More Low End Power Questions

[VTredneckgames]

This winter Im going to be pulling the head off my EX to have seals and guides put in it. (Smokes some at WOT and at start-up).

Im wanting to do alittle bit of work to increase the throttle response and bottom end. Top end power is not my concern. I ride mostly trails and there have been times that I wish I could pull in 3rd but the power wasnt quite there so I would have it way up in the rpms in second.

Unless I must Im not boring it yet. I was thinking some of the basic mods.
I heard that a timing key was good for a stock bike, any recommendations on how much? Isnt +6 the usual?
Stage 1 cam, would I see any bottom end benefit?
Any reason at all to even attempt a port and polish? Maybe just alittle bit of smoothing by hand by myself?
Muffler, Any recommendations on a quieter muffler that is good on the bottom end? Or one that i can put a silencer in?
Anything else that you would consider doing to help out the bottom end power?

When I have it apart, Im going to install a new timing chain, air scoops, and a CNC steering stabilizer. Any other recommendations? Thanks guys. I love this site!

[aDviSol2y]

Re-gear.....................................Drop a tooth in front, 3rd will be your main gear for trails.

[VTredneckgames]

Well, I dont really want to loose the max speed. I like the speed that is achievable the way it is geared now. (stock). There are times that we ride in places that we can run 5th gear almost wide open. I.E. In WV on some of the highways we will ride at a fast pace. Fast as in as fast as the honda 400s, timberwolfs, and big bears will run.

Ive got to take the head off the engine, I just figure there is somthing I can do to help out bottom end alittle bit.

[odog]

get the crank stroked but thats kind of pricey. a stage 1 cam should help out also. if u dont want to sacrifice to much top end on the gears just go down one tooth in the rear it will help a little

[Pipeless416]

Originally posted by odog
get the crank stroked but thats kind of pricey. a stage 1 cam should help out also. if u dont want to sacrifice to much top end on the gears just go down one tooth in the rear it will help a little

going down a tooth in the rear will give the opposite that he is wanting. going up a tooth in the rear will hardly be noticeable. definitely do a stage 1 hotcam, and an xr400 head gasket. if you're feeling that its time, make sure you go with an 11:1 compression piston. that combination, along with a 450r carb will give you all the low end you could possibly want.

[Honda#4]

You can hardly feel a 14t with my motor mods, with a 15 and mine you would be going pretty good.

[honda400ex2003]

you could also do a 4 degree advance on the timing or a 6 degree. i think the 4 gives a bit more low and mid and the 6 gives a bit more mid and top comparing the two. otherwise i think that you could take out the choke to help out the low end throttle response too. good luck, steve

[VTredneckgames]

I have to keep my choke, I cant start mine without it.

Thanks for the recommendations guys, keep them coming.

Brad

[honda400ex2003]

you can put in a 42 pilot and you dont need it anyways from what i have read. even a 45 if you want. it changes with the f/a screw position depending on what size pilot you use. you just pump it a few times and you are good to go. lol, steve

[VTredneckgames]

I have seen where some people say that too. but Im not sure yet. I have to choke mine atleast once a day to get it started. Even in the summer. During the winter, you cant hardly get it started. But it runs great when it warms up. So I do need to do some changes to it. I might change around the jets and see how that works before I pull the choke out.

[mmbintn]

I just did a top end rebuild on mine and I put a wiseco 11:1 piston with a stage 2 hotcam. It has gobs of power now compared to stock. I also have the sparks 6* key and an edelbrock 440 carb (those were on there before the rebuild).

I got about 10 mph out of it as before it just didnt have enough power to top out in 5th gear. The low end is really good and the mid is crazy. I think I spent about 300 bucks and that included the HD stud kit.

[VTredneckgames]

Originally posted by mmbintn
I just did a top end rebuild on mine and I put a wiseco 11:1 piston with a stage 2 hotcam. It has gobs of power now compared to stock. I also have the sparks 6* key and an edelbrock 440 carb (those were on there before the rebuild).

