Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: Neilp on December 07, 2020, 10:23:41 PM
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Hi
Just taken delivery of a recently restored CB550, they work on it looks great. I cant fault the bike in anyway except Cylinder 1 does not seem to be running as hot as the other 3?
Bike starts fine, with it being cold weather today, shortly after starting steam comes out of 3 of the 4 pipes. Headers on 2 to 4 get hot really quickly as you would expect, Number 1 gets warm but you can keep your hand on the header.
With it being recently restored (No history on the resto, however it has been a engine out, frame up job, with new nuts and bolts and engine paint, so not a blast with pressure washer quickie) I dont want to start pulling things off etc.
So fitted new plug.
Getting a healthy spark when you take the cap off the plug when running you can hear it jumping from cap to plug.
however No difference in RPM when you do this.
Bear in mind its been years since I worked on a bike (V8 and V12 fuel injection has been my staple diet for 10 years) so not sure if its a carb fault? they have been ultrasonically cleaned apparantly, air leak?
Engine sounds sweet??
When you build the revs from idle to 3K slowly no hunting or missing?
when revved quickly idle to 3kplus sometimes a pop from the exhaust.
Although not road tested due to weather, seems smooth up and down the garden.
I think I have covered it all
Any ideas ?
Thanks for reading
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I had vapour coming out of 1 and 4 which stopped after I replaced coils and caps. I think 3 lead was making a poor connection with the cap. Either way using DSS coils, NGK resistor caps, and non-resistor plugs sorted it. The DSS coils seemed good value to me.
You could try checking resistance of the coil leads, some useful tips on YouTube.
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Clearly not firing fully on no 1 if you can hold your hand on the header - I'd start at the basics - change plug, then plug cap then test values on the coil (from memory, HT to HT on same coil should be 14.5 ohms I think - Ash will be along to confirm shortly) - if they are original coils the leads will be 40+ years old and may have failed on no 1. I had an intermitent fault on a plug cap recently. Then it onto carbs!
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New plug, remove the plug cap and trim a small amount from the lead then replace cap and try again, possibly a dirty pilot jet
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I had exactly the same. Mine was a blocked pilot jet.
I'm down the road from you if you ever think 2 heads would be better than 1.
Got a carb vac guage if you wanted to balance carbs. Happy to help.
Paul
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As above , pilot jets are very fine and easily compromised on these.
Turning the idle mixture adjustment screw for that carb while it's ticking over may give you more to go on as it should change the running of that cylinder. If no response, then you may have a cleaning job to do.
A fair number of times it's been experienced on forum that ultrasonic cleaning hasn't fully alleviated blocked idle circuits.
Sounds like ignition is at least delivering to that lead from your description. Number 4 is of coure also on that coil, indicating that the points etc are functioning well.
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Yes one of my caps practically fell off the duff lead. I couldn’t trim any off as too little left so I’d try that first if you’ve already done the plug.
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Hi
Thanks for the great tips
I will start to investigate all of the above.
thanks for the offer Paul, will be in touch soo
Thanks again :)