Hey guys i got an 03 ltz 400. I blew the shift fork last summer and am now getting ready to fix it. I'm doing a top end with it. I have a k and n with a pre filter and a slip on big gun eco series. I was thinking of doing a wiesco hi comp piston and a hot cam. I do mainly trails and dunes. Will I be able to run pump gas still with this? Anything else or different should i do?

 

You want to stay south of 12:1 for pump gas. 11 is probably the highest I would do. I would look into a big bore kit, since you are doing a new piston anyway. Just stay away from the cheaper cast pistons kits for longevity. Both the compression and bb kit will gain power across the rpm range. Check with the kit builder, but if you go that route the right full exhaust may help more than the cams.

 

The Wiseco piston is 10.25:1 and you should be ok with pump gas. as far as a big bore kit, that is a heck of a lot more work as you will need to resleeve the cylinder. If all youre adding is the Wiseco piston, and youve already rejetted for the air cleaner, you shouldn't need to re jet further. Just bore and hone your stock cylinder, ( I had all my machine work and honing done at carquest along with a valve job and new seals for less than $70.) And did all of the installation myself. Youtube has lots of videos that will guide you, overhead cam 4 strokes are basically all the same. If you want to put a hot cam you can, but the high comp piston in my 230s makes a ton more power than the stock one. If it were me, I would just go with the Wiseco piston, bore and hone the cylinder, and love the power gain for not much money or work. But if you can afford it, and youre paying someone else to do the work, then go all out, lol you'll have one bad mother of a qaud. Let us know what you decide.

 

How is a bb kit more work? You are removing the jug either way. Since he is asking I have a feeling a machine shop is doing any of that work for him anyway. Generally with a kit you are just swapping jugs, no boring or honing required. Depending on make and manufacturer, the new jug may even have better cooling passages as well. Just depends how much you are able to spend and what kind of performance and look you want. It pays to research and not go cheap on these though.

 

Exactly. Since he is asking i have a feeling he is doing the build himself, and since not to many people have engine lathes i'm guessing he's farming out the machine work. And I dont know how many hours you have to work to afford a bb kit, but I have to work quite a few. I have right at $180 with machine work and valve job and parts. He said he's a trail rider and he's already riding an LTZ400. Last I checked that's one bad dude bone stock. I'm trying to give him the best advice for his money and I don't think he would ever need that much motor expansion unless he's in a pissing contest with his buddy. You're right about the bb kits being 'modern' to save some words but they can get expensive quick, like $300 and up. You're also correct about research. And that's the best advice there is. What is your purpose, how is that best achieved, and shop around. I got my $125 piston for $70 somewhere else and youtubed and took notes and read these forums for weeks before I loosened the first bolt.

 

Dunes eat hp like candy. A 440 kit will put him in the realm of 450 class power. Just a quick Google and I see 434 kits for under $600.00. Unbolt the old, bolt on the new. No machining. OP doesn't specify a price range or budget. Big bore and a higher comp.piston will really wake that engine up. I would just advise sticking with a forged piston, wiseco, cp, wossner, whatever you prefer. That is how I would build it anyway.