Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: Green1 on September 26, 2014, 05:31:22 PM
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Nigel got me thinking so before I messed around dropping needles I had a look at the plugs all are picture perfect so no worries there.
But what I have noticed is the HT leads are incredibly hard and even after trimming them the caps won't bite.
So do I trim and splice the leads or go all out new coils,leads and caps?
Mick
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Nigel got me thinking so before I messed around dropping needles I had a look at the plugs all are picture perfect so no worries there.
But what I have noticed is the HT leads are incredibly hard and even after trimming them the caps won't bite.
So do I trim and splice the leads or go all out new coils,leads and caps?
Mick
I am going to write up a full article on this but basically you can cut away the plastic carefully around the hump where the cable is embedded ( I used a B& D 'Powerfile'. This is cut back until you find the buried terminal post of the HT lead. You cut away the inner wire and peel away the HT lead leaving an almost semi-circuilar groove of around 7mm. You can them prepare some nice new 7mm OD HT cable (eBay) and resolder to the internal post and run the cable into the groove , bonding it in will non-rapid industrial epoxy ( if you need a small amount just ask me). After the epoxy has cured you cover the whole cut away area with black epoxy putty ( found that but not bought yet) and shape it to the original profile. When it's cured up you profile it with abrasive paper etc and then spray with satin paint. The outer rubber tube ID 7mm with 1.2-1.5mm wall thickness was hard to find but I have sourced that too. Obviously on a four you have two leads to do. 180 degree twins only one.
Cheers ... Ash
BTW Steve this was going to be Ashimoto's No.1 'Experiments from the Lab ;D'
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I have seen a post on this before with pictures, was it your post ash?
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LOL !! 3 weeks ago I spent about £76 on two new coils to cure this issue !!
mind you,they fitted ok,and I guess were easier to do,
so,if any of you guys want a pair of 703 coils,with hard cracked leads,make me an offer,
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I have seen a post on this before with pictures, was it your post ash?
No but they never sourced the correct blackepoxy putty to repair it or the rubber sleeve.
Cheers .. Ash
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I've always wondered about doing that Ash, I've worked on a few that have had the leads shortened so that they are stretched just to reach the plugs. It would be interesting to see some pictures if you do that.
As a matter of interest Mick which number plugs are you running currently?
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Hi John were did you get your coils from ? cheers Mick.
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Hi John were did you get your coils from ? cheers Mick.
Mick, I got these on Ebay from scooters and bikes, I haven't fitted them yet but they look really well made
http://www.ebay.co.uk/itm/New-Ignition-HT-Coil-Honda-CB750-SOHC-70-78-/191235992037?pt=UK_Motorcycle_Parts_13&hash=item2c868da9e5
And a set of caps from this seller
http://www.ebay.co.uk/itm/1x-NGK-Resistor-Spark-Plug-Cap-SD05F-red-8238-/361036539504?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item540f746670
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The bike is currently running NGK D8EA plugs.
Worryingly what I have noticed at some point plugs 3&4 have been over tightened and don't nip up tight.
Mick
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The bike is currently running NGK D8EA plugs.
Worryingly what I have noticed at some point plugs 3&4 have been over tightened and don't nip up tight.
Mick
That's not good news Mick, see this thread
http://www.sohc.co.uk/index.php/topic,7124.msg41347.html#msg41347
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Ash what black epoxy putty would I need.
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The bike is currently running NGK D8EA plugs.
Worryingly what I have noticed at some point plugs 3&4 have been over tightened and don't nip up tight.
Mick
That's not good news Mick, see this thread
http://www.sohc.co.uk/index.php/topic,7124.msg41347.html#msg41347
I was worried someone would say that.
They haven't blown out yet so fingers crossed they stay in.
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Those coils look alright Mark, be interesting to see how you get on with them when you get it going.
Mick, those centre two plugs often get avoided and corrode from water/crap from front wheel to the point when getting them out takes some of the aluminium threads with it in extreme cases. I've always heavily copa-slipped them even if not changeing the plugs to stop it happening. Doesn't sound too good if you can't get them tight though.
Be interesting to see if they stay within heat range if you run it hotter.
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Hi John were did you get your coils from ? cheers Mick.
dear old David silver items, if I remember £29 each plus 20% tax plus P&P !! wow doesnt it soon mount up
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Iv always used copaslip and I'm sure I didn't over do it last time they were out maybe they just stripped. :-\ There is a bit of corrosion around the plug holes.
I will take it for a run tomorrow fingers crossed they stay in.
I have a similar problem with my truck after a faulty glow plug heated the thread and welded itself in.
I think I'll order those coils when I'm playing around with the originals can't go wrong at that price.
