Author Topic: Ignition Analysis: Honda's coils  (Read 44388 times)

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eldar

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Re: Ignition Analysis: Honda's coils
« Reply #25 on: February 15, 2008, 02:31:42 pm »
Glad you love the movie but you must remember it was actually made in Minnesota, not fargo and only old-timers,such as yourself!, talk like that! ;D

Offline Terry in Australia

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Re: Ignition Analysis: Honda's coils
« Reply #26 on: February 15, 2008, 02:40:48 pm »
Is that really true, or are you just hiding your Fargo shame? ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

eldar

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Re: Ignition Analysis: Honda's coils
« Reply #27 on: February 16, 2008, 01:57:13 pm »
nope all true. Not filmed here other than maybe a couple small scenes.

Offline Terry in Australia

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Re: Ignition Analysis: Honda's coils
« Reply #28 on: February 16, 2008, 03:52:18 pm »
Have you got a woodchipper behind your house Eldy? ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

eldar

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Re: Ignition Analysis: Honda's coils
« Reply #29 on: February 16, 2008, 10:15:15 pm »
Nope but I do have a large field! :D

Offline w1sa

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Re: Ignition Analysis: Honda's coils
« Reply #30 on: February 22, 2008, 09:07:35 pm »
Hi Guys,

I'm a new member and I'm posting (again) to try and establish a successful connection with you on this topic.

Offline w1sa

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Re: Ignition Analysis: Honda's coils
« Reply #31 on: February 22, 2008, 11:41:54 pm »
Hello again,
It seems I can access.

I've been struggling with the question of ignition for my Kawasaki 650  (circa 1970). The original ignition is twin points/coils using  .3mf capacitors.
The engine is a 360 deg twin and is equipped with the OEM dc generator feeding a 7ah battery. (not the most generous of systems). Without a granted prayer, that the ignition will not only perform, but hold up indefinitely when re-installed, Ive gotta upgrade where possible.

But I'm limited within the following constraints:
Generator Output   - 100w (Upgrade not really feasible)
Battery                 - No real sense increasing capacity if you cant feed it
Points                   - OEM/New. Hard to find and expensive locally
Capacitors             - Cant find new/nos replacements, but could be
                             worked around using other values wired in parallel?
Coils  5/10000?      - OEM new/nos not available
Electronic ignition   - No aftermarket ignition found that doesn't require serious re-engineering of the points/distributor housing/base plate / shaft/rotor

The ignition fires once every 7.5ms @ 8000rpm (each coil firing once every 15ms) which appears more than adequate time to saturate and drain the coil.

I'm thinking of retaining the twin points and, utilise a transistorised coil control unit to fire a single dual tower coil. I want to achieve better ignition on less current draw (also gotta improve on 35w high beam).

I've seen it suggested that dual points can be joined to the single wire going into (say) a Dynatek DBR1 and the units single wire to the coil will fire a dual output 3ohm coil. If this is true I could use such a system (accepting the wasted spark). My calculator says that more than 240 crank degrees or better than 5ms might be available to saturate the single coil for each firing every 7.5ms @8000rpm. The rest of the time it would have twice the dwell time available. So, if I could control the dwell to commence at (say) 1/3 of the last firing time interval, there could be a reduction in overall draw. Even better if the dwell were to commence at a point (say)5ms before next firing at any given rpm.
I realise these are probably the dreams that computers were born of.

The reason I mention a single 3ohm dual output coil is not cost (sold as pairs). I can save space which can be used for the control unit etc. and, without any dwell control it appears the current draw would be lower than using two 5ohm coils while possibly providing more spark energy at the plugs.

Being the lifetime novice that I am, I still struggle somewhat with coil performance. eg How does Hondaman's real coil performance measurements relate to claimed voltage levels viz measured CBX coil 8kv against 30,000 volt claims for aftermarket coils. Or, the coils I have against either of these or a Dyna 5/17000dual output or 5/14400 singles

So, in considering a transistorised application as mentioned above;

Would a transistorised unit successfully fire a single dual output coil with both sets of points wired in parallel (ie together) to the unit. Wouldn't the continuous but variable ground through the points interfere with the unit's coil triggering?

Assuming the 3ohm dual fire coil application was workable, what comparative performance would you expect at the spark plug (as opposed to twin 5ohm coils)?

Am I correct in assuming an overall reduction in current draw with an increase in spark voltage using a single 3ohm dual output coil?

