Posted by Andrew on April 25, 2003 at 17:56:11:
In Reply to: 650cc posted by stinger on April 25, 2003 at 13:19:07:
Hi Stinger,
The capacity of an engine does not tell you it's power. A 1350cc Harley makes about 50 horse power while the Yamaha R1 (900cc) has about 140 odd horse power.
Although bigger engines have more power, it also depends on the state of tune. The single and twin engines you mention will both have a capacity of 650cc, but the twin is more powerful because it is more highly tuned.
The Savage is in a very low state of tune - that's why it's so slow compared with say a CBR600 which can do over 140 mph. The benefits are cheap running costs and a bike that in the real world is hardly any slower.
Singles can and are made with twin exhaust ports. Two exhaust ports will enable the engine to breath more and therefore to burn more fuel and be more powerful. The single exhaust port is not the cause of the backfiring on the Savage. It's caused by the engine being set up too lean in order to pass emissions regulations in the USA. Because the fuel/air mix is so weak, it can't burn when the throttle is shut off when slowing down. The unburnt fuel collects in the exhaust pipe. When there's enough of it, it is ignited and then you hear the backfire. The fuel/air mixture can be ritchened by raising the needle in the carb and adjusting the mixture screw - see the hundreds of previous postings. This will stop the backfiring, but also mean the bike won't pass the emissions tests so presumably it's illegal to do the modification ?????? It would be in the UK.
In the UK, cars are tested for emissions every year and such modifications would be spotted. At present bikes are not tested.
Happy Savage riding