Honda CB750 K2 - ignition system - a closer look Ep.4

Previously we discovered a weak spark on pretty much all 4 cylinders so it's time to inspect/test each component that makes up the ignition system in this classic Honda.
In this video we perform resistance checks on the Primary & Secondary windings of the ignition coils, inspect & test the plug caps & take a closer look at the ignition points too...
I'll be covering more on the ignition testing & repair in future Episodes on this Series of videos...
Enjoy
Andy
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Thanks for all your support, until next time...
Andy

[@thewheel69]

Andy's money shot quote... "dying art" servicing/replacing points... so easy and yet so under appreciated when getting things sorted. Cheers. You are a true master technician... thx

[@AndyMechanic]

Cheers John :-)

[@averyerickson7012]

Hi Andy. Great video. Thank you. Also I just bought some replacement coils and had to reassemble the plug caps, because they must have bumped around during shipping or something and feel apart . There were two springs inside between both ends of the plug caps. You'll see the flat head screwdriver slots inside the spark plug connecter. Unscrew it and those two springs should just fall out when turned upside down. If the internal springs are not contacting in-between themselves and the polar opposite ends of the plug caps, then it will not be a closed circuit.

[@daveco1270]

I replaced the coils on my 75 CB750 last year because cylinder 2 was giving me occasional problems. I had swapped out the points for a Dyna S electronic ignition so I figured I'd put some new Dyna coils on just for the heck of it. At the time I didn't do a diagnostic test on the old coils, I just figured new ones would fix the problem....which they did. Plus I didn't own a multimeter at that point...I'm still fairly new to motorcycles. After watching this video I decided to grab those old coils from the garage and finally test them properly. Sure enough, I found a problem on the cylinder 2 spark plug wire. Since I finally bought a multimeter I've been testing everything for fun.

[@AndyMechanic]

Great job :-) I'm looking forward to having some time available to get the ignition work done....over Christmas holidays I have scheduled the work Thanks for your feedback Cheers Andy l

[@randybrill5071]

I have a 1982 Honda gold wing that running like it new, but thanks I picked up some good things here with coils and wires. Thanks.

[@jonneville2287]

Has anyone ever said you look like John Thomson from The Fast Show? Thanks for all the how to's on the Honda 750, big help when you are a novice.

[@bradyoung6663]

Thanks for the video. I needed to check the coils on basically the same bike here in the U.S. today. A 76 model CB750F. Same color too.

[@lewisalansparkywhitton5074]

When you were measuring the plug caps, would you have to subtract the lead resistance from the total resistance? Great video

[@1crazypj]

The condenser is to give a better spark as the collapse of primary windings induces high voltage in secondary winding ,BUT, when secondary winding collapses, it re-induces a very high voltage back into primaries. On a scope it shows as a bounce. I've measured as much as 320v on primaries. You need a peak voltage adapter (DIY is probably better than the $4000+? Snap-On one as Snap-On had a production defect for a number of years) Preventing points burning is a secondary effect and not the primary reason it's fitted

[@garygarnett6469]

Last set of points I adjusted was on a Fantastic Ford Sport 1600 1978 overhauled the motor and installed a competition Cam Was a pleasure to drive During overhaul found someone had changed the crank to an older type which caused a different firing order to spec for the vehicle 1432 or 1342

[@mikegermain7033]

Great video and easy to understand.

[@AndyMechanic]

Thanks :-)

[@artwood4]

Good methodical work. Lots of mechanics struggle with electrics/electronics. Please keep the points, they’re easy systems to keep going, plenty of cheapo electronic systems out there that have bad advance curves or even good old Boyer that goes to full advance if battery voltage is low - ankle breaker on a kick start bike.

[@1crazypj]

I used to 'kick' start them by hand after service just to prove to owners how easy it is to start them using correct procedure.

[@mohammadabouaudi2443]

so smart work

[@jackofalltrades3654]

You got some great videos I wish I can get help like that. I can’t even get a second hand .

[@KK-mx2di]

Thank you sharing

[@sait33]

👍❤️🙏 Highly appreciate it for useful and helpful tips and information. ❤️🙏

[@aussiejas6599]

nice Andy

[@bobkinney2430]

IF you can't find or get the points, there should be an electric ignition kit that should work. You would be replacing the points and condensers out for an electronic ignition plate. I just recently saw an RD 400 2 stroke bike (around that same era) that had that done.

[@AndyMechanic]

Thanks Bob, yes, that's my recommendation to the customer but awaiting approval. Cheers Andy

[@jimhaines8370]

What I have seen is as the OE stopped using points along time ago the points and condensers available are not very well made even from companies that used to make quality parts but the points ignition parts just are not focused on anymore so you get what you can get.

[@61nimnim]

Hi andy By the book i have to use 10w40 oil in my car's engine but there is a chart indicating that ,according to weather degree if climate is over 10 degree you can use thicker oil like 20w50 , is that wrong ? And i should ignore the hot weather and use the 10w40 as the owner manual recommended ?

