Gain from cam and piston

[rhino99]

If I were to install an XR400 cam and a high comp piston, how much power gain can be expected on the stock bore? How much from the same mods and going to 416? How much from a stock bore with those mods plus porting? How much for the same with a 416?

I may be trading for a 400ex soon, and if so, I want to know my best power gains for the money. I dont realy know how much increasing the displacement by 18ccs or whatever over stock will help, but I know it will be a lil more expensive. I am thinking that an XR cam, or maybe even a ful blown race type cam and a high comp piston (race gas isnt an issue) would gain me nearly as much power as going ahead up to a 416. Do you agree?

Also, what else should I do to the motor to get it up to MX race standards? I dont know much about modding a 4-stroke, as I am used to my R.

i got all of my stuff from gt thunder and they said with me going up to a 12.5 piston their is no need to bore to a 416. i'll be putting everything in friday so i will post the results
cam and piston $385
valve job $50
porting $50

[trx400ex]

port it , pipe it , plumb it

[max400EX]

Originally posted by 2002-400EX
i got all of my stuff from gt thunder and they said with me going up to a 12.5 piston their is no need to bore to a 416. i'll be putting everything in friday so i will post the results
cam and piston $385
valve job $50
porting $50

Hey,
Whats all included in that valve job for only $50

thats a three angle valve job:devil

[inacoma91]

I was thinking about doing this also sometime in the winter. What if i just put in a JE 10.5 piston (stock bore) with a XR cam and do no porting. Would i have to do the porting, or could i wait later and do it.


Andrew

[2000ex]

To all those who are looking for info on a cammed, stock bore machine I did just that about a month ago and you will be more than pleased. I decided to go with the stock bore, as I felt that boring a perfectly good cylinder was not necessary. The stock bore will also tend to run a bit cooler than a 416, but it definitely runs hotter than the stock piston.

I decided to run the stock bore 10.5:1 JE coupled with the xr400 cam and gasket. I did all of the teardown myself and did some minor port work while I was in there. Basically cleaned up and port matched and polished the exhaust ports. I also ported the headpipes a bit where the welds were. I have been running a White Bros slip on for well over a year and am satisfied how it works with the modded motor.

First impressions were that the bottom end is really unchanged. While pulling through the midrange, the cam really begins to unwind itself letting the motor pull much harder than stock. Before I short shifted to keep the motor in the meat of its torque range, now she just pulls hard right to the rev limiter. I had only hit the limiter a few times with the stock motor, but now I find myself rev happy and hitting the limiter more often. I have not ridden a 416, but I am more than happy with the setup I have now. If the motor lets go (it probably never will, it is a Honda) I will be able to bump it to the 416 instead of re-sleeving it. Please feel free to ask me any questions.

[booneTRX]

Great reply 2000EX!!!!!!!!!!!!!!!

I think I will do the same thing. I also have a hard time punching out a perfectly good cylinder. What did it cost you and where did you order from????

[2000ex]

Thanks BooneTRX,

I ordered the piston directly from JE, you can get their number right on their site. http://www.jepistons.com
I believe the total was $135 to my door.

The cam and gasket set was from servicehonda and was about $140 if I remember correctly. I am sure with the deal we have with Terry at Marcums you may be able to get even a better deal from him.

Total cost around $280 plus my labor which does not cost me anything. If you want to chat on IM my screen name is Hotbot Master

PS I have a set of Works triples on the way ordered from Marcums and they were quite a pleasure to deal with. They said they have seen quite a few orders come their way through this site, so keep supporting our sponsors and buy your parts through them.