SOHC.co.uk Forums > CB500/550
Misfire and running on 2 cylinders when hot?
matthewmosse:
Ignition related I am sure from the pair of cylinders going like that - assuming the filters have had a similar life ( possible for outside pair to get more weather , maybe washing out any oil etc, depends on the pod filter type. I have had issues in the past with condensors malfunctioning when hot ( belive it was that, I described the symptoms to a collage mechanics tutor who recommended chainging the condensors and this seemed to resolve it.
mike the bike:
I agree. I rode home 70 miles on my 400four going like a 200two. I was just a dodgy capacitor.
Hudson.:
Thanks for the input guys!
--- Quote from: hairygit on September 18, 2015, 08:52:41 PM ---Ignition fault would be my first thought, so check the condition and security of the points, the condensors and all the wiring leading from them. Some Honda fours, 550's I think were prone to the yellow and blue wires working loose where the snap connectors join in the rubber shield near the back brake pedal.
--- End quote ---
Points look to be in nice shape, no pitting or grime etc. All the connections are secure and appear in good nick too, i checked at the connections you mentioned up behind the brake/frame and theyre solid and clean.
--- Quote from: Bryanj on September 18, 2015, 09:09:30 PM ---If its a 78K with PD carb and starts without choke then the carbs just aint set right
--- End quote ---
Thats what i thought! I have the screws set 2.5 turns out, too much? Mains are 110, stock idle jet, stock needle position, new clean pods and an open exhaust.
--- Quote from: Johnwebley on September 18, 2015, 09:17:43 PM ---check the resistor plug caps,
they normally have 5k resistance,but over time,when hot ,they fail,
I had one go 10 days ago,new cap,smooth as silk again ( I hope,well it run sweetly now)
does anyone understand electricity and resistance?
with electronic ignition,I get a FAT BIG spark,so I run 33thou plug gap,how does 5K resistor plug caps affect them,would the bigger gap
cause the cap to fail sooner ??
--- End quote ---
Checked the caps and they're all 5k ohm which appears to be right.
--- Quote from: mike the bike on September 18, 2015, 09:29:04 PM ---I does sound like an ignition problem. There's two separate, independent ignition systems, one firing 1 and 4 and the other firing 2 and 3.
Try to determine which by feeling the temperatures of the header pipes.
What ignition set up have you got; is it the original points or have you gone electronic?
--- End quote ---
Im pretty sure after the other evenings ride it was 2 and 3 that were down, as when i pulled the plugs they were really sooted up in comparison to 1 and 4. This was making me think ignition/coil/points etc too.
It's the stock points system, but could possibly be made up of after market non-genuine bits.
--- Quote from: matthewmosse on September 18, 2015, 09:43:16 PM ---Ignition related I am sure from the pair of cylinders going like that - assuming the filters have had a similar life ( possible for outside pair to get more weather , maybe washing out any oil etc, depends on the pod filter type. I have had issues in the past with condensors malfunctioning when hot ( belive it was that, I described the symptoms to a collage mechanics tutor who recommended chainging the condensors and this seemed to resolve it.
--- End quote ---
The filters are brand new UNI pods which i know a fair amount of people use on these bikes without issues, the condensors definitely dont look new on this bike so could potentially be an issue.
--- Quote from: mike the bike on September 18, 2015, 10:46:16 PM ---I agree. I rode home 70 miles on my 400four going like a 200two. I was just a dodgy capacitor.
--- End quote ---
70 miles is impressive! haha
Well, this morning i checked the plug caps and snipped the leads back a couple of mm's even though they looked good. I went for a 1 hour ride with a spare plug in my pocket, so if i started running on two i could check to find where the loss of spark was.
I suppose its a good thing that the bike ran faultless the whole time?! I tried a few WOT pulls aswell and it was fine. Although the clutch cable snapped and i had to ride back through the gears without stopping, good fun!
I rode it to its MOT on wednesday night and it was pouring with rain, a friend of mine said he had a few issues in the wet with cylinders 2 + 3 going down due to being soaked from the front wheel with no mudguard (i dont have a front mudguard either). This sounds possible, but is kind of weird that when i rode it the next day in the dry it was fine up until it got hot?
Heres the ignition
Thanks again!
Rich
mike the bike:
Make sure you seal where the HT leads exit the coils to keep the rain out. The best stuff to use is "STICKS LIKE SH#T". It's more permanent that silicon sealant.
Spitfire:
Yes that's where the rain gets in, in the olden days I used to seal where the HT leads go into the coils with Araldite, nowadays there are lots of other stuff available
Cheers
Dennis
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