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Sorry to hijack your thread Mick :-[, cheers for the coil and caps info chaps ;) cheers Mick.
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That alright Mick I think I do that more that anyone else. ;)
Thanks Ash I will probably take you up on your offer when I come to do them.
That's funny I just put that putty in my basket before you posted that.
I don't know what has happened to Araldite it doesn't seem to go as hard as it used to.
Mick
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That alright Mick I think I do that more that anyone else. ;)
Thanks Ash I will probably take you up on your offer when I come to do them.
That's funny I just put that putty in my basket before you posted that.
I don't know what has happened to Araldite it doesn't seem to go as hard as it used to.
Mick
It's not just araldite I'm having that problem with these days :(
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I wondered how long it would take for someone to say that ::)
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Sorry, I accidentally watched a carry on film the other day.
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I thought it was going toward "said the actress to the bishop" meself.
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When youre diabetic the little blue pills are free
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When youre diabetic the little blue pills are free
A stiff drink works wonders !
Seriously though, that epoxy from RS has been around Yonks.. at least 25 years, to my knowledge, and,although it takes ages to cure (but very quick if you heat the parts up) the bond strength is excellent. And without wanting to sound like a prick :D it goes off rock hard.
If you mix it to a putty with fine aluminium powder it acts as a plastic metal and has great thermal conductivity but still electrically insulating ( tens of megOhms) when cured. I also have some really finely divided (like dust)white ceramic powder which, when mixed to a putty consistency cures with the RS epoxy, had a hardness like it's on the old blue (or yellow!!) pills and you have to grind it to smooth it off. Not sure where you would get that white powder though as I was given a bag of it by a mate who's a plastic moulder so probably used in that industry as a reinforcing filler.
All this talk of stiffies and white powder making me sound like a right dodgy geezer ::)
Cheers ... AshD
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http://www.ebay.co.uk/itm/MILLIPUT-Black-Versatile-Epoxy-Putty-/250782828884 available in other colours
http://uk.rs-online.com/web/p/potting-compounds/1991468/
Above, This is the stuff for the pre-bond of HT cable into semi-circular groove left by the old lead .. been using it for years.. forget Araldite etc. etc. this is the dogs for bonding. If you just want a small sample to do coils I can send you some. A pack of it lasts forever and bonds everything around the house.
link to rubber sleeving I don't have at home but going to get a quantity of it soon.
Test coil was off a 1977 CB750K7 and its a black TEC FL703-12V 4 D SECONDARY MEASURES ABOUT 15k OHMS AND PRIMARY 4.5 OHMS. Like many other coils the HT lead insulation had gone stiff and the inner wire core fractured at the point of exit from coil and the rubber outer sheath was split. Funny, the rubber sheath is about 1mm wall thickness on this coil but more like 1.5 mm on the CB350K2 coil ( yellow colour coil body).
Cheers ... Ash
[/quote]
CUT AWAY (NOTE BRASS TERMINAL WITH HOLE IN IT TO SOLDER COPPER WIRE CORE TO)
[attachimg=1]
WITH NEW HT LEAD INSERTED AND READY FOR SOLDERING
[attachimg=2]
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Just observed that the inner of the original HT is rubber and still soft. It's the outer PVC jacket that Hardens.
Also noticed that the primary coil colours from the points are blue and other side yellow. Same colours as the two most popular male hardeners :D
Cheers ...Ash
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I wonder if the Microsoft anti porn sweeper has picked up this thread yet?
On a serious note though isn't it just better to buy new coils?, they are not expensive and I would imagine the coils deteriorate over time not just the leads (that said what do I know about electrics!)
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I wonder if the Microsoft anti porn sweeper has picked up this thread yet?
On a serious note though isn't it just better to buy new coils?, they are not expensive and I would imagine the coils deteriorate over time not just the leads (that said what do I know about electrics!)
No, TEC (OEM Honda) coils are very reliable electrically. My first 400/4 ones were wacked with 400v from the home made CDI I built and never broke down on insulation in 20k miles and never known of a primary burning out like the old Lucas 'Prince of Darkness' ones. You could get a spark more than 1/2 long from that CDI setup. Genuine ones are not cheap and who knows how good the after-market ones are. Personally I like to restore as much as possible and I would never trust the HT leads on a used TEC coil due to the hardening of the outer HT sheath and hence possible fatigue but once restored as I describe they should be fine. Each to their own I suppose but I would rather spend the money on cam chains, primary chains and perishable rubber engine parts.
Cheers .. AshD
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I wonder if the Microsoft anti porn sweeper has picked up this thread yet?
