What constitutes a spark arrestor?
 

Looking into the local forestry division, and something popped up that makes me think I might be in trouble if I want to ride in the national forests or management areas. This would be a spark arrestor. By definition, it has provisions in the pipe or muffler that trap and extinguish any carbon embers, thus preventing fires and possible injury.

With that in mind, I am finding vague explanations of a spark arrestor, and with building a custom 'frankenbuggy', the intended engine and exhaust combination does not show up on the forestry's approved arrestor list. The intended muffler I want to use had a plate/plug in the center of the inner baffle tube, but was knocked out prior to me getting them(popular low cost mod for harley owners). Does this mean I would need to install a screen, or blocking plate, like what was there previously?

I am asking this to answer my other question, is it really worth all the time and $$ making it so I can ride in the national forests?

Basically a screen at the exit of the muffler. I asked myself that last question a lot --to date haven't even had the time to head out for state land once this year.

why not just make a little cap with a screen in it that would slide over the nub of your muffler, you could stick a couple of screws into to hold it on while riding there just remove it when you get back. Or just buy a legal muffler and swap it out while there. I mean its only 2 or 3 nuts and bolts. Now I am gonna hear about the power robbing of it huh? LOL

search the "allowable" list for hammerhead 250s. The muffler on them is pretty decent has an arrestor, but has a construction issue that can be easily resolved. A lot of HH 250 guys put aftermarket on theirs and finding one isn't too hard. i got mine free plus S&H.

After some deep thought, I decided to scrap the harley muffler for forest riding, and utilize the Two Brothers can I got for cheap, for 2 reasons, both ends can be removed for clean out and repacking, and I can find the correct screen for this brand, no question of fitment of fabricating for the internals. The screens run about $15-$25, so its not a bank breaker.

@zman- the screen really won't effect the back pressure too much, since all it is is a small screen, not a real baffle. I would argue for the sake of arguing, but I'm tired, lol.

I do wonder if the screen should be at the outlet, or inlet of the can, I would think the inlet would make more sense.....

Inside that way the sparks will hit the screen splash and fall inside the muffler then the muffler blows it out without the sparks being lit.. if its on the outside the sparks will hit the screen splash thru it and instead of it falling inside the muffler it will fall out side with lit sparks causing a forest fire.... i have nothing to back up what i said its just my thought on this. :)

arrestor goes at the end; fuel can ignite within the exhaust at just about any point, cling to loose carbon and be expelled out the tail as a nice little brush fire starter. when you do a fast lift from full throttle, it's going to dump fuel into the exhaust. it's not so much something lit and hot traveling the length of the system, larger particles throughout can ignite after getting wet with fuel. the screen impacts and or breaks them up enough to put the fire out so to speak. ever turn a muffler into a can grenade? ))) it'll wake up a few blocks. )))

COOOOOL!! I get the ideas, I am going to put it closer to the inlet side of the can, just seems to make more sense there.

do two then, 1 inlet, 1 outlet. if anyone ever looks at it and doesn't see a screen at the outlet, game over.

Actually, there are two different styles of spark arresters. If you take apart an FMF Turbine core, it has what almost looks like a multi-blade propeller. The out going gases hit this plate and are forced to spin through the rest of the silencer. This way any burning particles impact this plate and swirl in the muffler and cool down.

The other type is the screen option and Xbird is right. It is on the outlet side of the silencer. The screen type does add a little bit of back pressure and also reduces the decibels a little. However, with the screen type they also tend to clog up with carbine, so you want to make sure that it is mounted so that it can be cleaned frequently.

That being said, you are still going to be playing Russian roulette with the forest service folks. From my experience with dirt bikes, I have run the gamete of how they check for a spark arrestor. In some cases, if it doesn't say on the silencer that it is forest service approved, you are dead in the water. In other cases I have seen the rangers grab a stick and poke it in the silencer to make sure that it wasn't a straight through muffler.

The only way that you can be guaranteed safe is to run a silencer that states that is forest service approved.

I put fmf universal spark arrestors on both our dune 150s and they are way loud in a bad way and without back pressure killed the performance. I just today got done making a tail pipe with a smaller tube 3/4 inch inside diameter welded to a washer and welded to the huge 1 1/4 stock tail pipe opening. Will try it out tomorrow and post some pics.

We went to Gorman in June and they require usfa mufflers or a possible 1,000 dollar or more fine so I heard. So for 105.00 a piece it was worth it just way to loud. I tried to rivet tail pipes on and had good success for the first hour until they vibrated loose. When I had to remove the tail pipes the sound was crazy loud with no power, we haven't been ridding sense but getting ready for this fall.

Good info Johnny, I see there is also a noise cap of 96 decibels, so that might not be do-able either. Seems like a lot of headaches just to ride out there, but here in N.FL, there aren't too many options, unless you know people with land.

Master here is another option for you. You can use what ever muffler you want and just clamp this unit on the end.

https://www.denniskirk.com/sparky-sp...prd/442468.sku

Sparkys have been around for years, and I think I might have a couple of them buried in my parts shed. I see if I have them and if they will work for you I will send you one just for the postage.

That is another idea, and if you would part with one, I would be gracious. I honestly didn't know there was such a thing out there, but it looks like they clamp onto a pipe, I'm sure I could make it work.

Below is the can I have, and I will be cutting it down by about half its length, and since I will have the caps off, I can easily add a screen, as long as 2 brothers makes one in that I.D. I was asking about the placement of the screens due to their different designs, come look like simple domes, and some look like wind socks, I assumed they would catch better at the front of the muffler and still allow for some of the flow characteristics of the baffles to take effect, but I see your point about ranger rick not being able to 'see' the screen easily, compounded with the angle I want to mount the can at, it makes more sense to place it at the exit of the muffler, so a flash light shine will reveal it is in place.

These are the arrestor screens available
http://www.amazon.com/Two-Brothers-R.../dp/B000MALLWY