416

[jeepthing07]

I am thinking about having my engine bored out .40 over. I don't know what combos make a moter a 416, 426 or a 440 i thought just boreing it out made it a 416. i don't want to stroke mine the crank and all the parts are to expensive. i just want to throw a weisco piston in mine and be done with it. i want to boost the compression up a bit but still run it off pump gas what would be a good compression to run for that?

I found this on another site is this true?
"The difference between the XR400 and the 400ex engine:

400ex: 85mm piston and 70mm of stroke. Comes stock with 9.1:1 compression ratio. Electric start only. The camshaft is a big difference. Lift and Duration .316 .302 .234 .238

XR400: 85mm piston and 70mm stroke. Comes stock with 9.3:1 compression ratio due to a thinner headgasket. The camshaft is also different. Lift and Duration- .326 .321 .240 .244

Just a fact about buying a piston for your 400ex from Wiseco. Whenever wiseco offers a piston for the 400ex engine they base their compression ratios off the XR engine. Example- If they say its an 11:1 piston its really going to be a 10.8:1 compression. To fix that problem you can put on a XR headgasket and that will bring it back up to the true compression ratio due to the 400ex having a thicker headgasket."


and how much does a shop normaly charge to over bore a cylinder? i have herd it was $20 a hole on car cylinders.

[shawndog360]

just do a 426 11.1 new piston and get a heavy duty crank so it dont go out on you and you wont have to worry about it blowing up on you and get heavy duty timing chain and get new guids and lifter tensioner and you should be good to go.

[honda729]

id do a 416 with 11:1 that way you dont have to resleeve, just drop a piston in and a cam and ull be good to go.
my honda shop did mine for 40 bucks i think.

[drew416ex]

.40 = 406
.80 = 416
.120 = 426
.160 = 435

Around here its $40-$50 to bore a cylinder. Those differences about the XR and EX are true. A 416 will have just as much power as a 426 and you still have another bore for when it wears out. You can make a 416 keep up with a 440 if built right. It would be a good Idea to go with maybe a hotcam stage 2 if you want to see all the benefits of the added compression.

[jeepthing07]

OK i will probably do a 406 or a 416. im not racing this quad but i never can leave well enough alone and figure i might as well hop it up a bit while i have it apart.

Is cooling a problem with a 416? im going to put air scoops on it anyways but id rather have a cool running reliable engine than a performance engine with overheating problems and other headaches.

I have seen some HD cam chains on ebay for $50-$100 is there much of a quality difference? they are probably all made by the same company anyways just thought id ask

[drew416ex]

There arnt any cooling issues with a 416. As for the chain, some claim to be better but arnt. The ones that are have extra plates in the links which makes it stronger. Ive never had a problem with the stock one (knock on wood), but the extra assurance couldnt hurt.

[honda729]

if you want a hd cam chain get a crf450 one same as an hd one, 50 bucks less

[bbender85]

could you put a XR headgasket on an EX just for the sake of bumping compression and be done with it?

Originally posted by bbender85
could you put a XR headgasket on an EX just for the sake of bumping compression and be done with it?

you bump up the compression by .2 with the xr gasket. so instead of stock 9.1:1 you have 9.3:1.

[400exrider707]

Cometic also offers a "thin" head gasket for these motors, which is even thinner than the XR one. I used one on my build.

Also a CRF cam chain is about $35 from servicehonda and is the same as an HD one from DID.

The 400ex is designed odd. The piston sits down in the cylinder .040" at TDC. Doesn't make a bit of sense to me...

I think even an 11:1 piston wont get you 10.8:1.... not sure though.

You can also leave the base gasekt off and use a very thin bead of yamabond or hondabond instead to bump compression even more.

[krt400ex]

Originally posted by honda729
if you want a hd cam chain get a crf450 one same as an hd one, 50 bucks less

bingo. you dont need a heavy duty crank though...your engine wont let out with a 426

[drew416ex]

Originally posted by 400exrider707
You can also leave the base gasekt off and use a very thin bead of yamabond or hondabond instead to bump compression even more.

This is what I have done for years with no problems.