SOHC.co.uk Forums > CB350/400
400 Four detonation
Rudi45:
Thanks Julie,
in 1976 i was 31 :'(
Mr. Google is my friend ::)
Rudi
Johnwebley:
welcome Rudi,enjoy the fun world of sohc.
back on subject,my 500 had similar issue about 16K miles ago,the piston on the RH outer was chewed,and rings gone,the one next to it,has a broken ring only,piston OK,other two were ok,.
it was put down to over revving when cold ,maybe detonation,no damage to bores,just one new std piston and 4 sets of rings
PS,I have emailed Boyer explaining the discussion and asking for the various advance curves and spark duration.
hopefully they will be interested
Johnwebley:
brief reply from Boyer,basically saying nothing,I am guessing commercial secrets ,but they did refer to the "wasted" spark,
not sure how that helps? or not .
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Re: Advance curve
B
Boyer Bransden Electronics Ltd <help@boyerbransden.com>
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Today, 15:30
You
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Re: Advance curve
Boyer Bransden Electronics Ltd <help@boyerbransden.com>
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Today, 15:30
You
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Thank you for your enquiry, sorry we don't publish this information as we have a few secrets that do give us an edge. You may note that we fire all cylinders every 180deg, this requies a little trickery, but it works.
Regards Tech Dept.
Sent from Samsung tablet
K2-K6:
Thankyou for asking them John, I guess they're in a position that's awkward from a commercial point of view.
No answer either way suggest they don't have one though. I worked with someone who always got hold of a manager when they came out on the factory floor and cornered them with awkward questions. If they didn't give an answer, her reply was "we'll just make something up" which generally made them nervous.
To be absolutely fair, it's a carburettor initiated problem as I view it and asking an ignition system to cope with that error is unlikely to happen in its entirety. The question for any aftermarket supplier is, does your system with its change in specs, match / shorten / lengthen the spark duration?
It's a very valid point if we believe it could lead to this type of engine damage.
Hondaman has specifically built his switching to match the Honda original, that seems to be the most competent answer I've so far seen.
Their (Boyer) firing at 180degree intervals appears related to emissions, I can't see the relevance in this context either John.
In common with Hondaman, (and by using the 400 advance curve for all the fours) they delay the max advance for the 500 and 750 a little, so that may assist the larger capacity examples in this area. Doesn't make make any difference to our little collection of damaged 400s though.
On current engines with knock sensors, when detonation occurs then the first reaction is to retard the ignition until it stops. It's this that limits performance of high output motors when they are run on lower octane fuel. Keeping them from damaging themselves reduces output.
I cover some more things in next post.
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