The K&L VSK25 25mm Valve Shim Kit is an assortment of 25mm-diameter valve adjustment shims in a storage box. It’s built for Hinckley Triumph engines that set valve clearance with a 25mm shim on top of the tappet bucket. That covers the carbureted triples and fours from 1991 on, the early T595 and 955i Daytona and Speed Triple, the 790cc and 865cc air-cooled twins, the Rocket III, and the Thunderbird 1600 and 1700. With a full range of thicknesses on the bench, you can measure, swap, and recheck in one session instead of stopping to order single shims.
Why a Full 25mm Shim Kit Makes Sense
- Finish the valve check in one go. Hinckley Triumph valve seats tend to wear in, which closes the clearance over time, and it’s common to find several valves out of spec at once. With the kit, you have the right thickness on hand for each one.
- Hardened K&L steel. K&L says its shims average 47.0 on the Rockwell C hardness scale, above the scale’s 46.0 maximum, so they hold their thickness under cam-lobe contact.
- Organized storage. The shims come in a storage box, so sizes stay sorted and you can see when one needs refilling.
- Good value for multi-bike garages and shops. One 25mm kit covers a wide range of Hinckley models, from a 1993 Trident to a 2015 Thruxton.
Which Triumph Engines Use 25mm Shims
Shim-over-bucket, cams stay in (use with the Triumph Valve Shim Removal Tool MBI-VSRT):
- 1991–1998 Trident 750/900
- 1991–2004 Trophy 900/1200
- 1992–1993 Daytona 750/1000; 1993–2006 Daytona 900/1200/Super III
- 1993–1998 Sprint 900; 1993–1998 Tiger 900 (up to VIN 124105)
- 1994–1996 Speed Triple 900
- 1995–2004 Thunderbird 900; 1996–2001 Adventurer; 1998–2001 Legend TT; 1998–2003 Thunderbird Sport
- 1997–2001 Daytona T595/955i and Speed Triple T509/955i (up to VIN 141871)
25mm shim on the bucket, camshafts must be removed:
- 2001–2016 air-cooled Bonneville, T100, Thruxton, Scrambler, America, and Speedmaster (790cc and 865cc)
- 2004–2017 Rocket III, Classic, Touring, and Roadster
- 2009–2018 Thunderbird 1600/1700
Not for: engines with smaller shims under the bucket, such as the 2002-on fuel-injected Daytona 955i and the Speed Triple 955i from VIN 141872. Always check the shim diameter in your service manual or measure an old shim before you order.
How to Use the Kit
- With the engine cold, measure every valve clearance with a feeler gauge and write it down by cylinder and valve.
- Remove the shim from each valve that’s out of spec, then measure it with a micrometer. Don’t rely on the stamped number, because the face can wear.
- Work out the new size: new shim = old shim + (measured clearance − target clearance). For example, a 2.65mm shim with 0.08mm measured on an intake and a 0.13mm target needs 2.60mm.
- Oil the new shim and fit it with the size marking facing down. Make sure it sits flat in the bucket recess.
- Turn the engine over a few times, then recheck the clearance.
For a full walkthrough on a carbureted triple, see our Hinckley Triumph Barn Find article. Need just one or two sizes? Order individual K&L Adjustment Shims MBI-KLSHIMS. See more workshop parts on our K&L brand page.
The product images shown are for illustrative purposes only and may not be an exact representation of the product received. Manufacturers occasionally make minor cosmetic changes to items, such as color, finish, label, or design. These changes do not impact the item’s function or compatibility. Please contact us if you have specific concerns regarding appearance.
____________________________________
Frequently Asked Questions
What Triumph motorcycles does the K&L VSK25 valve shim kit fit?
It fits Hinckley Triumph engines that use 25mm shims. That includes the 1991–2004 carbureted triples and fours (Trident, Trophy, Daytona, Sprint, Tiger 900, Speed Triple 900, Thunderbird, Adventurer, Legend TT), the 1997–2001 T595/955i Daytona and Speed Triple, the 2001–2016 air-cooled 790/865 Bonneville family, the Rocket III, and the Thunderbird 1600/1700.
What size are the shims in the VSK25 kit?
All shims in the kit are 25mm in diameter, which matches the factory shim on the Triumph engines listed above. They come in a range of thicknesses so you can correct both tight and loose clearances.
Can I change 25mm shims without removing the camshafts?
On shim-over-bucket triples and fours, yes. Use a holding tool like our Triumph Valve Shim Removal Tool MBI-VSRT to keep the bucket down while you lift out the shim. On the 790/865 air-cooled twins, the factory manual says to remove the camshafts to reach the shims.
Does this kit fit the 2002-on Daytona 955i or the Speed Triple 1050?
No. Those engines use smaller shims under the tappet bucket, not 25mm shims on top. Measure an old shim or check your service manual before ordering.
What are the valve clearances on a carbureted Hinckley Triumph triple?
The factory spec is 0.10–0.15mm (0.004–0.006 in) intake and 0.15–0.20mm (0.006–0.008 in) exhaust, as covered in our Hinckley Triumph maintenance and restoration guide. Twins, the Rocket III, and the Thunderbird 1600/1700 use different specs, so check the manual for your model.
How do I calculate the shim size I need?
New shim = old shim thickness + (measured clearance − target clearance). If the clearance is too tight, you need a thinner shim. If it’s too loose, you need a thicker one. Always measure the old shim with a micrometer.
Why do Hinckley Triumph valve clearances get tighter over time?
As the valve seats wear, the valve sits higher in the head, which closes the gap between the cam and the shim. Very tight clearances can point to seat wear. If a valve has almost no clearance, inspect the valve and seat before you just fit a thinner shim.
Which way up does the shim go?
Fit the shim with the size marking facing down, toward the bucket. That keeps the marking from wearing off against the cam lobe. Oil the shim lightly and make sure it sits flat in its recess.
Are K&L shims as good as genuine Triumph shims?
K&L shims are hardened steel. K&L says they average 47.0 on the Rockwell C hardness scale, above the scale’s 46.0 maximum. They’re made to the same 25mm diameter as the factory part, and you size them with the same shim chart.
Can I buy single 25mm shims instead of the whole kit?
Yes. Individual K&L Adjustment Shims MBI-KLSHIMS come in 2.30mm to 3.10mm. The full VSK25 kit is the better choice if you service more than one bike or don’t yet know which sizes you need.
How often should I check the valves on a Hinckley Triumph?
Follow the service interval in your owner’s or service manual. Many owners also check the valves when they buy a used bike or bring one back from storage, because tight valves can cause hard starting and rough running.