Does the Dynatek DBR1 or the Hondaman ignition incorporate any dwell control beyond the points setting?

Would the Hondaman ignition be suitable for my application and could it be made available?

Hope you can help......................................Geof

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Re: Ignition Analysis: Honda's coils
« Reply #32 on: February 23, 2008, 09:23:26 am »
Hello again,
It seems I can access.

I've been struggling with the question of ignition for my Kawasaki 650  (circa 1970). The original ignition is twin points/coils using  .3mf capacitors.
The engine is a 360 deg twin and is equipped with the OEM dc generator feeding a 7ah battery. (not the most generous of systems). Without a granted prayer, that the ignition will not only perform, but hold up indefinitely when re-installed, Ive gotta upgrade where possible.

But I'm limited within the following constraints:
Generator Output   - 100w (Upgrade not really feasible)
Battery                 - No real sense increasing capacity if you cant feed it
Points                   - OEM/New. Hard to find and expensive locally
Capacitors             - Cant find new/nos replacements, but could be
                             worked around using other values wired in parallel?
Coils  5/10000?      - OEM new/nos not available
Electronic ignition   - No aftermarket ignition found that doesn't require serious re-engineering of the points/distributor housing/base plate / shaft/rotor

The ignition fires once every 7.5ms @ 8000rpm (each coil firing once every 15ms) which appears more than adequate time to saturate and drain the coil.

I'm thinking of retaining the twin points and, utilise a transistorised coil control unit to fire a single dual tower coil. I want to achieve better ignition on less current draw (also gotta improve on 35w high beam).

I've seen it suggested that dual points can be joined to the single wire going into (say) a Dynatek DBR1 and the units single wire to the coil will fire a dual output 3ohm coil. If this is true I could use such a system (accepting the wasted spark). My calculator says that more than 240 crank degrees or better than 5ms might be available to saturate the single coil for each firing every 7.5ms @8000rpm. The rest of the time it would have twice the dwell time available. So, if I could control the dwell to commence at (say) 1/3 of the last firing time interval, there could be a reduction in overall draw. Even better if the dwell were to commence at a point (say)5ms before next firing at any given rpm.
I realise these are probably the dreams that computers were born of.

The reason I mention a single 3ohm dual output coil is not cost (sold as pairs). I can save space which can be used for the control unit etc. and, without any dwell control it appears the current draw would be lower than using two 5ohm coils while possibly providing more spark energy at the plugs.

Being the lifetime novice that I am, I still struggle somewhat with coil performance. eg How does Hondaman's real coil performance measurements relate to claimed voltage levels viz measured CBX coil 8kv against 30,000 volt claims for aftermarket coils. Or, the coils I have against either of these or a Dyna 5/17000dual output or 5/14400 singles

So, in considering a transistorised application as mentioned above;

Would a transistorised unit successfully fire a single dual output coil with both sets of points wired in parallel (ie together) to the unit. Wouldn't the continuous but variable ground through the points interfere with the unit's coil triggering?

Assuming the 3ohm dual fire coil application was workable, what comparative performance would you expect at the spark plug (as opposed to twin 5ohm coils)?

Am I correct in assuming an overall reduction in current draw with an increase in spark voltage using a single 3ohm dual output coil?

Does the Dynatek DBR1 or the Hondaman ignition incorporate any dwell control beyond the points setting?

Would the Hondaman ignition be suitable for my application and could it be made available?

Hope you can help......................................Geof


Hi, Geof!
The first answer is: yes, I have these ignitions on Kaws and Suzys, too. And on Honda Twins, the 350 and 450 variety. They work fine there.

The condensor is irrelevant with this Transistorized Ignition, as the electronics manage the coil instead. All that's needed is the points' trigger. I usually tell the riders to leave the condensor in place so if the unit ever fails, the original wires can be plugged in around the box and you can ride on, instead of towing the bike home (built-in backup, if you will...).

