This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.
Messages - K2-K6
1
« on: August 15, 2026, 11:26:43 AM »
Thanks! I was never good at math anyway!!! 
You were right though, in a way. Old car type multifunction meters for dwell, tacho, voltage etc you'd need to set to 8 cylinder to read from these engine in many cases. These Honda are effectively two twin cylinder engine "flying" in close company  two 360 degree twins 1&4 2&3.
2
« on: August 15, 2026, 10:45:02 AM »
Good info guys, thanks!! I'll check out the carbs AND the actual RPM!!
Am I correct that reading "frequency" across one set of points would indicate 1/2 of engine RPM? IOW, double that reading would be actual engine RPM?
It should be direct as the points cam lobe is not geared to crankshaft (as in a car distributor @ 1/2 speed, and needing correction) in these engine either of the points directly represents actual crankshaft movement.
3
« on: August 15, 2026, 09:04:16 AM »
The technical view in respect of this should give reason why its problematic.
The combustion event is a "burn" over specific time period (not explosion) which largely remains the same for most engine conditions.
That should be timed to reach peak expansion at 12 degree after top dead centre, which gives most advantageous push on the piston and conrod in applying the highest force to crankshaft, hence most torque developed.
The static timing is set to give this series of events at idle rpm.
As crankshaft speeds up, then it moves more degrees as rpm accumulate...... in the time frame of that combustion is "fixed" in it's own time frame ..... meaning that the crankshaft gets further and further (15, 20, 25 ish) past the ideal 12 ATDC figure, essentially wasting the combustion energy ultimately to give less torque.
The ignition advance curve has to "chase" that moving target if its not to lose its potency, it should produce it's most available power by trying to hold onto that ideal 12 degree target. 0
If the advance is delayed, as these springs, when shortened will do, then torque won't rise as it should. Not a flat spot as we ordinarily get (lean running, leading to missing combustion) but holding torque down/suppressed until the ignition is eventually allowed to get where it should have been.
Then it should do as described in lost thread, give a two stroke type step up in output and take off into higher torque output.
Notably, the CR 750 ignition deleted the ignition retard unit for reliability , and because there's not need to run it below about 2,500 rpm. It's just a straight 36 degree static setting as I understand it. I can't see logical reason in suppression of early ignition advance as this spring cutting targets.
It needs to get up and advanced as soon as practically possible in generating the power expected from this engine.
4
« on: August 15, 2026, 08:43:42 AM »
Look quite stretched!
*before cleaning!
Definitely, and likely to cause a problem set like that. Honestly feel you're chasing your tail with other consideration if this is not resolved.
5
« on: August 14, 2026, 07:31:20 PM »
Nice work John. What a cracking little bike it is. They are quite quick too, power and light weight makes a nifty bike. A friend had a gold one many years ago, this one more Jimmy Hendrix Purple
6
« on: August 14, 2026, 07:28:04 PM »
They're not that difficult to make, and can be done with minimal tools.
You'd need piano wire (basically spring steel) in same gauge as original.
Bend a right angle into one end, enough that you can form a loop like the original (just leave straight for now) clamp that tail along a small bolt that is sized to go inside the original spring coil bore ..... now wind the other part of the wire around the bolt to form the coils. Count how many you need to make factory spec.
At the end of coils, form another tail at right angle to coils. Then you can bend both tails into the spring ends needed to attach.
Finally, heat to cherry red (just a gas ring, camping stove type will do) and drop into cold water, this will harden the spring steel to make it ..... spring.
Don't stretch it, as it now needs tempering to remove brittleness. Heat again to cherry red and just let cool without intervention. Leave for a day, then temper again .... should now be usable.
7
« on: August 14, 2026, 06:52:10 PM »
No, not managed to sort the springs yet, cant find any, would giving them a slight stretch help?
Likely yes, it would help to stretch them as it should be most prominent in this range if they're too tight.
8
« on: August 14, 2026, 06:50:05 PM »
Worth noting that the tacho I am currently restoring was reading 500 high at 5000 rpm so if you have one like that it could easily screw things up.
I used to have a timing trobe that could measure rpm but haven't seen one like that recently.
Regards
Dave
Some of the relatively cheap DVM have a frequency read, across one set of points will count crankshaft revolution on these.
9
« on: August 14, 2026, 06:22:24 PM »
Did you get the advance springs sorted out (thought it was in the "infamous" thread) yet.
Some crude analysis may help initially. Go to 2 turns out airscrew and judge if better or worse than now.
11
« on: August 14, 2026, 08:34:54 AM »
To get a complete and instant stop, that suggests power supply as reasonable suspect. Do the lights etc go out too when it stops.
Obvious things like security and tightness of battery connection along with other terminals generally around the bike. Sometimes something may have been victim to general vibration.
I had similar recently on my 80s Honda, with ignition barrel position being sensitive to any slight misalignment from exactly centre. Felt like it was "hanging " slightly on detent positioning. I used a product I've got from Land Rover to spray into the lock barrel via key slot, which was very effective in making it wok smoothly with more free engagement of detent hold.
The product is something similar to a very thin chain lube, some light grease, ptfe, alcohol to propell into the nooks and crannies, usual type of mix that should permeate and then stay put after application.
