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Sx150. Have fantastic spark at end of ht lead as soon as I put on ht cap and plug, no spark. Baffled. Have tried 3 or 4 new ht caps and plugs. Using b9es plug and lb05f ht cap.

Sorry to ask the obvious but you are screwing the cap on to the lead aren't you?

Yes

Do you own a multimeter, if so set for continuity
(looks like a buzzer pic on meter) check cap first
then plug stick one end on screw and other end on
Where plug goes in if you get a buzz you have a good
Cap do the same on each end of plug not touching the
Metal body just electrode and where cap goes if ok
Then check spark from lead if yellow spark not good
You want good fat blue spark, if all checks out ok you
Are probably putting it together wrong, we’ve all been
there mate it’s just a process of elimination.

Or rather than faff around see if a mate has a running
Scoot and nick his or hers to check yours, sorry about the
Long reply,

good luck

flakeychrome wrote:Sx150. Have fantastic spark at end of ht lead as soon as I put on ht cap and plug, no spark. Baffled. Have tried 3 or 4 new ht caps and plugs. Using b9es plug and lb05f ht cap.

Nothing to do with the loss of spark but why are you using a B9es plug? they are for high performance engines which run a lot hotter than an SX150, B7es should be spot on or B8es if you are thrashing along the motorway all day.

Also, you will need to check for a spark on the plug in a shaded place as impossible to see in sunlight....and you are earthing the plug aren't you?

coaster wrote:

flakeychrome wrote:Sx150. Have fantastic spark at end of ht lead as soon as I put on ht cap and plug, no spark. Baffled. Have tried 3 or 4 new ht caps and plugs. Using b9es plug and lb05f ht cap.

Nothing to do with the loss of spark but why are you using a B9es plug? they are for high performance engines which run a lot hotter than an SX150, B7es should be spot on or B8es if you are thrashing along the motorway all day.

Also, you will need to check for a spark on the plug in a shaded place as impossible to see in sunlight....and you are earthing the plug aren't you?

Been using a b9es for over 30+ years. I do thrash it up and down the motorway all day everyday to work and back. Never had a problem. Never had a hotspot or holed piston and they last for ages. Always test for spark at night time and yes earthed been doing it for forty years. Never had a problem like this before hence I'm very confused.

Den08 wrote:Do you own a multimeter, if so set for continuity
(looks like a buzzer pic on meter) check cap first
then plug stick one end on screw and other end on
Where plug goes in if you get a buzz you have a good
Cap do the same on each end of plug not touching the
Metal body just electrode and where cap goes if ok
Then check spark from lead if yellow spark not good
You want good fat blue spark, if all checks out ok you
Are probably putting it together wrong, we’ve all been
there mate it’s just a process of elimination.

Or rather than faff around see if a mate has a running
Scoot and nick his or hers to check yours, sorry about the
Long reply,

good luck

Yeah thanks for that will have to get a multimeter and try this, someone else suggested this as well. Thanks again.

have you tried another plug ?

If you're using a non resistive plug (ES) then you should use a resistive suppressor cap.
So you appear to have the correct combination there.
Your plug grade (9) is very cold and is highly likely to foul until you get the engine very hot.
Premature plug failure very likely here. They spark just great outside the engine and give you nothing when pressed into service. Spark plugs, especially cold ones, do break down under compression.