4 valve head & Exhaust

[MEMPHIS91]

My goal is to drop in the 4 Vavle head and good exhaust before buggy bash.
Any one done the 4 valve head? Any suggestions?
And what about the exhaust? Who likes what best? for about $150-200

Thanks

[ckau]

a four valve plus a true tuned exhaust will give you aprox. 15 to 20% increase in performance. Couple of notes: four valves use longer than stock head bolts. make sure you get those with the head. You have to add approx.3 links to the cam chain. your going to need some cam chain links and a chain breaker.
The closest thing out there to a tuned exhaust is the MRP. not the best quality built, but it is the best that is offered at the moment unless you can build your own. You won't get the full potential out of the 4 valve head using the stock pipe. Using a flow through muffler like a supertrap on the stock head pipe will help but not as good as a true tuned exhaust. The stock pipe is approx. 3/4 inch dia. where idealy you need a inch dia. 27 to 30 inches long out from the head in order for it to breath good. You will also probably need to go up on jet size also. You state your using a 125 main. thats a touch lean with a uni but your using the stock exhaust so it should be ok, Most likely your going to need a 127.5 or higher with the head and upgraded exhaust. Are you using a velocity pipe with the uni? The rest of you mods are fine for this setup.

[MEMPHIS91]

Awesome reply, and thanks.
The hammerhead exhaust is larger than the normal blade, carter, or other brands. So I didn't mod it. The 125 jet right now is a perfect golden brown, but rejetting wont be a problem at all.
The kit I am looking at comes with the timing chain, cam, head bolts, and head. So I should be set. And I will grab the recommended jet when I pick it up.
Does hammerhead make a tuned exhaust? The MRP is gonna run me $265. So I would rather find something a little cheaper if I could.
And I am using the normal black pipe that came stock on the kart. It fit perfect to the Uni.

Again thanks for the quick reply, and good info.

[BuggyMaster]

can't wait to see how this comes out as it is on my hit list of things to do. Talk to Tom at SYC Powersports. He has done a lot of work in this area and could probably provide some good information.

[bige]

yes hammerhead makes a exhaust just for their buggies, but it will fit alot of others.

[ckau]

It may be easier to add links to your cam chain. otherwise you have to split the lower cases to install the new cam chain which means a total disassembly of the motor. you will need a full gasket set, fresh chain guides and tensioner. while you have the motor that far... might as well go back together with the big bore thing too! :biglaugh:....it never ends:banghead:

[BPNWMike]

The hard part about a 4-valve head kit is finding the 4-valve [b]piston[/] to go along with it! Even more so when you have a big bore kit and need a 4v piston for that.

That, and the 4v heads are really expensive!

Go with the exhaust and see where you're at after that. :)

[MEMPHIS91]

Yeah Tom has all the parts, and is gonna charge 60 for the work. I would rather have just the 4v head for now, I like to see the change in proformance at each step. After that I am gonna work a 300 EX in the kart

[SYCARMS]

We are running in my sons buggy a 3mm stroked crank, 62mm cylinder and the 4 valve head using the piston which come with the kit with 2 valve reliefs and have had no issues in the past 2 years. The important thing is to check for the proper valve to piston clearance which I have yet to run into any problems with. I've only located one person who sells a bore with the 4 relief piston and its only available in the 62mm so far, but as mike had said it is pricey probably due to the piston. TOM