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Discussion Starter #1
I have to rebuild the head as the intake valves are shimmed as low as they can go. I have a 2014 pretty much stock with HRC kit but with a HC2 instead, so HRC header and HMF slip on. Had a Rekluse but I’m going to stick with stock style clutch. I have long travel suspension, flexxbars and CCP stabilizer.

On the new build I was thinking of getting a 12.5 96mm piston and do a small head porting job since I do Xc racing. I like that low end grunt. I was thinking of doing a big bore kit as well but don’t know how I feel about that yet. Also I was looking at the hotrods cranks
Are they any good? Upon inspection mine doesn’t have a lot of play so I was thinking of just doing a top end.
i want to run pump gas, as we also trail ride sometimes.

thanks guys
 

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Truck Yea
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keep the stock bore, its the most reliable. port the head, keep the cam, full exhaust like hmf, dasa, monster, etc. Then do a pro x crank, cp or wosner. if you plan on doing hot rods THROW away everything but the crank itself and use OEM honda parts, the bearings are junk in the hot rods kit.. Do the heavy duty head studs as well. I get everything from the az quad parts site, very good to deal with and they answer the phone!

Only other way to do pump gas is to do a 470 or 490 but you need a 12.5:1 piston or lower.

For what its worth before I did my build I had a 12.5:1 CP piston I got from alba that was ceramic coated-it worked VERY well and was worth the money. But the umph with the 490 is dang nice compared to this.
 
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Discussion Starter #3
keep the stock bore, its the most reliable. port the head, keep the cam, full exhaust like hmf, dasa, monster, etc. Then do a pro x crank, cp or wosner. if you plan on doing hot rods THROW away everything but the crank itself and use OEM honda parts, the bearings are junk in the hot rods kit.. Do the heavy duty head studs as well. I get everything from the az quad parts site, very good to deal with and they answer the phone!

Only other way to do pump gas is to do a 470 or 490 but you need a 12.5:1 piston or lower.

For what its worth before I did my build I had a 12.5:1 CP piston I got from alba that was ceramic coated-it worked VERY well and was worth the money. But the umph with the 490 is dang nice compared to this.
That’s what I was thinking, I just found the that exact piston you were talking about. My cylinder and piston still look really good, but it would be nice for that little bit of compression bump. I’ll get that piston and use it with my cylinder. I’ll just re hone it. I was going to send my head to Rage in Houston and let them rebuild it and give it their small port job. I don’t need to have the most Hp out there since I just race Xc. I may look into a different exhaust. I think my crank is fine there was little to no movement in the rod.

now I’ve got to figure out what to do with my sons KFX400. He’s about to be 15 so he could race that 1-2 more years in the AXCC series. But he really likes my 450r. His quad was down the last 2 races of our series and he kickedbutt on my quad. He’s almost 15 but 185lbs and 6’ tall just pure muscle works out and plays football and baseball for thehigh school. I really think that upgrading his quad would be nice and he could run away with that class. But then we would be selling it in a year and getting him a 450. So he can race with the big boys. His bike is all stock other than revalved jet, suspension, flexx bars, bead locks, intake, fmf header and pipe. But I know I would have to get a new carb, and head work for his because it has to stay 400 to race in the axcc and Gncc classes.
151793
 

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That’s what I was thinking, I just found the that exact piston you were talking about. My cylinder and piston still look really good, but it would be nice for that little bit of compression bump. I’ll get that piston and use it with my cylinder. I’ll just re hone it. I was going to send my head to Rage in Houston and let them rebuild it and give it their small port job. I don’t need to have the most Hp out there since I just race Xc. I may look into a different exhaust. I think my crank is fine there was little to no movement in the rod.

