Champion spark plug fail

[Hughsie]

Frustrated as I’ve changed my plugs this time to Champs but my new plug has failed after only 2 rides. Assumed it was something else, however I did find a couple of poor connections that I fixed anyway, but when testing for a spark I found the other plug worked ok in the same lead.
Might just go back to NGK…?
Sill don’t think my mixture is the best, plugs are still a bit sooty (when they work)
I dropped the needle down one from middle to try and lean out, but that’s not made much difference, maybe drop it again.
I’m running a 220 jet on my a7 shooting star engine but I have short megaphone mufflers and an open trumpet on my new monobloc so not sure how lean I need to go.
Any comments welcome

[muskrat]

G'day Hughsie.
Any breed of plug will fail running that rich. I prefer NGK's and found with today's fuel have to use hotter protruded plugs (BP6ES).
Most of our riding is on the needle but if the pilot and slide are too rich nothing you do with the needle (within reason) will cure it.
What carb is it? What are all the jets, pilot and screw setting, slide, needle jet, needle and main?
Cheers

[Hughsie]

Hi Mate,  Yeah I kinda thought that, I ordered a new replacement Amal 1” 376 monobloc from a uk supplier, this was a few years ago, I asked for the standard A7ss settings as found in the manual at purchase (the engine has been rebuilt to standard other than +60 pistons) they gave me a 250 main jet due to my trumpet filter and open ish pipes. But this was way too rich so I dropped it to a 220. I don’t recall what the pilot jets are, so I’m really going to have to pull the carb and have a look into it again. I’ll get some numbers and see what’s what. I thought a 220 would have helped.
My engine is not an original shooting star, but does have the alloy head, so I’m not sure if this is throwing me out.

[Hughsie]

The supplier quotes these specs on my coms , but I’ll need to double check, any thoughts?

3.5 cutaway slide
106 needle
25 pilot
And I’ve a 220 main deffo

[muskrat]

G'day again.
That sounds about right. How many miles has that carb done? The needle and needle jet do wear so end up being rich. 1 thou" is enough to do it.
With that air ram and pipes I'd imagine having to go richer.
Is she burning oil at all? Did the SS head get new bronze guides?
Cheers
ps I'll move this over to the carb section

[Hughsie]

Yeah, so it’s really a fairly new carb in terms of mileage, bought the carb in 2015 but It’s been a long project, so I’ve really only done a couple hundred miles at very most.
It’s not burning oil I don’t think, from the exhaust end anyway, exhaust runs pretty clear.
Just double check my build sheet and new guides were included in the head work.
Strange eh? lol.
I’m going to dig out and pull the original carb apart and see what it was originally running pre rebuild.

[sean]

Frustrated as I’ve changed my plugs this time to Champs but my new plug has failed after only 2 rides. Assumed it was something else, however I did find a couple of poor connections that I fixed anyway, but when testing for a spark I found the other plug worked ok in the same lead.
Might just go back to NGK…?
Sill don’t think my mixture is the best, plugs are still a bit sooty (when they work)
I dropped the needle down one from middle to try and lean out, but that’s not made much difference, maybe drop it again.
I’m running a 220 jet on my a7 shooting star engine but I have short megaphone mufflers and an open trumpet on my new monobloc so not sure how lean I need to go.
Any comments welcome

you dont mention which plug range you are running ?
I have had good luck with Champion n4c ..if your running a cold plug it will give you problems with todays ethanol gas .

[BSA_54A10]

On short trips my bikes all carbon foul plugs unless I turn the fuel of and starve the engine rather than kill the spark.
those last 3 or 4 strokes will all be lean so will burn the plug clean

[muskrat]

G'day Trevor.
That is a very good point. I do the same.
Cheers

[RogerSB]

Me too, I always run the carb dry on both my A10 and Velo LE - unless I'm going to use them again soon  - same day.

The supplier quotes these specs on my coms , but I’ll need to double check, any thoughts?
3.5 cutaway slide
106 needle
25 pilot
And I’ve a 220 main deffo

According to A7 & A10 1959 Handbook:-

1955-62 A7SS:-
Bore: 1"
Main jet: 270
Pilot jet: 30
Throttle valve: 376/3.5
Needle position: 3
Needle Jet: .1065

1955-62 A7:-
Bore:15/16"
Main jet: 210
Pilot jet: 25
Throttle valve: 376/3.5
Needle position: 2
Needle Jet: .1065

The 1960-62 A10GF has a 250 main jet, so, to me, it seems you've been given a mixture of the three. Of course the specs quoted in handbooks are using o.e. air cleaners and with everything new and unworn.

Rog.

[Hughsie]

Hi Guys.
Ok, first of all, again thanks for taking time to reply. A couple of findings…

 I’ve not been turning the fuel off! I have been just pulling up and hitting the mag kill button.  So I am going to do this, can I ask when you kill the fuel how long do you sit and let it burn off? Like 10 seconds? 20 seconds? More less?

Rog, yes these are the same settings I found, thanks for this mate… the issue I have is it’s not a true SS, it’s a 1955 a7 engine number but has an alloy head fitted. However pretty much everything is new (mostly) so not much wear.

The interesting thing is, I have pulled the original carb, pretty worn and it had the following settings…. (Bike again had an open air trumpet, and was fitted with open pipes)

Original 376 worn carb
200 main jet
30 pilot
06 needle (I think the 1 has worn off, so 106)
3 1/2 slide
Needle clip at highest setting

Obviously I don’t actually know if the bike ever ran well on these settings as was off the road 20 years, but had signs of hard use and the motor was well worn lol.

Bike as I found it with the pull back pipes and me sitting on it.
The next photo in the field is how the bike looks now, (the always look better in the photos lol)

[Triton Thrasher]

You shut the fuel off and let it run until it stops.

[Hughsie]

Oh really!

[muskrat]

You shut the fuel off and let it run until it stops.

G'day Hughsie.
That way she uses all the fuel in the bowl and runs lean for the last 15-20 seconds and hopefully burns off the soot.
Try those settings but the only way to know is by doing plug chops, and with her at full operating temp (10 mile ride) not just idling in the shed.
Very nice looking bike mate. My Cafe started life as a 56-57 A7SS. I bought it to road race 500 class so was heavily modified.
Cheers

[RogerSB]

Oh really!

Yes, only takes a minute or two, may start to run faster for a bit, coughs and splutters and then cuts out. I let it run while taking off my gloves, searching for my keys and opening the garage door.

Edit: In the day, when riding every day, we didn't have to take these precautions, just pressed the red button, shut the fuel tap, kicked the prop stand down and jumped off. . . . Oh! if it was after lighting up time we had to leave parking lights on.

Rog.