hey guys
Im looking to get this 2004 yfz 480 big bore
i was just woundering what to look out for
it has a anthen big bore kit on it and the seller thinks it has a rot rod cam so on that note he wouldnt be sure if it was a strocker or not?
he bought it 2 years ago and only had to put a clutch kit in it .
so my question would be how good are the big bore kits and if it doesnt have a rot rod cam is the stock cam pretty much done?

im trading my 2002 ds650 baja with some up grades to it and custom beedlock rims

do u think that is a good deal ?

thanks

 

The 480 big bore does not require a stroked crank, so my guess is it has a stock length crank. It may have a 'Hot Rods' brand crank (not Rot rods), which is just an aftermarket crank, but does not mean it's a stroked crank. Hot Rods cranks are good, and Athena big bore kits are good, having those just means that engine has been completely rebuilt at some time, probably because the engine was blown up at one time (stock crank is probably toast).

The hot rod crank has nothing to do with the cam. It could still have the stock cam in it and be just fine.

 

Sounds to me like you are down grading.

 

Thanks for the replies
My buddies have yfz's and I like how the bottom end are a lot more snappy

So how often should new rings and piston be done in a 480 big bore

And also how hard is a 480 on the bottom end

 

Well that all depends on how its ridden and what oils u use and what compression ratio's ect ect ect. There is no real answer on ring life.
It is not really harder on the bottom end because the weight of the rotating mass is the same (or should be) as stock. So the balance of the motor should be the same. Good luck.

 

470 is the the limit on the stock '04/05 crank and still have decent reliability. Sounds like that engine has a +1 stroker(hot rods crank) which isn't really a big deal, since Yamaha originally had DESTROKED the motor to meet the 440cc racing restrictions at the time it was released. '06+ motors have the longer crank as oem to get them back up to 450cc. In fact it is hard to even get the '04/5 length oem crank anymore. Speaking of which, next time you rebuild, I would go with oem over Hot Rods.

As for piston/ring life, I would contact Athena. I have seen a recommended piston life of 10-25 hours, depending on how hard it is used, etc. With good maintenance and not racing, etc you can probably extend that somewhat. Just remember, if it fails while running you are looking at 2K to rebuild.

The 480 does tend to be harder on the whole motor. The short skirt 450 style pistons are more likely to rock at the extremes of the stroke, plus you have more power and heat in the equation as well. Anything stroked bigger than the +1 really should be balanced also. I know Athena changes the jug height a bit, so you need to be careful when replacing the piston you get the proper one if buying other than from Athena.