Spark plug gapping

Ok so I have two tomos a35's. Does anyone know what I should gap the plugs at? One has a 65cc kit on it and the other has a70cc. Also do you know if side gapping the spark plug is worth it? I read that they can make the bike run to hot and that's the last thing I need.

Re: Spark plug gapping

Side gapped works for me.

Re: Spark plug gapping

K cool but do you know what to gap the plug at on the top

Re: Spark plug gapping

Stock is supposed to be between .016" and .020". I run .015 on all my kitted bikes. It retards the timing slightly and makes for slightly lower temps. The smaller gap also makes it easier for the spark to cross the gap without being blown out at high RPM. (edited)

Re: Spark plug gapping

#CrazyWayne™ rocks. #CrazyWayne /

I never gap my plugs

Re: Spark plug gapping

Dirty Dave Stone Wrote:

-------------------------------------------------------

> Stock is supposed to be between .016" and .020". I

> run .015 on all my kitted bikes. It retards the

> timing slightly and makes for slightly lower

> temps. The smaller gap also makes it easier for

> the spark to cross the gap without being blown out

> at high RPM.

Running a smaller plug gap does NOT alter your ignition timing. Your cooler temps are most likely from a less-efficient combustion, aka the unburnt fuel mixture helping it stay cool.

Kool.

Re: Spark plug gapping

Overpriced Parts /

Hi Wayne

Re: Spark plug gapping

Smaller gap makes it easier for the spark to cross the gap, important with higher temperatures and over stuffing of the combustion chamber.

Smaller gap also fouls easier at low revs so you need to find a goodly gap if you are in mixed driving like traffic or hilly area.

Gap will not alter your timing or the temperatures unless they are bridging and not firing on every stroke.

Re: Spark plug gapping

Actually, a smaller gap will make your bike act as though you have retarded the timing to a small degree. On a regular plug, the spark is shielded by the electrode. Having a larger gap leaves the spark open to the combustion chamber and promotes flame propagation. Having the spark shielded makes the flame propagate slower in the combustion phase. It is essentially doing the same thing as a retracted nose plug.

So, no, it won't change when your spark occurs. It will however enable higher RPMs and slightly reduce the temperatures at those RPMs. Really though, you should gap your plugs and dial in timing after, so it shouldn't matter about the flame propagation. The main benefit on a high rpm motor is not having the spark blowing out.

Those surface plugs have very large gaps from the factory. They aren't conducive to high RPM. They are also prone to fouling because the plugs aren't blown clean during high RPM blasts. I've never had good results with them. I find that a regular B7HS works great for most of my mopeds. An 8 (like on the surface gapped plugs) is simply too cold of a plug. On the bikes that I have that do require an 8, I can go for thousands of miles without replacing regular plugs.

I do like side gapping my plugs though. It drops them about a heat range. Perfect for a kitted bike.

Re: Spark plug gapping

So what do you think I should gap at? Sorry if I sound kind of dumb but as fare as timing goes and spark I'm a total newb

Re: Spark plug gapping

Overpriced Parts /

Between .4-.5 mm

Re: Spark plug gapping

Thanks man. Also what's you view on side gapping?

Re: Spark plug gapping

Overpriced Parts /

I side gapped on a bike that wasn't my daily driver so on a everyday bike I didn't use.

With the hi power kits like polini and Gila that I run there was very little difference but on a small piston port kit I got a little more power and 1 mph

Faster.

I don't run any side gap now

Re: Spark plug gapping

roadent$ craig /

plug gap extends the duration of the spark for sure. much like a bigger gap on yet points. bell suggests a bigger plug gap when using a cdi as a cdi's spark duration is shorter than a points ignition.

Re: Spark plug gapping

#CrazyWayne™ rocks. #CrazyWayne /

Dirty Dave Stone Wrote:

-------------------------------------------------------

> Actually, a smaller gap will make your bike act as

> though you have retarded the timing to a small

> degree. On a regular plug, the spark is shielded

> by the electrode. Having a larger gap leaves the

> spark open to the combustion chamber and promotes

> flame propagation. Having the spark shielded makes

> the flame propagate slower in the combustion

> phase. It is essentially doing the same thing as a

> retracted nose plug.> motor is not having the spark blowing out.

>

> Those surface plugs have very large gaps from the

> factory. They aren't conducive to high RPM. They

> are also prone to fouling because the plugs aren't

> blown clean during high RPM blasts. I've never had

> good results with them. I find that a regular B7HS

> works great for most of my mopeds. An 8 (like on

> the surface gapped plugs) is simply too cold of a

> plug. On the bikes that I have that do require an

> 8, I can go for thousands of miles without

> replacing regular plugs.

>

> I do like side gapping my plugs though. It drops

> them about a heat range. Perfect for a kitted

> bike.

You don't know what your fucking talking a bought Dave!

P.S.

Please stop posting your fucked up info Dave

Spark plug chop reading.

https://www.mopedarmy.com/forums/read.php?7,2959417,2962746,page=1

Best spark plugs with points, NGK BU8H #6431.

And this one is special for low power CDI's, NGK BUZ8H #7447. No more dead plug at hi rpm's.

But you need to use the NGK resistor Boot PN#LB10EH 8351 with the BU8H & BUZ8H plugs.

https://www.mopedarmy.com/forums/read.php?7,2863601

https://www.mopedarmy.com/forums/read.php?7,2874767

https://www.mopedarmy.com/forums/read.php?7,2881821

A colder plug will show color faster then a hotter plug and you chop it so it has pinch more red than tan in the color and it will be close to 2 jet sizes rich. http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

Now go one plug hotter and your plug will read/be leaner, and safe, if the plug is not to hot for the compression and or peak RPM power.

I like running a pinch cool and rich on my plug chops, so if my engine get's hot on a long hill etc I'm tuned so it wont smear and seize.

To get the hottest spark gap the points at .016" to .017"

Use a B7HS in winter and a B8HS on hot days over 80f, gap the plug at .018" to.022"

Timing before jetting.

Timing will effect jetting symptoms.

Oxygen makes things burn faster.

Less oxygen makes things burn slower.

You get the best power at 11:1 to 13:1 with most pump gas setups.

Pump gas combined with 9:1 to 11:1 compression needs 20º to 16º BTDC for a proper power stroke burn with a mix of 11:1 to 13:1 with most pump gas setups spinning under 10.5K RPM's.

Over 10.5K you need to retard timing cuzs things burn hell faster in two strokes.

But you need less timing as the pipe starts supercharging/hitting in the powerband to.

Hell at 14K you might need just 12º BTDC with your setup.

This is why CDI's retard timing at higher RPM's

So if your timing is to late to give a proper burn in the power stroke.

It will give you the symptoms of being rich in the idle & throttle mid rang.

So you set the needle leaner, this makes the gas burn faster giving it more burn power in the power stroke.

But it makes to much heat in the cylinder.

And it will probably gave it a good blip on the stand to.

If you have to much timing you will find yourself jetting rich to slow the burn down.

It all needs to work together for things to work proper.

This why i post to set your timing before jetting.

Hi Ken. :)

Re: Spark plug gapping

Thanks man so I guess I need to figure out how to set my timeing. Cause I'm trying to tune my bike right now with the new alukit 70cc 19mm PHBG carb and idle was reading rich and I got Dow all the way to a 40 idle jet and didn't think that's was right

Re: Spark plug gapping

Overpriced Parts /

Thanks Wayne for your curve ignition info

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