special needs for a top end rebuild??

[07RedRider400]

I have an 07 400ex, i got it new in fall of 2008, i dont beat on it but i use it's performance, but have well maintained it. This summer i would like to get a 426cc 10:1 (or maybe 11:1) big bore kit and a stage 1 cam. My question is, should i do anything else like get new valves/valve springs, cam tensioner chain, or anything else like that? I already made a oversized secondary oil cooler for it so cooling shouldnt be an issue, thanks!

[CJM]

Pretty sure you will be fine. Its not really that old so I doubt much has failed (springs, bearings, etc).

When you take it apart Id take a look at the valves and see how they look and Id checkt he valve springs with a caliper (spec is in the repair manual)

[Blodg]

I am building a 2006 with relatively low hours into a 416 and for insurance I am installing a CRF HD timing chain and HD head studs. Neither are needed but I shouldn't have to rebuild the quad again for a long time. As CJM said valves and valve springs should be good but measure and check the clearances.

[07RedRider400]

Originally posted by Blodg
I am building a 2006 with relatively low hours into a 416 and for insurance I am installing a CRF HD timing chain and HD head studs. Neither are needed but I shouldn't have to rebuild the quad again for a long time. As CJM said valves and valve springs should be good but measure and check the clearances.

how much will adding those add to the cost of the build?

[CJM]

2002 crf 450r timing chain is like 40 bucks, HD studs are 50 then 50 to install by GT Thunder.

[jkosakowski]

I would look into a stage 2 cam instead of the 1 it gives you a little more power all the way around. I loved mine !

[Honda.rider5871]

Unless you have already bored it and need to go the next size up I wouldn't recommend a 426. The cylinder walls are very thin creating a lot of heat, I would go with your same build but a 406 that way you still have 2 bores left before you have to re-sleeve or buy a new cylinder. Bore is not where your power is made anyways, compression is where the powers at. You can run 11:1 and still run pump gas also as long as your not running a sparks timing key. A good cam would also compliment the build

[JOHNDOE83]

Really with any bore or any stroke is not going to cause a heat issue.

Thin cylinder walls is something a engine builder will tell you when they built you a motor and you call the guy and say "Hey this thing runs hot".

Bore size/stroke will not create heat, bad jetting and bad engine builders create heat, it doesnt even have to be a bad engine builder, a expert builder even makes small mistakes sometimes.

90% of the time jetting is the source of the heat issue.

90% of the time also, machine shops have no idea or even how to go about jetting.

Dont worry about heat or reliability, just jet it properly without that plug chop crap and youll be fine.

Jetting procedures in the faq section here www.jetsrus.com