Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: Clem2112 on February 17, 2014, 11:29:43 PM
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Anyone else re-wired the power supply to the coils using a relay?
This appears to be a "popular" fix on Japanese bikes with aged wiring.
I did this mod to mine because the voltage at the coil fed from the kill switch was over 1.5 volts down despite new RH switchgear, cleaned/tightened connections etc.
I thought the lowerd voltage must be making cold starting more difficult.
Bike also has Dyna S ignition.
Not much work - where to put the new relay was the challenge....under LH coil bracket.
Took a feed from the starter relay post to an inline fuse then to a 30A relay where the black/white wire is now used to switch the relay on and off.
The bike started much more easily than it ever had before.
Test ride will be on the next dry day!
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Will probably do this to clem.it sounds good.
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.... sounds a good plan. Outta interest will check the voltage @ my coils too, & may modify my K2. Cunning that the black / white wire is still used to maintain the integrity of the kill switch.
Thanks for the tip...
Another 'aid' to starting I've read about is isolating the gen field coil during start, as this will be drawing a couple of amps whilst cranking. In this case I guess the oil pressure light (out) could be the relay trigger to re-supply power to the winding.
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The starter relay's 'battery/rectifier/main fuse' threaded post is used as the supply to the new relay (using the relay's 30 connector) since it is always at full battery potential ....the other post is only live when the starter button is pressed. The black wire is always compromised as it is fed through the main switch and multiple connectors, splits hence the voltage drop :(
The new relay only supplies power (using the 87 connection) to the coils when it is energised by the ignition (black/white wire to 86 and 85 is earthed) being switched on so there is no battery drain with Ign off. :)
See diagram using the link below
http://www.wgcarbs.com/index.php/using-joomla/extensions/components/content-component/article-categories/89-coils
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Thank you CLEM!! You are great!!!
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Ah... cheers Clem, makes sense now. A pic is indeed worth 1000 words, have deleted the duff para from my previous post.
Simon
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I meant to add that I also have an existing mod to the charging circuit.... Another relay which uses the black sense wire as a trigger to take power directly from the starter relay post. Again, through an inline fuse .
This mod was one of a quite a few electrical fixes for wiring issues that appeared in the much-missed CB400F restoration site - forgotten the name?- a chap had created this useful guide from his own restoration experiences on a 400/4..... Where is he now? :'(