Author Topic: Super Rocket Spark Plugs  (Read 603 times)

Offline redmelons

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Super Rocket Spark Plugs
« on: 01.04. 2024 23:06 »
I put my Super Rocket into a dealer and had the magneto refurbished and a new AMAL concentric carburettor. The bike is still very hard to start. When I checked the plugs the dealer has fitted NGK B9ES. I was using Champion N3C previously.
I know the B9ES are a cold plug, but would they affect starting, or only run cold once it has started?
1960 RGS rep

Offline limeyrob

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Re: Super Rocket Spark Plugs
« Reply #1 on: 01.04. 2024 23:28 »
A cold plug has a smaller space between the electrode and the case so less flame gets into the space the electrode runs cooler but that means it gets more soot and doesn't get burned clean.  So I would expect no difference when the plugs are new but if its been run a bit they may be sooty.  You could clean them and try again but I doubt its the cause of poor starting.  Having run a BSA on plugs that were too cold it started and ran fine but oiled up in traffic and misfired until I got back on the open road.
You have had work done on both the ignition and the carburetor so its very hard to know.  Thinking out loud here:
Get a spare plug and kick it over like you would for starting, is there a good spark?
If its manual advance see how this affects the spark, it may be weak at full retard.  Does it kick back on full advance? (it should)
When it fails to start are the plugs wet?
Can you bump start it?
This may or may not be relevant, but I have just put a Matchless together with a rebuilt and rather stiff engine.  It was almost impossible to get enough speed on the kick to get a decent spark.  In the end I got a roller / paddock starter and used that. That allowed me to get it running and set the idle mixture and after 10 or so starts and about 1 hour's running the engine is free and starts fine on the kick-start.
Slough 59 GF/SR

Offline muskrat

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Re: Super Rocket Spark Plugs
« Reply #2 on: 02.04. 2024 08:08 »
G'day Red.
9's are too cold, 7's or even 6's would be better. 9's would only be good for 70-80mph highways and as Rob says a pig around town.
Years ago I would start and warm up on 5's then swap out to 9's to race.
Try hotter plugs and if starting is still hard we'll look at the tune of the carb. Is it a new Premium Concentric?
Cheers
ps: Due to the slight downward angle of the SR inlet the float height must be kept low. So if it was set at the usual height it will be way rich.
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Offline redmelons

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Re: Super Rocket Spark Plugs
« Reply #3 on: 02.04. 2024 09:18 »
Try hotter plugs

I'm going to try some Brisk L14C plugs which I'm told work better on classic bikes.

Quote
and if starting is still hard we'll look at the tune of the carb. Is it a new Premium Concentric?
No, it's a Mk 1 Concentric.

Quote
float height must be kept low. So if it was set at the usual height it will be way rich.
Good tip thanks, I'll check that!
1960 RGS rep

Online Sav

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Re: Super Rocket Spark Plugs
« Reply #4 on: 02.04. 2024 09:47 »
I use the copper core champions.

I'm assuming you've checked the plug caps have not been changed as well for resistor caps?
1961 A10SR, spent a fortune at SRM
1961 A7SS, finally the right green
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Offline redmelons

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Re: Super Rocket Spark Plugs
« Reply #5 on: 02.04. 2024 10:17 »
I'm assuming you've checked the plug caps have not been changed as well for resistor caps?
Yes, they're plain black caps with no resistor.
1960 RGS rep

Online BagONails

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Re: Super Rocket Spark Plugs
« Reply #6 on: 04.04. 2024 01:20 »
I found a lot depends on the fuel you're using. For a time I was running 98 Super unleaded as this seems to keep better if the bike is left over winter etc.  This stuff being higher octane burns slower and requires a hotter plug, I had issues with slow speed running and occasional whiskering up, starting on one cylinder etc. until I went to 7's from 8's (All NGK).  Now I start and ride the bike at least every two weeks regardless of the weather and keep the tank full up with 93 RON which is shite fuel for sure but actually seems to suit the Flash enabling me to go to cooler plugs without issue.

I think the best advice is run the coolest plug that causes no problems with the cheapest fuel. With my new regime I have no issues with wet sumping, dodgy fuel, flat tires, rusty chains hemorrhoids, heartburn or flatulence! *eek*
Ian
59 GF A10
67 Spitfire under resto
2013 kwaka W800 Desert Sled (ex write off)

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Offline redmelons

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Re: Super Rocket Spark Plugs
« Reply #7 on: 04.04. 2024 12:36 »
I have no issues with ... hemorrhoids, heartburn or flatulence!

Looking forward to Brisk plugs fixing all those problems  *respect*
1960 RGS rep