now I’ve got to figure out what to do with my sons KFX400. He’s about to be 15 so he could race that 1-2 more years in the AXCC series. But he really likes my 450r. His quad was down the last 2 races of our series and he kickedbutt on my quad. He’s almost 15 but 185lbs and 6’ tall just pure muscle works out and plays football and baseball for thehigh school. I really think that upgrading his quad would be nice and he could run away with that class. But then we would be selling it in a year and getting him a 450. So he can race with the big boys. His bike is all stock other than revalved jet, suspension, flexx bars, bead locks, intake, fmf header and pipe. But I know I would have to get a new carb, and head work for his because it has to stay 400 to race in the axcc and Gncc classes.
I was quite happy with that piston myself, although I prefer the power the big bore or high compression makes which is why I went 490. 470 is also a good choice. But of course its more reliable with the stock setup basically

Id just upgrade to a 450 for your son. sounds like he has reached the limits of the KFX. the 400 can be competitive but it sound slike he is ready for the 450
 

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Discussion Starter #5
I was quite happy with that piston myself, although I prefer the power the big bore or high compression makes which is why I went 490. 470 is also a good choice. But of course its more reliable with the stock setup basically

Id just upgrade to a 450 for your son. sounds like he has reached the limits of the KFX. the 400 can be competitive but it sound slike he is ready for the 450
Yeah I want to just be able to go ride with out having to get race gas, but a little extra power would be nice. I wouldn’t mind doing a big bore kit like a 470 with a 12.5 piston just to keep it pump gas. Main thing is I just want it reliable for Xc racing.
The axcc has a class that is called schoolboy Sr and it’s only for 400s and ages 14-17. However he is already beating most of the people in our series with built 450rs including mine lol. Just didn’t want to build that quad for 1 season. But they did say that he could race up in the college jr class 16-21 if he got a 450. I’ll figure it out I guess. He rides my quad better than I do lol.
CJM do you race XC?
 

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I dont race XC Ryan, actually never raced. but the riding by me mimics a lot of what an XC racer would do, trails, turns, switch backs, etc. Otherwise its wide open sand pits. What made me faster was the suspension and handling parts. Flexx bars, good shocks, good tires and extended arms. Then the power is more usable.
 

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Discussion Starter #7
I dont race XC Ryan, actually never raced. but the riding by me mimics a lot of what an XC racer would do, trails, turns, switch backs, etc. Otherwise its wide open sand pits. What made me faster was the suspension and handling parts. Flexx bars, good shocks, good tires and extended arms. Then the power is more usable.
So true that’s why the first think we did wear the suspension and flexxbars, steering stabilizer. That made a world of difference. We love to trail ride a lot but the competitiveness gets to our better side so we picked up racing. It’s a blast hanging out and going to the different places.

I have a question for ya. Is there a big difference between a full exhaust and what I have? I have the HRC header and HMF can.
 

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Well, a full exhaust of course will make more power: Links

Question is what do you wanna spend and is the cost worth it? Me, I have tried both a lonestar racing (no longer made) and a dasa. Ill take the dasa any day, its proven to the best.
 

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I guess I’ll be the devils advocate lol!

I say go with higher compression. I would do a 13:1 piston and if you want to go BB, go with a nice cylinder like an Athena. You can get an Athena 100mm cylinder and 13:1 piston in a kit from a couple different vendors. The extra pop from higher compression is so nice in the woods, and a BB will definitely help as well. Every situation is different, but I have never had a problem running 13:1 on pump gas in the woods. I use good non ethanol 91. And you can always have a can of quality octane booster on hand, and I don’t mean the stuff you buy at the gas station lol.

As CJM said, you can stick with the HC2 which is a good cam, or go with a WebCam that will give you a little more torque for woods riding. I’m not saying there is a ton of power to be gained by switching to a Web, but it’s likely there is some, and with a little bigger cam that will give you a little more wiggle room for running higher compression.

You mention wanting reliable power, and honestly, the reliability comes from a properly built, and tuned motor. You mention honing your cylinder, don’t hone it. If the cylinder isn’t in good shape with good cross hatching send it in and have it replated and clearanced for your piston (if you don’t do a BB). These motors run a very tight piston to cylinder clearance and you don’t want to increase that clearance by honing the cylinder. It’s things like that that will add up to a “reliable” motor and one that is not.