In your situation: the points cam probably prevents you from being able to parallel the points, as one set is probably always closed. Honda made many bikes in this 360 degree crank configuration, and used a points cam with dual-opening ramps to accomodate the single 2-output coil. It can remove some HP, though, because the engines and/or the points cams are seldom exactly 360 degrees: Honda's hallmark of these designs is usually more vibration, with less power, than you might otherwise expect, usually due to the points cam tolerances.  :(  That's how I first got into "tuning" points cams: I would stone off the "earlier" ramp until it was exactly matched to the other one, then widen the points plate's adjustment slots so I could turn the plate to compensate. It ALWAYS helped.  ;)

You might consider this: measure the resistance of your existing coils. Honda's coils are in the range of 4.0 to 4.6 ohms, using about 2.5 amps each, typically. With twin points, and the Hondaman Ignition, this translates to a continuous 2.5 amp draw with dual points, because one points set is open while the other is closed, always. And, the Honda coils are good to over 14,000 RPM with 1.5mS charge-discharge time, well past your twin's capability.

So, to reduce overall current: weld up an extra 30-45 degrees of "open" time on the points cam (you'll have to grind and smooth it back down, of course, and make it real smooth so the points' rubbing blocks don't wear faster). This will reduce the overall current draw by about 20-25%, since the points are open longer. Then, install a Hondaman Ignition and, if your coils are less resistance, install Honda coils.
The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
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Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

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Offline w1sa

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Re: Ignition Analysis: Honda's coils
« Reply #33 on: February 23, 2008, 06:16:50 pm »
Aaaahh.   I think I’m starting to see some light.

Having only fooled with the points setting on this machine a few times and always with the points insitu and difficult to get at, I had failed to realise the true cam lobe profile. So I went and measured it. It is as you say,( a 180 deg profile). So, the current draw across two coils is roughly equivalent to one coil drawing continuously.

Given this I don’t think that the dwell and ergo, re-profiling the cam is as critical. Especially since doing it would be beyond my ability and I’ve only got one guaranteed/available unit for anyone to fool with.

If I install twin Dyna 5/14000 ohm coils, current requirements would remain about the same. Without knowing specific Henry ratings, turn ratios/ and coil current fall times etc, should that give me an increase in spark energy/duration at the plugs over the original (remeasured) 4.8/9600 coils? What are the main variables to consider here?

If I forgo the current saving argument would there be any foreseeable drawbacks/ advantages to installing either the Dyna 3 ohm coils (limit coil voltage by resistor to equiv 4 ohm draw)  or the stock Honda coil.

Can you provide me with access to physical details of the Hondaman Ignition unit (dimensions, casing construction, vibration/heat etc., mounting method, cost, etc, etc, how where and when available).

Offline HondaMan

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Re: Ignition Analysis: Honda's coils
« Reply #34 on: February 24, 2008, 09:46:05 am »
Aaaahh.   I think I’m starting to see some light.

Having only fooled with the points setting on this machine a few times and always with the points insitu and difficult to get at, I had failed to realise the true cam lobe profile. So I went and measured it. It is as you say,( a 180 deg profile). So, the current draw across two coils is roughly equivalent to one coil drawing continuously.

Given this I don’t think that the dwell and ergo, re-profiling the cam is as critical. Especially since doing it would be beyond my ability and I’ve only got one guaranteed/available unit for anyone to fool with.

If I install twin Dyna 5/14000 ohm coils, current requirements would remain about the same. Without knowing specific Henry ratings, turn ratios/ and coil current fall times etc, should that give me an increase in spark energy/duration at the plugs over the original (remeasured) 4.8/9600 coils? What are the main variables to consider here?

If I forgo the current saving argument would there be any foreseeable drawbacks/ advantages to installing either the Dyna 3 ohm coils (limit coil voltage by resistor to equiv 4 ohm draw)  or the stock Honda coil.

Can you provide me with access to physical details of the Hondaman Ignition unit (dimensions, casing construction, vibration/heat etc., mounting method, cost, etc, etc, how where and when available).


Those Dyna 5/14000 coils will use the least current, saving some for the headlight you might want (and, don't forget to consider an LED taillight bulb, to save at least .75 to 2 amps!). If the choice is between the Honda coil and the [Dyna 3 + Resistor], my personal choice would be the Honda coil. Even with the resistor, the Dyna will draw more amps, overall. The Dynas are a short-charge coil, so they have high current moments that add up.

