# Spark Plug gap



## Honda4Life

Hi Everyone,

I would certainly appreciate your help/advice on something.

I recently bought a Troy-Bilt 2890 XP Vortex Tracker and the manual says the spark plug gap should be 0.03-0.06. 

This is quite a difference and I'm not sure what measurement I should use.

As a follow up question, what is the implication of having a small gap vs a big gap? Does one give a bigger spark and more power vs a smaller spark and less power?

Thanks!


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## tabora

Honda4Life said:


> the manual says the spark plug gap should be 0.03-0.06.


I've always used .030" for the BPR6ES. Are you sure about that spec? It should be 0.60 to 0.80mm which is 0.0236" to 0.0315"

MTD manuals are notoriously bad for typos... My manual for the 357cc engine says:

Measure the plug gap with a feeler gauge. Correct as necessary by bending side electrode. See Figure 6-4. The gap should be set to 0.030 in. (0.76mm). 
However, Figure 6-4 is a train wreck:


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## 140278

your used to us standard that measurement listed is metric , i can't find the measurement you posted in any of the service center manuals i have they list .60 to .80MM which is .024 to .031 inches for spark plug gap.

at the top of the cub cadet section you will find the shop manuals for your machine in a sticky thread at the top , troybuilt is a twin of the cub with less added bling
use the NGK tabora told you to use gap it as he stated 

good luck


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## Clutch Cargo

tabora said:


> I've always used .030" for the BPR6ES. The gap should be set to 0.030 in. (0.76mm). However, Figure 6-4 is a train wreck:


Unbelievable and very unprofessional. Spark plug gaps are listed as nominal for a reason. Most people won't have the feeler gauges necessary or understand how to deal with a mean of a tolerance or upper and lower control limits. This is what happens when everything is outsourced and no one is paying attention. I've seen it my own work where we make an engineering change and it takes months, and sometimes years for the documentation to be updated and even then there are errors.


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## JLawrence08648

I'd go with .030, it's recommended gap is measured with a round gauge, not flat feeler gauge. I have both but to me it doesn't make much of a difference.


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## Oneacer

I use .30 for small engines.


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## aa335

tabora said:


> However, Figure 6-4 is a train wreck:
> View attachment 175121


This is not very helpful at all. I interpret this as to set the gap between close but not touching, far but don't break the electrode. If the user doesn't have a way to measure, just leave as it came out of the box.


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## Clutch Cargo

JLawrence08648 said:


> I'd go with .030, it's recommended gap is measured with a round gauge, not flat feeler gauge. I have both but to me it doesn't make much of a difference.


I have both as well, and tend to use the round because despite what one sees in the diagrams, the center electrode and ground electrode surfaces aren't parallel. However, sometimes when dealing with a worn one, I will use the flat just to compare.


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## orangputeh

i prefer metric in all my shop work. never understood why the US stays on standard.


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## drmerdp

I keep mine ~.028 on everything except my 2 strokes, which I set a bit tighter.


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## 140278

orangputeh said:


> i prefer metric in all my shop work. never understood why the US stays on standard.


wasn't it back in the early 70's we tried to go to metric and the people all complained ? i know they didn't like us pumping gas in litters , OH i can't figure out my MPG's now, we had road signs reading both miles and kilometers , 
i wish we would, it's a lot easier to work with everything is in 10's than working for a german company i had to understand metric learning it was so easy


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## orangputeh

The OP also asked what will be the difference between the numbers. for example if the gap is supposed to be between .028-.031 inch then how does the plug fire different on 28 compared to 31?

I was told once to widen cap a little to make a hotter spark but i also understand too wide a gap can cause a weaker or no spark.


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## scrappy

orangputeh said:


> i prefer metric in all my shop work. never understood why the US stays on standard.


I prefer standard, never understood why I had to buy all new wrenches and sockets


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## Honda4Life

Thanks everyone for all of the feedback. I will go with 0.03 inch as I too have the 357 engine.


