Post by: allankelly1 on July 21, 2021, 05:55:08 PM
Need some advice pointers please
Got the old girl back on the road
(https://uploads.tapatalk-cdn.com/20210721/35c5e7fcd9ada704997f34fd8f382b1d.jpg)
Before she would not idle only run on two to three cylinders from cold and generally run like a bag of nails unless you nailed the throttle to the stop
But after several carb rebuilds due to leaks etc and still more uneven running (keeping the original brass wear) she is running well to take to work every day
On cold starts and idle she sits there and tick over very smoothly but on pick up from idle it’s a little hesitant till about 2500 and then all seem ok
It’s got a Boyer ignition system coils and the other electronic bits and bobs and this is all timed correctly and done all the other checks and plugs look a little black but not real sooty so I presume she is running a little rich
(https://uploads.tapatalk-cdn.com/20210721/69a6ad2f8b447506d7f2fffd100dfb59.jpg)
So would playing around with the air screws help or is there any other tips or tricks I could try?
Obviously the carbs are in theory 40 + years old and have 35k on them but wondered if I am missing anything obvious I need to check or adjust to improve this flat spot
Thanks in advance to all
Best wishes Al
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Post by: McCabe-Thiele (Ted) on July 21, 2021, 06:38:03 PM
Post by: allankelly1 on July 21, 2021, 06:45:52 PM
Waiting for the single seat to arrive next
More porn
(https://uploads.tapatalk-cdn.com/20210721/613b93eab5e8eca6cdb4fe7f1a938105.jpg)
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Post by: Nurse Julie on July 21, 2021, 06:53:23 PM
Post by: allankelly1 on July 21, 2021, 06:55:53 PM
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Post by: allankelly1 on July 21, 2021, 06:57:30 PM
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Post by: K2-K6 on July 21, 2021, 07:21:18 PM
I presume adjusting mixture screws can muck up your carb sync slightly?
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No it won't affect carb sync at all. There's so many myths about on t'internet that are mostly wrong and lead people to do things which are incorrect.
Carb sync is parity of the throttle slides to give equal air volume to each cylinder, although it affects idle smoothness when maladjusted it's not the final setting of idle smoothness. Once the balance of synchronisation is set that's ok for all engine speeds and remains in parity if the adjustment is properly secured.
The idle air circuits then trim the fuel demand at very small level to bring parity of combustion for each of the cylinders, in effect the "icing on the cake" of tickover refinement. Moving these screws has no impact on throttle slide sync.
In addition, the idle jet size sets it's ultimate flow which is tempered by the air screw adjustment. Going in or out with the screw doesn't change the final full flow of the idle circuit but alters the angle of the slope leading to that final full flow. So you can play with the airscrew with no other detrimental effect, just remember where you've set them , try it out and go again with another adjustment to see the affect as Julie indicates above.
Airscrew out further = weaker to lighten the plug, with of course the opposite if you needed rich.
What plug gap are you running?
Post by: Nurse Julie on July 21, 2021, 07:22:30 PM
I presume adjusting mixture screws can muck up your carb sync slightly?No, it doesn't affect the sync. 2¼ turns is a long way out to be showing soot like that 🤔 What position are the needles in and do you have standard size jets fitted? You're not running pods I take it? Edit... No, I can see the plenum chamber now I've put me specs on 🙄🙄🙄
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Post by: allankelly1 on July 21, 2021, 07:23:53 PM
HiI presume adjusting mixture screws can muck up your carb sync slightly?
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No it won't affect carb sync at all. There's so many myths about on t'internet that are mostly wrong and lead people to do things which are incorrect.
Carb sync is parity of the throttle slides to give equal air volume to each cylinder, although it affects idle smoothness when maladjusted it's not the final setting of idle smoothness. Once the balance of synchronisation is set that's ok for all engine speeds and remains in parity if the adjustment is properly secured.
The idle air circuits then trim the fuel demand at very small level to bring parity of combustion for each of the cylinders, in effect the "icing on the cake" of tickover refinement. Moving these screws has no impact on throttle slide sync.
