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CB500/550 / Carbs ... again
« on: January 11, 2011, 09:23:41 PM »
I'd just like to say to anyone starting out on refurbing their old SOHC4,
- 'heed the advice of the wise and learned folk in here, and make sure you THOROUGHLY clean your carbs!'
Me, I just dived in and to strip and clean the carbs. I cured the needle valves [http://www.sohc.co.uk/index.php?topic=2681.15]
only to find that (whilst making some improvement) only a marginal improvement on engine running was found.
- tickover was still awful; nothing less than 2500rpm if I was lucky! She was running on a knife-edge, less choke - she stalled, a little more revs raced upto 4kprm.
Over the xmas hols I spent time trawling thro this forum and SOHC.net, that for my CB550K3 has the Keihin PD46 type carbs with press-fit Slow Jets.
- I now realise that on me first strip/cleaning the carbs I had not extracted the press-fit "Slow Jet" ...Doh!
At the time I was afraid of the unknown, & feared I would damage something beyond repair, so they stayed-put.
From my research it became apparent that the Slow jets (or Pilot Jets?) are critical to smooth tickover.
Conclusion: they had to come out.
I decided to drain the petrol, and refil with Redex, and leave to stand for a week.
Then drained the Redex, removed & stripped the carbs.
(Over the past 12 months I've become well practiced at removing & refitting the carbs. First time it must have taken a whole weekend with several scraped knuckles along the way! Now, knowing all the tricks, its down to 40 minutes off, and an hour back on! Easy, when you know how.)
To extract the jets I was concerned about damaging the jets, so I decided to use my heat gun (on mid-setting, not full) to heat up the carb body; I wrapped some emery cloth around the jet, then using pliers, I firmly gripped the jet through the emery cloth, twisting and pulling the jety she came free quite cleanly.
Every Slow Jet had residue deposits all over them! No wonder I had problems.
- the photos illustrate my findings
Well then all back together. Already done valve clearances, point gaps and timing.
Refuelled her, set half choke, ignition on, primed the kick start to the point of compression...
and kicked.....she fired first time.
Ran on part choke for a few minutes, but hey! she then settled down to around 1200 to 1500rpm.
Yo! Result.
& on Sunday, the gods were looking down on me, the sun came out so managed a short spinout. Magic!
(- just a slight flat spot around 4-5krpm will be the next job to sort)
The moral: Research & Persistence is key.
sorry to bore you all , but I just had to share my story.
Andy C
- 'heed the advice of the wise and learned folk in here, and make sure you THOROUGHLY clean your carbs!'
Me, I just dived in and to strip and clean the carbs. I cured the needle valves [http://www.sohc.co.uk/index.php?topic=2681.15]
only to find that (whilst making some improvement) only a marginal improvement on engine running was found.
- tickover was still awful; nothing less than 2500rpm if I was lucky! She was running on a knife-edge, less choke - she stalled, a little more revs raced upto 4kprm.
Over the xmas hols I spent time trawling thro this forum and SOHC.net, that for my CB550K3 has the Keihin PD46 type carbs with press-fit Slow Jets.
- I now realise that on me first strip/cleaning the carbs I had not extracted the press-fit "Slow Jet" ...Doh!
At the time I was afraid of the unknown, & feared I would damage something beyond repair, so they stayed-put.
From my research it became apparent that the Slow jets (or Pilot Jets?) are critical to smooth tickover.
Conclusion: they had to come out.
I decided to drain the petrol, and refil with Redex, and leave to stand for a week.
Then drained the Redex, removed & stripped the carbs.
(Over the past 12 months I've become well practiced at removing & refitting the carbs. First time it must have taken a whole weekend with several scraped knuckles along the way! Now, knowing all the tricks, its down to 40 minutes off, and an hour back on! Easy, when you know how.)
To extract the jets I was concerned about damaging the jets, so I decided to use my heat gun (on mid-setting, not full) to heat up the carb body; I wrapped some emery cloth around the jet, then using pliers, I firmly gripped the jet through the emery cloth, twisting and pulling the jety she came free quite cleanly.
Every Slow Jet had residue deposits all over them! No wonder I had problems.
- the photos illustrate my findings
Well then all back together. Already done valve clearances, point gaps and timing.
Refuelled her, set half choke, ignition on, primed the kick start to the point of compression...
and kicked.....she fired first time.
Ran on part choke for a few minutes, but hey! she then settled down to around 1200 to 1500rpm.
Yo! Result.
& on Sunday, the gods were looking down on me, the sun came out so managed a short spinout. Magic!
(- just a slight flat spot around 4-5krpm will be the next job to sort)
The moral: Research & Persistence is key.
sorry to bore you all , but I just had to share my story.
Andy C
