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Shred Jesse

WR400F --> Tell me about the powerbomb header... got some questions!

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So, I've got a 99WR400F. I love the bike on the trails, even if it's old and heavy by modern bike standards. It's treated me great, and it's just what I'll need for a while to come.

Anyways, I'm interested in what the power bomb header has to offer the bike. I'm curious about the following things specifically:

1- Does it make it easier to get to the oil filter? Having to undo the exhaust headers every time seems a bit absurd for something as common as a filter change...

2- Does it actually deliver any noticable benefits to power? Is there anything lost? I'm all about this bikes low end grunt, so if this takes it away in favor of high end, it's not in the cards.

3- Does this require rejetting?

Thanks in advance for sharing your experience!

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Yes the power bomb runs a little higher making oil filter changes a breeze. It's almost worth the money just for that.

I put the p bomb on there so long ago that I cannot remember how it effects performance. Other 400 riders say mine rips. I have p bomb w/ white bros e series with 11 discs with yz carb and needle. FMF AOF CDI module with two programmable ignition maps.

2. If you favor the grunt I would leave the exhaust cam timing set to WR Specs. Just remember the YZ timing really snaps hard at the midrange. Makes it more fun to ride, but you do have to work a little harder.

3. You will want to talk to FMF about jetting to their specs after getting your header.

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i recently installed one on my wr450...oil filter change is a breeze...the power from the header is wierd...before i made the change i was always hitting the over-rev limiter, i found i got more power sooner so i didnt have to wind out the 4 stroke on the sand hills i like to climb...and it gives the motor a different sound.... i was told to rejet after any intake or exhaust mod to ensure your not running too lean...:thumbsup:

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2. If you favor the grunt I would leave the exhaust cam timing set to WR Specs. Just remember the YZ timing really snaps hard at the midrange. Makes it more fun to ride, but you do have to work a little harder.

.

Changing my 450 to YZ timing was the best thing to happen to my bike other than the pipe.

The WR timing just made a good motor run like crap

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The power bomb header on my 07 450 gave it better low end power.It will not make top end power with this header,but perfect for trail riding.had to go way up on pilot jet with this header.

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I've considered it, but I'm not entirely sure I'm unhappy with the power. Thus far it's great for trails, and I'm not really finding myself wishing I had more high end power (yz configuration). Only problems I'm feeling actually is low low end power when chugging up crazy gnarly hill climb rock gardens. I fear some of my issue relates to oil weight (15w40 rotella) and it being cold out though. I'm switching back to manufacturer suggested 10w40.

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I suppose slipping the clutch is an option, I just expected these bikes to have enough lug I wouldn't have to do that!

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i never understood the value of the cam until i put it on....it gave me power but much lower on the rpm range, the bike doesnt have to rev up to get power to move anymore...its really nice...

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Okay, so are you referencing just the aftermarket cam, or is it an aftermarket cam that is also advanced a tooth so it runs like the YZ configuration?

Also, which cam did you use? I've heard the hot cams auto decompress isn't that hot...

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One thing you might want to think about before throwing a bunch of money at motor mods you might not necessarily need is the state of the suspension, bearings and brakes on a bike that old. Everything more than likely needs a good rebuilding. Just saying you might want to factor that into your costs first, needs before wants......

Tear her down to the frame and see were she stands :thumbsup:

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Ahhh, see I'm a step ahead of you! I already ordered EVERY bearing on this bike and I've got a few months with which to go replacing everything. Every bearing outside of the engine will be replaced, and other common wear parts (chain, sprockets, etc) have already been replaced.

This bike will be a shining example of what maintenance on a dirt bike should entail.

I'm also investigating a new piston, as this motor undoubtedly has a good amount of miles on it. At that point I might as well go with the new exhaust cam with the auto decompression.

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Ahhh, see I'm a step ahead of you! I already ordered EVERY bearing on this bike and I've got a few months with which to go replacing everything. Every bearing outside of the engine will be replaced, and other common wear parts (chain, sprockets, etc) have already been replaced.

This bike will be a shining example of what maintenance on a dirt bike should entail.

I'm also investigating a new piston, as this motor undoubtedly has a good amount of miles on it. At that point I might as well go with the new exhaust cam with the auto decompression.

Good to hear :thumbsup:

I'm just saying that with a bike that old thats new to you a good idea is to tear the whole bike down to the internals and start measuring and inspecting parts for wear. All the little things can add up and be costly. I just wouldn't go buying parts before you see all you really need.

From first hand experience I'm going through a 03 RM250 I got this fall. Ran good and seemed in decent shape though I knew it needed work, bought cheap as a project. Did some basic work, bearings, gaskets, chain, sprockets, fluids, clutch basket and plates and then put 40hrs on it. Tearing it down this winter the list keeps piling up.....

Bushings, seals, fluids and broken parts in forks and shock- usually no biggie, normal maintenance but the state of the internals on this suspension was a horror show

Stator

Cylinder head

Piston, rings- no biggie, standard

Rear caliper rebuild

Bottom end bearings and seals

Every gasket on the machine

Still haven't actually split the cases to see if any gears need replacing, coming soon

The list goes on with little odds and ends. You're going about it the right way, just trying to save you from getting yourself in too deep, I know I'm getting close :ride:

I would say no brainer replacecments on your bike would be

piston, rings

camchain

fork and shock, seals, bushings, fluids

quite possibly the valves

check out bottom end

inspect clutch

Take a look at all these things and see were you stand :blah:

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my wr has the auto decompress pin on my Hotcam stage 1 and it works great for my 2005 450...i dont know about the 400 model. and tribalbc has a valuable point...i made all the engine mods first and the mods made my bike really fast last Fall...the problem is i made it too fast for the suspension...i ended up with broken ribs for the winter because the suspension wasnt right to handle that much more power and i crashed because of poor handling...i have since made a call to steve at factory connection and recieved my suspension parts so i can manage the power better...so the lesson for me was make sure the suspension can handle the power...unless you like to be in pain...

good luck

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On my 04 450, adding hotcam's REALLY changed the bike, some good, some bad.

The good - major power gains.

The bad - very early, and explosive, power delivery. Not good for trail/woods.

For the big majority of the riding I do it wasn't a big deal, but you had to ride the bike aggressively all the time, for tight nasty stuff, or when I was really tired, "nasty" seems to be a good word to describe it...lol.

You probably have seen my older posts on my unique way of smoothing the power delivery out, and the megabomb certainly played a big part in that I think, but I can't comment on how different the megabomb is vs a powerbomb.

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