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Honda CB125T poor spark

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ajb235
Two Stroke Sniffer



Joined: 25 Jul 2018
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PostPosted: 16:46 - 07 Jul 2020    Post subject: Honda CB125T poor spark Reply with quote
My CB125T has a poor spark at the plug, giving me poor starting and running.
When I check through the HT system I have copper cored HT leads, 5k ohm resistance plug caps and resistor plugs.
Seems to me that resistor plugs AND resistor plug caps is not right, and there is too much resistance in the HT circuit.
So, is it resistor plugs or resistor plug caps? What did Honda do originally?
I would also like to know the correct spark plug type.
Thanks
ajb
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ajb235
Two Stroke Sniffer



Joined: 25 Jul 2018
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PostPosted: 16:48 - 07 Jul 2020    Post subject: Honda CB125T poor sparks Reply with quote
It's a 1981 bike , which 6volt electrics.
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Fisty
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Joined: 11 Apr 2007
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PostPosted: 17:32 - 07 Jul 2020    Post subject: Reply with quote
Wall of incoherent autism incoming.
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jaffa90
World Chat Champion



Joined: 06 Apr 2016
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PostPosted: 17:42 - 07 Jul 2020    Post subject: Reply with quote
Fit a non resistor cap and a spark plug without the R and S, find a copper core if you can.
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gbrand42
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Joined: 23 Jul 2013
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PostPosted: 18:23 - 07 Jul 2020    Post subject: Reply with quote
Teflon is gonna have a field day with this, brace yourselves
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Fizzer Thou
World Chat Champion



Joined: 06 Aug 2011
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PostPosted: 20:58 - 08 Jul 2020    Post subject: Reply with quote
On my CB125T2 I had weak sparks when I first hooked up a battery so as to try and start the bike.But both spark plugs only had a very weak spark,so I checked the voltages feeding the coils,which are fed by the 6 volts via the ignition switch.As there is no kill switch there should have been 6 volts on the coils but there was only about 3 volts.Having rebuilt the igniton switch after cleaning the internal contacts I now had the full 6 volts on the coils and nice fat sparks from the new NGK standard CR8HS plugs and resistor plug caps.

As it happened,there was a smoke screen from both exhausts as the pistons and bores are extremely worn.But that is another story.
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ThunderGuts
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Joined: 13 Nov 2018
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PostPosted: 07:29 - 09 Jul 2020    Post subject: Reply with quote
Fisty wrote:
Wall of incoherent autism incoming.


I was assuming that, but barring a single post a week ago, he's not been seen since May. Thinking
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steve the grease
Crazy Courier



Joined: 26 Jan 2018
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PostPosted: 15:12 - 09 Jul 2020    Post subject: Reply with quote
Fizzer Thou wrote:
there should have been 6 volts on the coils but there was only about 3 volts.Having rebuilt the igniton switch after cleaning the internal contacts I now had the full 6 volts on the coils and nice fat sparks from the new NGK standard CR8HS plugs and resistor plug caps.


I have a lot of time for people who check things out - find the problem -take something apart and fix it.
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Fisty
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Joined: 11 Apr 2007
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PostPosted: 17:46 - 09 Jul 2020    Post subject: Reply with quote
ThunderGuts wrote:
Fisty wrote:
Wall of incoherent autism incoming.


I was assuming that, but barring a single post a week ago, he's not been seen since May. Thinking


Must be furloughed from BCF
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ajb235
Two Stroke Sniffer



Joined: 25 Jul 2018
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PostPosted: 21:33 - 09 Jul 2020    Post subject: Reply with quote
Fizzer Thou wrote:
On my CB125T2 I had weak sparks when I first hooked up a battery so as to try and start the bike.But both spark plugs only had a very weak spark,so I checked the voltages feeding the coils,which are fed by the 6 volts via the ignition switch.As there is no kill switch there should have been 6 volts on the coils but there was only about 3 volts.Having rebuilt the igniton switch after cleaning the internal contacts I now had the full 6 volts on the coils and nice fat sparks from the new NGK standard CR8HS plugs and resistor plug caps.

As it happened,there was a smoke screen from both exhausts as the pistons and bores are extremely worn.But that is another story.


Thanks , that's well worth a try.
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ajb235
Two Stroke Sniffer



Joined: 25 Jul 2018
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PostPosted: 13:37 - 25 Jul 2020    Post subject: Reply with quote
ajb235 wrote:
Fizzer Thou wrote:
On my CB125T2 I had weak sparks when I first hooked up a battery so as to try and start the bike.But both spark plugs only had a very weak spark,so I checked the voltages feeding the coils,which are fed by the 6 volts via the ignition switch.As there is no kill switch there should have been 6 volts on the coils but there was only about 3 volts.Having rebuilt the igniton switch after cleaning the internal contacts I now had the full 6 volts on the coils and nice fat sparks from the new NGK standard CR8HS plugs and resistor plug caps.

As it happened,there was a smoke screen from both exhausts as the pistons and bores are extremely worn.But that is another story.


Thanks , that's well worth a try.



Well, a success story to report. On the advice of fizzerthou I checked the voltage at the coils, which was low at 5.3 volts. I replaced the ignition switch and soldered the wiring connections to the coil. Who needs old push fit connectors anyway? I also replaced the plug caps and plugs with non resistor types. Started straight away with a good fat blue spark at the plugs. Result! Thank you!
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Fizzer Thou
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Joined: 06 Aug 2011
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PostPosted: 21:47 - 26 Jul 2020    Post subject: Reply with quote
Glad to hear that you have got it sorted Thumbs Up Very Happy Thumbs Up

Enjoy the first ride Cool

Have some kharma for a good effort Thumbs Up Karma
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jaffa90
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Joined: 06 Apr 2016
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PostPosted: 23:44 - 26 Jul 2020    Post subject: Reply with quote
""""I also replaced the plug caps and plugs with non resistor types. """"
What about thanks/ karma for me? Sad
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jeffyjeff
World Chat Champion



Joined: 02 May 2020
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PostPosted: 15:27 - 27 Jul 2020    Post subject: Reply with quote
jaffa90 wrote:
What about thanks/ karma for me?
...says the man with 3 gold medals. Wink
Respectfully, the karma you've acquired by helping out your brother cannot be measured in gold blobs. Its way more profound and deeper than that. it's the real deal.
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