What size bore to get???

[tgreenz400]

Well i have a 05 Z400 that's in really good shape and was wanting to bump the bore size up a bit....so im stuck between the 426 and 440. Which is the overall better size? I hear the 426 is pretty reliable and has good power, but i also hear that the 440 is kind of unreliable and makes a ton of power.

Please and Thanks

[trx400EXtreme]

id check out the Athena 435 kit. comes with a whole new top end... cylinder and all.

[tgreenz400]

Originally posted by trx400EXtreme
id check out the Athena 435 kit. comes with a whole new top end... cylinder and all. ehhh...thats tad bit expensive.I dont think ill need the whole top end, Mike can probaly hone it and stuff for me.

[honda8&3]

Any bore can be very reliable if done right. The 440 can be just as reliable as a 426 if done right. IMO the 426 is plenty of power for woods and for flat out riding! It will be a little bit cheaper too. What mods do you run now?

[tgreenz400]

HMF full system, K&N air filter, and a jet kit is all

[honda8&3]

Well IMO a 426 would open that up real nice. You would feel plenty of torque and it would give you much more power. A 440 would only be a little bit more expensive and is still reliable if built correctly;)

[tgreenz400]

Well could someone post a link of a good kit? As said before tho, cant be very expensive

my friend had a 440 stroker in his 400ex and the power was amzing. every gear pulled just as hard as the 1 before it. When you hit the gas it just went it was awesome

[GPracer2500]

Originally posted by tgreenz400
...As said before tho, cant be very expensive

Then you're going to have to go with an iron sleeve and find good prices on machine work.

Your Z has a coated aluminum bore (similar to a Nikasil'd bore). So, to retain your stock cylinder you'll need to either 1) install a sleeve or 2) bore your cylinder and have it re-coated or 3) get a new cylinder already setup with a larger bore. Your cylinder isn't like a 400EX, for example. An EX already has an iron sleeve so you can go up to a 426 with just a new bore in the existing sleeve. That doesn't work on a Z.

Example of option #3
https://www.partsforatvs.com/shopcart6/image_db/z435.jpg
https://www.partsforatvs.com/default.asp?p=1585&c=942&cn=M3Q+Z400+POWER

Example of option #2
http://www.partsforatvs.com/shopcart6/image_db/400ex-440cc-big-bore-kit.jpg
http://www.partsforatvs.com/default.asp?p=687&c=549&cn=Power

Installing a sleeve will probably end up being a little cheaper. But you're giving up the advantages offered by the coated aluminum bore your engine came with stock (e.g. better oil retention, better durability, better heat transfer properties, etc). And don't forget the machining costs of installing a sleeve. And don't dismiss the possible headaches of having a sleeve installed poorly my a machinest that screws it up (I've seen it and it's ugly). Option #2 isn't as inexpensive as it appears at first. Plus, with option #3 you've still got your OEM cylinder that you can sell or keep or whatever.

If it were my Z, I'd probably limit my search to the best value I could find on an aftermarket cylinder. If I couldn't afford it I might not spend my money on a larger bore. I might start looking at cams, stock bore pistons, and other things first. I'm not saying a sleeved Z is a bad thing. If done right I imagine they can run hard and reliably. I just don't personally think it's the most attractive option.

Maybe try the site sponsor, C&D Racing, and see what kind of deal they can offer on a new cylinder. But that Athena cylinder, piston, and gaskets linked above sure seems like a good value. I didn't really search--just Googled Athena 435 clicked there first. And don't forget to pay attention to compression. That's got just as much to do with performance as a few dozen CC's of displacement AND will determine what kind of fuel will be needed.

$0.02

[tgreenz400]

ok thanks

[honda8&3]

Ya the athena would be my choice. IMO Don't bore it. Get a high compression piston, Hotcam stage 2 and some port and polishing. Much cheaper and still produces great results. You wouldn't believe how much power is locked up in a stock engine!:eek2:

[tgreenz400]

What would be the best piston to get if i just got a stock bore one?

[trx400EXtreme]

wiseco, JE, and CP are all good brands.

[honda8&3]

Well JE piston's are really nice because they are true to their compression rating. Wiseco are also really nice. It's pretty much personal preference IMO.

http://www.partsforatvs.com/default.asp?p=683&c=549&cn=Power

You'll prolly need at least 91 octane with the 12:1. That's what I'd do if I were you with a HotCam stage 2 and port and polish on your head.;)

[tgreenz400]

alright thanks...im gonna take ur advice of just getting a high comp. piston into serious consideration. im also gonna try to get the cams too, but u have to buy 2 and that kinda sucks :ermm:

[honda8&3]

No you don't. Go to www.hotcamsinc.com they're in stages LOL. I don't understand the cams on that site LOL

[honda8&3]

Never mind LOL. I guess they don't make one cam for both the intake and exhaust valves LOL. But trust me You'll be happy with that setup. Everyone I know that runs a similar setup loves it! Check out some port and polish too. You wouldn't believe how much power is locked up in your stock head! Not too pricey either.;)

[tgreenz400]

lol ok i was getting confused for a second...my dad is friends with a professional drag bike builder so im sure he can help me out with the port and polish

[honda8&3]

Originally posted by tgreenz400
lol ok i was getting confused for a second...my dad is friends with a professional drag bike builder so im sure he can help me out with the port and polish

Ya dude most machine shops can do it. Get a professional machine shop though. Maybe ask your dad's friend he prolly knows some good ones.;)

[tgreenz400]

okidoke, is that usually very expensive?

[honda8&3]

Originally posted by tgreenz400
okidoke, is that usually very expensive?

Shouldn't be too expensive. Ask Colby at C&D he has some prices on the port and polishing. If you have any other questions feel free to ask. ;)

[tgreenz400]

alright, i think this round of questionaire is over lol. thanks alot

[honda8&3]

No problem.;)