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PMB Endo on my 09

By dvn,
in YZ400F/426F/450F/450FX

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dvn

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I really wanted to keep the shorty exhaust but was looking for a little more performance. I don't need a fire breather at this point as I've been riding 250's and 290's the last couple years. The Endo removes the secondary stock cone and I had considered removing the primary cone while I was in there but decided that I can do that later if needed. I can tell you that it is MUCH louder! I only ride moto so it's not a major concern. I haven't had a chance to ride it yet. I will be going to an indoor facility next Thursday. The other thing I liked about the PMB was the tune-ability aspect. I can run it open, with the provided secondary cone, or cone and sparky together. I also have the option of adding a megabomb header down the road. I'm looking forward to riding it and I'll give a report next Thursday night.

cid__downsized_0116001456.jpg

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  • 2 weeks later...
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dvn

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Finally got a ride in with this set-up. All I can say is WOW! What a difference. The bike pulls much harder out of corners. I recently injured my left MCL and was having trouble up-shifting. Fortunately, the bike pulls so much better that I was able to ride the entire track in third. Gotta love that 450 juice! It is a lot louder without the cone and screen installed. I ordered a megabomb header before riding it and I really don't think I need any more power. I'll try it and see if I like it. If nothing else, it should make it a bit quieter. If you want to keep the shorty exhaust, I'd say this is a great option! :ride:

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426 NOOB

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Finally got a ride in with this set-up. All I can say is WOW! What a difference. The bike pulls much harder out of corners. I recently injured my left MCL and was having trouble up-shifting. Fortunately, the bike pulls so much better that I was able to ride the entire track in third. Gotta love that 450 juice! It is a lot louder without the cone and screen installed. I ordered a megabomb header before riding it and I really don't think I need any more power. I'll try it and see if I like it. If nothing else, it should make it a bit quieter. If you want to keep the shorty exhaust, I'd say this is a great option! :ride:

looks very nice, this is a great mod. Cant beat the shorty style, and the extra ponies are a huge plus.

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  • 3 weeks later...
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Brawg

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Looks sharp!

I love the look of the stock shorty and I am going to modify mine(take out the cones) for running on MX tracks. I have a slip on that is quieter though for the woods.

I have not heard of this mod. I have an 08 and have the "shorty" exhaust on it. What do you do in order to mod this can? I would prefer not to have to buy a $500 exhaust system if i can get similiar results from the stocker.

Thanks:thumbsup:

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dvn

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I have not heard of this mod. I have an 08 and have the "shorty" exhaust on it. What do you do in order to mod this can? I would prefer not to have to buy a $500 exhaust system if i can get similiar results from the stocker.

Thanks:thumbsup:

You just remove the stock end-cap (which contains the longer, more restrictive cone) and install the PMB end-cap. You can run it any of three ways. Open, cone installed, or cone and screen installed. I am sure a full aftermarket system will perform better but this gives you a good bang for the buck. Actually, I'm now running a stainless megabomb header with this for about the same total investment as a slip-on muffler. Works great for me.:ride:

MufflerSideShot1.jpg

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dvn

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Like the guy posted a couple post before this, can you pull the stock end cap off and modify it and put it back on and not buy a pmb kit?

Yes you can. It may be a little difficult to get the stock cap off without damaging it. I actually used a blind bearing puller on mine.:ride: The thing I like about the PMB is, I can run the cone and sparky if I need to quiet it down.

Hey DVN, have you tried the 06 header with that set up? Was just doing alittle thinking.?

I have not. I'm running a stainless steel Megabomb.

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TRIPLE 5

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Would you say the megabomb header gives you substantial gains over the stock header? How was the fit, megabomb to stock muffler? What are the power characteristics with that combo? Is the megabomb designed for upper RPM's power increase and powerbomb more for the bottom? Sorry for all the questions just trying to figure things out.?

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dvn

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Would you say the megabomb header gives you substantial gains over the stock header? How was the fit, megabomb to stock muffler? What are the power characteristics with that combo? Is the megabomb designed for upper RPM's power increase and powerbomb more for the bottom? Sorry for all the questions just trying to figure things out.?

Substantial gains? Probably not. The fit was perfect, no issues. I think the Megabomb broadened and smoothed the power over the entire RPM range with a decent bottom end boost compared to the stock header. I think the stock header diameter is a bit large once the muffler is opened up. Not a night and day differance but I wanted the stainless header for durability anyway.

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grayracer513

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Substantial gains? Probably not. ... I think the Megabomb broadened and smoothed the power over the entire RPM range with a decent bottom end boost compared to the stock header.

That's the purpose of any header with a resonator/pulse damping chamber, whether it's configured as the 'Bomb headers are, or the "cans" attached to the sides like the Akro's. Exhausts are "tuned" by manipulating their length to match up with the pressure waves produced in the pipe. This makes them particularly effective in a narrow range of rpm but just OK everywhere else. Adding the resonator damps the pressure waves and makes the header "appear" to the engine as if it has no fixed length, and thereby widens the effective range of the header. The old PowerBomb was a wonderful thing on an '03 YZ450.

I think the stock header diameter is a bit large once the muffler is opened up.

Also quite true. The large header diameter was a compensation for the restrictive exhaust. It isn't very noticeable in either case, but it would be more obvious if the '08 header were installed on an '06, for instance. Often a drop in performance stands out more than an increase.
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