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Author Topic: Check this plug issue out. May save your head.  (Read 963 times)

chinoy

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Check this plug issue out. May save your head.
« on: January 29, 2010, 02:46:10 PM »
I have this theory that the spark plug bottom is not flus with the inside of the head.

You may actually have a complete thread or two sticking out into the combustion chamber.

How do you check ?
Simplly take out the plug and see if the last thread or two have any carbon on it.
Or
Take off the head flip it over and look at the plug.

If it does then you have a problem.

On a new bike its not such a big issue. But on a bike with a lot of miles. What happens is carbon builds up on the projected threads and then when you try to remove your plug it will strip the good threads in your head.

Whats the fix ?

a. Add an extra washer to the bottom of your plug
b. Grind off the threads that are projecting into the head. So carbon has no place to build up on.

ace.cafe

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Re: Check this plug issue out. May save your head.
« Reply #1 on: January 29, 2010, 02:59:08 PM »
Good tip!

It can indeed wreck the threads in an alloy head, if you have alot of deposits built-up in the exposed threads of your spark plug.

mbevo1

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Re: Check this plug issue out. May save your head.
« Reply #2 on: January 29, 2010, 03:14:52 PM »
On the other hand...

RE expert Tim Busby from NZ claims that a projected tip plug is better... improves burn or something.

I've been running an irridium NGK BPR8EIX ("P" is for projected tip) in my '07 iron-lung for a couple of years.  Plug is about 1/8 inch longer. No problems with fouling on the plug tip, but don't really notice any change in idle or performance, either.  Overall, probably not worth the cost, but hasn't hurt anything.

Is a plug thread more fun than an oil thread?  :D

Mike and Stumpy in Michigan
'07 Classic - Stumpy
'10 C5 Military - Sherman

chinoy

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Re: Check this plug issue out. May save your head.
« Reply #3 on: February 01, 2010, 02:43:08 PM »
This post is not about projected vs non projected plugs.

Any engine that uses a non projected plug from the factory will perform better with a projected plug its simple. Your changing your timing.

The exception would be if its a very tight combustion chamber and your projected nose is going to impede flow.

mbevo1

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Re: Check this plug issue out. May save your head.
« Reply #4 on: February 01, 2010, 06:50:00 PM »
This post is not about projected vs non projected plugs.

Gotcha...

But if carbon on a regular plug can cause problems, isn't the problem magnified on a projected tip?

Mike and Stumpy in Michigan
'07 Classic - Stumpy
'10 C5 Military - Sherman

motomataya

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Re: Check this plug issue out. May save your head.
« Reply #5 on: February 01, 2010, 10:40:09 PM »
No, Projected tip only refers to the electrode, It is longer and reaches farther into the combustion chamber. The threaded area is the same as nonprojected.

chinoy

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Re: Check this plug issue out. May save your head.
« Reply #6 on: February 02, 2010, 07:16:35 AM »
As long as the carbon is not building up on your plug threads your ok.
Projected plugs tend to have far less carbon build up because they are hanging way out there in the middle of all that heat. And fire.
Ive found they tend to foul much less and have less carbon build up.

The thing I love about Projected Plugs is that you can read your plug for both Ignition timing and fueling.

For years we used to set out optimum timing based on the ring arround the tip off the electrode.

Then we got engine simulators that would tell us what the optimum timing is.
But we still use the old method.