Ride report: FMF hiflo header XR650R


8 replies to this topic
  • Krannie McKranface

Posted March 16, 2008 - 07:54 PM

#1

Added the Stainless FMF Hi-flo header to my FMF Powercore 4 slip-on today.
**(Edlebrock, open side panel and airbox)

The good:
- way lighter
- much, much, improved throttle response above 2.5k rpm
- slightly faster reving
- now getting lean 'pop' on decel, meaning I can richen the Edle a bit
- very clean, tight, sano fit and finish
- very slight improvement in over-rev

The bad:
- the header leans in toward the rear tire more, and I will have to tweak it a bit, along with the muffler, as the muffler hits the tire right now
- lost the first bit of 'ultra-grunt' bottom end. There is still plenty, it was just cool to be able to wheelie from a standing stop with no clutch....

Overall: well worth it in throttle reponse alone. Now I can dial power with the throttle like a CRF does.

  • Thumpage

Posted March 18, 2008 - 01:27 AM

#2

Added the Stainless FMF Hi-flo header to my FMF Powercore 4 slip-on today.
**(Edlebrock, open side panel and airbox)

The good:
- way lighter
- much, much, improved throttle response above 2.5k rpm
- slightly faster reving
- now getting lean 'pop' on decel, meaning I can richen the Edle a bit
- very clean, tight, sano fit and finish
- very slight improvement in over-rev

The bad:
- the header leans in toward the rear tire more, and I will have to tweak it a bit, along with the muffler, as the muffler hits the tire right now
- lost the first bit of 'ultra-grunt' bottom end. There is still plenty, it was just cool to be able to wheelie from a standing stop with no clutch....

Overall: well worth it in throttle reponse alone. Now I can dial power with the throttle like a CRF does.


You really summed up the stock headers contribution to the very bottom end power of the bike,.. "ultra grunt", that surge I talked about right above idle.
But, the bike should still wheely right from the get-go even if it is not as quick to do so like with the stock header. Maybe if you tweak the needle setting to suit the new full systems flow, you may gain some more off the bottom. Maybe dial in the pump shot as well.
You did mention some lean popping.

The new header is lighter isn't it!

I spaced my muffler out as well but I did this even with the stock header. I found with bigger 120/100 or 140/80 sized tires, they can tend to rub on some mufflers without spacing them out a little. This is even with a pretty straight subframe. I have heard of other guys doing the same with some other mufflers and headers.
I use a shorter spacer and shorter bolt at the lower mount, (with the Hi-Flo but didn't with the stock header) and use 6 washers with a longer bolt at the top mount to space out the muffler and to keep the muffler angle alignment the same. You may not need or want to use a shorter spacer at the lower mount as I did. I just chose to do mine that way for a somewhat straighter alignment onto the header.

  • Krannie McKranface

Posted March 18, 2008 - 05:39 AM

#3

You really summed up the stock headers contribution to the very bottom end power of the bike,.. "ultra grunt", that surge I talked about right above idle.
But, the bike should still wheely right from the get-go even if it is not as quick to do so like with the stock header. Maybe if you tweak the needle setting to suit the new full systems flow, you may gain some more off the bottom. Maybe dial in the pump shot as well.
You did mention some lean popping.

The new header is lighter isn't it!

I spaced my muffler out as well but I did this even with the stock header. I found with bigger 120/100 or 140/80 sized tires, they can tend to rub on some mufflers without spacing them out a little. This is even with a pretty straight subframe. I have heard of other guys doing the same with some other mufflers and headers.
I use a shorter spacer and shorter bolt at the lower mount, (with the Hi-Flo but didn't with the stock header) and use 6 washers with a longer bolt at the top mount to space out the muffler and to keep the muffler angle alignment the same. You may not need or want to use a shorter spacer at the lower mount as I did. I just chose to do mine that way for a somewhat straighter alignment onto the header.


The most forward mount point for the muffler has a welded on spacer that a bolt threads into. Since I discovered it was crossthreaded by the last owner, I am going to cut it down about 10mm, and re-tap it. That should give me the additional bend to the right I am looking for.

