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Only $10 for all 2026 SX, MX, and SMX series.
Other than that everything on it was pretty decent. I seem to ride better on a KX250f, I am not fast though and the KX gives me confidence. I would like to pick up another 250 2 stroke for the woods though. The SX/TC chassis is near perfect IMO. It does everything well and held up well for the year I had the bike.
Oh, buy some frame guards ASAP too as the stock ones suck and will scratch the shit out of the frame in 2 hours.
I see people here saying 50+ hours but that's obviously not going to happen for a Pro/A level rider or even a decent B rider.
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If you are talking about a 125 or 150 then I'd say the life span of those would never get to 70 without a few top ends being replaced.
I don't want to risk anymore damage or injury than necessary and was curious what Jeff's intervals were.
70 hours is crazy btw and you should be careful. One of my worst crashes was my bike locking up on the face of a double. It's still my worst nightmare.
What are the pros of changing just one clamp?
A bit more rigidity instead of a lot more rigidity?
Im new to this...
https://youtu.be/l35YpJV_wi0?t=20
So there’s a handful of things to take into consideration here on the top end interval conversation.
1. I use Wiseco racer elite pistons. These pistons are made for top performance, not high service hours. I change them every 10 hours. They are an under-belly-milled single ring ounces lighter than the double ring. Less moving mass, less serviceable time.
2. If I was using the Wiseco double ring, I’d run it at 20-25 hours with consideration of whether we’re talking winter weather woods riding or multiple weekends at Bar 2 Bar and training Reynards on hot summer days.
3. I beg anyone to pull the stock vertex out and replace it. I’m unhappy with the performance, service hours, and weight of the piston. If you’re not going to run a Wiseco, find something other than the stock Vertex, but I implore everyone to try the Wiseco first and foremost. Good enough for Ken Roczen, good enough for me.
Bottom ends are a hard out at 50 hours. On the small bore it was 40. Could I get away with more? Yes. But I value my peace of mind over getting a few extra hours.
A few other notes about how I set my bike up- I run 91 pump at 40:1 with PJ1 goldfire. I also use a Lectron carb which comes with the bonus Domino style throttle housing. My head is modified by Millennium Tech. I use the yellow power valve spring. The red is exciting, but I can’t exit corners as easily with the red.
I agree with one word though. If a fellow A rider was telling me he was getting 60 hours out of a top end I would ask him if he’s praying for a skirt to dissolve into the crank on a triple face. 100 hours on a crank sounds like a B class woods rider number. I’m not skill shaming. It’s matter of fact. I could never get those hours out of a crank. Part of the reason I’m comfortable with getting 40 is because I run high quality premix at high ratio.
KTM, Motorex, Euro emission regulations and their 60:1 can kick rocks
Has anyone had a 17+ SX/TC with a bottom end that let go and at what hours?
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When I do a top end at 40 crank hours, I can tell the crank, rod, and bearing are getting away from tolerance. for those that don’t know, side to side play of the rod is normal. When at TDC and the rod has up and down play it’s time to replace. Usually for me at 40 hours I can get an inkling of up to down play.
Nate I’m not here to lay down the law of my way or the highway when it comes to cranks and top ends. It’s all about budget, comfort, and preference. I prefer to have a bigger budget to give myself absolute comfort that my engine is healthy and nothing less than tip top.
Has good power, handling, suspension (once setup), and quality. I sold both of my 3rd gen Hondas after getting this one.
Also to note: I like the feel of the frame on my 19 FC350 slightly better than the 17. Feels a little less flexible/tighter/more precise.
I like stock gearing or a 48 tooth rear. Have tried a variety of engine configs also: stock head, shaved head, shaved head with extra base gasket, 300 kit, PC pipe with both silencers, PWK swap, STIC insert, and probably other things. All had pros and cons.
Almost 77 hrs on mine.
I better like sx over tc... but your tc is really good looking🍑
Following this thread because I am 100% considering a KTM/HUS 2 stroke as my next bike. Interesting to read about there being up/down play on the bottom end around 50 hours. Just over 105 hours on my YZ and there is ZERO play. It's definitely getting a fresh crank at the end of the year though, play or not.
On the carb stuff: the PWK is less sensitive to temperature change and works pretty good once you’re close. For the TMX, after I had my head shaved it was also very stable over a pretty broad temp range (had summer jetting (85 F) and winter jetting (50F)) that could be managed with air screw.
If you don’t want to mess with it, PWK is easy. If you don’t mind tinkering a bit then the TMX performs better.
I also tried the STIC insert and it was too much of a good thing for me. I ran out of talent too fast.
For oil I run 32:1 for moto and 50:1 for single track trails. I use race gas everywhere. It just runs cleaner and smoother and I don’t have to worry about pinging. I’m obsessive about air filter maintenance and my top ends last a really long time.
I've had a 14 and now an 18 tc250. I've had no major issues with either. On the 14 I did the 300 kit at the 40 hour mark and it was incredible. Spent the next few months taming it down with flywheel weight and gearing. Never broke anything other than crash damage stuff over 4 years and I don't think I ever even put a clutch in the thing. The forks were ehhhh but totally rideable with some KB5 industries love. My 18 is just over 60 hours now also did top end at 40 hour mark and everything was still almost new looking. Kept it a 250 this time as I'm totally happy with the motor. the mikuni is a bit more temp sensitive but with a little jetting it was good. The suspension was good right out of the box but its awesome now with some work. Also KB5. Over 30 years racing and I've never been happier with my bikes or dealer.
40+ expert and 45 plus classes
Hope this helps and good luck!
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