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High-performance big bore power valve kit engineered to match enlarged cylinder bores, restoring smooth exhaust port timing, optimal low-end pull, and crisp throttle response for high-output two-stroke engines. Manufactured to strict specifications using durable, high-strength materials designed to resist carbon buildup, thermal warping, and mechanical wear under the intense pressures of aggressive racing environments.
| Make | Model | Engine Type | Year Range |
| Yamaha | YZ 250 | Two-Stroke Motocross / Big Bore | 1999–2025 |
An absolute necessity when stepping up to a big bore setup on your YZ250. Standard power valves will not clear an enlarged 72.00mm cylinder bore properly; dropping in this matched big bore power valve kit ensures correct port clearance, smooth governor actuation, and reliable power delivery across the entire RPM range without risking mechanical interference.
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Overall rating: 4.9 / 5 from 58 reviews.
Shipping was fast, the product is great! When you could still buy the shift forks from Kawasaki they came out of spec :-( These are in spec and far better quality than Kawi's forks. They are in the bike and vastly improved the shifting on this KX500 BEAST!!! Thanks Luke!
Unfortunately, the gas cap got scratched during shipping, but after a few friendly emails, the problem was resolved perfectly for both sides. Friendly service, quick solutions, absolutely reliable Top-notch shop👍
Perfect product... Perfect all around transaction!!
Great solution for KX500 airbox seal issue. Very nice product.
1989-2004 Kawasaki KX500 Billet Air Filter Sealing Kit (1989-2004)
Everything I have received from TSO has been excellent, I was excited to see TSO had the pressure plate because they was the only ones , thanks for amazing products and service
1988-2004 Kawasaki KX500 88-91 KX250 KDX250 Clutch Pressure Plate 13187-1060
Amazing!!! Luke is so helpful. These cases are amazing and a direct fit of my old cases. All parts are equally made and not one is below my standards
Very well made pipe fits good have not been riding yet so don’t know if it leaks out two stroke oil like the stock one does we will see when it gets cool out for riding
My first order and I'm very happy!
Killer cover!!! Great fitment
Fitted without issue and looks the part, just need to upgrade other parts to look as nice.
Great communication they help me out when I question about how curtain things go I highly recommend them
Great product
Part works great!
The best machined pieces I have ever seen. I have wanted a two piece KX500 billet side cover for a long time and can't wait to install it. So trick!
Very quick shipping, and super pleased with the quality of this stator cover! The anodized black blends nicely with the satin black powder coat on my KX500 engine.
Two strokes only is the place to get hard to find KX500 engine parts. The best machined parts I have ever seen.
1989-2004 Kawasaki KX500 Center Power Valve assembly| 12023-1058 & 12005-1111
Great quality, exceptional service
Fine quality piece too bad it's hidden away from the eyes 😎
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head look great and quality is superb
Quality parts!!! Very happy with what I received for the money!! Fit and finish is top tier. Also happy to support a company who is helping keep these two strokes alive! I will be back for more parts soon!
Bearings were a perfect fit. A couple of shaft bearings were on back order, which I reicieved shortly after a majority of my orders arrived. Quality of everything is immaculate I would certainly do business with Luke again. I honestly wish I could have purchased the billet cases for my kx500af build after seeing the precision on the covers and head. Highly recommend TSO
great shipping
Very thankful people out there make this stuff!!
Haven't installed these parts yet but the maching and quality looks better than OEM. Looking forward on trying out their other specialized parts offered.
Quality piece, may buy another. Can't wait for LT500 heads to become available. Will buy 2 when that day comes.
Finally a great after market head for the lt 250! Fits, looks and runs great!
My suspension guy loved the shock, which is high praise. He has seen a lot of custom suspension components in his career.
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KX500 Engine Rebuild Bolt Kit for Kawasaki KX 500 Specbolt Nickel Wurks Ti Look
Quality piece. I should have bought 2.
Great outlet, must have if using the billet clutch side cover on a steel frame bike!
Great quality part
Good quality
KX125 Engine Rebuild Bolt Kit for Kawasaki KX 125 Specbolt Nickel Wurks Ti Look
I ordered the case saver for my 98 kx250, the price of the TSO case saver was very close to the same as the original kawasaki one. The difference is huge, The TSO case saver is made of stainless steel for extra strength and great looks. Shipping and customer service was very fast and included mounting hardware. First time I ordered from TSO, but it won't be my last. Thanks TSO for offering a quality part and great customer service!
Kit had everything needed for the rebuild
Great service and product. Modern design for the motorcycle
So the cylinder head is immaculate and performs perfectly with the decompression valve. Much much easier to start this 500cc 2 stroke. I just wish I the decompression valve was coming off the side instead of straight out the top. Decompression valve creates interference taking out the spark plug when everything is mounted and the bike is together. Purchased a new wrench to remove the spark plug and all is ok. Overall happy 😁
nicely made product. fit was perfect
great product and excellent customer service
Lighter pull for sure. Great customer service.
