These adapters fit neatly into the stock plastic end cap by replacing an existing rubber grommet (see installation instructions for more info). The adapter provides just enough exposed tube length to mount the included TRS-1 spark arrestor external to the plastic end cap, just pick your spark arrestor color (Red, Black, or Blue) at checkout.
The inside diameter of the adapter exposed to exhaust flow matches that of the existing tube so no additional flow restriction is created. Use of this adapter allows the spark arrestor to be mounted outside of the end cap for easy removal & cleaning.
Also identify the type of heads the endcap screws on your bike have before ordering. Since mid 2025 Beta started using Tamper Resistant T15 screws for the endcap. If you have Tamper Resistant T15 screws and do not have the correct Torx bit, click here to include a Tamper Resistant T15 bit with your order.
BT-4 installation instructions rev.4
TRS-1 installation & cleaning instructions rev.4
Applications: Beta EVO two stroke models,125-300cc engine sizes for years 2009-2025. Note: The BT-4 adapter will not fit the new Beta Sincro model, the BT-5 adapter fits the Sincro. Link to TRS-1-BT-5 kit.
Note: Anodized color will fade due to heat, UV light, & chemical exposure.
Kit Part# TRS-1-BT-4
Part # BT-4 Technical Data:
PATENT PENDING
Body-anodized 6061-T6 aluminum
Sealing/Fitting- (2X) size 123 viton O rings
Weight- 43 grams/1.5 oz
TRS-1 Technical Data:
PATENT PENDING & USFS APPROVED (REF. FILE#0880-03)
USFS screen type spark arrestor
Body-anodized 6061-T6 aluminum
Screen-stainless steel
Sealing-size 125 viton O ring
Set screw- stainless steel 4X0.7mm metric 2mm allen head
Weight- 18grams/0.63oz