On a serious note though isn't it just better to buy new coils?, they are not expensive and I would imagine the coils deteriorate over time not just the leads (that said what do I know about electrics!)
No, TEC (OEM Honda) coils are very reliable electrically. My first 400/4 ones were wacked with 400v from the home made CDI I built and never broke down on insulation in 20k miles and never known of a primary burning out like the old Lucas 'Prince of Darkness' ones. You could get a spark more than 1/2 long from that CDI setup. Genuine ones are not cheap and who knows how good the after-market ones are. Personally I like to restore as much as possible and I would never trust the HT leads on a used TEC coil due to the hardening of the outer HT sheath and hence possible fatigue but once restored as I describe they should be fine. Each to their own I suppose but I would rather spend the money on cam chains, primary chains and perishable rubber engine parts.
Cheers .. AshD
And there's the enjoyment of fixing them as well I guess so yes as you say each to their own.
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I don't know how you do it Ash I haven't even checked to see if the plugs stay in yet.
I'm all for repairing as much as possible not only that I may learn something along the way.
Yet another job on the too do list.
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I suppose this would already have been done by someone if it were possible/worthwhile, but is it possible to tap a piece of steel tubing with a spark plug thread, then cut an external thread on that piece of tubing and cut a matching thread into the cylinder head, then braze the tube onto the spark plug and screw the plug into the head as normal, so basically you have created a spark plug with an oversize (bigger diameter) thread and then tapped out the cylinder to suit, no insert to come loose cos it's part of the plug, (actually you could turn the threads off the plug and braze an externally threaded bush onto it), it's possibly less work than taking the head off?just a thought!
EDIT; Apologies, wrong thread (excuse the pun) I'll move it.
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I don't know how you do it Ash I haven't even checked to see if the plugs stay in yet.
I'm all for repairing as much as possible not only that I may learn something along the way.
Yet another job on the too do list.
I suppose it's using the knowledge you have from your daily work/trade/profession/hobbies and satisfying yourself when you do things on a shoestring and then pass it on to others . If you look at the attached picture, everything apart from a few connectors and sleeving is from my rusty old '69' 750K0. Every part was stripped / plated repaired. It was a well used UK bike so you can imagine the state of things before the refurb. Also the rectifier had one dodgy diode (working but loose cathode pin)and I managed to de-solder a good diode from another duff 750 rectifier and fix it. The hardest thing to find was the glass woven/silicone treated sleeving. Have loads of it now, if anyone needs to 'have a go' you can have some. The only thing missing is the little Hitachi decal on the regulator but thanks to David at Saisei I will soon have one to fit to it from Yamiya. One little tip on the regulator... It has tiny bore glass/silicone sleeving on the green tapped resistor... if you open up a scrap energy saving light bulb you usually find some inside of one ::)
Did that electrical stuff before my period of gloom in 2011. My latest thing, now I am not gloomy, is re-furbing the points leads & alternator leads for both the CB750 and the CB250/350 twins plus the HT coil repair in this posting.
... Oh and repro'ing those pesky 400/4 'hens teeth' clips.. already working on that one.
Cheers .. Ash
[attachimg=1]
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Great results ash, you have a superb attention for detail, and a lot of patience
pete
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Great results ash, you have a superb attention for detail, and a lot of patience
pete
I'll second that - takes a patient (or should I say slightly obsessive) person to achieve that attention to detail..great work Ash
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Thats the dogs bo!!!!!s well done if I had one I would give you a blue peter badge and I am NOT taking the mickey
Cheers
Bitsa
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Probably better than new given that its been done carefully rather than mass produced, nice one!
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Blooming hell Ash looks better than new
I have something to follow when (if,still waiting for photos ,promised today)
i get the 69 K0.
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Bloody hell Ash your just trying to show us up. ;)
I won't post a pic off my loom it's still full of those horrid red&blue bullets that everyone uses when they butcher them.
To scared to start mine yet if I pull it apart it probably wont go back together for years.
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Ash
Start your own company mate you will be the next Richard Branston
Cheers
Bitsa
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Just ordered the coils in Marks link as a temporary measure so I can play with the originals.
Still haven't run the bike yet to see if the plugs stay in so I'm going to risk a 60 mile ride to work tomorrow
Fingers crossed.
Mick
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Cheers for the great comments guys. If I can help anyone out with the 'raw materials' or tips, just shout !!
Ash
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Ash
Will do mate
Cheers
Bitsa
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Um... wow.
My bikes suddenly look rather 'tired'
Thanks Ash!
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Just got back and the plugs stayed in :) So that's one less job to do.
Weirdly the bike runs better than before even though the HT leads just pull out of the caps.
It wasn't even affected by the rain on the way back. ???