Honda-SOHC

SOHC.co.uk Forums => CB500/550 => Topic started by: paulbaker1954 on April 18, 2016, 02:28:46 PM

Title: Ignition Timing and Unleaded
Post by: paulbaker1954 on April 18, 2016, 02:28:46 PM

I am assuming that the timing marks on the '71 K0 500 were set for leaded fuel. Does anyone recommend advancing the timing any on these engines to account for the slower burn rate of unleaded vs leaded fuel.

If so any tried and tested level of advance?

Title: Re: Ignition Timing and Unleaded
Post by: florence on April 18, 2016, 02:38:19 PM

My understanding is that these engines were designed for unleaded fuel in the first place.

Title: Re: Ignition Timing and Unleaded
Post by: Chris400F on April 18, 2016, 03:48:31 PM

Here's a page from what purports to be the Owner's Manual for a 1972 CB500.
Don't know if it helps or not ....
Normal unleaded nowadays is 95 octane.

Title: Re: Ignition Timing and Unleaded
Post by: deltarider on April 18, 2016, 04:29:17 PM

Just experiment. Many 500/550s have better driveability with a tad more advance. At full advance I have mine just right of the double F marks. I guess mine has about 33 degrees advance.

Title: Re: Ignition Timing and Unleaded
Post by: florence on April 19, 2016, 10:08:10 AM

Be very careful though, I know someone who advanced his ignition timing too much and ended up burning a neat little hole in one of his pistons.