425 is the SH*%T

[Blackguywithouta400]

Well ive been talking about the 425 long enough. I finally got all the .120 over boring done and the complete race port job on the head back. I installed a JE 88mm 11:1 piston with the XR head gasket. My quad already had the XR400 Cam and DMC exhaust, with a K&N. I jetted the carb with stock needles by moving the clip down one to towards the point and installing a 172 main jet 42 pilot with 2 turns in. I am running 101 Trick racing fuels. After braking in the engine I was very impressed with the power the head work must really help out the top end because with the stock gearing and tires I am able to do 5th gear wheelies now no problem at the top end of 5th, this seems to pull for ever when drag racing I didn’t have enough room to pull rev limiter yet in 5th this much torque renders 1&2nd useless gears now and will require me to go to a 37 or 36 rear. I would suggest this to anyone looking to add more power to there 400. I did all the assembly and disassembly myself and had no problems at all doing it. The assembly only took 3hrs once I got the parts back. One thing I noticed that with the higher compression the motor wants to idle at a higher speed. I cat wait to race a raptor and see how I do. I think the next mod will be getting the carb bored or get a FCR to take more advantage of he port job and shaving the fly wheel. I don’t see any reason to have to resleeve the engine when taking it apart you have to notice how thick the steel sleeve really is I feel my motor is just as reliable as a stock 400 and with appropriate maintenance should last me until next winter when I stroke it. The motor not me Jabber :D

[CranMan]

I'd like to know what the whole upgrade cost you, parts , machine work etc...Also did you need any special tools to do the work? By the way, thanks for your post, it's good info man!!!

I told ya you'd be happier than a sissy with a bag a peckers when ya got the motor rebuilt. So she's pissed off huh....thats great ta hear everything went OK and ya didn't have any problems,,now go kick some rapturd butts..:D

[Blackguywithouta400]

Lets See what it cost me:

Bore .120 over 65$
Piston Je 11:1 88mm 141$
Head Work 120$ <- major hommie hookup
Topend Gasket Set A 26$
Xr400 head Gasket 15$
Total {367$}



2 hr tear down
3 hr install

[CranMan]

Not bad...so I guess without the "Homie" hookup, it would cost me about $500. What about any special tools needed. And did you have a book, if so what kind???

[Blackguywithouta400]

Main tool used was a Honda Service Manual
Second a torque wrench <---- A GOOD ONE
then your all set, you can compess the rings with your fingers so
no ring compressor needed

[Tommy 17]

dude when u comin to pa i wanna kick ur ***:D haha i will get brandon after u:D :D :D glad to hear it worked out... so how many times did u do the 4 block drag race....

[Dave400ex]

$500 is not Bad. I`m still not sure if I want to do a 416 or 425. I think the 416 would be better. I guess it depends on what TC tells me. I just want a TC Piston Kit, TC Cam, Viton Valve Seals, and Labor.

[Chef]

Stroke it, then make it an alcoholic :D I did it, its grrrrreeeeeeeeeeaaaaat!!!!!! lol

[Duner400ex]

What kind of Xr cam did you get and how much was it. Where do you get the head bored out at, would any mechanic place do it or do you have to send it in.


thanks Duner

Stock XRcam is gonna run ya about 120- 130 bucks shipped to your door from marcums. Also marcums has the 416 piston kit which includes boring the cylinder for like $155.