big bore

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seth86

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Joined
Jun 12, 2014
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just wondering if anyone has done the big bore kit on an xb9r. If so im trying to find the best bang for my buck
 
Numerous people have done the kit, but I'd say best bang for ur buck realistically would be to sell ur xb9, and get a xb12. Everyone says they're capable and ambitious, but the main questions are funds, time, resources and the knowledge! Four years ago I picked up a xb12 for 3900 bucks, and it had a clear title, 4k miles and some pricey mods done to it. Deals are out there, sometimes u just need to go to them.
 
How many bucks do you have? That will determine how to best spend them
 
best bang for your buck realistically would be to sell your xb9, and get a xb12.
IF that's what you want...strictly a little more torque. No real comparison between a big-bore 9 and a stock 12 though.(Especially if you do the 9 'right'....cams, heads, good crank and bump the rev-limiter up to 7800 or so). THEN you have a seriously fun ride! Erik Buells' favorite personal bike was a big-bore 9 bike. It's probably an SX now though! Lol! But even with just a big bore kit, those extra RPM (vs the 12) coming out of the twisties (and rolling INTO them!) feel SO good!
How many bucks do you have? That will determine how to best spend them
No better question to be asked. Guys came into the engine shop and this was one of the FIRST questions we asked.
 
2003 XB9 (1050cc)
Big Bore kit from Revolution Performance.
Heads ported and polished by NRHS
Ceramic Headers
Swapped out the pushrods and upgraded with polished tubes.
D&D exhaust, Race ECM plus a few extras, then had it dyno tuned.

I didn't care about the cost, performance was worth it..
As a guess.. $3000-$3500 (back in 2011)

Pulls strong, no 3k dip, high arc dyno curve..
 
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Stock bore XB9 984cc with Hammer Performance Crush Level head service (1.9" intake valves vs. stock 1.8" and 1.615" exhaust valves vs. stock 1.5" ) heads were milled .020". I'm running Redshift 567 cams, Jims Lifters and Hammer Performance .050" shorter solid push rods. I'm also running an xb12 throttle body 49mm vs xb9 45mm and an xb12 header 1 3/4" tubes vs xb9 1 5/8" header tubes. still in break in process, but it runs okay on a xb12 fuel map...i still need to tune it. Here is my thread on the build.

10176221_10204574501142936_8696628247784617988_n.jpg
 
In reality the 1050 kit is only 1021cc and only 4% increase in displacement. You gain very little power from that increase...the real power comes from higher compression and head work. I couldn't do both so I went with head work and cams, over head work and big bore. I had my heads milled and used a thinner head gasket to bump up commpression with stock xb9 pistons (although I had to rework the intake valve pockets and smooth down the eyebrows of the valve pockets so I would have clearance while setting my squish)
 
I have the funds but just seems like a lot of work. I just love the look of my xb9r. I might search for the 12r but then again the 1125r is pretty sick with the other front end
 
In reality the 1050 kit is only 1021cc
I never did the math on the small bore kit to verify this, but I'll take your word for it! :) This is a fine 'upgrade' if you're just freshening up an engine that has a bunch of miles on it, or somehow got the cylinders hurt. For a real upgrade, go with the big-bore kit. (3-13/16" bore). with a bore of 3.8125 inches and stroke of 3.125 inches gives you 1,169.42cc. Yes, you must bore the cases....so be it. At this point of a build it isn't a big deal. (I sure would imagine you'd want the WHOLE bottom end done right anyways if you're that serious about it. I know I do.).
 
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