Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: McCabe-Thiele (Ted) on June 16, 2022, 09:29:15 PM
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This evening I fired up the 400 from cold I let it run at between 2- 2500rpm for some 20 seconds then checked the front pipes.
Number 1 & 3 cylinder are virtually cold - number 2 & 4 nice & hot.
So where do I start to diagnose what the problem(s) are please?
An Idiots guide if you will of the best logical steps I need to take in sequence please?
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Tap the float bowls Ted in case the floats are stuck shut.
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Also get the plugs out and post decent pictures of them to help identify problem.
Are the 1+3 just wetted with little combustion?
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Yes I clearly need to remove the plugs & see what's going on with cylinders 1 & 3 thanks for the initial pointers.
Off to Wales for this weekend with a planned boat trip over the Pontcysyllite Aquaduct - bike will have to wait until Monday unless I can sneak the plugs out before we go.
I've only ever walked over the Aquaduct when I was a teenager in 1968 - it's just taken me a while to re-visit the marvelous piece of Telford engineering.
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Enjoy the aqueduct, Ted. It's quite an 'interesting' perspective if you admire the view from the West facing side, (not the towpath side!). Mike.
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Hi Ted, where did you get your plugs from? I had an intermittent fault on my KH 250 which I finally traced down to a sparkplug breaking down, my fault as I bought them off eBay, as soon as I replaced the plug normal service was restored. Although I do appreciate that as it is with 2 cylinders it is unlikely but worth a check.
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Enjoy the aqueduct, Ted. It's quite an 'interesting' perspective if you admire the view from the West facing side, (not the towpath side!). Mike.
I guess you mean the sheer drop looking over the side of the tank sections - yes looking forwards to it.
I did visit briefly once since 1968 with a fellow student only to find the hand rails were missing on the tow path side - it was a windy day so what started as a walk ended up with me crawling a short distance before common sense prevailed and I turned back.
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Hi Ted, where did you get your plugs from? I had an intermittent fault on my KH 250 which I finally traced down to a sparkplug breaking down, my fault as I bought them off eBay, as soon as I replaced the plug normal service was restored. Although I do appreciate that as it is with 2 cylinders it is unlikely but worth a check.
The plugs were purchased from e-bay via UK seller that had good feedback - I have a new set from DS in reserve.
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Mini update I have removed Plug 1 photo below it was clean but wet with fuel.
Plug 2 looked pretty normal - slightly on the rich side perhaps.
I'm confused as all 4 manifolds show heat discolouration as 1 & 3 have a cold front pipe find it hard to believe it would run on just 2 good cylinders.
(https://live.staticflickr.com/65535/52153316950_1cb84d1166_o.jpg) (https://flic.kr/p/2nsBo8Q)Plug No 1 (https://flic.kr/p/2nsBo8Q) by Macabe Thiele (https://www.flickr.com/photos/187487200@N03/), on Flickr
Number 2 below.
(https://live.staticflickr.com/65535/52153316920_8abdd69af3_o.jpg) (https://flic.kr/p/2nsBo8j)Plug No 2 (https://flic.kr/p/2nsBo8j) by Macabe Thiele (https://www.flickr.com/photos/187487200@N03/), on Flickr
Numbers 3 & 4 will have to wait until next week as I need to do some tasks round the house first.
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#1 definitely wet with not enough spark-age or too much fuel-age, question is which one? #2 looks fine for combusting (slightly in shadow to see exact colour) but clearly dry and carbon as expected from continuously running cylinder.
Could be as Ken says, a sticking float valve that is giving it a bit of a soaking.
The #1 plug, just try it for sparks in another system to see shat it does (independent ignition scource) that will point you to what's happening and give you clear answer if plug will spark at least.
Enjoy the aqueduct trip Ted, often seen it on TV but not visited and looks pretty spectacular to cross it.
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What plug caps are you using Ted as the screw on top nuts are still on yours and if your using NGK caps they don't tend to have them as they use the threads to grip.
A better picture of No1 plug would help to see if it's a cheap copy, look for smudging on the lettering, the top nut should also have a small indent, the crush washer isn't a good copy and tends to come off when pulled down. Also look for machining marks on the metal parts.
No1 doesn't look to have fired as it's wet through, which is worrying as you need to find out why it's like that.
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After a little research Ted I'd say the plugs are copies, the electrode should have a curved surface and the copies are known to look very square looking. Yours look square to me.
They are known to fail very quickly, the NGK symbol is quite bright whereas the genuine can look faded. If you had the box you can tell as the box is bigger and has some wrong writing on, like TSE when it should have EAC. Amazon are known for having sold a lot of copy plugs. Maybe get them from a known source is better, like The Green Spark Plug company.