I got about 10 mph out of it as before it just didnt have enough power to top out in 5th gear. The low end is really good and the mid is crazy. I think I spent about 300 bucks and that included the HD stud kit.

How did it not top out in 5th before? Not enough room or had you regeared it? Ive had mine wound pretty tight in 5th. It felt like I shouldnt rev it anymore. But I was on a good spot that you could top out on.

[mmbintn]

I don't know but it just wouldn't do it. I could have been the carb or the key or the rev box but it just wouldn't do it, it has stock gearing. I would get to about 55mph and I know it felt like it should do more, my buddies would walk past me in 5th and he has the same year. Now It tops out at about 70mph, although that is really scary so I have only done it once.

[VTredneckgames]

well just to update this thread:

smoking worse now at WOT. Only smokes at WOT and startup. If Im just lugging it around it doesnt smoke. But the last time we went to WV riding, we rode 60 miles and I had to put just over 1/2 qt back in it throughout the ride. Going to pull the head either this weekend or next, depending on the weather.

Ordered the sparks +6 timing key.

Decided against the cam for now.

If I need to bore it I will. Probably go alittle higher on the compression then stock. But not too much.

Muffler will remain stock. I like it quiet.

Going to grind down the header welds and I bought some outerwear material for a custom air box lid.

Then of course a rejet.

[supertrooper90]

I'm pretty sure you can use the stock piston and the xr400 head gasket and use high temp rtv on the base gasket to bump compression a little bit

[honda400ex2003]

yup you could do that too just to get a little extra compression. dont know if that little bit is noticable but you have to buy gaskets anyway. sounds like a good list there and your valve seals are going. lol, so it is good to get them done. steve

[VTredneckgames]

Cometic Gasket set is in. Im really happy with the quality of it. But for some reason, it didnt come with valve seals. I thought all complete gasket sets came with them.

Anyways, head and jug is at the machine shop. The jug would probably be fine with a slight hone and new rings. However, for the price, Im just going to go with a 1mm overbore to 86mm. Also went with 11:1 Namura piston. I know of several Namura pistons in atvs around here and they are doing fine.

Ive heard mixed opinions on the +6 and 11:1. I always run 93 and I will be installing a spal fan. If the 93 isnt enough, I have access to 100.

Also ordered a couple of different main jets. Also a 42 pilot.
Any recommendations on jetting? I figure I will start out with a 42 and a 155.

My sheet outerwears came in too. Im trying to decide if Im going to use a bolt in frame for it, or velcro.

[bigbad400]

you will be happy with the namura piston thats what i got in the 440, 11:1 also. wait till you see the piston.... its one sexy mama jama!!! i have it as the background pic on my cell phone its so nice. i think you have a good idea what your doing here so im not gonna say much but.... you should really do good valves and springs if your doing them, i like the +1 kibblewhites they are good quality and they have 10% stronger springs so they are less likely to float. also when you have the jug bored and honed you should ask about the cross hatch hone, it just reassures a good ring seat so that there is no rifling like in a gun barel. (makes things want to spin)
the cross hatch is the way to go. it cost me 10$ at the local dealer.


the sparks website says its not recommended to use the sparks key in hi compression applications. i blew mine up cause of that key... it was too advanced and it caused overheating and then detonation, it sank 3 of 4 valves into the top of the piston. had i had the kibblewhites it wouldnt have allowed the valves to float like that with the timing advance and toast it like that. its my fault cause i didnt pay close enough attention to motor noise but i sure do now.

win some..... lose some. you loose start over. you win you live to fight another day. -some black dude-

[VTredneckgames]

Originally posted by bigbad400
the sparks website says its not recommended to use the sparks key in hi compression applications. i blew mine up cause of that key... it was too advanced and it caused overheating and then detonation, it sank 3 of 4 valves into the top of the piston. had i had the kibblewhites it wouldnt have allowed the valves to float like that with the timing advance and toast it like that. its my fault cause i didnt pay close enough attention to motor noise but i sure do now.

