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zrt1

FMF Power Bomb or Hi-Flow header xr650r

5 posts in this topic

Has anyone ever done any real back to back tests between the FMF Power Bomb header and the FMF Hi-Flow header? If so what were the results? Where in the rpm range were the changes. Does any one know what are the differances between the two other than the power bombs chamber?(bigger tube diameter?) Ive got an xr with the stage two Hot Cams , opened air box, uni, JE 11.1 piston, FMF Ti4 muffler , mid pipe and Im up in the air on the head pipe. Street only and at 5200 ft. thanks..

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No personal experiance with either.

However while I was shopping for a header I was considering FMF 's for a bit. I ran across a thread on another board (can't remember which). Anyway - the word was the "bomb" & an edelbrock carb were an interference fit. In order to run it, you needed to put a "big" dent in the bomb to clear the bowl.

"Denting" a header to clear something is NBD, done all the time on other stuff (cars) & has little effect on flow if done right. Rather than any sffect on flow, I was more concerned about having the pipe that close to the bowl & any boiling issues &/or any power loss from feeding the engine a "hot" fuel that might cause.

Like I said I've no personal experiance with it & I know you didn't mention having an edel. - But it's something to keep in mind in case you think you may go there.

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My powerbomb on my first bike was slightly dented from the previous owner who was trying to fit it in a 650R custom quad.

The powerbomb is supposed to give more low end grunt according to the website. I didn't notice any low end difference, but the top end was vastly improved.

My newer bike has a large diameter straight header system. It flows even better up top with a HRC cam.

In my opinion, the powerbomb for the 650R is mostly gimmick.

With your 11:1 piston/cam combo and street riding, I would go for the largest diameter pipe you can get. You want high-RPM range power for street.

Moriwaki makes the sickest pipe I have seen for the XR650R so far. I have seen custom white brothers and pro-circuit reverse megaphone mufflers on a few race bikes or on e-bay. With the high comp piston, the reverse megaphone starts to come alive. I think you can contact pro-circuit to inquire about the race-only systems.

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Where do you get the Moiwaki, and how much $.

I bought mine off someone on ADVRIDER. com for $400. I'm not sure if they make them anymore. Some guys on ADVRIDER were trying to get Moriwaki to fire up production again and they had to get a few orders in to get them to start. Check it out there. I think they are about as much as a full Pro-Circuit T-4 exhaust brand new (~$500-600) but better quality and lower noise level with the spark arrestor installed.

The moriwaki does NOT have a USFS approved spark arrestor, but it does have a removable spark arrestor. Its no big deal where I am at, but you may want to see if its a problem where you ride.

The moriwaki has the absolute best exterior TIG welds I have ever seen on an exhaust. The pipe couplings are all super tight tolerance and seal up well with a little RTV. The internal mig welds at the header to cylinder interface were big, so I ground them down to improve air flow.

Good luck with your search.

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