I went two clicks richer yesterday, and took her for a short spin. The decel pop is gone, but I felt no change in power. I must say, the power band I now have is ruler flat. I mean no surge anywhere. I guess this is a very good thing for a 325lb off-road motorcycle. The throttle response is so amazingly better it's scary. I have complete control over rear wheel spin now, no matter what the traction. There is also more over-rev, allowing me to go 90 on the fwy, even geared down. Oh, it's screaming all right, but before it would not pull 80.

That , combined with the new ESP suspension, and the bike feels completely different. Now it feels like a heavy, real dirt bike. Before it felt like a heavy, squishy, wollowy playbike. I now think I could ride just about any terrain with confidence.

  • johnnyinc

Posted April 05, 2008 - 10:02 PM

#4

Hello,

So I think I have about the same set-up on an XR650 I just bought, FMF Powercore 4 w/ header pipe (power bomb). The bike has many small drill holes in the air cover. Not sure if the carb has been re-jetted. Before I take it into the shop I was hoping I might be able to cure this popping issue. It occurs on deceleration; usually multiple small pops with a backfire (or loud pop) once in a while. In your post "I went two clicks richer yesterday" and I wanted to give it a try. I am not useless when it comes to wrenching (and I have the shop manual) but I don't know this bike (first 4-stroke dirt) and was hoping you or others could help. Any help is appreciated.

Thanks,

Johnny

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  • scalejockey

Posted April 06, 2008 - 05:38 AM

#5

Do you have a stock carb?If so look at the decell diaphram on the side of the carb.Has someone blocked off the air port? Is the diaphram good?If that's good you could have a leaking header or a slightly clogged pilot.
Have you tried turning the fuel screw out yet?

  • Krannie McKranface

Posted April 06, 2008 - 01:41 PM

#6

Hello,

So I think I have about the same set-up on an XR650 I just bought, FMF Powercore 4 w/ header pipe (power bomb). The bike has many small drill holes in the air cover. Not sure if the carb has been re-jetted. Before I take it into the shop I was hoping I might be able to cure this popping issue. It occurs on deceleration; usually multiple small pops with a backfire (or loud pop) once in a while. In your post "I went two clicks richer yesterday" and I wanted to give it a try. I am not useless when it comes to wrenching (and I have the shop manual) but I don't know this bike (first 4-stroke dirt) and was hoping you or others could help. Any help is appreciated.

Thanks,

Johnny


Johnny

I have the Edlebrock carb with the externally adjustable jetting. This is not possible on the stock carb. Do a search for 'jetting' and you will get the scoop on what jets and settings you need for the stock carb.

  • BWB63

Posted April 07, 2008 - 05:56 AM

#7

Some stock carb. help can be found here:

http://borynack.com/...r_caruretor.htm

  • johnnyinc

Posted April 07, 2008 - 07:47 PM

#8

Do you have a stock carb?If so look at the decell diaphram on the side of the carb.Has someone blocked off the air port? Is the diaphram good?If that's good you could have a leaking header or a slightly clogged pilot.
Have you tried turning the fuel screw out yet?


Thanks for the reply. So the guy I purchased the bike from told me that he had blocked of the air port but didn't use a kit. I am going to check (working on the bike is kind of a pain as I have no garage so until then its on the sidewalk). I would like to try adjusting the pilot screw however been through the service manual and the only thing i can see in terms of extrenal adjustment is the "pilot screw" is this what you are referring to? Sorry for being dense.

I dont think it a header leak, but I ocassionally get the float stuck, you know tons of gas pouring out the vent tube infront of the rear tire.

Thanks again. johnny

  • johnnyinc

Posted April 07, 2008 - 08:00 PM

#9

Thanks for the link, super interesting the guys seems to know his sh*t. Have you or anyone else tried this? Either way it seems I am going to have to take the carb off an spend some time on it. Last time I had a card apart was on a RM250 and I was 15 and it was kind of a nightmare. I am going to get all the stuff I need (jets & gaskets) and give it a go. (first time on this forum, you guys rock :thumbsup: )





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