Plugs carby tune

C

critter39

Junior member
Hi all had a ride yesterday plug inspection running NGK B9ES with Sachse ignition on curve 7, carbs all correct as Mark and Red tune done about 250ks since any ideas to sooty plug cheers Chris
 

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Those plugs look pretty normal to me, but it's a bit hard to tell. Plug chops are not a reliable indicator with the unleaded fuel we have these days. If you wanna know if your mixtures are right, you really need to put it on a dyno or fit an oxygen sensor in the exhaust. I think Red has some exhaust headers with sensor probe spigots in them. Maybe he'll let you use them.
 
but it affects if the spark plug is able to burn free or not...:

http://www.enginebuildermag.com/2011/05/understanding-spark-plug-heat-range/

surely you haven't added 70-100HP as said on that article, but choosing the right heat range also depends on your riding style... If you only cruse below 5.000, your engine never gets cold and you might need a different spark plug than with going on a track where you almost never stay below 5.000...
 
Was using B8es 5 ignition setting very black and sooty both plugs, changed to B9es and 7 ignition setting hoping it would burn hotter to clean the plugs up has on the right plug but still quite sooty on the left tip
 
Jumping around with your settings will get you nowhere... alter ONE thing at a time to observe changes, however minute they may be.  Changing 2 or more is a waste of effort imho.

Why should a colder plug burn hotter??

piet
 
A colder plug will soot up more easily since it's not burning the soot as easily. Unless you're wringing the engines' neck which is why you're using cold plugs in the first place.

Paul
 
critter39 said:
Was using B8es 5 ignition setting very black and sooty both plugs, changed to B9es and 7 ignition setting hoping it would burn hotter to clean the plugs up has on the right plug but still quite sooty on the left tip
Click to expand...


I recently switched to B7ESs to cure a similar problem: it did.
 
What engine and state of tune are we talking about?
A triple runs B8ES easily, especially with the lower compression pistons.
B9ES is used by some folk who run higher compression pistons and higher state of tune in general.
 
You don't say how you did the plug chop.  If the pic is of the plugs pulled from an engine after normal riding, then not particularly meaningful at all. If Red & Mark set up the carbs, I reckon float height will be spot on. Certainly don't go hotter than B8ES ... B9ES should be the go although I don't think NGKs are the best option.
 
They actually look a bit rich, unless they were pulled after some low speed riding. Unless you are wringing its neck all the time colder plugs aren't really called for. The center electrode can be almost white before heat range becomes an issue. If there is a problem [detonation] little black specks will appear on the center electrode. There are many online articles about reading plugs and in my experience running a marginally higher compression ratio doesn't require a colder plug unless the engine is a big hunk of cast iron and it's on the edge on too lean.
 
Even a dead stock SF1/2/3 will run without issue on B9ES. I wouldn't run 8s unless you are not going anywhere near high speed roads - the consequences can be very expensive. They will run fine on 8s but with 9s not presenting any issues there's no point taking risks. Twins run colder plugs than triples.
 
At first i would check the balance between both carburatores with a cheap trick:

You need only
- one more spark plug
- a grip pliers or a throttle with a screw to blockade or a tape or a second person

- Drive normal some kilometers/miles till the motor has his normal temperature at work.
- put the bike on the centerstand (motor off).
- take away the left spark-plug cap, stick the third spark plug in it and ground the spark plug on ground (engine case)
- start the engine (right cylinder), sometimes you need additionally the choke
- turn the motor to 3.500 u/min and blockade the throttle safely with a methode i wrote at the beginning.
- turn off the ignition
- change the external third spark plug from left to right (of course the left spark plug cap has to be on its normal place)
- ignition on and start the motor (left cylinder), maybe with choke
- if your balance between the carburators is correct, your motor should have the same rpm at 3.500 as the right cylinder from the first run.
If not, depending of your rpm you have to tight or loosen the throttle-cable on top of the left carburator.

With the correct adjustment the motor will work like new born.

If you want to to the maximum, you can check/correct before this cheap trick the clearence of rhe rockers (?) of your cam and the ignition.

After that, normaly the color of the spark plugs will be identical if you don't have generally a problem with your carburators or your motor.

Try it out, you will see it works!

Best Thomas aus LAU
 
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