GPracer,ZR,Pipeless,Nacs,beags,Wilkin, I'd like to get your opinions on a question

[tri5ron]

Just wanted to hear some comparative feedback from you guys on a question I had.
(I'm sure I left some other knowledgeable members out, and sorry about that),
you guys all know who you are, and we would like to hear from you too.

Please see the last post on page 4 of GPracers "How to pick a cam" thread...

http://www.exriders.com/vbb/showthread.php?s=&threadid=237131&perpage=10&pagenumber=4

Thanks,
Ron

I'd like to hear the opinions of anyone else,...
WHO HAS SOME ACTUAL EXPERIENCE AND INTELLIGENCE.

I just don't want to get inundated with all kinds of useless responces from "The Peanut Gallery" or "Wanna-be Experts".

If you are offended by that, then you probably fall into one of those catagories.

Try to hang on to your hats here and don't get all pissy, and we ALL just might learn something here.

BUT,...

If you ARE just overwhelmingly compelled to be offended by that simple request,...

and you feel that your panties are all in a wad, over it...
then please do your whining and flaming of me here.
IN THIS thread,...
And respectfully refrain from dirtying up GPracers thread.

[honda400ex2003]

subscribed after discussing this a bit with ron. we are both interested in getting more info on the subject.

i added some of my thoughts on how a key effects overall performance based on the same setup.
steve

[beags86]

so... you want my opinion, or my wyotech trained answer?

i will hit the other thread up later tonight when i get a chance, ron

[tri5ron]

Originally posted by beags86
so... you want my opinion, or my wyotech trained answer?


Haha,... either one will do, or better yet, Both.
It might be an interesting comparison.

Still looking to hear from the other guys too.

[JOHNDOE83]

Well for the how to pick a cam question, I havent read through the whole thread of Gpracers so If it was already answered I dont know but Im gonna give my opinion on both questions.

Well when I picked my cam, I read the directions....lol.

I went with hotcams because they are a very reputable company thats been around for a while.

When buying a hot cam as we all know, they show the use's for the different stages, stage 1 is for piped and filtered bikes, stage 2 is for bored motors and stage 3 is for strokers.

Since I wanted the most power I went with what was recommended by the manufacturer, I know theres alot more companys out there that probally have better cams, with hot cams it seemed simple and to the point and not to aggresive, so I went with them.

Really unless you have incredible knowledge on the workings of these machines and can custom tune cam lobes and all that picking a cam should be as easy as reading the instructions.

Find out what the specific company your going to chosse reccomends.

Ive seen people with 416s running a stage 3 and cant figure out why it doesnt run that well, well its letting in way to much or way to lil air and the timing for the valves will be off for the forces that the piston and crank produce, dynamic/static...etc.

Even ericcrip tryd to run a stage 3 on his motor and it didnt run right and lost power because its not a stroker.

As far as picking a name brand goes, anything youve had experience with in the past or have heard good feedback on is a good choice. IMO.

If you really want to get technical, you can dig into durations and circumfrance's, valve size, timing and find something that will get the most power out of your bike, but in the end youd probally be better off going with whats recommended by a specific manufacturer and youll be saving time and effort, also making it a more reliable machine.

If you want the best performing cam with the most bang, Check all the cams that apply to your motor, lets say a stage 2, there are charts on the valve durations and lobe size for different brands of stage 2 type cams out there.

I "Think" but am not %100 sure, the longer durations and shorter lobe height is what makes it a stage 2 or 3, so to pick the best performing cam power wise for your motor, which would also create the risk for more engine failures, youd want the one with the most aggresive lobe and duration numbers.

I went with the hotcam stage 2 because it was best suited for my motor and hotcams is a very quality company. Its Not the most agressive Stage 2 cam out there, but my motors reliability has been excellent and performance wise, well just look at some of my drag racing videos...lol.

Its a long conversation with this whole how to pick a cam thing, I have to stop for now...lol.

