wossner Pistons, the Wossner part is the same length as the OEM piston 72.3mm intake length.
We are aware of the OEM piston having some crankshaft contact, and this is less to do with the skirt length as the inside dimension of the piston skirt is cast too thick. Due to this the piston can make contact on the inside edge.
The Wossner part is machined in this area, there are no clearance issues with our part.
Kind regards,
Dave
Nice! Usable information.
Thank you for sharing that.
I did get a top end kit from my Ktm dealer and it says 2017 300xc on the piston. I haven’t taken mine apart to compare them but the parts manager swore up and down it was the same.
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