The Hondaman ignition (Basic unit) is about 4" L x 2" W x 1.1" thick. They are typically mounted in the areas near the battery or under the seat. Cooling is not an issue, so long as the bare Dyna 3 ohm coils are not used. The BASIC unit (this batch) costs $64 plus $6.40 shipping (lower 48 US States), comes with a 5-year, 100% warranty (i.e., if you manage to break it, send it to me and I'll fix or replace it, free, period). In you arrangement, I might ask for some estimated wire lengths and also which type of connectors your bike has, so it can come to you complete, ready to plug in. The main advantage of this device is this: if you should find a way to kill the Ignition, you can unplug the points & coils from it and plug them back into each other, and ride on. I've found this approach to be much simpler than finding a truck ride to get it home...   8)
The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline w1sa

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Re: Ignition Analysis: Honda's coils
« Reply #35 on: February 24, 2008, 04:04:28 pm »
Thanks Mark,
I'll take one of the Hondaman Ignitions. I live in the land of Aus, so I'll send an email to you (mgparis@concentric.net) with details................................Geof

Offline nowayjosey

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Re: Ignition Analysis: Honda's coils
« Reply #36 on: February 27, 2008, 02:34:11 pm »
Hi Hondaman,
I have a K2, in which I had installed a Dyna S and kept the standard coils. I really noticed that at high regimes the bike just wouldn't go (like more than 85 mph on a horizontal road).
Reading your explanation, I decided to buy the 3 ohm Dyna coils and just tested the bike.
It is now working much better, from medium to high RPMs. Without much effort I went to 100 Mph (don't spread that, cause the speed limit was 60)
I would like to thank you for the lesson !
Jose

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Re: Ignition Analysis: Honda's coils
« Reply #37 on: February 27, 2008, 07:14:55 pm »
Hi Hondaman,
I have a K2, in which I had installed a Dyna S and kept the standard coils. I really noticed that at high regimes the bike just wouldn't go (like more than 85 mph on a horizontal road).
Reading your explanation, I decided to buy the 3 ohm Dyna coils and just tested the bike.
It is now working much better, from medium to high RPMs. Without much effort I went to 100 Mph (don't spread that, cause the speed limit was 60)
I would like to thank you for the lesson !
Jose

Way to go! (Ssshh...)
Yeah, the longer spark really helps!
The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

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eldar

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Re: Ignition Analysis: Honda's coils
« Reply #38 on: March 03, 2008, 07:58:07 am »
Strange. I wonder if issues like this can be traced to certain years. My K8 is all stock engine-wise and pretty much everything else except for my dyna S. I do not have the difficulties with rpms of speed or anything like that. I have not done the ton but that is by choice as I have kids and would rather see them grow then see a ton.

My coils are original too only change is the plug caps. I also have not done any real work to my wiring either. I wonder if later years have more powerful systems?

Offline Terry in Australia

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Re: Ignition Analysis: Honda's coils
« Reply #39 on: March 03, 2008, 08:07:02 pm »
I wonder if later years have more powerful systems?

Nah, they're just ridden carefully by timid old farts Eldy, so nothing wears out! ;D
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So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

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Re: Ignition Analysis: Honda's coils
« Reply #40 on: March 03, 2008, 09:37:35 pm »
Strange. I wonder if issues like this can be traced to certain years. My K8 is all stock engine-wise and pretty much everything else except for my dyna S. I do not have the difficulties with rpms of speed or anything like that. I have not done the ton but that is by choice as I have kids and would rather see them grow then see a ton.

My coils are original too only change is the plug caps. I also have not done any real work to my wiring either. I wonder if later years have more powerful systems?

Yeah, I'm slowin' down...that's why my 17-tooth front sprocket is OK now (only...126 MPH at redline in 5th).
Here's how you can "test" the scenario: we used to call it "the tall gear wall", and it was noticeable from the K2 onward, in increasingly worse degrees to the K5: on a warm summer day, get into high gear at 40-45 MPH, then just roll on the throttle and see how fast it will go. Frequently, they would "hit the tall wall" at about 80-90 MPH and stop accelerating. If you then dropped into 4th and poured it on, they would break to the ton, and then would pull 5th to the top. On real hot (90+) days, it sometimes would not pull past the 4th gear's top speed, but would slow down in 5th (CB500/550 suffers this more often).