[@claywbaker]

Andy, very helpful video. I have an older model Honda, the 12V voltage regulator is separate from the rectifier. Is there a procedure to bench test the voltage regulator. Its got three wires (black, green, yellow)

[@1crazypj]

You need a bench power supply to properly test regulator. Much easier (and way better) to fit an aftermarket 'all in one' regulator rectifier unit

[@springy-2112]

I change everything on my classic bikes and cars. Plugs boots leads coils condensers breaker points .. dizzy cap (cars) just to have a safe starting point ..i know it's cash but classic vehicles equals classic spending !! I'm no billionaire collector just a scaffolder who loves classic vehicles ! extra hours / extra parts !! Ok obviously I can see from comments you're probably going to fit electronic ignition.. but some new leads wouldn't hurt .. peace and love brother 👍🏻☮❤

[@AndyMechanic]

Hi, thanks for that. Yep, electronic ignition definitely on the table - awaiting owners instructions. HT leads are bonded into the coils so not really able to replace unfortunately - agree they do really need to be changed as crazy old now. Pleased you enjoyed the video, more Episodes to come for sure :-) Cheers Andy

[@springy-2112]

@@AndyMechanic thank you and yes always love the content 👍🏻☮❤

[@ImTheJP]

I’m not getting any sparks out of my spark plugs on this same bike. Any idea what it could be? I’ve checked the ignition coils, cables and covers, all are good. I checked the points and those look fine. But still no spark. Thanks

[@juanmanueldrackzara5084]

Hello, any caps values found? In farads. Thanks

[@macpherson3182]

watched youre video and ichecked my coil and have 0 resistance is that good or bad? is some resistance necessary to operate right?

[@AndyMechanic]

No, it must have some resistance & the reading needs to be within spec Cheers Andy

[@jfunk5329]

Link for the microscope? Or brand/info please. Great cheap bit of tech

[@johnjackson5465]

andy i have a old fireblade with resistors in the caps they have gone can i use a plug cap that will just about fit in length with no resistor in the cap? regards john GOOD VIDEO THIS EVEN SHOWS METER SETTINGS

[@AndyMechanic]

Hi John, the resistor rating of the plug cap is actually very important so see if you can find the correct caps - NGK do a good range - check their web site. Cheers Andy

[@whiterosemotors9026]

I'm having an issue with a 1981 cb750 f SS. Cylinders 1 and 4 won't fire. Coils are in good shape, stator charges, "cdi" boxes have been replaced...where do I go from here? Carbs have been gone through and new spark plugs. Getting no spark to 1 and 4. 2 and 3 run fine.

[@robbenalfans5501]

I have trouble with my spark plugs Carbs are ok and new air filter new spark but spark one and spark 4 are going out of function after 10 km maybe the coil are bad i need to change

[@jasonputtock4428]

i did post on previous video about the plugs. I think I removed the comment afterwards. However, i did say, make a new ign system. Make them into coil sticks. mod the system into coil sticks. We all do this on the CBR1000F.

[@AndyMechanic]

Hi Jason, yes, I read the info you sent through. Thank You. However, the owner wants to keep the bike looking original so we are currently looking at an electronic ignition pickup to eliminate the old points etc....more to come in future Episodes. Thanks again for your input. Cheers Andy

[@jasonputtock4428]

@@AndyMechanic youre welcome

[@bobdelaplage690]

Hi Andy, Does that mean that nr 2 and 4 didnt let through a spark at all? Being open circuits? You mentioned weak sparks in beginning....is it now confirmed as “ no spark possible” cause open loop on yr multimeter? bob Belgium🇧🇪

[@Zahnfz]

So my cb900c drains the battery could it be the coils?

[@AndyMechanic]

Well....when the ignition is turned off there shouldn't be power to the coils. A simple way is to connect your ammeter between the battery + post & the cable that normally connects to it - you will need to disconnect it for the test. Now, with the ignition turned off you should see a very small to zero reading (in amps). If your battery is draining then this will be higher than normal. Normal will be less than around 0.3 Amps (lower the better) anything over this then you'll have a parasitic drain. So, now go to your fuse box & remove one fuse at a time, when you see a substantial drop on the meter reading you have identified the circuit responsible for the drain. Now you'll need to inspect that circuit in more detail to find the problem Hope this helps Andy

[@bobdelaplage690]

Lets say u reuse the points, for the time being....with what grain would you rub them, i would like to see the difference on the microscopecamera, after use of sandpaper....thanks for nice info mate! bob Belgium

[@jamiestanley8774]

Hi mike . Some advice please im stuck changing a plug cb750/4 k5 and cyl 2 aswell . Now it may b srtiped or i need a very thin walled plug socket. Ive had k5 only 2 weeks . How do ya get a striped plug out please . Jamie newzealand

[@simonrawle7885]

good old points . im sure i have a set of points files somewhere

[@polar627]

Wtf is that intro lmao 🤣

[@joemalloy4224]

I 7nderstand you doing this for the video, but once I saw the rip in the boot, I would have called the customer, told him he needed plug wires and be done, I wouldn't waste the customers time (IE money) testing all of the wires individualy. Please take this as constructive criticism, I am by no means saying you aren't doing the right thing, just think it is an obvious problem. That microscope camera is bad ass. Would you be kind enough to share the manufacturer name please

[@DilaGumrah]

Bro i need your help i have honda cb 550 1977 current issue coil current

[@AndyMechanic]

Okay. Explain more what the problem is so I can help Thanks Andy

[@DilaGumrah]

@@AndyMechanic sir there is 2 coil.right the problem is that 1st coil have two wire but in only one wire ghe current is passing and from 2nd coil same issue two wire but one wire passing current

[@1crazypj]

You need the Honda General service manual that covers pretty much everything that is common to all the Honda motorcycles. It's available online. The coils were not very well insulated even when new (I was working at Honda dealers when these were still current) BTW, with dual output coils, one lead fires negative and the other positive so it's a real good idea to swap 1/4 and 2/3plugs over every so often as they erode at completely different rates. If one plug sparks, the other has to to complete the circuit. Your not using the meter specified in service manual so anything within 10% of spec is fine. You are a member at SOHC4.net?

[@alexwilson9940]

Where do you get these girls from?

[@AndyMechanic]

Under the house. Oh, do you mean originally? lol

[@shotsrodder]

Talk about milking a video 😂 🤪