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Thumper Racing 660 Kit....to Port Or Not To Port????

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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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dont worry it will have a mean bottom buddy a friend of mine let me ride his while i was repairing mine his head has a port job done even done some polishing on the backs of the valves you touch up the intake nothing serious and hog the exhaust and super slick do your head pipe to there is a little welding in there but not much usually i done some work to my head while i had it off slick ex side touched up intake and head pipe i am only running stock compression piston though did the valve job also new chain wont hurt and my tensioner was junk i found so make sure it is working ok one of those little plastic thingys inside of it was gone

my needle and seat was wore slap out also after i did all the motor it seemed rich thats what is was be a good time to look at yours while carb is off no specs on these pieces though i could feel the difference after i got a new one the old one had lots of play in it the new one you could just feel the play in it big difference

thats about all i know to look at and i am sure you will enjoy the power :)

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dont worry it will have a mean bottom buddy a friend of mine let me ride his while i was repairing mine his head has a port job done even done some polishing on the backs of the valves you touch up the intake nothing serious and hog the exhaust and super slick do your head pipe to there is a little welding in there but not much usually i done some work to my head while i had it off slick ex side touched up intake and head pipe i am only running stock compression piston though did the valve job also new chain wont hurt and my tensioner was junk i found so make sure it is working ok one of those little plastic thingys inside of it was gone

my needle and seat was wore slap out also after i did all the motor it seemed rich thats what is was be a good time to look at yours while carb is off no specs on these pieces though i could feel the difference after i got a new one the old one had lots of play in it the new one you could just feel the play in it big difference

thats about all i know to look at and i am sure you will enjoy the power :)

Umm,no offense, but punctuation is your friend :)

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Has anyone had one of these, or a regular XR600 ported...not just cleaned and polished?

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I've owned a few XR600's and ride with guys who've had them as well. Our group concensus(sp?) was that it was a waste of money to port.

I once read XR's only description of why they port and polish because of casting flaws and such. I got charged up to port/polish my six-honey and called Eric Gorr ( Dr.Dirt) at his shop. He told me old suzuki's could benefit greatly from polishing but he told me not to expect much on the honda........they just don't have the flaws. He also told me that the benfits would be pronounced on the top end if at all and most XR6's just don't live life at full throttle.

Spend the money on an HRC cam or an IMS -HRC-copy cam and youll have some increase in boost.

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If you have to port the XR6 head, only do a mild job on the intake side just tidying things up so the port is unobstructed and smoothish, you will get a power gain similar to adding a set of large header pipes (small top-end boost 2-3 hp). Major porting can actually loose you power so be careful!

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You may never really notice a differnce unless you really hog every thing out which I'd recommend against doing, Just do a clean up job by removing casting flash and port matching and polishing the ex. ports, You don't need to polish the intake, You can leave them a little rough because that helps to atomize the fuel better.....TMO....... :naughty:

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Rode with a fellow that made his 650 into a 680 last year in Baja. The bike ran great everywhere and was popping wheelies in 3rd and 4th gear down the highway. As for the question on XR 600's, HRC makes a 628 kit for them. I had one and the only thing I didn't like was the piston. With the kit, you8 have to go to race gas. Get everything BUT the piston and you get great overall power boost and can still run 87-91 octane fuel. XR's Only have extended fins that can be welded to your barrel as well to help with cooling. I had those on my 94 XR 628 as well. Steny :naughty:

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I had porting done to my 95 600 yrs ago by Precision Concepts and it ran great. I noticed more topend w/out sacrificing much on the bottom. I had the FMF power core IV silencer as well. It seemed to run better than other 600s that I ran with so I would say do it if you got the cash, it was $225 back then.

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Update. I went with the 9 to 1 660 kit, and had my head cleaned up locally. I put the powerbomb header on it. I love this bike now. TONS of grunt off idle with a solid pull all the way through. I am running 92 without a problem.

Thanks for all of your input!

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Why did you shy away from the 10.5:1 kit? You certainly wouldnt have needed race gas with that compression level.

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Thumper Racing recommends 100 plus octane on the 10.5 to 1 kit. I wanted to be able to run pump fuel, if needed, on long rides. I was told that seat of the pants feel would be the same between the two ratios.

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I gotcha. Usually even 11:1 works fine on pump gas, but they know better than I do. :) Have fun!

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Thumper Racing recommends 100 plus octane on the 10.5 to 1 kit. I wanted to be able to run pump fuel, if needed, on long rides. I was told that seat of the pants feel would be the same between the two ratios.

Your bike will run a lot cooler with the lower compression ratio, it's not as hard on the bottom end and easier for the starter to crank it.

I didn't know they had a 9:1 kit for the XR650L. I may reconsider now.

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This kit is for the XR600R....It kicks plenty hard as a 660 with the low compression piston...would hate to bang away at the tight one!

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Eli,

I have a 98' 600r, can you fill me in on the upgrades you have on yours. What worked, what didn't.

The 660 kit sounds like it gives a little extra, but doesn't take away from the low end.

Let me know.

SoCalTrailrider

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I bought a 96 XR600R with a Supertrapp IDSE 2 muffler. I initally put the Hotcam Stage 1 cam in, and the bike pulled all the way through the rpms without dying off at the mid/top end like the stock cam did. I then installed the 660 kit, Powerbomb header, and cleaned up head. Way more low end, and pulls harder all the way through the rpms, still.

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That sounds sweet! I was researching the powerbomb kit, but no one here rides the 600 anymore. I currently ride this baby bone stock, except for new Excel Rims, all about the SoCal Area and have not had any reliability issues. I definitely want to breathe some new life into though. I am am the second owner, but have no clue how much time is really on the bike/motor. The best part is it is a California legal Dual Purpose bike.

I have entertained the thought of going Supermoto w/ it too.

SoCalTrailrider

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