There are very few modifications you can perform on an engine that will improve power and torque right through the rev range, but TTP's 904s big bore kit is one of those modifications. Increasing cubic capacity and compression ratio give improved performance from idle to the rev limit, with no downside.
In use the extra top end horsepower is excellent for acceleration and top speed, but the revelation is the extra torque through out the rev range. It makes riding a Triumph twin far more exiting as when you open the throttle, the engine just pulls and pulls to the red line.
Designed by TTP, the 904s kit includes race quality pistons, a custom 904 MLS steel head gasket together with OEM cylinders which are bored, Nikasil plated and then powder coated externally to give a virtually new set of barrels.
**790/865 CYLINDER CORE EXCHANGE REQUIRED BEFORE SHIPPING**
Core must have no broken fins and no scratches on the bore or mating surfaces.
Shipping details will be on your emailed order receipt.
The later barrels have machined and polished edges which after processing need to have the powder coat removed and the fin edges polished back to a shine. Like for like core exchange only.
OEM Gasket Kit:
This gasket kit includes all of the OEM gaskets required when installing the big bore kit. (except head gasket which comes with 904s kit)
Green Clutch Springs:
With a 904s Big Bore Kit installed, the standard clutch springs are pushed to their limit, so we offer the Barnet Green clutch springs along with a Triumph clutch case gasket as an upgrade.
The Safe Start is a good preventative measure for a standard engine, with the 904s Big Bore Kit installed giving an increased compression ratio, the Safe Start will give protection from the only
engine structural weakness of the air cooled Triumph twins.
NB: If you're upgrading to the green clutch springs, why not install the Safe Start while the clutch cover is off, for complete peace of mind.
TTP 904s Sports Big Bore Kit
*Not for sale in California.
- 12:1 compression ratio.
- Larger valve pockets for +2mm valves.
- Tight quench to improve tubulence & combustion burn.
- Anti-friction coating on the piston skirts.
- Pistons hand balanced to within 0.1gms of each other.
- Nikasil plated barrels give tighter cylinder/piston clearance.
- Hand gapped piston rings.
- Custom 904 MLS steel head gasket.
- Optional OEM gasket kit.
Available for the air cooled Bonneville, Thruxton, Scrambler, America
and Speedmaster from 2001-2016.