is a high comp piston worth it?

ive been looking around for some fairly cheap engine mods for my fo hundred. im considering a advance timing key, cdi, and piston. what i want to know is how do all these products work(seperately) and will a piston alone give me noticeable power? what compression should i get? im gonna start riding mostly tracks but still gonna screw around in the woods and feilds. the cdi box will probly be the last mod if i even get it at all. how about the timing key? does it make a noticeable difference? thanks for the info. later

keep it real:devil

[kabd69667]

Sparks said that the timing key does have a noticable difference if you have like a mostly stock bike. Like one w/ a pipe filter, small stuff like that. But if you have a 440 or 416 w/ a cam, ect. you won't really notice it very much. For only $15, i don't think you can go wrong w/ it

[MichaelS693]

hey kabd69667 is ur sparks loud does it have a arrestor in it? im lookin in to gettin one

[wyndzer]

Just my .02 but next motor I build will have a stock bore high compression piston. Probably 12:1.

[400exRacerX]

A high compression piston is a big gain in low end, the only down side is because the engine revvs so fast and has all that low end, when on deccel the bike deccels alot faster too. If your gonna pull the motor apart a high comp. piston works best with a more aggressive cam. I would get a HRC cam and a JE stock bore high comp piston.

Blow off the rev box--- go with the advance key and piston,10.5:1 or more!:D

[stocktires]

there is absolutly no need for a cdi in your type of riding. The high compression piston doesnt do a whole whole lot. But you will notice it. Are you gonna geta stock bore or likea 406, 416, or 428?Do you have an exhaust? If you have over 11:1 compression you should at least run a 50/50 of race gas and 92 pump gas! You probably wana run just 92 pump gas (ALOT easier and cheaper!) so I reccomend staying under 11:1. You probably would't get your full use out of a cam since you ride mx and trails (bottom end power). A cam gives you good top-end. If you have about $250 to play around with i would get:

#1. Sparks advanced timing key
#2. Wiseco 416 11:1 compression
#3. Save for exhaust or maybe a cam!

[400exdad]

:cool:

I've only been coming to this forum for a couple of days, but from what I've read I'm going to use the JE stock bore, 10.8 to 1 compression piston. $121.96 from Marcums. Now, I'm trying to justify the HRC cam. $277.09 from Service Honda. Xr's only has a copy of this cam for $179. Before I came to this page I was considering the stock xr400 cam. I think these guys have pretty much talked me out of that.

[stocktires]

The JE piston are a little better piston, but Wiseco isnt a bad piston! Not bad at all! The JE is a 10.5 not a 10.8! It is 10.8 in a XR400, In a 400ex its 10.5! I wouldnt get the XR cam if i were you. Why do you need a cam?

[Wheelie]

If I were in your shoes, I would go with a GT Thunder or HRC cam, 11:1 stock bore piston and play porting. Supposedly posting isn't worth it on a stock disp. 400, but more air never hurts.

If you have the engine down to the point of replacing the piston, replace the cam while your there---JMHO.

[400exdad]

Stocktires, I knew someone would tell me I was wrong! I was guessing and I hate to be wrong. Thanks for the correction. The reason I want a new cam is to open up the upper and mid ranges of this motor. It has plenty of power down low now and its power gets flat pretty quickly. The cam would take care of that. Of course, to keep things "all sweet" I would then need a piston to compliment this newer longer duration camshaft. I was also considering play porting the motor. Airflow is a good thing for any motor if you don't go crazy. Port too big and you loose to bottom end. From my car days a cam would turn a grocery getter into a weekend warrior if it was chosen correctly for the proposed purpose. However, it has got to be a package deal. The factory packaged it to be mild and last a long time. I want to improve on that.

Of course, one could ask: Why do anything to it, just ride the dang thing!!:D

Oh, BTW, I gladly accept all (nice..heh heh) corrections and comments. Thanks

why does everyone say the hrc cam? get a higher compression JE piston, and a white bros all around cam. no matter what type of riding you do, you can always benefit from a cam, they are not just for top end

[stocktires]

hrc= honda racing coporation or company

I don't feel the need to correct anyone about anything, this forum does very well at sharing ideas and experiences. What works well for me might not work for the next guy!

Just some thoughts on your motorwork though.

I put the 10.5:1 JE piston in and really appreciate the increase in bottom end.

Everyone on here will probably tell you that a pipe will increase the spread of the powerband---- because it's pretty noticable.

I did some pocket porting behind the valves, don't know if it helped but look in there and you'll see that it won't hurt either.

I put in a wb allaround cam and believe that the specs are pretty similar to an XR cam. Anyway I like it.

Overall my engine "package" is a result of a lot of internal reflection about what am I REALLY going to do with my quad. Taking into account noise, reliability,power, and cost. I really,really enjoy the engine now. No it's not the most powerful out there, but it will do anything I want and the power spread feels very similar to stock---EXCEPT more power from idle to top end---yeh he he! :macho

BTW--- I usually mod everything I get in some way, usually right after I get it. Most ask why? My answer-- BECAUSE I CAN !!!

[quadfamily]

2Slow,
I have that same disease!

Well if you guys got diseases you might wanna go to the doctor...you know that anthrax thingy is goin around,,ya might wanna get checked out...:D

[quadfamily]

Rico, Are you trying to be like Jabberjaw? He's funnier!

[Tommy 17]

U can get a 10.8:1 piston in a 400ex from je all u have to do is put on a xr400 gasket. the set up i am using is.
1. je 406 10.8:1
2. tc mx grind cam
3. porting and polishing
4. mod stock pipe
its around 750$ wit all parts and labor. remember when u buy a cam and stuff u have to change the rockers and gaskets and stuff its just not the piston and cam its the other littel things that cost u the money.
i am goin to pick it up in about 1 hour or so. to bad i can't put it in my quad bc they stripped out the one clamp that goes after the carb that hold the carb to the boot and its on back order for a while. i want to run it so bad but i can't till i get that. i still have to put the enigne back in the frame and stuff tomorrow so i hope i can ride by monday.

and i see nuttin wrong wit ricos posts about being funny i like them. who cares if jabber did that 2 and they both are funny.

speakin of jabber wheres he been i haven't heard from him much since his bro in law passed away.

Quadfamily

Yea- the disease gets in the way of sanity sometimes, and things don't always work out. BUT, it's the most fun sickness to have!

[quadfamily]

I was only kidding with Rico. No offense Rico in case you didn't know.

[The400exExorcist]

My HRC cam($140) should be here any day now, and from what ive heard its a direct drop in cam( no mods to springs, rockers etc)
Plus its a genuine honda part...so you know its reliable. White brothers I have heard require stiffer valve springs, and hardened rockers) so this is where you save money by buying the honda cam over the wb...plus with The HRC there is no core charge....more saved $

just my .02

[stocktires]

exactly

[Wheelie]

Where did you pick up the HRC cam for that price? Previous posts tell the price to be in the 250 to 300 range.

[The400exExorcist]

e-bay.....

[400exRacerX]

The reason why everyone wants the HRC cam is because honda designed it for there motors and its completely a drop in cam, there is nothing you have to do to the motor besides install the cam and a piston if you have the motor ripped apart. Cams like the white bros and GT thunder you need to harden your rocker arms with some types.

Originally posted by quadfamily
Rico, Are you trying to be like Jabberjaw? He's funnier!

Ok,,so basically I need to just keep my mouth shut.:D Yeah I kinda figured you was just joshin...

Yeah I looked into a HRC cam,,NEW,,but it was twice the xrcam so Since I wasn't born last night I chose the cheaper version,,I can't see the HRC cam making that much bigger of a difference for a $130 difference.