Triumph Twin Power
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TTP 904s Sports Big Bore Kit

TTP 904s Sports Big Bore Kit
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  • Description
  • Reviews



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 excellent quality high compression race pistons with exceptional quench properties for powerful combustion, 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.

Available for the air cooled Bonneville, Thruxton, Scrambler, America and Speedmaster from 2001-2016.

Kit Features:
  • 12:1 compression ratio.
  • Larger valve pockets to accommodate +2mm valves if required.
  • 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.

**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.

 
5 Product Reviews - Average rating 5 / 5 (Show All)

Click to review this product

Transformation !

- 19th August 2019

After deliberating for some time I had the 904 kit installed on my 06 Scrambler and haven’t stopped smiling since, the bike is transformed at all levels. I had TTP do the installation and highly recommend their services.

Click to review this product

 
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.

Early Barrels  Late Barrels
Early Barrels                    Late Barrels
 
The Stage 2 Power Induction Kit comes complete with
fitting kit, DNA Performance pod filters, installation
instructions and the required jetting or EFI tune for
the 904s kit.

Carb Stage 2 Kit            EFI Stage 2 Kit
Carb Stage 2 Kit          EFI Stage 2 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)

904s Gasket Set
904s Gasket Set
 
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.

Barnet Green Clutch Springs
Barnet Green Clutch Springs
 
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 Safe Start
TTP Safe Start
 
Installation of the 904s Big Bore Kit at our
workshop in Bournemouth, Dorset, England.
List Price: £922.00
   Discount on this product.
Price: £830.00 (£996.00 Inc. VAT)
€993.93 EUR (+VAT)    $1,110.67 USD    $1,606.13 AUD
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