The problem is 3-fold, really: it's a subtle change in efficiencies from the K1 onward, starting with the pipes. To keep the plugs clean in slow driving, Honda had to lean out the (very) rich open-pipe mix of the earlier open pipes for the newer HM341 pipes. Rich mixtures fire much easier, and burn longer, at higher RPM (as any cafe' or RR rider has learned) with any given spark. With a leaner mix, the engine needs a longer (or wider-gapped) spark to ignite more of the flamefront to get it all to burn in time. If you then throw in the taller gearing of the K2-later bikes (18T front sprocket instead of 17T) and add the 2-row output bearing on the countershaft, the engine pressures rise enough to stall the flamefront in the leaner mixtures at wider throttle openings (2/3-3/4) and lower engine speeds (typically about 6500 RPM in 5th gear). This is where it appears: the roll-on creates a lean mixture just as the torque requirement rises, and the mix isn't rich enough to carry the cooler flame through the whole stroke, so it "stalls" at building torque.

If you add a wider plug gap and the voltage to jump it, a wider flamefront appears, which burns faster, hotter, and more efficiently. You can also make a longer spark, which the Honda coils are compared to the Dyna, to try to ignite a wider swath of the moving mixture. The Honda coils do have their limits, particularly if the points are burned somewhat or are cheapies (tiny mating faces make poor instantaneous peak currents), so the Dyna S units appear to prolong the "new points feeling" better after 1000 miles than did points. The Dyna coils discharge faster, so they need a wider plug gap to get that wider flamefront, and they have the volts to do just that.

The later carbs (late K4 and on) showed some attempts to improve the richness at higher RPMs to deal with this issue. Although fairly rare, some carbs came equipped with "lifting collars" like the ones used on 2-stroke big-bore port-timed engines (these carbs also have non-changeable jets!). These increased the suction on the needle jet at 2/3 throttle & upward, distinctly returning the "K0 feeling". I saw some of these just as I was leaving Illinois in 1974, on a pair of K4 bikes from California that I was tuning for some passers-by. These mods did, however, lower the MPG, to be like the K0's 35 MPG hiway numbers (the K4 was approaching 50 MPG without them).

So, for any given stock bike, improving the coils' performance turns the key to improved passing with No Fear on mountain roads. The "HM" Transistorized ignition does this by pretending to be perfect points, forever, through a little built-in electronic trickery. The Dyna S does it by being better than 1000-mile old points. The Dyna 3-ohm coils (with or without resistors) do it by heating the plug tips more if stock-gapped, or by widening the flamefront more with bigger (.050") gaps. The Dyna III does it by stretching the OFF time of the Dyna S-like trigger, to simulate the points' healthier dwell times. Any of these methods help fell the "tall gear wall". Richer jetting helps fell the wall, too, but with stock HM341 pipes, you'll pay for it in dirty plugs, unless you use higher voltage coils to keep them heated and burned clean.

One way to modify the carbs to get past "the wall" while keeping the in-town plugs cleaner is to open the mainjets and drop the needles, while at the same time installing low-restriction air filter(s). This 3-way mod will lean out the "dirty" range and reduce the in-town torque a little, but the personality shifts from Mr. Walker to Mr. Wheeler (remember him?) when you hit 6500 RPM. This is one of the things Honda did with the first "F" 750s, while improving the pipe and compression ratio. They also laid back the cam about 5 degrees, which enriches the top end, too. That's why the "F" feels like a rocket at top RPM, but the "K" tends to out-pull them with heavier loads. The "F" usually does a superior job of cleaning the plugs, as a result. And, some say, it's more fun to ride that way (right, RXman?).  :D
The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

fuzzybutt

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Re: Ignition Analysis: Honda's coils
« Reply #41 on: March 03, 2008, 10:06:58 pm »
would getting an adjustable cam sprocket and retarding the cam a bit help at top? as my 74 750k with the 76 k motor does indeed "hit the wall" in 5th, right at about 90-95 mph

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Re: Ignition Analysis: Honda's coils
« Reply #42 on: March 04, 2008, 06:43:23 am »
would getting an adjustable cam sprocket and retarding the cam a bit help at top? as my 74 750k with the 76 k motor does indeed "hit the wall" in 5th, right at about 90-95 mph

With that 76K, like GammaFlat, you'd want to advance the cam about 3 degrees or so. It's already retarded, and is likely the "F" cam in sheep's clothing. I've seen that, now, in several K6 engines, stock. I am beginning to believe Honda was morphing, depending on which parts were available (they were famous for that, not just with the 750!).  ;)

I only wish that I had been around the K5-6 as much as the earlier engines, so my notes would have told me for sure...but, that's what I suspect. You can check it with a degree wheel (make one from a school protractor) and a .001" feeler gauge. I've promised some others hhere that I'll make a post about how to do that, as soon as it's warm enough to work in my garage again.
The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