[JOHNDOE83]

As far as the stage 1 or 2 cam on a stock bore with +6 key goes.

On GP's thread the last post I saw after reading Ron and Steves posts was a guy said the stage 2 made it lazy on stock bore, thats where the timing advance would come into play.

With stock bore and high compression its the same but different, because the piston is a different size the timing is also slightly different, thats why I say stick with manufacturers recomendations and youll be in the safe spot.

You dont "HAVE" to use Matched parts when building even a stroker but be ready to do some custom timing, machining and looking into durations and lobe heights.

Will a stock bore work with a stage 2 perform better then the stage 1, yes IMO, youll need the pipe and the key to do it, It will not be any faster then the stage 1 on stock bore till your in 4th or 5th gear, only then it will be faster.

Basically...lol... The stage 2 needs the key to do it.

Ive typed to much, I feel like Im rambling and slightly off topic...lol.

[zrpilot]

Everyone, consider motor work as a recipe. All the ingredients work together to make the final product. if you have to much of one thing...well you know what would happen.

This is and extremely hard subject to describe as there are many variables, such as static and dynamic compression ratios, absolute cylinder pressure, intake and exhaust tuning for scavenging effect, ETC...

Here is my opinion:

An after market cam does alot of things, lifts the valves more, lifts them faster, and keeps them open longer. The result (hopefully) is putting more fuel/air into the cylinder for combustion.

The more time the intake valves stay open the more important it is to have a high(er) compression piston. This is because with the valve open there is more opportunity for air to escape back through the valves as the piston begins its compression stroke. Even on the stock cam, the intake valves are still open when the piston begins its compression stroke. With an aggressive cam (like the Stage 2) more dynamic compression is lost through valves that stay open for a long time. This must be made up for with a higher STATIC compression piston. An aggressive cam with a stock compression piston may actually perform worse than the stock cam because too much DYNAMIC compression is being lost through the valves being opened so much.

Also the only real difference between the Stage 1 and Stage 2 cams is the duration or length of time the valves stay open.

So why do people report seeing more power on the stage 2 vs. stage 1 at higher RPMS on the same motor? First, IMO, seat-of-the-pants dynos are inaccurate. Second, maybe the speed of the piston/valve closure reaches a point where the scavenging effect of the intake tuning is maxmized and the valve does not stay open long enough for the air/fuel mixture to escape, therefore leaving more air/fuel in the combustion chamber to be ignited. This COULD create a noticeable bump in the power band, feeling like it makes more power then another cam. (see note 1)

Now you are thinking why add a cam? OK, good question, IF the static compresion were higher AND you had an agressive cam that resulted in the DYNAMIC compression ratio being equal to or slightly higher then the motor was stock, the engine is then breathing better, making more power.

That is why I think the Stage 1 with a stock compression 400ex is a better choice, you will lose less dynamic compression and compression is a dominating factor for producing low end torque.

If you read JJE02EX's post he said it best:
"i agree i have a stock motor with a stage 2 cam and i had to some major gearing to get anything out of bottom end they suck." There is real world proof about the Stage 2 and a stock compression motor.

Here is a quote form another member here, Def-E-nition, who just put in a HOT CAMS stage 1 on a stock motor.

"One can never understand what guys mean when they tell you - " yeah , this thing'll go Nicely with a stage 1 cam in ..." ."

As far as the +6 timing key, all this does is to cause the spark to be delivered 6 degrees earlier in the crank rotation cycle, allowing the air-fuel mixture to be ignited at the correct time, thereby making maximum pressure occur in the cylinder sometime after the piston reaches TDC. Doing this allows the ignited mixture to push the piston down the cylinder with the greatest force. Ideally, the time at which the mixture should be fully burnt is about 20 degrees ATDC. This will utilize the engine's power producing potential. When Honda engineered the 400EX they delayed the timing to prevent detonation from occuring under extreme conditions. And NO! rev boxes DO NOT advance the timing curve.

