Question on performance mod for 400ex

[Ispep1012]

I was planning on upgrading my 01 400ex with a hot cam stage 1 and a wiseco 11.1 standard bore piston. But I found a post on here about how to pick a cam and it made me question whether I want to leave the stock cam and add the 11.1 piston or do both. I prefer more torque and low end power than top end but I do not want to bog the top end down either. I would appreciate some comments and suggestions on what you guys think would be a good setup. Below is the quote that made me re-think. I only want to spend roughly $300.00.


Originally posted by GPracer2500
I see a lot of discussion about the HC stage 2 vs. the HC stage 1 for a stock compression engine. I've done some calculations to define how much the stage 2 might hurt bottom end performance. If you read the entire first post then you know that the issue is the loss of compression from the intake valves staying open a long(er) time. Compression is a dominating factor for producing low end torque. Here's the difference:

Taking into account the valve specifications:

Stock cam cranking compression at 1000ft = 8.2:1
HC stage 1 cranking compression at 1000ft = 7.8:1
HC stage 2 cranking compression at 1000ft = 7.6:1

If you go to a 11.0:1 piston (instead of the stock 9.1:1 piston) then the numbers change to:

stock cam: 9.9:1
HC stg 1: 9.5:1
HC stg 2: 9.2:1

(figures may not be absolute but the comparison is accurate)

[2004exrider]

I wouldnt worry about losing lowend power at all, I still have a stock piston and put in a HC stage 1 and i gained a pretty good amount of lowend and midrange power. With a higher compression piston you'll gain some more power too, so I'd say go for it!

Jimmy

[GPracer2500]

I'd get the piston AND cam for sure. When I wrote that I was just trying to show how it can be possible to have too much cam for a "well rounded" engine build.

That data was not intended to be an unequivocal proxy for expected torque production. But rather, it was intended to illustrate the relationship between cranking compression and intake valve closing. Perhaps I should have left the stock cam data out of the comparison.

The reason I say that is because compared to a HC1 or HC2, the stock cam almost looks attractive if low end is all your after. The problem with that thinking is even though the stock cam will get you higher cranking compression, there's so little lift and duration that it's likely to quickly strangle the cylinder filling ability of the engine once it's actually running. Neither a HC1 or HC2 is going to have that issue. At some point the superior cylinder filling and scavenging abilities of an aftermarket cam are going to overshadow the benifit of the early intake valve closing found with the stock cam. The HC1 is going to be so much better at stuffing the cylinder with air/fuel charge that it probably overcomes the cranking compression difference pretty quickly.

That data is probably best used in making comparisons between the HC1 and HC2 rather than comparing the stock cam with the HC1.

[Ispep1012]

Thanks for the reply's!


Originally posted by GPracer2500
The reason I say that is because compared to a HC1 or HC2, the stock cam almost looks attractive if low end is all your after. The problem with that thinking is even though the stock cam will get you higher cranking compression, there's so little lift and duration that it's likely to quickly strangle the cylinder filling ability of the engine once it's actually running.

This was exactly what I was wondering so I appreciate the feedback on that. I am planning to do this myself to save some money, but I have never done anything like this yet. As a matter of fact my buddy has a 06 400ex and we are both planning on doing this at the same time. Luckily I am one of those type of guys that learns things quite quickly and blessed with common sense :D . Is there anything when doing a cam and piston swap that I should be extra cautious about and are there any specialty tools that will be required other than the sockets and hex wrenches. Also just out of curiousty what type of power gains should be expected. I have tried searching for some dyno's for comparison but came up short. Again I appreciate the feedback guys.

Rick

[94F450SD]

i did the hotcam stage 1 in mine.i cant tell you how much power i gained but it feels like the lowend almost doubled.not saying it did just it feels like it did.i used to have to pullback to get it to wheelie.i put the cam in and now all i gotta do is snap the throttle and im on a wheelie.the best 170 bux i spent on performance mods.drill or remove the airbox cover and it will really wake up!!.

install was easy.go pick up a repair manual for it.you will use it more than you think.

[Ispep1012]

I have already done a few minor mods to it. I bought it new in 01 and feel like there just isn't as much power as I would like. The minor things are WB CDI, K&N with Outerwears, re-jetted & custom made air box cover(see pic). I just cut it out and fabbed a piece out of sheet metal with a filter in the opening. I appreciate the feedback on the stage 1 cam and it sounds like it is what I am looking for.