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Well spotted Ken, I hadn't looked at that end :)
Definitely check the caps Ted as all the NGK I've used are without those ferule screw tops. They'll fire but sporadically as the spark needs to jump across from HT points to the ferule which will sit out of contact with it.
Likely if this is the case only two plugs will work as each coil being double ended has an HT polarity that maybe more effective in positive or negative orientation, and so two of them may tolerate better than the other two.
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What plug caps are you using Ted as the screw on top nuts are still on yours and if your using NGK caps they don't tend to have them as they use the threads to grip.
A better picture of No1 plug would help to see if it's a cheap copy, look for smudging on the lettering, the top nut should also have a small indent, the crush washer isn't a good copy and tends to come off when pulled down. Also look for machining marks on the metal parts.
No1 doesn't look to have fired as it's wet through, which is worrying as you need to find out why it's like that.
I'm no expert at spotting fake NGK plugs they cost me 10.99 for a set of four the packing looked genuine NGK, the washers are well fitted in place etc, I have a NGK spare set from DS I will try them.
I'm just using the plug connectors that came with the Dyna Kit 8mm silicone leads with the carbon string type centre.
Ideally I would have liked ready made leads but no local supply now. The local auto spares shop closed during Covid - it's now an Estate Agents, buying fittings locally seems a thing of the past.
My spark plug ends are just a straight metal connector with a moulded rubber type end came with my Dyna Kit - it needs the top nuts on the plug to fit securely.
I cut the leads to length crimping on the Dyna coil connectors - they are like the old BMC coil type fittings - I used a crimping tool.
Personally I prefer copper wire leads as you know there is a good connection - I'm minded to make a new coil end for No:1 lead as it's long enough.
I will fit a plug on the end of the lead to check for spark first.
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Fake NGK plugs obviously a brand worth faking then.
I will try the DS set of NGK plugs with the leads as they are & see if I can get 4 warm front pipes for starters?
Brief Update: Number 3 & 4 plugs were exactly like Number1 & 2 virtually identical in colour etc.
I've fitted the new NGK's from DS & run the bike for 10 seconds still the same with No 1 & 3 manifolds being cold. I checked the spark on number 1 lead on an old plug there was massive
spark.
I've run out of Garage time now until next week when I return from Wales - do I check for compression next or am I missing something obvious before I take the carbs off?
I can access this site whilst I am in Wales as my phone does internet if there is a signal at the Hotel.
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Also get the plugs out and post decent pictures of them to help identify problem.
Are the 1+3 just wetted with little combustion?
Exactly 1+3 are both clean but slightly wet, 2+4 are virtually identical - if all four were like these I would be happy.
Would a sticking float not shake down from the engine vibration whist I've done the first 114 miles?
I'm thinking bizarre thoughts like can the plug leads break down when the relevant cylinder is under compression. Should I remove the electronic triggers & go back to points I have the back plates?
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Hi Ted, I've attached a link to recent pics of my plugs as I have been going through the process of getting my 400 running after rebuild, as you know. I thought you could compare the look in terms of whether fake or not, as the images can be zoomed in so you get a good look at the plug construction. Pics 1 to 4 show plugs at about 300 miles, and they look lean to me so I've been tweaking airscrews to richen them up. The last image is more recent and shows just one plug, now looking about right, (to me). They all look like that now.
I had 1 cold down pipe, number 2. This was very early on. I suspected carbs, I hadn't really serviced them fully, just a clean and new float valves and o rings. I found an air screw spring missing, and also a lot of gunk came out with carb cleaner spray from all 4 air screw holes. However I suspect the biggest problem was the pilot jets. No 2 was definitely restricted compared to the others. I proved this when using carb cleaner wires on it. OK some will frown but if it's good enough for Alan Millyard it's good enough for me. So pilot jets cleaned, new air screw spring fitted, freebie from Steve Cooper, and No 2 down pipe now hot and running much improved.
https://photos.app.goo.gl/YexezRBYLzAgXvjSA
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Have you tried swapping round the HT caps Ted? Put 1 on 4 and 2 on 3 etc
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Have you tried swapping round the HT caps Ted? Put 1 on 4 and 2 on 3 etc
I do not have the traditional HT caps Ken just the moulded connectors. I could try swapping leads instead - might have to remove the petrol tank as they are a good fit in the coil end.
That will be next week now no Garage time left today.
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I'm now wondering if it might be the coils instead now Ted, if they have moulded HT caps then they are not genuine Honda ones, I presume they are something like Dyna coils. I wonder if the primary or secondary circuits are the problem, seems strange it's 2 cylinders acting up and neither are using the same coil.