So in summary:

IMO, on a stock COMPRESSION 400EX, you will get best performance with the Stage 1 Cam and the +6 key. But one must make sure that you don't experience detonation from the +6 key. Running 93+ octane should help if you do.

Or simply bolt on this mod and be done with it! Best Mod ever!! (http://kalecoauto.com/index.php?main_page=product_info&cPath=1&products_id=30)

[tri5ron]

Thanks ZR,

anybody else have some thoughts ?

[wilkin250r]

Ron, I didn't mean leave you hanging on this thread. I rarely check the 400EX section.

ZR has a pretty good post, but he doesn't touch on a VERY important aspect of aggressive cams. The whole reason the valves are open longer is to take advantage of the inertia of the air as it moves into the cylinder. The valves are still open even as the piston begins traveling upwards. At low RPMs (air is moving slowly) this can actually force some of your fuel/air mixture back out of the cylinder, reducing dynamic compression and reducing power, and resulting in rough idle and poor low-rpm performance.

However, at high RPMs, air is moving much faster and has considerably more momentum behind it (air does indeed have mass, therefore moving air has momentum). This means it's not going to stop instantaneously. Even as the piston begins its upward travel, the momentum of the incoming fuel/air continues to stuff the cylinder, and in extreme cases, can even pressurize the cylinder higher than atmospheric pressure (almost like a turbo-charging effect). This is why really aggressive cams with long durations make more power at high RPMs, with the trade-off being poor low-rpm performance.

[zrpilot]

Wilkin,

Well said. Thanks for your contribution.

[honda400ex2003]

very nice, thanks for the input guys!
steve

[wilkin250r]

Now, a little disclaimer. I know electronics, so I know how ignition systems work and how sparks are created. However, the actual effects of ignition timing on cylinder pressures, temperatures, and power is one of my weakest subjects, ESPECIALLY on 4-strokes. But I'm not completely clueless, so I'll add my thoughts.

First, some background info.

Higher compression (not calculated ratio, I'm talking the actual cylinder pressures) burns faster, and therefore requires less timing advance. Logically, the opposite is also true, less cylinder pressure burns slower, therefore requires more timing advance. If you look at the timing curve of a 2-stroke, they have HUGE timing advance at low RPMS (like 30+ degrees) because the cylinder isn't filling very well, and there is a lot of exhaust left during the next combustion cycle, so the engine needs a LOT of timing advance in order to get any power. However, when the pipe effect comes on, the exhaust is pulled out efficiently, new fuel/air is brought it, and the returning pressure wave from the pipe helps build compression. So when the engine hits it's powerband, timing advance drops to like 8 degrees or so.

Just like throwing a pass to a receiver, the faster he's running, the further out in front of him you need to throw that ball for him to catch it. The faster the piston is moving, the more timing advance you need in order to give the fuel enough time to burn and create peak cylinder pressures at the proper piston location. Higher rpms require more timing advance.

[honda400ex2003]

what would you say is a good recommendation based on a certain compression to get it best?

steve

[wilkin250r]

Originally posted by tri5ron
How would a 400EX stock piston/bore with a stage 2 hot cam, and a +6, timing key perform,...

vs.

a 400EX stock piston/bore with a stage 1 hot cam, and stock, (OR,... +6) timing key ?

(Keep in mind, this question/comparison is for a STOCK Bore, STOCK Compression 400EX)

Well, let me answer Ron's question.

Since the Stage 2 cam is a little more aggressive, with higher duration, it is going to build higher cylinder pressures at high RPMS, and worse cylinder pressures at low RPMS compared to the same engine with a stage 1 cam.

So I think the additional timing advance of +6 timing key would help bring back some of the lost low-end performance. Lower cylinder pressures require more time to burn.


Now, I can't find a timing curve for a 400EX, so I can't answer this question with 100% certainty, but if it's anything like other motorcycle ignition systems I've seen, the timing advances a little bit as RPMs increase, but stops advancing around 4K rpms or so and flattens out. I think the motor could use additional timing advance after this point.