In addition, the idle jet size sets it's ultimate flow which is tempered by the air screw adjustment. Going in or out with the screw doesn't change the final full flow of the idle circuit but alters the angle of the slope leading to that final full flow. So you can play with the airscrew with no other detrimental effect, just remember where you've set them , try it out and go again with another adjustment to see the affect as Julie indicates above.
Airscrew out further = weaker to lighten the plug, with of course the opposite if you needed rich.
What plug gap are you running?
Plug gap is the Haynes manual 0.7 to 0.8mm
Best wishes Al
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Post by: allankelly1 on July 21, 2021, 07:30:56 PM
Every thing is standard other than exhaustI presume adjusting mixture screws can muck up your carb sync slightly?No, it doesn't affect the sync. 2¼ turns is a long way out to be showing soot like that
Sent from my iPhone using TapatalkWhat position are the needles in and do you have standard size jets fitted? You're not running pods I take it? Edit... No, I can see the plenum chamber now I've put me specs on
When I was rebuilding the carbs jetting was standard but they are the original jets and correct to the Haynes manual 40 pilots and 75 mains so I have no idea if they have been attacked with a piece of wire in the past judging by the rest of the bike when I got it
As for needles not sure what clip position they are’s in
Haynes manual is not very clear on how the slides disassemble so any advise on how to take out and check they are in third groove? should be most helpful as I guess maybe I need to drop the needles one groove maybe?
Also before the rebuild plugs were very sooty and the current plug is much better
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Post by: allankelly1 on July 21, 2021, 08:13:43 PM
From where it was to now is light and day but want just to crisp up the initial throttle response
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Post by: K2-K6 on July 21, 2021, 08:35:30 PM
Or question for all as it looks a tad rich at 2 1/4 turns out do I drop the pilots to 38s?
From where it was to now is light and day but want just to crisp up the initial throttle response
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Yes to this. If you are running a certain size idle jet and you have to wind the airscrew out near to 3 turns, then that indicates it "wants" a smaller jet.
Essentially the airscrew should be somewhere near to 1 1/2 turns out to give a linear response with using a slightly smaller jet to then bring the circuit into competent range.
Equally, if you had to use less than 3/4 turn airscrew just to get it rich enough, that would prompt a larger jet size to approach from the opposite direction.
Just to test and asses, try it with plugs at 0.5 gap. It won't change the jetting at all but may improve the flat spot by more consistent combustion propagation.
Post by: allankelly1 on July 21, 2021, 08:55:41 PM
Hi K2-K6Or question for all as it looks a tad rich at 2 1/4 turns out do I drop the pilots to 38s?
From where it was to now is light and day but want just to crisp up the initial throttle response
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Yes to this. If you are running a certain size idle jet and you have to wind the airscrew out near to 3 turns, then that indicates it "wants" a smaller jet.
Essentially the airscrew should be somewhere near to 1 1/2 turns out to give a linear response with using a slightly smaller jet to then bring the circuit into competent range.
Equally, if you had to use less than 3/4 turn airscrew just to get it rich enough, that would prompt a larger jet size to approach from the opposite direction.
Just to test and asses, try it with plugs at 0.5 gap. It won't change the jetting at all but may improve the flat spot by more consistent combustion propagation.
Ok I will order some 38s and while I am waiting for them I will close up plugs to 0.5 as suggested
To be honest from where I was to get where I am is fantastic as it’s gone from a bag of nails to something that pulls right thru the Rev range other than the initial pick up
If I can just crisp up this that would be the icing on the cake
Will update all as I do small changes
Ride safe all Al
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Post by: allankelly1 on July 21, 2021, 09:04:33 PM
Where is the best place to get the pilots please?
Any recommendations
I have used Allen performance for my rd but customer service was sketchy at best so any other supplies or does anybody on here supply please
Saw this supplier on eBay??
