[mrjarrod]

Hi,

I've been put in charge of making my nephews quad faster. He has a 2008 kfx450. I've read every engine related post in three forums... riders, hq, and of course kfx450central, and decided to go with the following choices:

Exhaust: already has Curtis Sparks installed, he spent a fortune and not really wanting to change though may be persuaded to.
Intake: FCI intake, just purchased
Piston: JE 12.8:1, +2mm 470cc, just purchased
Cams: KX dirt bike intake/exhaust cams, just purchased

We're going to drop the motor today, and send it in for port/polish, valve job, cylinder bore/replate, and send the throttle body in to get is bored. Were going to call Dasa Racing and Hetrick Racing to ask for price quotes on port/polish and valve job but to be honest we're on a tight budget and as p/p isn't as critical for this engine I would like to save money in this area. Any suggestions on a good budget p/p & valve job?

Going to also look into advancing the timing three degrees instead of buying a Power Commander ignition module.

Am I making the correct decisions? Am I overlooking something? It's not too late to send stuff back. Any well informed information will be well appreciated. Our goal is to get over 55 whp after tuning. Thank you.

 

[walshyfz86]

your on a great path so far. Not a fan of JE pistons but they are good. Hetrick bores tbodys for around 170 and does port jobs for pretty good price. Rage also does a awesome job on port and polish. Thats who just did my head and its amazing work. He nos his chit. I just dont no if your cranks going to hold all this.

 

[masterp0606]

yea i would prolly replace the crank thats why i only went with the je 12.8:1 stock bore.

 

[mrjarrod]

So the crank is a weak point in the kfx450 engine or just a weak point in engine builds of this magnitude in general? I don't remember reading anyone doing similar mods and doing something with the crank. Anyone have crank failure? Should I send in the stock crank to get it modified or buy a modded crank? Any recommendations? Thank you.

 

[walshyfz86]

Ive seen a bunch of cranks go trough stock motors and a bunch trough built motors. its just the quads weak part. Ive talked with nate walsh a few times about this and cody gibson went trough a few stock ones in a month a few failcons witch are supposed to be amazing and now they designed there own that so far had great luck with. They charge 400ish for new rod and balancing and everything. If you have the cash do it right.

 

[mrjarrod]

You are referring to Walsh Race Craft, correct? If so I'll give them a call.

 

[walshyfz86]

yea there getting big into motors now plus having some hi tech equipment and top riders for testing id trust them.

 

[mrjarrod]

Ok, so I'll definitely strengthen up the crank. Any other recommendations, lessons learned, or mistakes I could be making? Thank you.

 

[Extent Racing 21]

if you plan on replacing the crank, then you can also bump the compression to make more power, i would go with a CP piston, 14.5.1 compression prefrebly, then some web cams or pro circuit cams would compliment them nicely, i would also consider sending your head, or at least call curtis sparks about headwork/porting. They are well known for having huge power making motors and they too know there stuff, plus you have a sparks exhaust, its nice to have work done by the same company. Talk to them and tell them your goals and your parts list and see what they recommend.