This basically means that as the Stage 2 cam becomes more efficient at higher rpms, and is filling the cylinder better and getting higher cylinder pressures, you would normally retard the ignition advance a little bit because the higher cylinder pressures create a faster burn. But since the ignition is already behind because the timing curve has flattened out, additional timing advance isn't dangerous.

So in my opinion, a stage 2 cam and timing advance key will probably out-perform a stage 1 with no advance. The cam will cause you to lose low-end performance, but the timing key would likely give most of that back to you, and the stage 2 cam would have vastly superior top-end performance.

*Now keep in mind, this is a STOCK compression motor. A high-compression motor is likely to have detonation with additional timing advance brought on by the timing key)

[honda400ex2003]

would you say a stage 2 & key would perform better than a stage 1 & key?

thanks for all the info,
steve

[wilkin250r]

Originally posted by honda400ex2003
would you say a stage 2 & key would perform better than a stage 1 & key?

thanks for all the info,
steve

Well that depends mostly on your intended use and riding style. If the stage2 cam performed better than the stage1 in all situations, then they would never sell the stage1. The REASON they offer both cams is because they have different characteristics for different uses.

[honda400ex2003]

definitely agreed there. lol

anything is possible.
steve

[tri5ron]

wilkin,
thank you so much for taking the time to consider and evaluate the questions I raised. you brought up the point of the mass and inertia of the air flow, which I had failed to lend proper consideration.
good point, and clearly explains why a stage 2 will lose bottom end, due to that lack of inertia.

equally, it clearly explains WHY the stage 2 will have a greater improved level of performance at higher rpm's due to the higher inertia of the air mass.

I suppose we could liken the performance of the stage 2 cam,... to a 2-stroke "coming onto the pipe".

It also stands to reason, that IF we were to have the stage 2 in a STOCK COMPRESSION motor,....
That the increased ignition timing would logically compensate some of that lost low end torque.
This was the basis of my contention, when Steve and I were discussing it.

I raised the question of a stage 2 cam w/+6 timing,... vs.,... a stage 1 cam w/ stock timing, (on a stock compression 400ex), simply to stir some dormant brain cells, and observe what others might think.

Simply as food for thought, and certainly as a hypothetical comparison.

I have not tried the stage 2 in a stock compression engine, and can't see why I ever would.
It was just a question towards the thoughts of whether the +6 key would compensate for the low rpm torque loss.

(So with that,... I get to stick my tounge out at Steve,... and blow some razzberries in his direction) Hahaha, here ya go Steve,... http://i111.photobucket.com/albums/n148/tri5ron/Emoticons%20and%20funny%20pics/smiley15.gif

:D http://i111.photobucket.com/albums/n148/tri5ron/Emoticons%20and%20funny%20pics/crackmeup.gif http://i111.photobucket.com/albums/n148/tri5ron/Emoticons%20and%20funny%20pics/rotflol.gif

It might be fun an interesting to actually do this comparison on a dyno, just to see how the numbers would fall.
But alas,... I don't have that kind of cash or time to burn.

so with that, I'll stick with what has been proven as a winning combination for the stock compression 400ex.

That being, the stage 1, +6 key, along with my 450r carb, pipe and foam filter.

AND,... to say Thank You to my good buddy Steve, for loaning me the cam just to see how I like it.

(but I'm not taking back the razzberries)
:D :D :D

good stuff !

by the way,...
the Stage 1 is now in, and she fired right up. I will likely not get a chance to ride it before taking it with me to the Baja 500 race.

that should be a good test to see how she runs !

Thanks again to all who have contributed to this thread .
now I've got to start getting the moho ready for the Baja !

[wilkin250r]

Originally posted by tri5ron
Simply as food for thought, and certainly as a hypothetical comparison.

And let me drive this point home for those members that are new to engine mods and looking for a direction to go with their motor.