(https://uploads.tapatalk-cdn.com/20210721/795a8bef7e5ce30993a8b46f6116724a.jpg)
TIA
Best wishes Al
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Post by: K2-K6 on July 21, 2021, 10:24:26 PM
Sounds like you're quite close in how it's running, certainly good when you get decent progress in sorting something out like this and with a little fine tuning left to get there.
Just a quick thought though, have you a good condition air filter installed as they can be fairly sensitive to anomalies there.
Post by: allankelly1 on July 21, 2021, 10:46:09 PM
Best wishes Al
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Post by: allankelly1 on July 22, 2021, 05:21:56 PM
Ok wound out all four air screws 2 1/2 turns and center electrode are a bit lighter and browner than the plug in the picture if that make sense
Also bit the bullet and got some 38s on order from Allen’s performance so I can down down size from 40 to 38 to lean the mixture slightly
I guess when I fit the jets should set screw around. 1 1/2 turns out to avoid a possible lean mixture and do another plug chop
Also notice on a warm day she is almost happy to do a cold start without choke so I presume that also points to a too rich idle jet
Fingers crossed this sorts things
Catch up soon
Best wishes Al
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Post by: K2-K6 on July 22, 2021, 10:47:28 PM
There's a very good routine for setting and evaluation of idle airscrew adjustment in Honda's own manuals from this era (often overlooked or ignored) that will let you see what you've got.
Warm engine and set tickover on main adjuster to give smooth running (after setting airscrew to 1 1/2 out) then on one cylinder at a time wind the screw out while running until it reaches a peak rpm, any more lean it should start to falter on that cylinder and confirms you're too far. Then from that peak rpm setting, wind the screw in again very slowly to get a 100rpm drop, at which point you've put just enough fuel back into the cylinder to run it slightly on the rich side of true combustion equivalent.
Then adjust the overall tickover again with your main tickover speed facility and start on the next cylinder, repeat until finished and that will set the mixture competently.
As Julie indicated, you can end up with slightly different settings from carb to carb , but this is the true setting calibrated for each of your individual cylinders as it exists then.
If you want to record where each one ends up, that's the baseline tailored calibration for you engine.
Post by: allankelly1 on July 24, 2021, 05:33:31 PM
Just a quick one to say thanks for all the advice
Got jets last night from AP and as it’s wet out spent some time in the garage and now all fitted with 38 idle jets and I have set the air screws 1 1/2 turns out.
Interesting with 2 1/2 turns out on all carbs and running the original 40 idle jets after a run out last night to a bike meet plugs now look like this for cylinders 2 and 3 checked today (checked 1 and 4 originally as plugs easy to get too
(https://uploads.tapatalk-cdn.com/20210724/0b4c642718b7991b48d0c9288b3dab39.jpg)
(https://uploads.tapatalk-cdn.com/20210724/5f0d0caf4255bf1b9f06d02842870eba.jpg)
So a nice clean central electrode with some soot on the earth electrode so cannot it be too far away from idea set up and hopefully going slightly smaller for the idle jet will allow the bike to run with air screws out by about 1 1/2 turns and improve / crisp up the initial throttle response
Also now set the plug gaps at 0.5mm as you suggested
Raining hard now so will call it a day but looking forward to testing the new set up
Have a good one
Best wishes Al
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Post by: Laverdaroo on August 03, 2021, 03:01:46 PM
Post by: allankelly1 on August 03, 2021, 03:02:36 PM
Best wishes Al
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Post by: Laverdaroo on August 04, 2021, 11:52:01 PM
Post by: allankelly1 on September 07, 2021, 01:57:13 PM
Quick update
Took bike to work today and plugs look a bit better cleaner with less black soot generally
(https://uploads.tapatalk-cdn.com/20210907/142a10331cc3ede65b036e3d727c81e8.jpg)
(https://uploads.tapatalk-cdn.com/20210907/494235925b7bcd4626d9232758b7f25b.jpg)
Pilots now 38 air screw out 1 1/2 turns and plug gap is 0.8mm
Better pick up and a smooth idle too
Happy days
Best wishes Al
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