Adding a spark arrestor

I have a 99 400f with the stock exhaust. I want to add a spark arrestor to it, but I don't want to purchase a new exhaust. Is there a way I can add just the cap and/or screen to the muffler I have?

I have the same problem but I'm using an FMF powercore IV. I've called FMF to see if I could change the end and they informed me that I have an older model and they don't stock the spark arresting screen for it. Is there any hope for me, or will I just have to buy a new spark arrestor? Anyone have one for sale?


I have an 01-YZ426 that I bilt a stainless mesh cone to go inside the stock exhaust system. I have use of a spot welder that I tacked the cone inside the pipe with. It cost me less then $5.00 to build :) . However, it did take quite some time to fab up.



Promotobillet makes one that replaces the stock end cap on the 99 yz. If you have access to taps, when you order it tell them you want to bolt it on and not pop rivet it. They will send you the bolts rather than the pop rivets. That way you can remove it easier.

b-bike, thanks for idea, I was trying to figure a way to create one myself and I think I'll dosomething like what you did...

I have the Pro Moto s/a its an awesome piece of work. it aint cheap but you get what ya pay for. It's also USFS aproved, and you need that here in Kalifornia..


dont mean to sound stupid but isn't a spark arrestor just a screen inside the end cap?

Sounds like an easy homemade fix,take the cap off and tack weld or rivet a screen in.

I don't know ,.no woods here in nyc

I can blow flames out of my pipe and no one cares.

Sanch, check where you ride if it needs to be Forest approved. Here in Mo, it has to be approved. Otherwise you get the 50 dollar ticket, even if yours is homemade and works. I don't ride with one yet. I feel they are pricey but I'm sure I will change my mind after the first ticket! :-) If I feel the need I will go with the promoto one. It looks like the cheapest alternative to a new pipe.

YZF Virgin, I have the powercore IV squared which is the new one that they sell the end caps for. I've seen pix of the older round core and the end caps don't look a whole lot different. Maybe check with a local dealer and see if there is a way to rig up a square core end cap with S/A on your round core silencer. Better than shelling out $260 for a new silencer. Also, if you still have the stock exhaust, you could put the promotobillet on that and use it when you go woods riding.

I already tried putting the newer squared end cap on the "old oval" style FMF, NO GOOD. Don't waste your time, not even close. They don't make the "old" style inserts anymore, how lame is that? No more FMF pipes for me. 300+ dollars for the pipe and its on a 99 yz400 not an 89! Anyone need a replacement sparkaresstor end cap for the square FMF? 25$ I'm goin' promotobillet. :)

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