Spark Plugs

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Spark Plugs

Postby Justdrew » Tue May 21, 2013 5:30 am

I went to start my bike and after an initial burst of life it refused to cooperate. I took my other bikes to the event. Later I removed the plug NGK BP7ES and it was dead, no spark. I put another plug (Bosch) into the ignition lead and bingo a good spark jumped the gap. A friend has had similar problems with NGK plugs in his 500cc BSA. Has anybody else had problems with NGK plugs in their SRs. Can anyone suggest an alternative plug?
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Re: Spark Plugs

Postby speedshop » Tue May 21, 2013 6:35 am

NGK everytime. Been using them for 20 years.
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Re: Spark Plugs

Postby stewross » Tue May 21, 2013 7:38 am

Yes NGK for me too ;)

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Re: Spark Plugs

Postby davedunsboro » Tue May 21, 2013 9:09 am

speedshop wrote:NGK everytime

Me too .
Could be a fuel mixture problem ?
98 octane can load up the plugs if the jetting isn't right .
Also fuel additives can cause the plug to foul too .
I went back to 91 on my SR500 , which is stock with a VM36 & 1 of Rex's CDIs
Have only had the plug foul once in years & I had the choke on for too long & I
rarely use it now .
I also found that once the plugs are fouled that's the end of them too
Cant seem to get them to spark again no matter how much you clean them up!
Cheers Dave
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Re: Spark Plugs

Postby speedshop » Tue May 21, 2013 2:00 pm

Seconded. Plug problems are usually down to something else not being right with the engine/carburation.
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Re: Spark Plugs

Postby Justdrew » Wed May 22, 2013 12:59 am

davedunsboro wrote:
speedshop wrote:NGK everytime

Me too .
Could be a fuel mixture problem ?
98 octane can load up the plugs if the jetting isn't right .
Also fuel additives can cause the plug to foul too .
I went back to 91 on my SR500 , which is stock with a VM36 & 1 of Rex's CDIs
Have only had the plug foul once in years & I had the choke on for too long & I
rarely use it now .
I also found that once the plugs are fouled that's the end of them too
Cant seem to get them to spark again no matter how much you clean them up!
Cheers Dave



Last tank of fuel was 98 octane!! While on the subject what should be added to the fuel to protect the valve seats? Is there one valve saver better than another?
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Re: Spark Plugs

Postby davedunsboro » Wed May 22, 2013 4:46 am

Justdrew wrote:While on the subject what should be added to the fuel to protect the valve seats

Give that shite a big miss ;)
Some guys like it ,but the Yammy singles were designed to run on standard fuel & don't require it .
I find it causes plug problems as builds up in concentration in the tank .
If you must ,only every 4 - 5th tank full though !
Most of us here pull our engines down to change things so we do the valves when we're at it
& its usually other things that cause teardowns ,not the valve seats .
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Re: Spark Plugs

Postby stewross » Sat May 25, 2013 7:11 am

Seats are designed for unleaded fuel.

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