This is just a hypothetical comparison, Ron was asking two specific examples. If you were actually building an engine, there are better routes to go, and WAY more aspects to consider. For example, I'm not sure the stock head will flow enough at high RPMs to really take advantage of the stage2 cam, and I'm not certain the stock ignition will rev high enough to get there either. So if you were going to build a motor like we've described, you would need to take those aspects into consideration.

[400man]

I recently won a aftermarket cam off ebay for really cheap, was almost hard to pass up. the auction stated it is a megacycle X2 cam. but as far as confirming that 100% I cant cause it only has a few numbers scribed on the cam to idientify it. I done some reading on here before buying it and its suppose to be one of the more aggressive stage 2 cams.

so I was wondering, would it damage my motor or anything if I wanted to just pop it in and test it out? I currently have a stage 1 hotcam with a lightened flywheel, stock piston, and a 39mm fcr carb. I think your suppose to use hardened rockers and stiffer springs with this cam so thats why I was wondering if it would hurt anything, even if I only ran it for a few minutes. I know it would most likely make it perform worse than with the stage 1 cam, but I was just courious to try it.

[honda400ex2003]

i still think my machines had better top end with both the stage 1 and 2 cam with the key installed and 10:1 but with no way to prove it, ill go with what wilkin says. :D his explanation sounds better anyway. :D

my parts for that motor are all over now.

thank for the raspberries (LOL at your spelling, i got the joke LOL), ill eat them as a nice snack a bit later.

steve

[tri5ron]

:D http://i111.photobucket.com/albums/n148/tri5ron/Emoticons%20and%20funny%20pics/points.gif

[wilkin250r]

Originally posted by 400man
I recently won a aftermarket cam off ebay for really cheap, was almost hard to pass up. the auction stated it is a megacycle X2 cam. but as far as confirming that 100% I cant cause it only has a few numbers scribed on the cam to idientify it. I done some reading on here before buying it and its suppose to be one of the more aggressive stage 2 cams.

so I was wondering, would it damage my motor or anything if I wanted to just pop it in and test it out? I currently have a stage 1 hotcam with a lightened flywheel, stock piston, and a 39mm fcr carb. I think your suppose to use hardened rockers and stiffer springs with this cam so thats why I was wondering if it would hurt anything, even if I only ran it for a few minutes. I know it would most likely make it perform worse than with the stage 1 cam, but I was just courious to try it.

Sometimes a thread will change directions, and I'm okay with that, but this is a completely different subject. Start a new thread and we'll answer it in there.

[honda400ex2003]

to go along with the previous with lower pressures at low rpms and higher at high rpms with a stage 2 and having advance helping out the lower rpms.

i might have this backwards:
stage 1 with more advance up top would increase top end since the pressures are not as great as they would be with a stage 2, thus increasing performance higher with advance.

sort of the opposite of the stage 2 with advance since the cylinder pressures do not build as high in a stage 1 at the same upper rpm as a stage 2.

not to get away from the dynamic compression and other information too much but these would also be good to discuss too. Im sure compression also goes into these also.

how about a specific style of porting, compression, and timing and how they are related?

i would assume it would be the same as a bigger cam but any info to expand on? more flow requires

decking the head too? I dont hear of anyone doing that really on these machines.

just food for thought, i might have it backwards. I will think about this a bit more.

steve

[tri5ron]

I find this to be an interesting discussion.
makes the brain cells stir a bit.

I'd also like to hear what some of the more knowledgeable members have to say, with regard to the expanded questions that Steve has raised.

Good stuff.

Where has GPracer been ? Pipeless ?, Beags ? ZR ?, Wheelie ?, Pappy ?,
I'd really like to hear your take on these.

[wilkin250r]

Originally posted by honda400ex2003
i might have this backwards:
stage 1 with more advance up top would increase top end since the pressures are not as great as they would be with a stage 2, thus increasing performance higher with advance.


