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To Port or Not to Port?

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Sorry about this being an XR, but I am not getting much for responses in the correct forum.

I have a 97 XR600R with a Stage 1 Hotcam, stock carb, and will be getting either a WB or FMF header.

I am sending in my cylinder this coming week for the 660 kit. I'll be going with the 10.5 to 1 piston, as I have over a barrel of race gas left over from snowmobiling this year (no snow!).

Should I have the head ported? How much power will this really make? I use the bike in all types of riding, and dont mind the gains to be mid to upper rpms, but I don't want to lose much on the bottom.

Any help is appreciated....Thanks!

Eli

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XRs are good, just a differnt deal entirely.

I road raced an XR 650 R and you can do some seriouse work and make some great power from one of those. i say go ahead, take the dremel and die grinder to it, at least clen up the intake & exhaust poerts and tracts, oyu dont have to go crazy, but you can...Go to XRs only . com they have a lot of parts, but search around for who ymight have the best prices and service

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I picked up the bike used, and it is in great shape. Before I purchased it, Race Tech resprung and revalved both ends, is mechanically fine, has a liscense plate. Here in Washington, it's hard to get a plate for an XR or CRF unless you buy it out of state and transfer it over. When I did that, there was no inspection I had to go through.

Back on subject, will a good port job from XR's Only, etc, kill some bottom end?

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Back on subject, will a good port job from XR's Only, etc, kill some bottom end?

If the porting and valve seats are modified correctly with the objective of increasing low to mid range performance and priority given to the lower valve lift points you'll end up with better low end response even with a the longer duration cam. Done correctly porting for lower speeds tends to focus on good low lift flows and minimizing flow reversals at part throttle opening and lower engine speeds. This is an important consideration when going to a bigger cam. The engine will tend to feel more cammy (or peaky) with a bigger cam and no porting than it would with the ports and valves seats modified.

The old XRs have a lot of manufacturing flaws that come from the maching and installation of the steel valve seat into the port throat . Flaws in this throat to seat transition area can really impact low lift flow.

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if you port it yourself dont make it to smooth. i got my engine ported before i fit it into my quad so i can't tell you the performance difference but i asked the guy who ported it why it wasn't shiny inside and he said if it's too smooth it"s more for topend he roughed it up for mid range.

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asked the guy who ported it why it wasn't shiny inside and he said if it's too smooth it"s more for topend he roughed it up for mid range.

huh? :)

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