[Ispep1012]

Okay definitely planning on going with the standard bore 11.1 wiseco piston and hot cam stage 1. Where do you guys buy your parts from or where can I find these at the best deals. I will need 2 stage 1's, 2 11.1 standard bore pistons, 2 top end gasket kits and 2 cam tensioner gaskets.

[Choppers]

The site sponsor. Colby C&D.

[skragg]

mill your heads as well for more bottom and mid

[400exrider707]

Originally posted by Ispep1012
I have already done a few minor mods to it. I bought it new in 01 and feel like there just isn't as much power as I would like. The minor things are WB CDI, K&N with Outerwears, re-jetted & custom made air box cover(see pic). I just cut it out and fabbed a piece out of sheet metal with a filter in the opening. I appreciate the feedback on the stage 1 cam and it sounds like it is what I am looking for.

Just a suggestion, lose the WB CDI, one of the worst you can buy...which doesn't say much since about 98% of them are all the same... they are an XR250 CDI, you will have starting problems with it. Only good ones to my knowledge are Stock, TC racing, and GT Thunder, as far as non-programmable ones go anyways. Search the topic.

[Ispep1012]

Okay guys appreciate the help but I have a final question for ya. I ordered everything for an awesome deal, installed everything fine in both quads but the power gains were not quite what I was expecting. Then again I have not had the chance to really rip on it either. I am wondering if I need to fine tune my jetting. I started out with a 155k main 42 pilot and stock needle position. Do you guys have any recommendations on an average roundabout jet size to start fine tuning on.

Again my mods now include, WB CDI, modified open airbox, K&N w/outerwears, wiseco 11.1 piston & stage 1 hot cam.


400exrider707- I hear that alot but unfortunetly I fell into the hype that ooh an easy bolt on power mod, but anyways I have had it in since 2001 with no issues. Everyone says I am lucky but heh.

skragg - Too late I did not check the thread before I tore into, but thanks.

[fast426]

Im not positive, but if you do not have an aftermarket exhaust, it could be why you are not seeing the power gains you would like. When most people install a high comp piston and cam they have an aftermarket exhaust, which would also help with bottom end.

[Ispep1012]

Yeah that is what I want to do next but I just dont have the cash to shell out right now. It was basically a decision to go with the cam and piston or silencer. I thought the most gains would have been internals. I think I just need to pin down the jetting as well.

Then again the gains may not be what I expected because I have been expecting it to be a whole new quad and also I have been riding my crotch rocket so that could be why.

[stocktires]

Jetting is key, also get the slip-on ASAP!

[2004exrider]

You'll deffinitely feel more power once you get a new exhaust. The stock muffler on the 400ex is really restrictive.

Jimmy

[Ispep1012]

I am trying to talk the Miss's into letting me get one :p . I was looking into the WB E2. Anyone here anything good or bad on them? They are marked at $295.00 at the moment.

[88_Pathy]

I just got a HMF slip on and it is great so far.

[stocktires]

Originally posted by 88_Pathy
I just got a HMF slip on and it is great so far.

Ideal for a mildly modded 400ex. Slip-ons are the way to go and HMF is good stuff.

[Ispep1012]

Okay I worked my magic and have a slip on on the way so I guess I will see if this makes up the performance or not. I have been tinkering with the jetting and picked up a little more performance so the slip on should hopefully blend it out.

[Ispep1012]

Got some more questions for ya's. Not the right area but I figured I would try here before I start a new post. Okay while the pipe is on its way I would like to adjust my stock shocks. I have never adjusted them from factory (sad I know) but from reading these forums it has given me the urge to tweak everything to the best I can get out of it.

I can no longer find my owners manual and the service manual makes no mention of this. Bare with me here guys & gals.

Preload - Rear Should be 30% of a specific measured difference with the shock fully extended. So for example I measured mine to 13 inches so when i put my full weight on the bike I should sag 3.9 inches to a measurement of 9.1 inches correct? Same with the front as well except the sag should be 20%?

Compression & Rebound - I am a little lost on but I am gathering that it is a test ride tune, per style of riding. I see there is some adjustment screws on the top of the rear shock as well as the bottom. Which one does what and turning what direction does what?

Sorry for the long winded post but your reply's are greatly appreciated.

Rick