excelent points.

I have a question on your last sentence and that is what exactly do you do when performing the very important porting on the 400ex head? Any secrets you want to share with the rest of us members?

I have managed to get some info from a couple of engine builders (and their ideas on where to remove a little extra or leave it etc seem to have worked very well) but I know theres much more for the "right porting".

Dont worry if you decide not to share with the rest of us as most who know this stuff are pretty greedy with the info [img]i/expressions/face-icon-small-smile.gif[/img]

 

I agree with your thinking there but I also added builders or dealers in places I wouldnt mind visiting when I would have to fly there to do any throat massaging [img]i/expressions/face-icon-small-happy.gif[/img]

 

Hey 440ex, It would be pretty hard to explan in text. I have spent many years building restrictor plate stock car engines and have figured out ways to make big power with small carbs (and ports).
First of all you need to get the throat diameters correct (87-90% of the valve diameter, intake and exhaust on this head) with a nice 5 angle or radius valve seat. Then widen the long side radius (around the valve guide) That's about all I could explain to you this way.

 

Thanks for the info, and I appologize if I may have "baited" you a little but its not easy getting any answers on this not just good answers [img]i/expressions/face-icon-small-smile.gif[/img]

I have ported a couple ex heads and seem to get good results but without a flow bench and couple other tools I would like its hard to be 100% on the results etc.

There have been many people who have questioned me in the past (I think this is more due to my willingness to answer and being honest about the things or parts I seriously dont know) and I have advised those without experience to not go beyond a general "clean up" porting, and due to my lack of experience or knowledge I didnt recomend much more to those who thought they had better skills or experience etc. This is something that has frustrated me that beyond equalizing the runners, port matching, and removing the casting marks there isnt much more that I am 100% on with this head (OK I do know two more tricks on the intake and one on the exhaust but these were offered under an oath of silence after hours of badgering lol) and since most of us are only able to volume match the left and right runners we cant be sure on added flow or changes to velocity but only the static volume.

I was taught by a ole machinist that was a big block chevy fanitic (like my self) to do my own port matching and some other little stuff, so I am not a pro by any means but i do understand the basics and theory. One thing that has had me thinking lately is the two or three people I have read on the net that have claims to excelent results with just increasing the velocity without changing the volumes etc. Do you have any thoughts on this or how it would relate to the head on the EX?

Do you know of any other "tricks" that would help my 440 thats set up for bottom end grunt?

Thanx

 

just put a CR450R in there then big bore it later won't over heat
Text

 

Guy's 440 cc's dosen't rev less (unless you don't have enough cylinder head) it likes to rev more. see dyno sheet in my pics. (sorry for poor quality, my scanner broke. There is a 416, two 425's and a 440(highest reving, lower power because of low compression piston and head being salvaged after a dropped valve) The difference between a 416cc and 435cc is about 5%. If every thing is right, including porting and other head work your looking at a 43rwhp bike, 5% of 43hp is 2.15hp (most head porting, stg 2 Hotcam, good complete exhaust, CDI box and 11:1 will only make 30-35hp, 5% of 30 hp is 1.5hp.
Moral of the story is, if your sleeve is still good, build a 416 or 425 as others have said.
Put your money into an R4 or Biggun complete exhaust.
Ray

 

440ex026, check out the dyno sheet in my pics. (sorry about quality, in have to get a new scanner) Top green line is a 416cc on pump gas I built, 30hp at 4500, 43.6 hp at 7800, 30 hp at 10,000 rpm.
Why settle for bottom end when you can have it all, LOL
Ray

 

Just put the CRF450R motor in for the same prices and no heating

 

hey i have a 400ex and i was wondering whats the best bore...i was thinking of 416 or 440, but i heard 440 overheat and how much would labor be putting in 440kit ??

 

hey, i have a 400ex w/ t-4 exhaust and paddles, and i was wondering the best bore kit for 400ex ? and how much you think it cost for labor ?