Atermarket parts FMF/head/cams

11 replies to this topic
  • sigops

Posted October 25, 2011 - 08:22 AM



I have been trying to research this to death. I am considering buying a FMF powercore 4, for my yz426f. My direct question is, do I need the PowerBomb head to go with it. Every wheres I shop, they don't include the head. In my mind, you would need both. I never bought and exhaust before so maybe I'm delusional.

Second I'm also upgrading my cams, to HOT CAMS stage 1 with twin air intake. I believe this should increase my power all around. More air coming in, more air coming out.

And of course I will need to re-jet.

Thanks. Kevin.

  • crf450319

Posted October 25, 2011 - 09:37 AM


You wouldn't necessarily need the header, depending on what you're looking to do power delivery wise. The Powerbomb header will widen the delivery a little as far as I know, but I don't know if you'd feel the difference in the seat of your pants kinda test. It wouldn't hurt, but isn't a must.

Installing Hotcams won't really increase your power "all around", changing cams will change where your bike makes power. With a stage I set-up, you will gain bottom to mid but at the same time you will lose some mid to top.

I put a stage II Hotcam in my CRF450 and it made more power mid to top, but there was a definite decrease in the bottom to mid delivery. In corners where I'd been able to lug the bike in 3rd, had to be run in 2nd. On the other hand, where I'd had to shift into 3rd - I could wring it out in 2nd and it didn't go flat.

re-jetting would be a good idea with either a new pipe, or a new pipe/cams/intake.

Good luck !! :thumbsup:

  • YZ426_F

Posted October 25, 2011 - 08:11 PM


Like crf450319 said, Stage one hotcams don't really change power much. What makes them great is the auto decompression.

I would for sure get the full exhaust.

I'm running a full yoshimura exhaust with a twin air filter, dynojet jet kit. and the power is plenty. Something that really needs attention and I need to do my self is pick up a boyesen quickshot for the carb.. its a must.. the bog before power is terrible on these bikes.

  • sigops

Posted October 26, 2011 - 08:13 AM


well thanks for the info. I though cams would increase power and not diverted. I feel like there is only a few people getting the head for this exhaust. I'm starting to question if I should bother spending all this money as there is nothing wrong with the stock I have right now.

I'm looking for more bottom end, but I don't want to lose much top end either. Is there much of a difference between the pipes, "stock/fmf"? How about the intake, you guys play much with that.

  • YZ426_F

Posted October 26, 2011 - 12:50 PM


full exhaust, rejet, accel pump mod/quickshot. thats about the best you can do without spending a ton.
You will feel more power from a full exhaust and rejet, you will feel bog/lag if you punch the throttle without a quickshot/ or accel pump mod.

  • wags450

Posted October 26, 2011 - 02:58 PM


FMF sells everything alacarte so thats why its separate. Even the combo pricing is just the prices combined.

I have the megabomb my brother has power bomb. I suggest the power with the power core if you go 4.1 get megabomb

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  • sigops

Posted October 27, 2011 - 12:31 AM


those quick shots, I have read some reviews on them. I like the sound of them, because my bike is always bogging. Would that fit on a stock carb? I'm trying to research that a little, how it works anyway. I don't really understand how this works.

You convinced me, I think I'm going to get the full exhaust, I think I will still get the stage 1 hot cams because I can get it a good price. The air intake, I'm still doing some research on it. I may be able to get the twin air flow kit for xmas, that may work, but I still want to research it, to make sure its not just a gimmick.

Thanks to all of you for your comments.

  • grayracer513

Posted October 27, 2011 - 07:16 AM


Before you waste a bunch of money on a Quickshot, try tuning the accelerator pump per manual instructions, getting the pilot circuit set up correctly, and then do the "BK Mod":

  • sigops

Posted October 28, 2011 - 12:03 AM


ok I might take a look at that once I get home, I'm still in Afghanistan, but I won't be long now. I just want to make sure I have everything I need when I get home. I also have another project bike that I'm rebuilding, yz250f. Pretty bad shape. I like the info I'm getting on this site. I normally don't touch aftermarket equip.

  • sigops

Posted October 28, 2011 - 09:15 AM


Another question, I notice they're are quick pumps for 39.99 and boysen quick start's for 159.99, big difference. Is there a difference?

  • grayracer513

Posted October 28, 2011 - 09:24 AM


The quality of the check valves in the cover, and the difference between US and Chinese manufacture.

But don't buy either one until you've done the steps I posted.

  • sigops

Posted April 25, 2012 - 05:45 AM


just to keep this post updated, just wanted to add, Ive put the fmf powerbomb full exhaust/twin air intake and the hot cams stage 2 w/ decompression. I love the fact it is auto decompression, the bike seems to run a lot smoother but different now. When I get home again I will rejette, I'm sure that will be a nightmare for me since I've only done this once before. Then I can move on to my next few projects, my 250 two stroke then my 250 four stroke. :banghead:

Thanks for the input, your guys are tons of help!!!

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