Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: MrDavo on April 25, 2016, 12:11:15 PM
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I have just fixed a horrible misfire that has been driving me nuts, more by accident than expertise.
When I first bought the bike, I had noticed occasional spitting from number 2 exhaust, and the first ride was very disappointing as I was riding a very flat Honda 3! Suddenly a spit, a bang and all was well.
A couple of weeks ago, out for a ride in the country I suddenly had a bad misfire, but it went as soon as it came. I did think at the time that it can't be anything good, and would inevitably come back to haunt me.
Last week I changed the pilot jets for new ones, as a couple were partly restricted by crud, and the finest wire on my carb cleaning set wouldn't go through. To my disappointment when I put everything back together the result was a bike on 3.5 cylinders, with occasional forays to 3 or 4 pots. I spent ages b*ggering about with the carbs, to no avail, but did convince myself that number 3 pot was the culprit. I changed that plug, burned my hand on the exhaust (then put a glove on) and all seemed Ok for a few miles. Then back to the misfire! :(
Saturday, I pulled the plug cap from number 3, resistance seemed Ok, so I unscrewed number 2 cap to compare it to. Both were the original 'full metal jacket' caps, the outer two were already the plastic type when I got the bike. Got my multimeter out, er, shouldn't number 2 cap at least conduct electricity?
Down the local bikeshop, where after a hunt they found me a new NGK straight plugcap, cost £2.84. Went home, fitted it and started the bike. A huge bang as unburned fuel in the exhaust lit, if you have rusty or weak silencers I guess this could do damage. But the misfire is gone and a lesson learned.
I have ordered a new cap for number 3 as well, Ash you can have the metal one if it floats your 'originality' boat.
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Well done , a cheap and simple fix to a irritating problem
pete