I ride mainly motorcross, and I have heard that the best investment you can make to a yz 400 is a pipe. What kind of pipe whould be the best?

thanks
Nick

E-Series Pro-Mega..
The ONLY pipe for the YZ4

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**Ride it like you Stole it!**
Matt Porritt
99 YZ400F
Rubber Chicken Racing

I run an FMF Power Core IV SA for both Desert and MX. It was quite an improvement over stock, to my surprise. Keep in mind, there is no free lunch, some pipes are great "dyno" pipes, but are not so hot in real life riding. Take a look at the local track and see what people are running....

I know people that have White Bros and Big gun pipes and love'm.

I bought the FMF because it was a great Moto pipe with a spark arrester. I need the sparky for riding desert and didn't want to be changing back and forth.

I almost bought a Big Gun but the SA add on was $89 on top of being the most expencive already.... Too much $$ for me.

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Chris in the Mojave
'98 YZ400F

chris, what improvement in performance did you get? are you using the stock header or not? i have a '99 yz400f and after reading a lot of posts about aftermarket exhaust systems, it almost seems the stock yz system isn't that bad. except of course for removing the filter cover and maybe 1-2 pounds.

I'm running the stock header for now, I may go to an FMF head pipe later. I'm waiting to see how the new ones work.

I think the Stock system is fine. I bought the FMF PC SA because I had to have a SA for Desert Races. But there was an improvement across the board with this pipe, part of the improvement may have been from the rejet I did at the same time. I have not put the stock system back on, I think I got my moneys worth with the FMF.

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Chris in the Mojave
'98 YZ400F

I just recieved a FMF MegamaxII from dirt-deals.com with spark arrestor, quiet core and tuning discs that I got for $100.00 brand new but I am probably sending it back because I just ordered a FMF powercore 4 from them for $110.00 but does not include the sparky..

These are just the silencer only not the complete header system and the sparky kit from FMF for the power core is $20. I hope I made the right decision to go with the powercore 4 instead, I liked the looks a bit better. If it's too loud which I am affraid it will be I will have to buy the quiet core from FMF for $24 bucks.. Still I think these are really awesome prices for either set up.

If you are interested you can search the clearence deals at www.dirt-deals.com - supplies are limited!

Anyone have thoughts on these two silencers?

I have not sent the megamax back yet so I still have time to choose. I went ahead and ordered the power core so I would have it before they run out.

I would love some feedback from anyone running the power core 4 - again it does not have the quiet core or spark but I think I will order those later.

I forgot to mention it's going on a 98 400.

Does anyone know if adding a silencer will require re-jetting?

...Dubach Racing Developement (DR.D) or the Thunder Alley pipes are by far the best pipes out there! You can search the site for the addresses for both. Im not sure if they fit your model year, but Im sure you can ask them.

ONE WORD THUNDER ALLEY !!!!! IF YOU DONT BELIVE ME BE AT LAKE EELSINORE ON THE 5& 6 OF JAN FOR A FREE DEMO . MY YZ426F