From what I have heard, 11:1 will be okay and that any higher will not be good. I still have the stock rev box, and I dont rev mine alot. I have never hit the limiter with the stock box. I like low end. Sucks that it happened to you, but I think rpms caused your problem.

And any good machinist will always cross-hatch hone a cylinder.

Thanks for the reply

[mmbintn]

I have the timing key in mine and I have found that I need to run higher than 93. So I run a mix of 50/50 110/91. The heat issues went away and it runs like crazy.

[IcutMetl]

I had great luck with my Sparks advance key, and all I had on my 400 was a Yoshimura slip on, rejetted stock carb with the airbox lid on. My riding buddy at the time put in an 11:1 Wiseco piston and advance key at the same time; ran wicked after that with no problems at all.

I know a lot of the guys at that time just used the XR400 cam and if not the Hotcam Stage1 for the riding you describe- both seemed to have unquestioned reliability. Definitely check out the XR400 head gasket, it's a cheap and easy pick.

For an airbox lid; go to www.ehsracing.com- much better than cobbing together an outerwears type lid by yourself.

[0101]

Drop 1-2 teeth up front, and a stage 1 hotcam.

[VTredneckgames]

thanks for all the help.

Ive decided against the timing key. Atleast for now. The possible problems just outweigh the possible improvements for me.

I really dont want to put a cam in it yet. Maybe sometime further down the road.

[IcutMetl]

I think you'll still see a killer improvement just from a high compression piston- that's exactly what my friend did at the time and it was a night and day difference. If you were to change sprockets, I would rather add teeth to the rear if possible before subtracting them from the front- you want all the teeth engagement you can get on a front sprocket; smaller front also places the chain engagement at a more drastic angle...not good for wear.

Good luck!

[Miami_Vice454]

DO NOT BUY A NAMURA PISTON. my friend had one in his 450 and i dont what went wrong put the piston completely blew apart, the biggest piece was like 1 in long, got a pic of it on my cell, lemme see if i can upload it.

[Miami_Vice454]

http://s807.photobucket.com/albums/yy353/miami_vice454/

Check it out

[riotact]

Same here I would never buy a Namura piston.There is a reason they are 40-50 bucks cheaper then a Wiesco or JE.It's probly the lack of a QC department.

[IcutMetl]

Back when I had my 400, the 3 pistons that were discussed the most (positively) were CP, Ross, and Wiseco. I believe all 3 are forged. I always wanted to use the Ross, because it were supposedly the lightest of the 3. I've had Wiseco pistons in a few of my machines now without any problems, but I'm sure that doesn't go for everyone. All in all I think they make a stand-up product.

[bigbad400]

theres nothing wrong with namura iv had namura pistons in all kinds of bikes. never had a problem with the piston itself. i would have got a je but i have no reason to doubt the namura piston, so i saved me 60$ and i dont feel bad about it. i had one in a rm125 for like 8 years without a problem.

[riotact]

I've always used Wiseco too but when I do my rebuild I am going to giv a JE 11:1 a shot.

[VTredneckgames]

well I am going Namura. I already have one on the way.

Every brand has its ups and downs. Ive seen several with them in it. Im not pushing this one to the extremes like some people do. If I have a problem with it, I will post up. But obviously, I dont see that happening.

Thanks for the input though.

[IcutMetl]

I'm sure you'll be more than fine. I tell ya what...I wouldn't trade my 250R for one, but I still really wish I still had my 400ex; that thing really treated me right...it was a no b.s. 'wheeler that kept on going and going and going.

[Miami_Vice454]

thats true every company has its up and downs, maybe it was because his motor was already a high-performance motor. he had a cam, p+p, bored, etc. but generally things that are cheaper are not of the same quality as more expensive things, i say spend the extra 50 bucks and have the peace of mind that you know you have a piston that can be trusted more