What replacement spark plugs do you use? (chinese 2-stroke)

[gone_fishin]

gonna risk looking dumb (again): i believe gap will make a difference in how much of the fuel actually fully ignites. if we're unwittingly going so hot that we do successfully ignite ALL the fuel, we're also burning up our lubricant. smoke is unburnt or partially burnt fuel. i wasn't there in the olden days of 2-strokes, but i understand that just a wisp of smoke was a sign of a healthy engine.

if i need correcting also, someone else please jump in.

 

[Scottm]

Went to autozone yesterday and just happend to be helped by the motorcycle enthusiast. When i mentioned NGK he got a big smile on his face and told me all the places in town that sell them and wouldn't sell me a comparable champion plug.
None of the stores I went to that sold NGK had a B6HS. I may have to order them online. NGK does have a good website listing their plugs like hot sauce. Mild, medium and hot.

at ngksparkplugs.com in the tech info section they have a good 5 page lesson on spark plugs and how they work. Although I'm like doc and don't understand why more or less fuel would be burned. A spark is creating an explosion thatone would think would burn all the fuel. I'll keep googling.

 

[Alaskavan]

Your Autozone should be able to order them for you. You might have to pay up front, but if you don't rush the order, you shouldn't have to pay shipping. Buy a box, and put one in your tool kit.

 

[Dockspa1]

I am at a loss with reasoning when it comes to people saying that they get a more complete burn with some plugs than other. If you start a fire in the cylinder, is part of it going to go out? I say, If it ignites, it burns all of it not just some. I do understand the extra depth threads compounding oil, so ya the right length but as far as splitfire plugs etc. fire is fire!
Please repair my thinking if possible and only if wrong. Thanks
Doc
__________________
Doc be gone!

The only thing that could make the difference would be the air/fuel mix entering the jug.
Right? I mean if it sparks and ignites the little spark is not going to make a difference as to how much of the fuel burns or doesn't burn. Am I way off track here? It just makes common sense.
Doc

 

[Alaskavan]

Doc,
Your reasoning seems, well, reasonable. But. The plug I just pulled out of my motor would work fine untill high RPM. Then the motor would start missing. With the new plug, no problemo. So, though the old plug produced spark, it was in some way inadequate at high RPM. You may have hit it when you mentioned air fuel mix. The dynamics of the flow through the combustion chamber may be different at high rpm. Or, perhaps the spark was a little weaker and took a milisecond longer to propagate through the chamber. Perhaps this milisecond was of little consequence at 3,000 RPM, but made a difference at 7,000. I don't know. I don't know that I need to know.

 

[Dockspa1]

Ya I see what your saying Van and I think the balance of the pickup coil spark and the plug spark is where the real differences are. that is why there are differtent gaps.
I had a Kowasaki that would foul at high speeds, no matter what plug I put in. It would run great for a few laps then sputter. It was the timing in the pickup coil. off by just a hair but if it's too far advanced then it will not be able to keep up. in other words it will fire too quickly.
We have the electronic ignition modules so that just shouldn't be a problem un less the plug it self has a hairline fracture that once heated would seperate thus causing a miss.
Just guesses!
Doc

 

[skymfmike]

what plug is the right one

Doc,
Your reasoning seems, well, reasonable. But. The plug I just pulled out of my motor would work fine untill high RPM. Then the motor would start missing. With the new plug, no problemo. So, though the old plug produced spark, it was in some way inadequate at high RPM. You may have hit it when you mentioned air fuel mix. The dynamics of the flow through the combustion chamber may be different at high rpm. Or, perhaps the spark was a little weaker and took a milisecond longer to propagate through the chamber. Perhaps this milisecond was of little consequence at 3,000 RPM, but made a difference at 7,000. I don't know. I don't know that I need to know.

So what kind of plug I really need so I don't miss fire at high rpm.

 

[gone_fishin]

i found this on the ngk site.

3. Gapping

Since the gap size has a direct affect on the spark plug's tip temperature
and on the voltage necessary to ionize (light) the air/fuel mixture, careful attention is required. While it is a popular misconception that plugs are pre-gapped from the factory, the fact remains that the gap must be adjusted for the vehicle that the spark plug is intended for. Those with modified engines must remember that a modified engine with higher compression or forced induction will typically require a smaller gap settings (to ensure ignitability
in these denser air/fuel mixtures). As a rule, the more power you are making, the smaller the gap you will need.

A spark plug's voltage requirement is directly proportionate to the gap size. The larger the gap, the more voltage is needed to bridge the gap. Most experienced tuners know that opening gaps up to present a larger spark to the air/fuel mixture maximizes burn efficiency. It is for this reason that most racers add high power ignition systems. The added power allows them to open the gap yet still provide a strong spark.

With this mind, many think the larger the gap the better. In fact, some aftermarket ignition systems boast that their systems can tolerate gaps that are extreme. Be wary of such claims. In most cases, the largest gap you can run may still be smaller than you think.

5. Heat Range selection

Let's make this really simple: when you need your engine to run a little cooler, run a colder plug. When you need your engine to run a little hotter, run a hotter spark plug. However, NGK strongly cautions people that going
to a hotter spark plug can sometimes mask a serious symptom of another problem that can lead to engine damage. Be very careful with heat ranges. Seek professional guidance if you are unsure.

With modified engines (those engines that have increased their compression) more heat is a by-product of the added power that normally comes with increased compression. In short, select one heat range colder for every 75-100 hp you add, or when you significantly raise compression. Also remember to retard the timing a little and to increase fuel enrichment and octane. These tips are critical when adding forced induction (turbos, superchargers or nitrous kits), and failure to address ALL of these areas
will virtually guarantee engine damage.

An engine that has poor oil control can sometimes mask the symptom temporarily by running a slightly hotter spark plug. While this is a "Band-Aid" approach, it is one of the only examples of when and why one would select
a hotter spark plug.

here's the whole page: http://www.ngksparkplugs.com/techinfo/spark_plugs/installation.asp?nav=31300&country=US

 

[Alaskavan]

Okay. There's something I needed to know. I'll keep in mind that I need to go a heat range colder when I add 75-100 hp.

Probly need to add wings too.

 

[gone_fishin]

well, i do know (now) that i'm not supposed to be pursuing the hottest plug available, i probably shouldn't be after anything hotter than the cheapo stock one.

now to try and cross reference the "happy-time for making spark to smoothly ignition"...this outta be fun.

http://www.bosch.com.cn/new/web/boschinchina/company_nhsp_en.htm