Most bikes (and gasoline feed engines for that matter) would require two crucial elements to start/run: 1) fuel and 2) ignition. A hard starting engine then could be caused by:
1. fuel starvation - there is no fuel in the carbs (or high pressure fuel pump for injected). This could be brought about by the fuel tank's valve which will only allow fuel to flow through if there is a vacuum, the engine is already running. In some models, there is a setting on the fuel valve ON, RES and PRI. On is just that one but requires the vacuum from the intake manifold, RES is for reserve, same as ON except that it the inlet sits lower inside the tank but also requires vacuum. PRI is ON and will allow fuel to flow even without vacuum. Before starting the bike, moved the fuel valve control to PRI if the Yamaha has one. Additional on cold start, putting on CHOKE to about 3/4 up would also enrich the fuel/air mixture making an easier start.
2. Ignition - At every engine start, the battery supplies power to the starter motor and to the ignition system. In some instances when the battery is going weak, the starter motor will gobble up most if not all of the power output of the battery leaving nothing for the ignition system to use. This is especially evident if the bike was used at night with the lights open and the bike did not have a chance to re-charge its battery before switched off. Starting on the next morning would be on a bike with its battery partially depleted. In some instances, the charging system may be at fault if and when it fails to deliver sufficient charging to the battery. Often causes are corroded or loose connection or even a a partially defective voltage regulator.
Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.
Good luck and kind regards.
Thank you for using FixYa.
May 30, 2008 |
Yamaha RX-V661 Receiver