FMF muffler
 

Anyone running an FMF muffler on their 250? Know which model will work with out stock pipe once cut? Also, is there a problem running the cheaper 2-stroke FMF, or do we have to use the 4-stroke FMF mufflers?

I'm currently running a 2stroke muffler off an ond DT175. Havnt had anyissues and a has a good tone

I have the fmf on my 150 but im curious about the 250. I dont want to gut the exhaust and make it sound like sh*t. Im just curious if the universal 2-stroke fmf would work with 250 well. The universal 4-stroke fmf mufflers are all around 160 and up.

Generally a muffler is a muffler. However, the main difference is in the diameter of the muffler itself. Generally for the same amount of CCs the 4 stroke will have a larger diameter internal core (don't really know why). What I do know that the 4 stroke use a different packing material then the 2 stroke. The 4 strokes generate a far higher exhaust temp then the 2 stroke. This higher heat can cause the 2 stroke packing to break down quicker and blow out of the muffler. So if you want to try it, run it until the stock packing blows out, then go to your local motorcycle shop and get some 4 stroke packing.

I have two fmf 2 stroke universal mufflers on our dune 155cc and 183cc and they were loud with the large 1 1/4 opening. So I used the tubing that came with the muffler kit and made a turn down tail pipe. It was quieter but still crazy loud and lost power even with jetting the carbs up. The aluminum rivets that I used to attach the tail pipes failed in the first hour and I had to remove them. But we were at 3600 to 4000ft altitude and we usually ride at sea level in the low desert. I ended up welding the turn down tail pipes and adding a 3/4 inch tail pipe welded to a washer and then welded to the inside of the turn down pipe to get some back pressure and it works great and is a lot quieter.

If I could do it again I would get the 4 stroke muffler due to the larger size and baffling inside. Also these mufflers get hot compared to the stock muffler. The fmf stickers are baking off but it got us to ride at a different place were usfa spark arrestors are required and it was worth it.
The 1000.00 dollar or more ticket for no spark arrestors is the only reason I changed the mufflers. The stock muffler with a 3/4 inch tail pipe worked great on our buggies. Not enough back pressure is bad for low and mid range power.

I don't think a 2stroke muffler works better on a 4stroke motor or the manufactures would of made it that way from the beginning...... manufactures spend millions of $$$$$$ to per-fect there product before distributing it out to dealers for us.to save time, money, headache, and taking chances, mufflers and pipes play a biger roll then you may think. There size, shape, curveture of pipe, diameter of exhause opening is all for a reason not for looks. I'm no mech. Nore einsteine, this is my perseption on this........ my point is 4stroke is for 4stroke and 2 stroke is for 2 stroke. Its apple and orange so to speak. Sorry I babble to much. Just something to think about unless you got time and money and patience then go for it. Trial and errer. :)

I am thinking on the same lines, 2 and 4 strokes benefit more from different frequencies in the exhaust, just looking at an expansion chamber will show you that. Also, the baffle tube designs are different, I'm sure one can be used for the other, but at what cost to either ones performance.

Another problem that we face on the buggies is the short header / midpipe section. The length and bends in the pipe itself helps to quiet down the exhaust note. In many case we are running little straight pipes like a Top Fueler. Then we stick a muffler on the end and expect it to be quite. I can tell you from experience, that our buggies are going to run louder, then the comparable dirt bike since we are running shorter pipes. I am running the exact same muffler on my HH as I am running on my son's hopped up dirt bike. There is no comparison between the noise outputs. On the HH the noise gets very old quick, if you do not have a helmet on, but on the dirt bike you could ride it all day without a helmet and your ears wouldn't pay the price. The best way to go is to get the mufflers quite insert, then have the end cap shoot the exhaust towards the ground

Toomanytoys; I agree or you can pack it with packing for lower decibals. But I think mb1134 wants to know is performance wise wich exhause would work better for his buggy.I use to own a yamaka banshee 2stroke screamer if I were to put a 4 stroke pipe she wont scream she will cry without a doubt ( no power). I'm sure it be the same vise versa. :)

True, for optimal performance, you want a 4T muffler on a 4T engine and vice a versa. However, due to the fact that a 2T has a shorter power band then the 4T, the 2T will suffer more ill affect from the wrong muffler then a 4T will. Now, if I needed a muffler and I had a 2T one lying around, I would give it a shot. However, if I had to buy one from the start, I would buy the correct one 1st. Also noise is an issue as well. As master mentioned, the 2T and 4T motor have a different frequency exhaust output. While a 2T motor may sound obnoxious up close, the sound doesn’t carry very far. However, the 4T motor’s sound waves tend to carry a large distance and this is one of the reasons for the different construction. I have a left over muffler from my KX250F dirt bike that would probably make a pretty good muffler for a buggy. However, it would probably be on the loud side and doesn’t have a SA, so it is useless to me out here in CA. That is one of our biggest challenges when it comes to exhaust. We have to find the balance between what the law books say and the search for the best power for the least $

As far as go fast is concerned, 4 strokes only need a little back pressure to make the most hp, add some more back pressure and you will lose a bit of hp but will gain torque, with the proper baffling and pipe size, you can dial in exactly what you want. Thats where the exhaust companies come in with their R&D, they make it work and take all the guess work out of for us, the consumers.

Toomanytoys is right though, we are compromising on our buggies, using what we can find and what we have room to fit in the spaces we need, and the results can be good and bad, noise, too much flow, restricted flow, are a couple issues I can see.

I went with the fmf muffler because it was a bolt on and it was fast and easy so we could ride at Gorman. The noise and power loss was a disappointment, but after I made a tail pipe and 3/4 insert it works really good. It did take me some time to make and a 4stroke muffler would have been better now that I can look back. But I will know for sure if the power is better when we go to the desert in October to get a better feel of the power at sea level.

Have you guys considered this?
http://www.supertrapp.com/product_se...t.asp?CatID=35
light, compact, small, about 18"overall, tuneable by the amount of disc/diffusers used.
fewer discs used adds back pressure and noise reduction. More discs added = loud and horsepower. Means your able to adjust for less than optimal lead pipes or to suit your riding conditions.
Forestry approved spark arresting and a simple slip on installation.

Wow that's too funny!! Many years ago back in" 87 " I had a honda 250x atv fourtrax. I ordered a dg pipe that came with those discs a bunch of em, I didn't understand what those disc were for so I just bolted it on the exhause all of them and rode it like that for 15years. And now is when I understand what there for. It never made any sence to me till now that you explained it. I've could of added hp to my fourtrax all that time. Lol.