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I'm now wondering if it might be the coils instead now Ted, if they have moulded HT caps then they are not genuine Honda ones, I presume they are something like Dyna coils. I wonder if the primary or secondary circuits are the problem, seems strange it's 2 cylinders acting up and neither are using the same coil.
Sorry Ken I probably did not mention it in this post - I have the Dynatek electronic ignition kit with their coils - bought new by me in 2020.
There is a massive spark at No 1 Cylinder when I attach a spare plug to it.
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I think I will need to do a compression test just to eliminate a possible head gasket issue.
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The US site keep talking about dyna systems peeing about
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The US site keep talking about dyna systems peeing about
I was recommended the Dyna Kit by my BiL he has fitted them to most of his bikes over the years he rates them. Can you post me a link to the article(s). I've only tested for spark on No1 cylinder using a spare plug on the engine casing. It was a very good spark. I can switch the leads for 1& 2 and see if the problem moves to a different cylinder? I have the option to fit the points again to eliminate the electronic points.
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It does look like that originally fitted plug may be suspect Ted, especially as you've got decent spark with substitute. New set I'd try first to take that out of equation easily.
The carbon corded HT leads I think are fine (I seem to be in a motoring minority on this, but used them for years on cars very successfully) mostly they'd fail from people pulling the lead rather than cap to get them disconnected and fracturing the connection there, but the NGK on wire leads are similarly vulnerable if treated the same way.
Often the crimping goes through the insulation to connect but when the centre is paired back like wire stripping and bent outside the insulation to be fully captured by the crimp they seem very competent in my experience. That's if you need to remake an end connection.
If they are the Dyna leads to their spec I'd encourage the continued use as the resistance can affect switching on these system.
I'll be careful taking about that topic, may attract the attention of the Dutch resistance police ;D careless talk costs sparks an all that :)
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I'm going stir crazy in my head regarding the plug leads is it possible that I have them connected up wrongly firing order wise?
At present the left side coil has two HT outputs I have one connected to number 1 cylinder & the other to number 2 cylinder.
The right hand coil has two HT outlets one is fitted to cylinder 3 the other to cylinder 4.
Is this the right firing order?
When I bought the bike there was only one plug lead lead on each side hanging by a thread - one of the coils was also cracked. Hence why I went for the Dyna S system on the advice of my B-i-L.
If I have the leads fitted correctly then I can eliminate the Dyna S magnetic switching system by re-fitting the original base plate, rotor ponits & condensers. (I will do a compression test first).
The Dyna coils are 3 Ohm is that likely to cause a problem if I return to a CB points based system for the test ?
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Ted,
1 and 4 on one coil. 2 and 3 on the other. (CB750). Almost certainly all the fours will be like this.
Jerry
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Yes you have the coils wrong, also 3 ohm coils draw more power which means you can not afford to poodle about as you will need at least 3000 rpm for the bike to charge.
There was no individual link to the us site but quire a few individual reports of failures and i can never post links anyway on my dumfone same as i cant watch videos linked for some reason
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Ted,
1 and 4 on one coil. 2 and 3 on the other. (CB750). Almost certainly all the fours will be like this.
Jerry
Well spotted Jerry, yes you're correct and I think for all the Japanese fours ever made which all do this.
Ted, you'll not be the first as many others have done this over the years too including my local bike shop years ago. They asked me to look with them at a problem bike that they could not sort, they'd done exactly this, :-[ all round.
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Yes you have the coils wrong, also 3 ohm coils draw more power which means you can not afford to poodle about as you will need at least 3000 rpm for the bike to charge.
Yes definitely Bryan if using 3ohm with points ignition.
With most fully electronic electronic triggering they normally go to fixed dwell time that doesn't over saturate the coils at low speed as I understand them. That aspect taken out, should make them no more demanding than conventional as the "wasted" dwell time won't be there to heat the coil unnecessarily.
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It'll be faster now Ted with all the plugs in the right order ;D
And should be about 50~60 mpg.
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I will definitely need a couple of longer leads probably go for some proper caps too.
Anyone have a link to the right type of cap presumably screw on ends from a trusted source?
Is the angle of all four caps the same please?
Still can't get my head round the fact that the bike would even run on two cylinders - my feelings of stupidity will ease with the passing if time as long as I am not reffered to as "Two Cylinder Ted" for too long. lol
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NGK, I suppose, would be the correct ones - DSS seem to be as good a value as anyone else. I think they were out of out of stock of the 2 & 3 red ones last week but that may have changed.