The type of contact blocks on the back of these ignition switch can also get a bit gummed over time, that to provide patchy inconsistent contact too.
12
« on: August 13, 2026, 04:48:53 PM »
Good work Ted, and decent progress. At least you're not getting cold in this weather currently
13
« on: August 13, 2026, 02:11:16 PM »
With the above detail and understanding, we can use this in a real case to test the data in finding out whether there was false analysis.
Our Dutch co-respondent wrote the technical details of how he made his projection in regard to this topic.
Stating that his bike would not respond correctly in the phase that starts to open the throttle, usually meaning a flatspot from lean running.
He identified, in his solus example, that the airscrew needed to be turned inward during closed throttle idle in eventually bringing the co value from typical of 1% up to the range of 3 ~4% from my recall. This to give correct response to opening the throttle.
If we look at this from the Honda's manual perspective and setting routine, it shows us that the engine needs more fuelling as throttle opens, this is correct. But the method of achieving this he's used is wrong.
What should happen is to give the extra fuel needed by changing the size of the idle jet to a size larger. Then reset the airscrew to give the correct idle mixture metering with throttle closed.
The "fault" he's installed through his action is that he's accepted the error in total peak flow of the idle jet, and then incorrectly used the screw to compensate, which is not its task.
The result is now TWO mixture errors. Too low peak idle jet flow, too high off throttle mixture enrichment.
What this does is run excessive fuel through the combustion chamber (co target of 3-4% gives something in tbe oder of 12.8~13.1:1 A/F ratio) which is not needed off load, furthermore it's not burnt. This excessive fuelling will go toward washing lubrication from cylinder bore and help in promoting internal exhaust corrosion effects. It's effectively running it on partial choke continuously.
Changing the size of idle jet first will give the low throttle opening response, along with the higher end of the initial phase leading up to the main jet supply coming on stream.
Airscrew can now set, correctly, the closed throttle mixture, independently, to it's optimum point. There's no need to compromise.
There's further effect too. Notably he's put on forum before about not being able to get a stable low rpm idle with the setup he used. Thats no surprise as running around 12.9:1 ratio at idle will always need more throttle opening to keep some semblance of equilibrium on what is essentially part choked running condition. This resulting in elevated idle rpm.
He doesn't need a video (as demanded) to demonstrate the Honda method, his own evidence in data and setup given on this forum is absolutely proof his assessment is wrong.
That's why his stance should not be taken by us as any way to set up these carburettor for the forum.
I did suggest he came with more conciliatory outlook in tbe deleted thread, that was clearly refused. We could have discussed this at more length to appreciate properly how this system is designed and works, before now.
But he chose to " sanitize" us, the great unwashed on here. He clearly hasn't understood which part of the equipment relates to which problem is experienced.
14
« on: August 13, 2026, 10:57:41 AM »
There's very good advice in those Honda manuals, but takes some additional understanding to fully appreciate certain aspects of the written words.
I refer to them so others can appreciate what was explained by the manufacturer when they made them, specifically to not claim them as my own thoughts, but give full credit to their understanding and foresight when they were published.
That information was though never intended to go as far as I feel we can delve into them now.
My understanding now, and this changes as variously problems bring up different error and force me into reappraisal of my own experience.
I noted on the deleted thread that 3 key parts exist in how the idle circuit is made to meter fuel for different load scenarios.
#1 The idle jet size. This gives the total/maximum flow of fuel the circuit is capable of delivering. That is set for peak demand under acceleration load, too little here will flat spot (too lean) before the carburettor moves onto main and needle metering.
#2 The aiscrew and it's position when set through adjustment. This is SOLELY there to give reduction of the potential fuel delivery from #1 above. Specifically, to set the exact air fuel ratio at closed throttle position, that to give a co reading of 1.0% which should equal 14.2:1 air fuel ratio in combustion. It has absolutely no load on the motor, only internal friction , heat losses, alternator etc.
More over, it holds the key to stable idle which these were originally renowned for.
It has no function in compensation for any other aspect.
Between these two, running concurrent/concentric whatever way you want to describe it, they can be set completely separately by change of jet and adjustment of screw. This is vital to understand in how to specify them.
#3 This is the "hidden" function that links the two above (you'll have to go a long way to find description in general working instructions) but gives the translation from idle mixture flow in "ramping" up delivery to ultimate flow of idle jet size in response to throttle slide being opened. In effect, the sizing of the components along with entry and exit ports, gives a airfuel proportioning function, and that without moving parts.
Overall it allows separately the setting of peak, floor and transition rate of this circuit by understanding how to set them and knowing which part of rpm response is giving a problem in running conditions.
The really clever part of Honda's instruction is that by moving the airscrew it will show you if there's response and by the range the screw us moved, it tell you tge existence of faults by that "measurement" if you know what to look for.
If it doesn't change anything, that would indicate more fundamental fault ultimately to direct the attention toward finding what is wrong to cause that failure.
In essence, this is like an engine check light on a modern vehicle. If that screw shows out of range when trying to get response, it shows the low speed metering or something else (ignition? or leaking intake) is present.
|
Show Posts