We thought we would give you a preview of our 904cc Sports Big Bore Kit pistons for the air cooled twins. They give a compression ratio of 12:1, have a tight quench, anti-friction coated skirts and have +2mm valve pockets. The big bore kit should be available in 6-8 weeks. Regards Mike https://www.triumphtwinpower.com
Hi HalfTon, the kit will be based on core exchange of your barrels. We have a supply of bored and nikosil coated barrels that are also externally re-finished and will look new when fitted, so no heavy cast iron liners are required.
Hi All, thought you may be interested in the first dyno run for our new 904s Sports Big Bore Kit. On this dyno there are three runs showing, EFI 865 OEM, EFI 865 with TTP Stage 2 Power Induction Kit and 904s with Stage 2 kit. The bike was an 865 EFI Bonneville fitted with the TTP Stage 2 Power Induction Kit, Tune 12 & short free flowing silencers vs. the same bike with 904s Big Bore Kit installed with 904s Tune 12. 904s St2 vs. 865 St2 - Peak Power +12% (78.76 bhp), Peak Torque +18.1% (61.21 ftlb) & Max Torque Increase +20.5% @ 5,735 rpm. 904s St2 vs. 865 OEM - Peak Power +29.8%. Peak Torque +30.6% & Max Torque Increase 34.3% @ 4,173 rpm. We're really pleased with the results, not bad for an OEM engine using the 865 cams and 904 big bore. The bike pulls really well through the rev range, which isn't surprising as it has more mid range torque than our carb 904 with Stage 2 kit, 790 cams, less CR and Keihin FCR39's carbs. The carb bike had 4bhp more at the top end due to 790 cams and FCR39's. Next will be the same EFI configuration, but using the early 790 cams for more top end power........
Mike: I know this is an old thread, but I have been wondering what ignition modifications are available that are well suited to this mod ? I know from experience your static timing requirements will stay about the same, but you are going to need less total advance. As these ignitions are not very tunable, what choices are out there ? I currently have a 790cc [270°]. ...J.D.
Hi JD, sorry for the delay getting back to you. We have new maps for the 904s Big Bore Kits that take care of the ignition advance with the higher compression, larger bore engine. We have the brand new Fire Starter Performance igniter units for the 904s kits or the igniter remap service for your own igniter unit using the same maps and rev limit as used for the Fire Starter units. Regards Mike