Sort of, but the main difference lies in the real-world benefit of all these factors.

I'll be honest, I don't have a 100% complete understanding of exactly WHY, but timing advance seems to help the low end more than the top. So when we were talking about the loss of low-end with a stage2 cam, the timing key would probably regain half of that, or more.

The timing advance isn't really going to help the top-end performance on a stage1 cam, because at that point it's not so much a matter of timing, but a matter of being able to BREATH. The ability of of the stage2 cam to just put more air and fuel into that cylinder is MUCH more significant than any timing advance.

[wilkin250r]

Porting is more significant that people realize, but like most other aspects, it really need to be considered as part of an entire engine package.

Remember back a few posts where I talked about air having mass, and thus it has inertia and momentum. This is really important when it comes to porting, because bigger isn't necessarily better.

Momentum has two aspects to it, mass and velocity. You can't really change the mass of air, but you CAN change how fast it's moving. If you're pushing 400cc of air, it has to move a lot faster through a small tube than a large tube.

Camshaft profiles take advantage of the momentum of moving air, so exhaust VELOCITY is really important. But the drawback is that velocity is higher in smaller tubes, but bigger tubes flow better.

It's easier to explain with exhaust headpipes. Small headpipes are better for low-end and midrange, because the smaller diameter has higher exhaust velocity, but the small diameter is too restrictive at high RPMs. Larger headpipes are better for high RPM power because they flow really well, but since they have lower exhaust velocity at low RPMs compared to small headpipes, they give poor low-end performance.

The specifics of your porting really need to take into account your camshaft and overall riding style, a high-flow porting and a low-end camshaft is going to be a terrible combination.

[Pipeless416]

sorry about the delay.. i haven't been spending a whole lot of time in the 400ex section lately.. didn't see this thread.

most of the stuff wilkin is discussing is way over my head :p , but i do have some experience with a couple of setups.

first setup.. 10:1, 406, hotcam stage 2

this configuration fell on its face, plain and simple. i don't even think i was running aftermarket exhaust at this point. it was simply too much cam for the compression, along with the stock carb and exhaust. it was basically a tad quicker than stock, but it had to be revved out more to make the power. the cam was in there because i knew i would be building it up.

10:1, 406, stage 2 cam, +6 key, exhaust

exactly the same setup, but with the key and aftermarket silencer.. this woke it up quite a bit, but i don't think it was actually that much quicker.. all it really did was make the throttle response much faster..

11:1, 416, stage 2, +6 key, dual HMFs, 450r carb

this is where the power is.. everything works together so nicely and it really has neck snapping throttle response. everything really works well together, and power is available throughout the rpm range.

same as above^, but with the stock timing key

i took out the sparks key because i'm really trying to make it a more hassle free trail quad, and i felt any extra heat is unnecessary because it has all the power i need. honestly, my butt dyno could not tell one bit of a difference. i think that when an engine is mostly stock it makes a slightly noticeable difference, but on a highly modified engine, its just not really adding much. i took it out for peace of mind.


i know these experiences are vague, but i have had quite a few different engine configurations, so i thought i'd share.. :macho

[tri5ron]

Pipeless, Thanks for sharing your various configs. and your assesments.
In my opinion, they are are not vauge in the least!
You have laid out 3 different configurations,...
of progressive performance modifications,...
from personal, knowledgeable, hands on experience.

Even WITH the butt dyno factor, I still say it is the valuable, and informative input, that this thread is all about.

And besides, it gives me another oppurtunity to blow a few more razzzzzzzberries to Steve !

:devil:
haha, just kidding Steve,
you know that we are all just waiting for you to announce your Presidential Campaign and get this country back on it's feet ! You've got my vote !
Let me be the first to say it,...

Steve for President ! :D

and a EXTRA Special thanks to Wilkin, for taking the time to engage here,...
(you and Steve could share the ticket, and make it a landslide !)

You have shed some very clear light on a sometimes foggy subject of discussion, that is all too often fraught with misinformation.

