Re: tach and speedodmeter?
It's helpful if you indicate which engine model you are having problems with-to make sure you get the correct answer. The tach gets it's signal from the rectifier or the rectifier/regulator-depending on which engine you have. The tach signal wire is usually not fused, but the hot to the tach could be. The tach counts pulses that the stator creates to recharge the starting battery. If you have no tach signal, it is possible that the engine is not recharging the starting battery. You may be able to check the charging by observing your voltmeter while you run the engine. Possible that your speedometer is bad. It it supposed to work off of air pressure. If you ever get water in the bladder of the speedo gauge itself and it freezes (over the winter) it is likely that the bladder arm in the gauge will forever get out of adjustment. The adjustment that goes out usually starts at the zero reading (in your case, at 25 mph.) It will continue to provide a reading, but will always be off by some amount, perhaps that 25 mph. Look to replace the gauge.
