Description
Yamaha Blaster Wossner Forged Piston Kit
The Yamaha Blaster Wossner forged piston kit is an excellent choice for rebuilding a stock, trail-ported or high-performance Yamaha YFS200 engine. Manufactured using Wossner’s precision forging and machining processes, this piston is built for the heat, RPM and demanding operating conditions found in two-stroke ATV engines.
This is a dual-ring piston designed for Yamaha Blaster YFS200 models from 1988 through 2006. Each kit includes the components required to install the piston in a correctly bored and honed cylinder.
Wossner Forged Piston Kit Features
- Fits 1988–2006 Yamaha YFS200 Blaster engines
- Forged aluminum piston construction
- Dual-ring design for dependable sealing
- Permanent piston-skirt coating helps reduce friction
- Precision-machined for consistent fit and performance
- Suitable for stock and modified Yamaha Blaster engines
- Available in multiple bore sizes
- Wossner 8101D-series piston
Kit Includes
- Wossner forged piston
- Two piston rings
- Wrist pin
- Two wrist-pin retaining clips
A wrist-pin bearing and top-end gasket set are not included unless specifically selected or listed with the product.
Available Cylinder Bore Sizes
| Finished cylinder bore | Wossner piston size | Part number |
|---|---|---|
| 66.00 mm | 65.94 mm | 8101DA |
| 66.25 mm | 66.19 mm | 8101D025 |
| 66.50 mm | 66.44 mm | 8101D050 |
| 66.75 mm | 66.69 mm | 8101D075 |
| 67.00 mm | 66.94 mm | 8101D100 |
| 67.50 mm | 67.44 mm | 8101D150 |
| 68.00 mm | 67.94 mm | 8101D200 |
| 68.50 mm | 68.44 mm | 8101D250 |
| 69.00 mm | 68.94 mm | 8101D300 |
| 70.00 mm | 69.94 mm | 8101D400 |
Choosing the Correct Yamaha Blaster Piston Size
Always choose the piston according to the cylinder’s finished bore size. For example, the Wossner 8101D050 uses a 66.44 mm piston and is intended for a cylinder finished to a 66.50 mm bore.
Do not order a piston based only on the size stamped on the old piston. The cylinder must be accurately measured for wear, taper, out-of-round and remaining oversize capacity before the correct replacement piston can be selected.
The cylinder should be bored and honed to the specifications required for the exact piston being installed. Ken OConnor Racing recommends having the new piston available before final cylinder machining.
Professional Yamaha Blaster Cylinder Boring
Ken OConnor Racing operates a complete engine machine shop and offers professional Yamaha Blaster cylinder boring and honing. Your cylinder can be machined specifically for the Wossner piston supplied with your job, providing the proper piston-to-cylinder clearance and correct final finish.
If you are unsure which size your cylinder needs, send the cylinder to Ken OConnor Racing for inspection and measurement. We will determine the smallest practical oversize required to restore the bore.
Important Installation Information
Check piston-to-cylinder clearance, piston-ring end gap and wrist-pin bearing condition before assembly. Install the piston in the correct direction and perform a leak-down test after the engine is assembled.
Proper jetting, lubrication, warm-up and break-in are essential with any freshly rebuilt two-stroke engine. An incorrect bore size, air leak, lean fuel mixture or improper assembly can quickly damage a new piston and cylinder.
Frequently Asked Questions
Does this Wossner piston kit fit every Yamaha Blaster?
Yes. It is designed for Yamaha YFS200 Blaster models manufactured from 1988 through 2006. You must select the correct piston size for your cylinder.
Is the Wossner Blaster piston forged or cast?
This is a forged aluminum piston. Forged construction makes it well suited for properly assembled stock, trail and performance Yamaha Blaster engines.
Does the kit include piston rings?
Yes. The kit includes the forged piston, two piston rings, wrist pin and wrist-pin retaining clips.
Does it include a wrist-pin bearing?
No. The small-end wrist-pin bearing is not included with the standard piston kit and should be inspected or replaced during a top-end rebuild.
What is the stock Yamaha Blaster cylinder bore?
The standard Yamaha Blaster cylinder bore is 66.00 mm. A cylinder that is worn, damaged or previously bored may require an oversize piston.
Can I install a larger piston without boring the cylinder?
No. An oversize piston requires the cylinder to be professionally bored and honed to the correct finished diameter. Never force an oversize piston into an unmachined cylinder.