Yes a full exhaust will make more power. I personally haven’t had good success with DASA pipes. I’ve had lots of problems with them, and I don’t feel they are very durable for the type of riding you say you are doing. However CJM says he hasn’t had any problems with his. I have a thread talking about different pipes that you can take a look at, and you can see what my favorite pipe is.

Just my thoughts. . . . .
 

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Another thought since it is a 14 is to run the card head gasket which best I remember is a 2 layer instead of 3 so that will bump the compression a little. The 06 up have a higher compression then the early 450s so going to a 12.5 piston isn’t a huge gain but noticeable. Just to be safe if I wanted pump gas I would stay 12.5 if I wanted race gas I’d go on up to the 14 or wherever I could get in that range. I like cp 2 ring pistons. I like the bb kits. Just the 470 or whatever the next bump up is on the 06 ups is noticeable and usable. IF you think you might want to go to a web talk to whoever works the head because a lot of the webs need shorted guides. The 208 was a popular XC cam or if you can find an early hrc I like them a lot more than the hc2 personally.

You will see some gain with a full exhaust but maybe not a whole lot like mentioned. I like my Rossier but Hmf has proven to me in Xc to hold up. You might think about getting the carb bored instead of the new pipe. Once you get a little more power you will want a little more, never ending.
 

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Discussion Starter #11
So I ended up buying a head from Johnny at JH racing, sparks Xc ported head with +1 ferrea intake and exhaust valves with kw springs. I’m going to stick with my my cam and exhaust for the time being, HRC header and HMF slip on. I’m going to stick with the stock piston for now my cylinder and piston still look good. I’m going to get a BB 470 with a 12.5 cp piston. I think for the time being this will be a nice upgrade. Johnny at jh said to not run the CRF head gasket unless I run race gas? We have 93 where I’m at and I can get 100-110 from the airports close to me. But I just want to stick to pump gas for now.

I think this will be a little jump in power with the ported head and valves. I need to learn to ride better anyways before adding anymore. I wanted to do the piston now, but we have to rebuild my sons atv and we are getting that set up for Gncc! He’s going to kick some butt! He’s getting a similar head to mine with webcams and a new cylinder and 12.5 cp piston for it. Thanks for all the input guys!! I’ll keep ya posted once I get everything in.
 

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Sounds like a solid plan. But I would do a CRF gasket myself. That will bump compression up to 12.5 and with 93 and a HC2 I think you would be totally fine. Stock 12:1 bike runs extremely safe on 91. I dunno, I just think compression is where it‘s at. . . . .

should be a decent head for ya, hopefully your butt dyno will see an improvement. But the CRF gasket would definitely help lol!

what web are ya putting in your boys bike?
 

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Discussion Starter #13
Sounds like a solid plan. But I would do a CRF gasket myself. That will bump compression up to 12.5 and with 93 and a HC2 I think you would be totally fine. Stock 12:1 bike runs extremely safe on 91. I dunno, I just think compression is where it‘s at. . . . .

should be a decent head for ya, hopefully your butt dyno will see an improvement. But the CRF gasket would definitely help lol!

what web are ya putting in your boys bike?
Yeah we have 93 here I didn’t know how much the CRF head gasket would bump up compression. But sounds like a better alternative than getting another piston atm. I know a couple guys that run 13.1 pistons on 91 and are fine that we race with. For now I’ll just keep it with the stock piston.

My sons quad, we are sending the cylinder and the head to ct racing and It will get ported and put new valves in it. I don’t remember what cams he said they were for the LTZ400. I really wanted to make his a 440 it’s the same price since we have to buy a new piston. But if we run A couple Gncc races we have to keep it a 400. So putting in a higher comp piston in that will be nice. They come stock with 11.1 I believe.
 

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Discussion Starter #14
Got my head today. 1 valves, new seats, kw springs. Sparks XC port. Im looking forward to installing this! Now just have to figure out jetting. Currently I have 165 and 42 with 2.25 turns. He did send me a TRX head gasket. I was thinking of ordering a CRF head gasket. Just don’t know what year I need?
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Head looks pretty good, nothing crazy, but should be nice for XC.

02-08 IIRC.
 
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