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## Honda4Life

Since my machine is fresh out of the crate, I'm trying to take the advice of those on this forum, and some video bloggers, and trying to do some preventative maintenance (synthetic grease and anti seize to various areas of the machine) before using my machine for the first time. So far I've found a loose wheel in the tracks which was causing the right track to bind when trying to manually push the machine (I have both triggers zip tied down to engage neutral). I also found a missing screw in the mechanism which attaches to the chute which makes it rotate. I also removed the spark plug to check the gap. It was 0.015. I couldn't even get the tool in to raise it because it was so low. I used a pair of needle nose pliers to create enough space to get the tool in, where I re-gapped to 0.03 as per the discussion above. I still need to put some synthetic grease on the chute pitch and spray the auger as best I can. I know I should remove the tracks and put synthetic grease on the wheel shaft but it looks like a really big job. Oh, and I need to buy gas for it!😅
I'm moving out of my house soon, and it will have to go into storage until my new house is ready, so I don't really want to leave the gas sitting in the tank if I don't have to.
Take care everyone!


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## ST1100A

The smaller the gap, the less voltage to jump it, and a smaller spark that doesn't ignite the fuel as well.
The larger the plug gap, the higher voltage required to jump it, which the ignition system is capable of, will produce a bigger broader spark to ignite the fuel mixture better.
Many times if you have a 'Fouled' spark plug, you can make it 'fire' by removing the cap from the plug and placing it an inch or so away from the contact of the spark plug and make it 'Jump' across the large air gap from the spark plug cap to the spark plug.
By doing that, you increase the 'Voltage' tremendously and it will 'Jump' the air gap of the spark plug to make it 'Fire' in the cylinder combustion chamber and ignite the fuel mixture and therefore make the engine start and run again.
By doing that you take the voltage induced to make the spark plug 'fire' at a tight gap that may only use less than 10,000 volts, and increase the voltage to upwards of 40,000 volts, which a small engines coil will do, and make the engine start again with a 'wet fouled' plug.
Once it starts, let it run for a little while like that to get the plug tip hot and burn off the excess wetness and carbon, then re-connect the spark plug wire.
It works many times to get an engine to fire and start when you have a fouled plug, try it sometime. It doesn't always work, but most times it does.
When you have a tight air gap, say .020" the voltage will be a lot lower than a gap of say .035" which might change from 10'000 to 20,000+ volts which a small engine coil will produce.
The higher the voltage, the stronger the spark which the engine needs to ignite the mixture to make it run.
I normally set my air gap to around .030" to .035" and rarely ever have starting problems or 'Wet-Fouled' plugs by doing that.


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## Honda4Life

ST1100A said:


> The smaller the gap, the less voltage to jump it, and a smaller spark that doesn't ignite the fuel as well.
> The larger the plug gap, the higher voltage required to jump it, which the ignition system is capable of, will produce a bigger broader spark to ignite the fuel mixture better.
> Many times if you have a 'Fouled' spark plug, you can make it 'fire' by removing the cap from the plug and placing it an inch or so away from the contact of the spark plug and make it 'Jump' across the large air gap from the spark plug cap to the spark plug.
> By doing that, you increase the 'Voltage' tremendously and it will 'Jump' the air gap of the spark plug to make it 'Fire' in the cylinder combustion chamber and ignite the fuel mixture and therefore make the engine start and run again.
> By doing that you take the voltage induced to make the spark plug 'fire' at a tight gap that may only use less than 10,000 volts, and increase the voltage to upwards of 40,000 volts, which a small engines coil will do, and make the engine start again with a 'wet fouled' plug.
> Once it starts, let it run for a little while like that to get the plug tip hot and burn off the excess wetness and carbon, then re-connect the spark plug wire.
> It works many times to get an engine to fire and start when you have a fouled plug, try it sometime. It doesn't always work, but most times it does.
> When you have a tight air gap, say .020" the voltage will be a lot lower than a gap of say .035" which might change from 10'000 to 20,000+ volts which a small engine coil will produce.
> The higher the voltage, the stronger the spark which the engine needs to ignite the mixture to make it run.
> I normally set my air gap to around .030" to .035" and rarely ever have starting problems or 'Wet-Fouled' plugs by doing that.


Hi ST,
Thanks so much for the great explanation, I certainly appreciate it!


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## Rooskie

aa335 said:


> This is not very helpful at all. I interpret this as to set the gap between close but not touching, far but don't break the electrode. If the user doesn't have a way to measure, just leave as it came out of the box.


You would think that would be OK and back in the day, they usually were at least close. 
It seems as though every plug I've bought in the last 10 years needs to be adjusted before installation


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