Spark Arrestor (info please)

[michaelaverett]

Hey Guys,

Could someone please provide me with a little info about the spark arrestor. I have tried a search and came up empty-handed. I know that my bike has one but I am not even sure what exactly a spark arrestor does/looks like/located/can be removed/etc.... As much info as you can provide would be greatly appreciated.

Thanks,
Michael Averett

 

[Mavrick70004]

The Spark arrestor is a device intended to prevent combustible materials, usually sparks or other tiny flaming debris, from being shot out the Exhaust and starting a wild fire. what does it look like can vary MX bikes do not come with Spark Arrestors from the factory while "off-road" bikes do. they can be a cone shaped wire mesh or actually a metal plate desigen as in the FMF "Q" whatever they are made of they are usually located at the very end of my muffler in order to not obstruct any of the flow characterisics inside the muffler. if you stick your finger inside the end of the muffler you should only be able to insert your finger a couple inches before hitting an obstruction that obstruction is the spark arrestor, and most importanly can it be removed well of course it can be removed some are simply bolted or rivited on while other might be welded on eithier way they can be taken out simple plan, take the muffler apart as if you were going to change the packing hold the big fat end to your face and point the smaller outlet end toward the light see anything that obstructs your view? well that is the spark arrestor and that is what would need to be removed.

 

[Mavrick70004]

If you remove your Spark arrestor though there is a possibility you will not be able to ride if caught by a ranger or whoever else is in charge. they have been known to grab a stick and put it down the exahust, if stops a couple inches then they know you have a spark arrestor. if it goes in all the way in then they know you do NOT have a spark arrestor and will not let you ride and tell you to leave, or they will "hold" your bike while you go buy one if you really want to ride. eithier way you wont be going into the riding park without one unless u remove it once u get in but serisouly your there for fun not to race and compete and try to get every little bit of power out of your bike while passing lil 6 year olds so just leave it in lol

 

[michaelaverett]

Maverick,

Thanks for all the info. I really appreciate it. I currently have a spark arrestor in the bike but I am looking for a little better performance. I did my first race this weekend and I am looking to do a few more. So, if I understand you correctly I can make the bike a little faster by removing it? If so, would I need to rejet?

Thanks,
Michael Averett

 

[Mavrick70004]

Theoreticly yes you would gain a lil speed just becuase the exhaust has less resistance. would it be noticble? probably not it takes quite a bit of tuning in order to actually feel power differences for example change the pipe and you will "feel" the power, run better gas and you will "feel" the difference as for the spark arrestor once you have it out of the silencer you will probably laugh at how dinky it is and probably wont fell the difference but it does restrict the exhaust flow so if your looking for evey bit of power then just take it out and no you will not need to rejet. if you are going to be racing then i would look into a different Silencer. where i ride there are sound restrictions and spark arrestor requirments so i did not really have a choice but to get the FMF "Q" if i wanted to ride. but FMF makes other silencers as well that do not come with Spark arrestors and will give you better power.

http://www.fmfracing.com/products/catalog.aspx?CategoryID=9

 

[flyingfuzzball]

yea i have found that the ammount of power i have with out my spark arrestor vs the ammount of power i have with is not noticeable. you really only need that little bit of power if you are competing in some MAJOR race and need to sqeeze every billionth of a hp out of it.

i just leave it in then i dont have to worry about forgeting it when i ride trails

 

[keefbikes]

I can take mine on and off very easly. I have noticed no power gain with it off. If you do want more power you will have to pay for it. Get a new pipe, change your fuel to a higher octane (big boost for me), search the web for hp boosting parts. You can't gain alot out of small mods to your bike unless you realy know what you are doing. I dont so I pay for the extra hp parts.

 

[rmc_olderthandirt]

The spark arrestor is either built into the silencer (the last part of the exhaust system) or it could be a part added onto the silencer. Either way, if it is an approved spark arrestor it will say so, I believe the text is "US Forest Service Approved Spark Arrestor". If you don't see words close to that stamped into the silencer then it is not an approved spark arrestor.

As for performance, many people believe that removing silencers/mufflers or "reducing backpressure" will make a significant improvement in performance. That is not necessarily true on a four stroke engine and it can be totally false on a two stroke even to the extent of hurting performance.

The expansion pipe is a vital part of a two stroke system. To a lesser degree the silencer is a part of the equation. A significant change to the silencer may require a change to the carburetor jetting, and without making that change the performance might actually suffer.

Unless you are racing and need that last little bit of performance I suggest that you leave the spark arrestor in place. As others have said, it is doubtful that you would really notice the difference.

Rod

 

[michaelaverett]

Much thanks to everyone who has contributed. So it looks like I'll just leave it on and search for power in other places. I have the aftermarket pipes and have even regeared by changing the teeth on my sprockets. What else can I do and what is this about fuel? (I just run premium from the pump)

Thanks,
Michael Averett

 

[Mavrick70004]

Gas Station Premium is only 91 or 92 Octane there is only one Gas Station around me that sells 100 Octane and thats what i use in my 06 since yamaha stats say it needs at LEAST 95 Octane. i kno there are higher octanes and im sure someone will respsond and tell you where u can buy higher octane Fuel. but pretty much a Higher Octane Gas is more stable at higher temperatures, the gas itself is cleaner and more potent therefore a bigger better and more efficent spark is created. Also think about this when you add oil to your gas it lowers the octane so if you are running 91 octane it could be as low as 87 or 89 when you are done mixing, that is why my bike requires at least 95 so after the oil is mixed i still have a octane of around 92.

 

[Mavrick70004]

As for More power that would depend on the bike, which bike are we talking about here? and is it a 4 stroke or 2 stroke?

 

[rmc_olderthandirt]

Regarding the fuel:

The octane rating of the fuel is measure of how high a temperature it can be raised to before it self ignites. When the air/fuel mixture is compressed in the cylinder it gets hot. The cylinder is hot due to prior cycles, and the head (and especially the spark plug) can be really hot. If the fuel ignites before it is supposed to bad things happen (often referred to as "pinging").

Higher octane fuels allow a greater compression ratio to be used in the engine and makes it a bit more immune to cylinder heat. A low performance bike (trail bike) will be just fine on regular gas. If you are running a "performance" engine (most MX bikes) then it probably requires a minimum of 90 octane gas (premium). Modified race engines with even higher compression ratios need even higher octane racing fuels.

Using a gas with too low of an octane can destroy the engine.

Using a gas with a higher than necessary octane won't hurt anything (except your wallet) but it will NOT provide any additional power.

Rod

 

[michaelaverett]

Thanks guys!