I am VERY much enjoying this thread, and I hope that others are learning from it too.

Now where the hell are the other guys, who's input we can all benefit from ? We're waiting !

You think A LOT of people aren't watching this thread ??? it's now got almost 600 views, whats that tell ya ?

Now back to our regular programming,....
http://i111.photobucket.com/albums/n148/tri5ron/Emoticons%20and%20funny%20pics/smiley16.gif
keep it coming guys !

[honda400ex2003]

this was one of the 5 emails i didnt delete without reading it first after being gone on vacation.

very good info here guys! thanks!

steve

[honda400ex2003]

bump :D

steve

[CJM]

Ill add my 2 cents:

I went from having a stock EX with nothing more than a filter and a pipe to a 416, 11:1, stage 2 HC, open airbox (outwears but yea open pretty much), uni, my custom header pipe slip on combo, and Im still running the EX carb. I also kept stock 15/38 gearing. I got a 170 main and 42 pilot.

I have excellent power all around. Down low is tons of torque, no question about that I can wheelie if I want to at almost anytime (sometimes it even surprises me). The real raw power is pretty usable in the entire rpm range-higher I rev the more the power of course. It revs very quickly and Im pretty much gunning (hitting mostly mid rpm) 2nd or 3rd to do any larger jumps or fast paced tight trail riding might take advantage of 4th. I find the most usable power is in the midrange. Low end torque is good but power just pulls the more you rev it.

If anything up top theres tons of power too. Infact in a drag im often searching for a 6th gear b/c there is still power but Im limited by the sprockets at that point. I find that Im able to keep up but never really best a 450-they just have flat out more power-am I able to keep up-hell yes. They leave me in a drag maybe 1-2 lengths or so. If I threw on the 450r carb Im sure it would be more evenly matched.

Lets compare apples to oranges for a sec:
1. My buddy (hocman123 on the forums) had a stock EX with just a stage 1 HC. It was ok, made decent power, nothing insane of course.
2. Other buddy has a pure stock 08EX. He claimed it just didnt have enough power to keep up with me and the 450s.

Both rode my quad and a decently worked YFZ. Both LOVED my quad, one rebuilt his to a 406, kept the stage 1 cam and did 11:1 and loves it, other one since his is so new will be doing the sparks key.

Honestly. Im rather happy with the power I have. Im able to lug it around if I wish. I have the idle slightly high and can let off and just roll in 1st if I want too. I can climb hills and feather it up if I want, I can gun it and fly.

Not saying its all that, but from stock to what I got (pretty much same as steve) its night and day and the main reason that although a 450 would be nice-EX is paid for and as we all know super reliable.

Bottom line imho is more compression means more power. your compressing the gas that much more violently and getting more usable power out of it. I have had many people say to me that they are amazed its a 400EX for how fast it is. Its also super reliable, never an issue with heat (I did the spal fan and a larger tank just for the heck of it) and I can run on 93 pump all day with no issues.

[MtnEX]

OK, since you guys are talking cams, ignition timing and throttle response, let me pose a question about all this...

Not a 400EX motor, but.....

Say you have an engine and it has more throttle response than anything you have ever pressed the gas on in your life, to the point of almost too much throttle response...

But the trade off is... it is either on or off, all or nothing... off the bottom it either yanks your arms out of socket, or chokes up and stalls when you flick the throttle...


What can you do to smooth that out... and how can you go about getting to where you can lug it on out of that point-break spot where it can't instantly build the RPM it wants to?

Which way do you go with ignition timing right off the bottom? Do you advance more or start retarding?

And would a higher stage cam mellow it out down low.

It is almost like this motor tries to do too much too quick all at once, which makes it very exciting... but also very tiring... and often it is like it gets ahead of itself trying to respond so quick which leads to choking out and stalling.


Just trying to understand how cam profiles and ignition timing fit into the recipe on throttle response and low end ridability.