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SOHC.co.uk Forums => Other Bikes => Topic started by: fishermanferg on July 30, 2015, 04:35:30 PM

Title: rpm drop
Post by: fishermanferg on July 30, 2015, 04:35:30 PM

as I am new here don't know if this topic has been discussed before I have fitted very low powerv led lights to be seen better I have four at 5 watt each when I switch them on and my dipped beam the revs driop a little if I switch them off the revs go back up again my main headlight bulb is 60/55 I think its called an h4

Title: Re: rpm drop
Post by: SteveD CB500K0 on July 30, 2015, 04:43:55 PM

Is this on your CM400?

Title: Re: rpm drop
Post by: fishermanferg on July 31, 2015, 09:26:35 AM

it is indeed on my cm400

Title: Re: rpm drop
Post by: Lobo on July 31, 2015, 02:19:04 PM

Fishermanferg..... unsure what the question is.

However, what you describe is perfectly normal, if you switch your lights on the energy has to come from somewhere ... and very basically it's the engine. (ie the alternator is 'loaded up' & this in turn saps power / rpm from the engine.)

Your car is no different, switch on the lights + heated rear window & likely the same result.

If your CM 400 Alternator is the same output as the 400F (156 W) you're running it close to its limit .. eg (55+ 4x5)w headlamps + 5w tail + 20w alternator field + 25w ignition = 125 watts
Brake light 21w and / or indicators 42w will soon exceed the alternator output - but they are only transient loads & will be absorbed (temporarily) by the battery. Point is, if your alternator is  rated 156W then don't add in too many extra loads.

Lobo.

Title: Re: rpm drop
Post by: Chris400F on July 31, 2015, 02:59:31 PM

This guy sells LED Daytime Running Lights that consume only 1.5W each. Might be worth considering if power consumption is an issue.
http://www.norbsa02.freeuk.com/GoffyDaytimeLights.htm
He also sells various other LED bulb replacements if you want to replace standard bulbs with LED equivalents.