SOHC.co.uk Forums > CB350/400
400/4 is popping & banging with poor mpg where to start?
Oddjob:
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.
Oddjob:
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.
K2-K6:
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.
McCabe-Thiele (Ted):
--- Quote from: Oddjob on June 17, 2022, 01:16:15 PM ---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.
--- End quote ---
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.
McCabe-Thiele (Ted):
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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