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Re: Ignition Analysis: Honda's coils
« Reply #43 on: March 04, 2008, 07:30:47 am »
So what you are saying is that the new improvrd best version wont kick the early bikes butt  :o :o

 who woulda thunk it??

 and that a lot of them cant get past 90mph in a high gear roll on.... gotta rush out and try one...
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Re: Ignition Analysis: Honda's coils
« Reply #44 on: March 04, 2008, 09:00:04 am »
So HM, do you have much on the 77/78 bikes? The gearing is different since the 630 was used then and the ratio was something like 2.63-1.  The later bikes are heavier than the 69/70 but hp was the same or even higher from what I have been able to find and performance times are about equal or slightly greater than the 69 depending on the bike mags from those days.

I know that the few times i have hit 90 or so, there was no wall, I just didn't want to go faster or get  ticket.

It is too bad there was not much done on the 78K/F but by then there were dohcs everywhere getting the attention and there are also so many pre 77K riders that just cannot accept that the later bikes may be better. It is like telling a bible thumper that they are wrong! :D

"btw 754, I know what you are referring to. Why cant you just come off it?"

Offline HondaMan

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Re: Ignition Analysis: Honda's coils
« Reply #45 on: March 04, 2008, 07:15:03 pm »
Sadly, most of my "in depth", hands-on knowledge stopped at the K4, since the Colorado shops I came to work in by that time didn't know me, and wouldn't let me "play" with the customer's bikes. When I was Shop Manager in IL, I made my own rules.  ;D

My understanding, from studying the Honda sheets, is that the "F" engines found their way into the K7-8 frames, along with the carbs that had an accelerator pump (which the earlier bikes would have loved, by the way...). That #$%! 630 chain was a real power-waster, both from the standpoint of extra weight, O-rings, and the gearing restrictions. The 18/48 was 2.67 ratio, the 17/48 hotter at 2.82. The K0 originals were 16/45 for a 2.81, and weighed 1 lb. less overall. But, the smaller sprockets flipped off the lube too fast, leading to a host of troubles. So, the K7-8 ratio was even taller, which didn't help on the streets. I seldom saw the K7-8 in touring service, but I don't know the reasons. I would think they would have been very comfortable.

I understand why Honda went to the 17" rear wheels and 4.50 tire: 4.00x18" rear tires didn't last on these bikes. But, it added nearly 3 lbs to the unsprung weight, which dropped even more power from the performance curves. All in all, I simply would have to say I don't "appreciate" or "understand" the later "K" like the earlier ones. They did have real pretty pipes, though, looking much like the Yosh roadrace pipes of the '60s and '70s. And, the paint and chrome were much better, along with a dozen other little refinements. Didn't they also have a stronger alternator? They also used resistor sparkplugs with non-resistor caps, which was a modest ignition improvement over the caps that burn out all the time, even if the plugs are harder to get (at least, the ones I really like are hard to find in "R" type).

I have seen a couple of kick-ass K8 cafe' bikes, though...
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fuzzybutt

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Re: Ignition Analysis: Honda's coils
« Reply #46 on: March 04, 2008, 07:17:52 pm »
well i ordered an adjustable sprocket from cyclex this afternoon.

eldar

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Re: Ignition Analysis: Honda's coils
« Reply #47 on: March 05, 2008, 06:11:44 am »
Well from what I have found, it seems the 77/78 K engines were somewhat derived from the 75/76F with a power bump coming probably from the new style of carbs and some other refinements. I see what you mean about the weight of the tire since it is bigger, this spring I will be able to offset that since I will be getting a cycle jack! I can remove the center stand.

As for the chain, the only time I saw any issue was on initial takeoff, It was a bit slow for a couple feet then you could dump the clutch and pour it on and it went very well. I switched to the 17/8 setup and noticed slightly better off the line but other than that it does not feel like accel was improved. The 630 seems to work very well. Course I used 630 rollers and not o-ring.

Offline Terry in Australia

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Re: Ignition Analysis: Honda's coils
« Reply #48 on: March 06, 2008, 02:51:44 am »
Cough, cough, cough, boat anchor, cough, cough...........  ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

eldar

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Re: Ignition Analysis: Honda's coils
« Reply #49 on: March 06, 2008, 06:10:00 am »
No we are not talkin HDs here! ;D