going to a 416 11:1 compression piston

[slowleak]

ok, i am new to this site, and thank goodness i found it. i have owned my 400ex for 4 years now (its an 01) and have done nothing to it but a dirt digger clutch, now its time to play. i have had the 416 piston for about 3 years, along with a hotcams cam. my questions are as follows

1. what do i bore the cylinder to? i already pulled it, just ned to know what to tell the machine shop.

2. with the new piston and camshaft, along with a full yoshi system, what kind of jetting will i need?

3. does anyone have any links to some good write ups on engine re-building on these bikes?

sorry for the long first post, but i like doing things right the first time.

thanks

[CSR400EX]

as far as the machine shop, if you still have the box for the piston, thats all they need. adding a full yoshi and a cam, id start around a 160 main, 42 pilot for jetting.

[GPracer2500]

Ideally, you should hand the piston over with your cylinder. In my experience, most machinists will be hesitant to even do a bore job without having the piston in there hand to measure. Knowing it's a 87mm piston doesn't cut it. They need to know exactly what it measures to in order to set the piston-to-cylinder clearance with any precision.

[Choppers]

when i did the 416 kit this weekend we had to bore the stock cylinder .080.

[drew416ex]

Like GPracer2500 said, take your piston with you. They are all slightly different. It may only be by like .002" to .004", but when there is only a .002" cylinder to piston clearance that is a big deal. Jetting your looking at around a 160-165 main and a 40-42 pilot.

[slowleak]

allright guys thanks for the info. im bingin it to the machin shop now. i will let yall know how it turns out.

anyone with some links to re-builds?

thanks

[GPracer2500]

You gotta get a service manual. If for no other reason, you need the torque specifications.

Check E-bay for used and/or PDF versions of the OEM manual for cheap.

[slowleak]

cool thanks. i also found a parts site that shows extremely detailed exploded views of every last little part. but now i cant find it anymore, and its buggin the hell outa me.

[slowleak]

Originally posted by Choppers
when i did the 416 kit this weekend we had to bore the stock cylinder .080.

just got off the phone with the machinist. he said it would be bored .080, and that if i ever went bigger i would have to get a new jug, or re-sleve it. does this sound right? how does the 426 and 440 kits fit then?

[416exfreak]

They bore the stock sleeve completely out of the cylinder and press a new, larger one in.

If you plan on doing anything over 416, I would get the HD head studs from GT Thunder. I made the mistake of not using them one time....I regreted that.:eek:

[slowleak]

i should be safe with the 416 though, right?

[416exfreak]

Yes, at 416cc's your perfectly fine.:)

[JOEX]

I'd be more concerned with the compresson ratio than the size of the bore when talking about HD studs.

[F-16Guy]

For what they cost, I would do the head studs for any high compression piston, regardless of bore. There are too many examples of people having problems. My 11:1 416 didn't last ten hours before the head gasket blew. I replaced the gasket and it blew again on the starting line for the first round of WORCS in 2006. After that, the cylinder went to GT Thunder and for about $100 I got studs, a head gasket, and a hone for some fresh rings. Absolutely no problems since. Why mess around? If you build it right the first time, it will last for years.

[slowleak]

wouldnt the compression ratio go up with a bigger piston? mine is 11:1, so i think i will be safe. do i have to run special gas for this? ie: higher octane instea of plane 'ol 89 octane?

on edit, what exactly differs in the head studs? are they shorter to hold the head down more or what?

[drew416ex]

It doesnt matter if it is a larger diameter, its still 11:1. I would run 93 octane with it. The HD studs are a larger diameter and a coarse thread. They also thread into the cylinder a little further than stock.

[416exfreak]

With 11:1 you should be fine with 93-94 octane.

Any higher than that and you may want to start running a minimal octane race fuel or just adding some octane booster to your gas.

the HD studs have a courser thread. They also are thicker all the way down and they screw farther into the head.

[j450rking]

you have to run 93 or higher octane gas. and gt thunders head studs are a good idea

[F-16Guy]

Originally posted by slowleak
wouldnt the compression ratio go up with a bigger piston? mine is 11:1, so i think i will be safe. do i have to run special gas for this? ie: higher octane instea of plane 'ol 89 octane?

on edit, what exactly differs in the head studs? are they shorter to hold the head down more or what?
The compression ratio has nothing to do with displacement, it is a ratio of how much a certain amount of air is compressed from BDC to TDC of the compression stroke. You can increase or decrease the displacement and still have the same CR. Whether or not you need to run race fuel depends on a lot of things, including altitude, outside temperature, jetting, etc. With a static compression ratio of 11:1, you may or may not need it; my advice would be to run the highest pump octane you can find, and if you hear any pinging or knocking, take it back to the trailer and run 50/50 the next time out. I would need it on occasion at the dunes, but now that I'm at 5,000 ft., I don't need it because my cylinder pressures are lower.

As far as head studs go, the 400ex is notorious for pulling studs. The studs are threaded directly into the aluminum cylinder, and when aluminum reaches a certain temperature, it weakens and allows the stud (or studs) to pull out. Because it's nearest to the exhaust, the forward stud is what usually goes first. The GT Thunder studs are slightly larger in diameter and longer, but what really adds strength is the way they are installed. Instead of using a normal tap that cuts the aluminum away to make new threads, they use a roll form tap that compresses the aluminum, causing the threads and surrounding metal to become more dense, and therefore stronger. If Honda would have done that in the first place, studs probably wouldn't be an issue. It's probably the best money you can spend on your build as far as reliability is concerned.

[Ruby Soho]

like said before, get the studs