Author Topic: LT500R head spark plug angle (Read 1357 times)

Rainman56 · « **on:** February 12, 2013, 03:07:35 pm »

Bought my Zilla in pieces so i don,t know but is the spark plug off center in the head for clearance reasons?Doing some head mods and if there is clearance I,m going to weld and move the plug hole to the center while modifying the dome/squish are.

Like I said wondering if the plug being offset is for clearance issues?

Rainman56 · « **Reply #1 on:** February 12, 2013, 05:21:20 pm »

Anyone?

Stpltn250r · « **Reply #2 on:** February 12, 2013, 05:57:08 pm »

yes its offset. assuming to remove it easier when bike is fully assembled.

Dezsled · « **Reply #3 on:** February 12, 2013, 06:11:15 pm »

It looks like its at an angle to easily remove the spark plug.

Oops it's already been answered.... Duhhh

Rainman56 · « **Reply #4 on:** February 12, 2013, 07:13:34 pm »

Is there enough room to remove it if it were to be placed straight up in the center of the head?Like I said my 500 was purchased in pieces so I don,t know how much clearance it has.Basically would the plug be able to be removed and installed if it was dead center straight out?

Dezsled · « **Reply #5 on:** February 12, 2013, 07:29:05 pm »

This pic might give you an idea of the space available

If it was straight up removing the plug might be a problem

Rainman56 · « **Reply #6 on:** February 12, 2013, 07:38:25 pm »

Hard to tell in the pic but looks like it may be too tight up against the arch/backbone?

Dezsled · « **Reply #7 on:** February 12, 2013, 07:42:18 pm »

Yeah I'd hate to steer you in the wrong direction.

Rainman56 · « **Reply #8 on:** February 12, 2013, 07:51:15 pm »

Checked out a few more pics and beings a cool head has the plug on an angle I,m pretty sure it must be for clearance.If there was room to move the plug to a better location(the center) I,m sure the aftermarket would have done it already.

Stpltn250r · « **Reply #9 on:** February 12, 2013, 09:27:36 pm »

there is way more than enough room for clearance on the plug. the domes in the cool head also turn in any direction but are still at an angle. its fine the way it is. no need to reinvent the wheel. T

The reason its angled the way it is is so when the spark plug fires the flame front does not rock the piston from front to back, it aims it parallel to the wrist pin so there is no rock in the piston. No one wants the piston to rock back and forth at 8k rpms do they??

Rainman56 · « **Reply #10 on:** February 13, 2013, 07:04:38 am »

So does anyone have a clear up close pic of a Zilla engine in the quad to show how much clearance there is?Preferably with the fuel tank off.

Rainman56 · « **Reply #11 on:** February 13, 2013, 07:16:23 am »

[quote author=Stpltn250r link

The reason its angled the way it is is so when the spark plug fires the flame front does not rock the piston from front to back, it aims it parallel to the wrist pin so there is no rock in the piston. No one wants the piston to rock back and forth at 8k rpms do they??
[/quote]

Generally piston rock is dealt with more so by the pin location being offset on the piston itself no???

Dezsled · « **Reply #12 on:** February 13, 2013, 10:02:36 am »

This is the best I've got atm......

Rainman56 · « **Reply #13 on:** February 13, 2013, 11:39:36 am »

Thanks Dezsled,you,ve been a big help.Looks pretty tight in there.Looks like the angled plug is for clearance issues.Looks like I,ll be leaving things as they are and just fixing the squish.

WestTexasKing · « **Reply #14 on:** February 13, 2013, 04:23:34 pm »

...I need to read all these threads before I post.
Seems you guys already have it figured out

Rainman56 · « **Reply #15 on:** February 13, 2013, 05:23:57 pm »

Quote from: WestTexasKing on February 13, 2013, 04:23:34 pm

...I need to read all these threads before I post.
Seems you guys already have it figured out

Not 100% yet,still all ears.

Nickisgod · « **Reply #16 on:** August 24, 2013, 10:39:58 pm »

hey sorry to gave dig this, but why are the spark plugs offset angled? is the official answer for ease of access? ive always wanted to know

WestTexasKing · « **Reply #17 on:** August 25, 2013, 05:04:46 am »

It's so you know that the cylinder is on the right way.
If the plug is pointing left, you're good.
If the plug is pointing right, you put it on backwards.

Motoman991 · « **Reply #18 on:** August 25, 2013, 06:56:18 am »

Quote from: WestTexasKing on August 25, 2013, 05:04:46 am

It's so you know that the cylinder is on the right way.
If the plug is pointing left, you're good.
If the plug is pointing right, you put it on backwards.

This is the reason why. I put a cylinder on once and thought the spark plug hole was facing the wrong way. Then I noticed the exhaust was pointing to the rear. Ram air FTW

MotorGeek - Jerry Hall · « **Reply #19 on:** August 25, 2013, 08:24:17 am »

The only reason the spark plug is angled is so that the spark plug and spark plug cap can be removed. The angled spark plugs have the electrode located so close to the center of the combustion chamber it does do not effect flame propagation. Locating the spark plug in another location other than the center of the combustion chamber will effect burn speed and when the combustion process is complete. We want to complete the combustion process as quickly as possible.

Detonation is more apt to occur as the time for complete combustion to occur increases.

Remember the basics: the pressure front travels at the local speed of sound in the combustion chamber, the flame speed is controlled by the turbulent intensity and heat travels at the speed of light. Flame speed is relatively slow as compared to pressure and heat velocity.

The speed of sound is governed by pressure and temperature. The speed of sound in free air at sea level is approximately 1100 ft per second. The speed of sound in the exhaust at export opening can be over twice the speed of sound in free air. The speed of sound in the combustion chamber at peak pressure and temperature can be many times the speed of sound in the exhaust. Knowing these facts we can see that the pressure distribution on top of the piston is distributed evenly at any time during the combustion process.

Spark plug location has nothing to do with pressure distribution on the top of the piston unless we are strictly being theoretical. The instantaneous effect of the pressure distribution on top of the piston would not cause the piston to rock unless the piston was mass-less. Piston rock is controlled by piston pin offset, offset of the cylinder axis over the crankshaft, connecting rod length, the length of the piston skirts, and piston skirt clearance.

Kyle T · « **Reply #20 on:** August 25, 2013, 09:26:47 am »

Nickisgod · « **Reply #21 on:** August 25, 2013, 10:14:31 am »

whoa! thats a whole lot of theory right there. i guess i just wanted to know if there would be any benefit to have the plug vertical in the head. i noticed cr500 have there's angled back towards the intake side. anywho, thanks for the info!

Kyle T · « **Reply #22 on:** August 25, 2013, 10:26:02 am »

Oh yeah. When Jerry speaks, he gives good info.

WestTexasKing · « **Reply #23 on:** August 25, 2013, 12:02:05 pm »

...and when Kyle speaks, he gives good head (specifications)

MotorGeek - Jerry Hall · « **Reply #24 on:** August 25, 2013, 02:37:39 pm »

Quote from: nickisgod on August 25, 2013, 10:14:31 am

whoa! thats a whole lot of theory right there. i guess i just wanted to know if there would be any benefit to have the plug vertical in the head. i noticed cr500 have there's angled back towards the intake side. anywho, thanks for the info!

Sorry for such a long answer. This could also be added to my above response.

Manufacturing the dome so the the spark plug is in the center of the combustion chamber is desirable. It also simplifies machining and reduces manufacturing cost.

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Author Topic: LT500R head spark plug angle (Read 1357 times)

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