So my dads kfx needs a rebuild. Gonna go with a 440 big bore kit cylinder works or Athena, there's a $130 price difference between them. Also should I do anything to the head, cams or valves? Want a reliable rebuild but get good power out of it. Any suggestions of opinions are greatly appreciated. And I know its a kawi but its pretty much the same bike as a ltz.
I have a friend with a KFX400.
He is running the Hotcams and a Full Yosh pipe. It made a substantial difference.
Head port and a serdi valve job matched to a cam with a nice exhaust, add a dash of compression and serve hot. voila.
Head port and a serdi valve job matched to a cam with a nice exhaust, add a dash of compression and serve hot. voila.
+1 old style hotcams are pretty nice, and I would recommend the full Yoshi pipe.
But really you don't need to get it ported just get in that 12. compression reange (13+ will require race fuel), some old style hot cams (new style are fine just OSHC seem to be better), full exhaust, and a 434 kit. I cant really give insight on which one but Im pretty sure I see good results out of both of them!
Also don't be surprised if your threads are stripped on the cam journal cap(s) its very common in these machines.
My dads not a fan of cheap parts so he'll likely go with the Athena kit. I'm pretty sure he already has a yosh exhaust. Thanks for the input guys keep it coming gonna be my first 4 choke rebuild.
Valve and port profile are key in making 4 stroke performance. If your looking for performance with reliability, Freshen up your bore and spend some money in your head. Just my .02.
Thanks Gillio ill let my dad know see how much money he's ready to sink in this rebuild/beef up.
Head port and a serdi valve job matched to a cam with a nice exhaust, add a dash of compression and serve hot. voila.
Some of the worst valve jobs I have had to re-do were from Serdi valve machines run by inexperienced/in a big hurry operators. Shops buy a Serdi seat and guide machine, then advertise their valve jobs on EBay. The operators must assume the Serdi machines are idiot proof. They need to check their work after they cut the seats!
Aren't athena's 430 kits?
Oh for sure Jerry, You definitaly want to send it to someone who knows how to use their tooling. This takes us back to the old "you get what you pay for" discussion. I have come in behind people all the time who went the cheap route in my shop.
He actually has a Jardine full exhaust. He's not really interested in making big power the bike just needs a top end and wants to go big bore. He doesn't want to affect the reliability of the atv.
You guys make a descion yet bucky?
Going with the Athena 440 kit probably ordering it this week or next.
He actually has a Jardine full exhaust. He's not really interested in making big power the bike just needs a top end and wants to go big bore. He doesn't want to affect the reliability of the atv.
If you do not want to affect the reliability you do not want to install a big bore kit. I see too many head gasket problems with the big bore kits.
My dad is really hard on his bike too. Anything we could do to get a big bore kit to be reliable? O ring the head? Idk never worked on a 4 poke.
My dad is really hard on his bike too. Anything we could do to get a big bore kit to be reliable? O ring the head? Idk never worked on a 4 poke.
I do not know if there is enough room for a rubber o-ring on the big bore setup. On a four stroke head it would require an o-ring on both sides of the head gasket and would require a single ply head gasket. Now we can hold the compression but now there may be coolant or oil leaks because of the single ply head gasket. Sometimes we install a very small diameter wire type 0-ring but it is usually a one time deal on aluminum heads and cylinders. Next time you remove the head you have to mill the head or cylinder so that the wire has a new surface to embed itself into.
I agree with jerry, if reliability is a big factor on a quad that is ridden often b.b. Isn't the way. Some people are dead set on an idea and won't budge.definitely get the head checked out even if u don't port it, valve job and have resurfaced. Look in to an fcr carb swap, the stock carbs on the ltz will hold back your bb. Kit. Toss in a cam to complement that bb and you are good to go. I would also stay close to stock on compression ratio since its nit a race quad.good luck
What about doing a 426 kit instead of a 440?
Derrick I think the "440" is actually a 434 not that its that much of a difference.
Also from all I have seen not to say that Jerry or PCS are telling you wrong, but I have seen many ltz/kfx with the 434 kit and they are rode very hard and have no reliability issues and all the owners love em.
Just my
if it were me I would get one with no worries just do your research and see which kit is best.
So my pops is wanting to hold off on the big bore kit till the next time he needs a rebuild. What all do I need to order parts wise to get his top end back to like new status? I'm clueless on 4 strokes.
New piston, rings, top end gaskets, and i would have head resurfaced if it needs it, valves lapped, new valve seals. Change filter and oil, new plug
