Who knows there 'spark plugs'

[dangerous]

Spark plugs people, anyone out there know their shit on the NGK?
right my MB100 bucket (RGV carb & chamber)

I have been having troubles with the bloody thing so am replacing bit by bit (yes Kick coil next)
The plug in the bike is a NGK B8HCS yet the NGK book of words says it should be a NGK BR7HS
So whats the differance?
Do I replace the plug with the same or should I put in what the book says... remembering that its a worked motor, so the previous owner may have chosen a plug more suited to the bike.

ps: I know that the plug in the bike is a slightly colder plug (8) than the recomended plug (7)
HS100 same motor as the MB says 8

[XTC]

The C suffix means "low angle ground electrode" Should be ok to use in the MB in place of the B7HS. Still if the MB has been modified a bit i'm surprised that you're running a 7 rather than a 8 or even a 9. Just read your post properly.... Go for the 8.

[Sniper]

Its "their" not "there" and you know my history with spark plugs, I don't really know

[Bonez]

The "R" designates the plugs are a resister type for fitment with non resister type spark plug caps- http://www.kaila.net/tl125/tl125ngkcode.html

[dangerous]

The "R" designates the plugs are a resister type for fitment with non resister type spark plug caps- http://www.kaila.net/tl125/tl125ngkcode.html

Thanks for the link B

So....
BR7HS means
14mm
resistor
heat range
12.7mm
std electrode

B8HCS means
14mm
temp range
12.7mm
special ground electrode
STD electrode

so the difference is one plug has a resistor and the other has a special ground electrode...
But what differance will that make for the bike?

[TwoSeven]

The manual is telling you to use a resister type plug. Also, the 8 is colder than the 7 (in ngk terminology - which is important).

You can find out about it here

[gav]

What book? A MB100 workshop manual? See I've been thinking about this too, these MB's are what late 70's model, thats nearly 30 years old. I'm thinking that spark plug technology has probably moved on abit since the MB was released. Why not a platinum or Iridium plug. I'd check with these guys too Maybe a BR9EVX?
Hey look, a section for your Guzzi too!

[Posh Tourer :P]

the resistor thing is important - if your coil is standard....

[dangerous]

the resistor thing is important - if your coil is standard....

Why?
What does the resistor do???

I am using the std coil, and after 3 laps on the track the bike is breaking down... coil it might be.

What book?

NGK book at repco

[sAsLEX]

a highly important engineering saying to think about:

If it aint broke dont fix it!


It works with the current plug so just replace that one.

[F5 Dave]

Don’t worry too much about what was std, the bike is no longer std or being used for hauling 5 family members & the prize goat around to sell it’s wares at the local village market in one of these dreadful third world economies, like Taranaki.

Ok. I did some tests in my H100 which is to all intents an MB. I found that in my setup, which was fairly mild, revved to 11,000 & produced 17-18hp which isn’t astounding, but was faster than many bikes out there (frame wasn’t going to cope with any more & it was my play bike, not my 50)

. . . anyways, on the dyno I found that B8HS was the best plug, better than a fine wire type. I'd run this. Maybe a B9HS for long tracks.

But if I had the engine spinning somewhat faster & water cooled/high compression, long tracks, I’d go for a B9EGV. Which turned out to be the best for my 50, even better than million dollar race plugs. The point is like high octane petrol, there is only advantage in specific setups.

I found that the std ign chewed through plugs so I’d want to chuck a new one in every couple of meetings or a misfire would creep in. When I replace the ignition it was much less likely to degrade plugs.

PS: if you have the std ign they often have a dirty great flywheel weight on the outside which can be removed by grinding/drilling the rivets.

[Posh Tourer :P]

Why?
What does the resistor do???

Resists.... If you are getting the wrong current through from the coil, it can bugger up plugs right proper (ie cause the electrodes to wear or foul up)....Try replace the coil, and put a new plug in. If not, replace the spark plug cap with a resistor one of the right ohmage. This might help the coil too....

[stanko]

What does the resistor do???

On some bikes it is used to suppress electrical noise caused by the ignition.
Yamaha RZ's are supposed to use them to prevent interference with the powervalve controller. I think resistor plugs are more likley to foul than non resistor (but that may be crap, just what I belive).
Im putting a non resistor plug in my bucket for Sunday

[F5 Dave]

You aren’t trying to match anything, it is just a simple coil generating as large a voltage as it can & jumping over a gap. The resistor is a RF suppression device, either in the cap or plug so it doesn’t interfere with your telly. At Ohakea when we used to race there (sigh) we had to do a ride-by to check we weren’t noisy on their radio system.

[dangerous]

. . . anyways, on the dyno I found that B8HS was the best plug, better than a fine wire type. I'd run this. Maybe a B9HS for long tracks.

Sweet, right I'm on my way down to repco now for the plugs... so thats with out the resistor Dave?

Don’t worry too much about what was std, the bike is no longer std or being used for hauling 5 family members & the prize goat around to sell it’s wares at the local village market in one of these dreadful third world economies, like Taranaki.

LMFAO... now that is worthy of a greenie rep

a highly important engineering saying to think about:

If it aint broke dont fix it!


It works with the current plug so just replace that one.

Ahhh... but it is broke, and I'm wanting to elimanate the plug. I explained the problem I have above.