airraptor

My Feedback: (66)

I dont own a gas engine yet but on some of these 50cc and smaller engine do still run the larger park plugs that have the large cap and all. Why not use smaller plugs like the 8mm plugs or go even smaller and run plugs that are in the Saito engines. Will still produce a spark big enough to light the fire and will have a smaller foot print. When i goto the Dle 20,30 and 55 i will make a plug and use these smaller plugs myself.

I know cost may have alot to deal with these but the 8mm plugs are only 2 dollars at parts stores.

HunkaJunk

Many engines run the smaller 10mm spark plugs, I have never seen an 8mm spark plug.

I use the NGK CM-6 plug in most of my engines, I have thought of changing some over to tiny 1/4 - 32 spark plugs, but the benefit of doing so did not justify the cost IMO, so I haven't done it.

Tired Old Man

My Feedback: (1)

Ignitions must have caps to fit the plugs. The smaller you go the lower the availability of cap choices. Glow plugs are pretty simple. Nothing goes on top of them since their is no external electrical source required.

spaceworm

You can buy already made adapters to use the 1/4-32 plugs or the 10 mm plugs in the engines designed for and supplied with the larger plugs. About $10.00 each from several sources. As mentioned you have to match the plug with the cap on the ignition system. Some systems can be fitted with other caps to fit the alternate plugs. Check out C&H for more details.

Richard

airraptor

My Feedback: (66)

thanks space. I will get the number that i have for my 8mm plugs i have a yamaha raptor single cylinder engine where i run two of the 8mm plugs with the stock plug to gain some power.

Tired Old Man

My Feedback: (1)

Then you have to deal with reach and heat range issues. Adding an adaptor changes the usable reach of the plug. You can end up losing a little performanc, and throttle response that way. If buying a different plug is an economical difficulty you need to stay with glow.

captinjohn

<hr />Wrong answer....Glow fuel is too expensive

Tired Old Man

My Feedback: (1)

I do not disagree, but I've very curious why using a recommended spark plug seems to be an issue for this newbie.

captinjohn

I think he said in post #1, he could make a spark plug. Hey...why not make the entire engine to what he wants. My friend did!!! I will have a photo of it here....soon! Capt,n
<hr />Here we go!<hr />

Tired Old Man

My Feedback: (1)

Ahhh yes. A labor of love, skill, pride, and accomplishment. Never cost effective, but worth every cent and minute of the endeavor. Looks great!

captinjohn

Here is a video of the Holt engine George built. He even built the spark plugs! Just had to share what a top notch machinist can do. He could have bought castings or had the gears already cut...nope he made them the hard way. Such a good finnish...it would be a shame to paint that engine! Thanks for Viewing. Capt,n now back to spark Plugs!!!
<hr />http://www.youtube.com/watch?v=tl0nD1smbAg

av8tor1977

My Feedback: (6)

Now that is what I call "ART"...

Are you still working on your Holt Captain?

AV8TOR

airraptor

My Feedback: (66)

Tiredold man i know about different reach plugs and all. just everytime i look at smaller gas engine and the long plug sticking out the cylinder when the plug is almost as big as the engine just doesnt look right. I was asking why dont these mfg's try to use smaller plugs and caps that look correct for the engine. i know if these mfg's have shorter plugs more people would be inclined to buy them to put in thier scale planes.

I love glow engine for thier power out put, and havent wanted to get a gas engine yet. i know some are getting close like the new DLE 20 that is very close in weight to most 120's.

I am not trying to save money tired old man maybe should put glasses back on lol the Saito plugs are about 20 bucks each[X(]

spaceworm

If money is no object, as was said before you can get or make an adapter, use 10mm or quarter inch plugs, buy a new, or put a new plug cap on your oold, ignition system, and then make yourself happy by installing it in your warbird. Most of us don't need to do this for whatever the reason. I don't understand your "beef". I am older than TOM, and I need glasses to read the fine print, but even with them on, I can't read your message.

Regards,

Richard

airraptor

My Feedback: (66)

lol i guess i need pics.

Industrial cylinders will large plugs in a small chamber. It just one of the reasons never went to small gas is because of the full size plug and cap sticking out as long as the cylinder is it self.

There isnt no beef, i am not trying to change your ways old men lol. i am 39 my self and have been flying for 32 years. i see my question is just over your guys head and will get pics of different engine soon to show what i am talking about. If not then never mind i know how to fix my issue just wanted to know why havent moved on to smaller plugs.

JNorton

My Feedback: (2)

The plugs physical size also has to do with how it dissapates heat also known as a heat range. Great tutor on plugs. http://ngksparkplugs.com/tech_suppor...lugs/index.asp
John

airraptor

My Feedback: (66)

lol then how does the tiny Saito plug work.

i know smaller plug = less frontal area exposed.

i kow enough on heat range's of plugs, i know how to read them, i know about flame front, i know about flame kernal, i know how fast it take for the fuel to burn in the chamber and all.


I am not asking a tech question just why dont these MFG's using weedeater cyclinders run smaller plugs. i know why and that is money. i dont like the looks of a 4" long cylinder with a 2" plug sticking out of it. the angled plugs are a bit better . the bigger the engine in CC size and the plugs starts to not be an issue for me.

spaceworm

Please, show us some pics of those 8mm plugs you have in your Yamaha. Or, at least a part number. Thanks

Richard (Dat ol' man richar', dat ol' man richar', he jus' keeps talkin' along)

airraptor

My Feedback: (66)

Space i will do that tonight if get some time. i am at work now. then soon as get home have to kids ready to go to GF house tonight. they are small plugs. Like i said i use them on my raptor four wheeler. i have bored and stroked it to 760cc and produce just over 80.7 hp at the wheels around 85 at the crank. the stock engine had one plug in the middle of the five valves. i used these smaller plugs on the outside of the combustion chamber so the i could reduce the negative torque and increase hp. running the extra plugs will help because the bore is over four inches. the extra plugs will develop three flame fronts and will help burn all the gas in the cylinder/chamber. on engines with a bore over 4.1" the fuel doesnt burn fast enough to burn all the fuel near the edges of the chamber. the negative torque is the piston rising in the cylinder under compression and where you have the plug light the mixture. as the fuel is burning and the piston is moving toward tdc you want that fuel to reach max pressure just just past tdc. So most engines have anywhere from 32-38 degrees total timing at near high rpm. with the extra plugs i have reduced that to 24 degrees 36 degrees was optimal for the single plug. this 12 degree reducton has given me an additional 4 more hp.

ok back to small engines and small plugs. yes i will get some pics for ya.

Truckracer

My Feedback: (19)

I guess I once objected to the full size, automotive style of plug once used in gassers but since many engines switched to the NGK CM-6 plug, I really don't see a problem. For example, on my DLE-30, the plug cap only extends 1 3/16" above the cylinder fins ... hardly the 2" you refer to. The special (might I say delicate) caps used on the 1/4 -32 plugs are not much shorter and usually offer more operational problems than the more reliable 10MM, CM-6 plug setup.... and the small plugs are expensive. Most of us just accept plugs as a trade off for the advantages of gas operation.

Now my question ...... why are you so worried about something that you don't even use yet? The so called problem isn't nearly as bad as you make it out to be.

Antique

My Feedback: (4)

You want small ??
morrisonandmarvin.com