Matt
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An easy mistake to make it would be logical for the leads on one side to go to the cylinders on the same side, but we live and learn, and that's what life is all about.
Cheers
Dennis
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Ted,
1 and 4 on one coil. 2 and 3 on the other. (CB750). Almost certainly all the fours will be like this.
Jerry
Well spotted Jerry, yes you're correct and I think for all the Japanese fours ever made which all do this.
Ted, you'll not be the first as many others have done this over the years too including my local bike shop years ago. They asked me to look with them at a problem bike that they could not sort, they'd done exactly this, :-[ all round.
Nice to know I am in good company K2-K6.
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It's not vital Ted but it's common to fit the coil for 1 & 4 on the left hand side of the bike and 2 & 3 on the right. You've clearly got them the other way round. TBH it's so common to do it that way that if you'd have said 2 and 4 weren't firing I would have suspected the leads on the wrong cylinders right off as I've seen that a few times, 1 and 3 not firing just didn't set off the warning bells for some reason and it really should have.
It's no wonder you thought the engine was underpowered ;D ;D ;D be careful when you get it right or you may be pulling wheelies ;D ;D ;D
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Thought the leads for these are resistance in the carbon lead and their favoured setup to go with the complete system. It may be wise to get new std spec (for dyna) leads to install to their technical specification.
It can impact the load on switching transistor (and looks to me one scource of unreliability in some of these electronic system) as debate about them often doesn't include that nuance.
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It's not vital Ted but it's common to fit the coil for 1 & 4 on the left hand side of the bike and 2 & 3 on the right. You've clearly got them the other way round. TBH it's so common to do it that way that if you'd have said 2 and 4 weren't firing I would have suspected the leads on the wrong cylinders right off as I've seen that a few times, 1 and 3 not firing just didn't set off the warning bells for some reason and it really should have.
It's no wonder you thought the engine was underpowered ;D ;D ;D be careful when you get it right or you may be pulling wheelies ;D ;D ;D
I connected my coil wiring as it was when I bought the bike taking a photo plus a note of the wiring colours & ignition wire runs so I duplicated the previous back to front arrangement.
That's the best defence I have your Honour.🫣
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Thought the leads for these are resistance in the carbon lead and their favoured setup to go with the complete system. It may be wise to get new std spec (for dyna) leads to install to their technical specification.
It can impact the load on switching transistor (and looks to me one scource of unreliability in some of these electronic system) as debate about them often doesn't include that nuance.
My plan is to get some lead from the original source of my kit if possible.
Failing that The Green Spark Plug Co they seem to have a lot of options.
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Yes finally 4 hot down pipes - running on all four cylinders, Yes all 4 cylinders - I have a massive grin on my Mush even though I can't ride the bike today due to C2H5(OH) intake.
I will need to trim down the HT leads as I have left them slightly on the long side for the first fit!
Can't wait to try the bike on a run to Ashbourne probably tomorrow.
YES, YES, YES, YES. that's four yes's for four cylinders!
To be on the safe side I plan an oil change asap in case of sump dilution as a result of 115 miles on 2 cylinders.
Moped power to 400/4 now the HT leads fitted in the right order.
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Woooohooo Ted, now it'll feel good to ride :)
At least not too hard to correct and get you back on track.
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NGK, I suppose, would be the correct ones - DSS seem to be as good a value as anyone else. I think they were out of out of stock of the 2 & 3 red ones last week but that may have changed.
Matt
Never mind the Red I've gone for stealth. Black!
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Yes finally 4 hot down pipes - running on all four cylinders, Yes all 4 cylinders - I have a massive grin on my Mush even though I can't ride the bike today due to C2H5(OH) intake.
I will need to trim down the HT leads as I have left them slightly on the long side for the first fit!
Can't wait to try the bike on a run to Ashbourne probably tomorrow.
YES, YES, YES, YES. that's four yes's for four cylinders!
To be on the safe side I plan an oil change asap in case of sump dilution as a result of 115 miles on 2 cylinders.
Moped power to 400/4 now the HT leads fitted in the right order.
Ted, Be as generous as you can with lead lengths, as you may need to re-attach the caps one day, and the leads do deteriorate/ get mangled when you manhandle leads to get the plugs out! Having some slack will help.
Have fun,
Jerry
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Ted, Be as generous as you can with lead lengths, as you may need to re-attach the caps one day, and the leads do deteriorate/ get mangled when you manhandle leads to get the plugs out! Having some slack will help.
Have fun,
Jerry
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Thanks Jerry you make a valid point - i'm leaving them slightly overlong for now. Ted
PS No more popping & banging - its gone!