Update: FMF Universal Spark Arrestor at 10,000 Miles

[SpudRider]

I have now ridden about 10,000 miles with my FMF, Universal Spark Arrestor installed on my Zong. Therefore, I think it is time for an update. My FMF TC2 is still in excellent condition, and is operating superbly. I am still very pleased with this spark arrestor, and I think it is a superb value.



As with many lightweight, high-performance silencers/mufflers, the FMF TC2 is designed with a central core, surrounded by packing material. Two-stroke silencers, such as the FMF TC2, are packed with two-stroke packing material, while four-stroke mufflers are packed with four-stroke packing material.

The exhaust from two-stroke engines is much cooler than the exhaust from four-stroke engines. Therefore, two-stroke packing material is usually a little less expensive, and less resistant to heat. Fortunately, the two-stroke packing material in my FMF, Universal Spark Arrestor is still in excellent condition after 10,000 miles! I believe FMF packs these silencers with very good material. However, I also believe the 196cc engine in my Zong is less punishing on the FMF packing material than a larger engine would be.

Spud

[SpudRider]

When used with a four-stroke engine, silencers/mufflers need to be repacked for a variety of reasons. Packing material is placed around the central core of the silencer to lower the sound of the exhaust. The packing material also insulates the aluminum canister of the exhaust silencer from the very hot exhaust gasses. However, hot exhaust gasses, pressure, and vibration eventually cause the packing material to degrade, and be blown out the rear of the exhaust system. Also, any unburned fuel entering the silencer/muffler will slowly damage the packing material.

When the packing material becomes sufficiently degraded, your silencer/muffler will get much louder. Also, you will experience a mid-range power loss, since the exhaust gasses will encounter turbulence as they pass the voids inside the silencer caused by the missing packing material. :( In addition, as the packing material disappears, the aluminum canister of the silencer will be less insulated from the very hot exhaust gasses.

Fortunately, all FMF silencers/mufflers are designed for easy repacking. Also, you can buy four-stroke packing material from many vendors for less than $10. You can download the repacking instructions for the FMF, Universal Spark Arrestor at the FMF website.

http://www.fmfracing.com/Content/tec...rbinecore2.pdf

Spud

[SpudRider]

So how do you know it is time to repack the FMF silencer on your four-stroke motorcycle? An important visual clue is to examine the FMF sticker on the silencer’s canister. As the packing material disappears, the aluminum canister is increasingly subjected to greater heat. This intense heat will cause the FMF sticker to blister, and even melt completely away! Therefore, if your FMF sticker is still in good shape, your packing material is likely to be in good shape as well.

Another visual clue is to examine the front end of your silencer’s canister for cracks. Once again, as the packing material disappears, the canister is less insulated from the hot exhaust gasses. These hot gases can break welds, and crack the case of the silencer.

Your silencer will become noticeably louder as the packing material disappears. In addition, if you knock on the side of the canister, you will hear a hollow sound. A silencer with good packing material will sound solid.

Finally, the canister of the silencer will become very hot when the packing material disappears. When you stop your motorcycle, you should be able to place the palm of your bare hand on the canister for a second or so, if the packing material is still in good condition. Needless to say, be very careful if you choose to employ this particular test! If the canister is very hot as you hand approaches, you don’t need to touch it. A canister with good packing material will be warm, but not too hot for your approaching hand. Of course, if the FMF sticker is blistered, or melted away, don’t get your hand near the hot canister! 8O

After riding for 10,000 miles, the two-stroke packing material in my FMF TC2 is still in excellent condition! Therefore, I have not needed to repack my FMF, Universal Spark Arrestor. However, I will continue to monitor the condition of my FMF, TC2, and I will report my findings on this forum.

The FMF, Universal Spark Arrestor is an excellent product, and it is very durable. I am very pleased with this silencer, and I consider it an excellent value.

Spud

[AZ200cc]

I'm amazed that front tire is still trucking along, Things been through heck and back.

[SpudRider]

Originally Posted by AZ200cc

I'm amazed that front tire is still trucking along, Things been through heck and back.

That's a different front tire, AZ. The first photograph shows my Zong with the stock, 18-inch front wheel. The second photograph shows my Zong with a 21-inch, front wheel I laced in November.

Spud

[Weldangrind]

Thanks for the update Spud. I've always wondered what FMF mufflers would be like long-term, and you've answered the question. I find it quite remarkable that you haven't needed to repack it yet. Will you switch to four stroke material when the time comes?

[SpudRider]

Originally Posted by Weldangrind

Thanks for the update Spud. I've always wondered what FMF mufflers would be like long-term, and you've answered the question. I find it quite remarkable that you haven't needed to repack it yet. Will you switch to four stroke material when the time comes?

You're welcome, WG. I am also pleasantly surprised at the longevity of the FMF, two-stroke packing material!

The four-stroke packing material is designed to tolerate higher heat, and it only costs several dollars more than two-stroke packing material. Therefore, I certainly will repack my silencer with four-stroke packing material.

Spud

[SpudRider]

There is another important factor to consider concerning the longevity of your exhaust system. Your engine will run hotter if your fuel/air mixture is too lean. The resulting, higher combustion temperatures are not only harder on your engine, they are also harder on your exhaust system.

Running your engine too lean will greatly increase the heat of the exhaust gasses, and more rapidly deteriorate your muffler packing material. Also, once the packing material is compromised, the hotter exhaust gasses will also more easily damage the canister of your silencer.

Therefore, it is always better to set your fuel/air mixture a little too rich, rather than a little too lean.

Spud