my 400ex needs more lower end

[GW_400ex]

I was at a track tuesday and as i goin around the track i noticed i couldn't clear the jumps because when i come out of the turns it just don't have the guts to just take off.

Now i was wondering i what i could try first to get my lowerend torque. I have been reading that people are lowering there sprokets my 1 tooth and loosing speed, now im racing a track and i also climb hills some speed really aint a factor for me, i just need to be able to come out the turns punch and have instance rpm spones. so if you guys could please help me out on what i should try first that would be great.

also i forgot the ask is if you drop a tooth do you have to change the chain to?

[brapbrap13]

if u drop a tooth u usally dont have to change the chain. ther ussaly is enough play to change that.

[swva400ex]

you dont lose that much on top speed going with 14 tooth sprocket. really need to know what you got now, so people could give you some suggestions.a full system exhaust , cam would help

[jsmith2232]

14T FRONT SPROCKET WILL ADD ALOT OF TORQUE AND ITS CHEAP

[jason43050]

Originally posted by jsmith2232
14T FRONT SPROCKET WILL ADD ALOT OF TORQUE AND ITS CHEAP it depends on the year of the quad too. a 2005 and up have 14 tooth sprockets on them,therefore he'll need a 13 toothe. :)

[tim colston]

Originally posted by jason43050
it depends on the year of the quad too. a 2005 and up have 14 tooth sprockets on them,therefore he'll need a 13 toothe. :)


Good point Jason

[jason43050]

i just got my 13 toothe sprocket for my 2005 400 ex. haven't put it on yet but i'm just dieing to see the difference. mine is all stock except i got a 150 dynojet in it. (148 is stock) and soon i'll have a new set of handlebars, bent mine pretty good now. had to bent them back lol.

[GW_400ex]

its a 2001 400 ex, k&n oil and air filter, slip on E-series white bros pipe, not jetted yet. But i am also lookin to get ride of the slip on to go with pro sercuit full exhaust system.

Also if i get a cam do i have to bore and jet it ? what all has to be done with a cam ? and what is the best brand i been lookin on post on here and i see weisco is good.

[yellow400ex05]

Originally posted by jason43050
it depends on the year of the quad too. a 2005 and up have 14 tooth sprockets on them,therefore he'll need a 13 toothe. :)

so the older models had 15 tooth front sprockets?

[swva400ex]

hot cams are not expensive. i put the cam in mine after i did every else.yeah the 99' thru 04' had 15

[400exstud]

Originally posted by jason43050
i just got my 13 toothe sprocket for my 2005 400 ex. haven't put it on yet but i'm just dieing to see the difference. mine is all stock except i got a 150 dynojet in it. (148 is stock) and soon i'll have a new set of handlebars, bent mine pretty good now. had to bent them back lol.

I would imagine that you lost quite a bit of power by putting a 150 dj in your bike. If you didn't know, the dj scale is a lot different then the K scale. You need a much lower dj to equal that of a K. Your bike is probably rich enough to support a full exhaust and possibly a cam.

I would suggest trying out a smaller jet.

[GW_400ex]

its a 2001 400 ex, k&n oil and air filter, slip on E-series white bros pipe, not jetted yet. But i am also lookin to get ride of the slip on to go with pro sercuit full exhaust system.

Also if i get a cam do i have to bore and jet it ? what all has to be done with a cam ? and what is the best brand i been lookin on post on here and i see weisco is good.

[jason43050]

Originally posted by 400exstud
I would imagine that you lost quite a bit of power by putting a 150 dj in your bike. If you didn't know, the dj scale is a lot different then the K scale. You need a much lower dj to equal that of a K. Your bike is probably rich enough to support a full exhaust and possibly a cam.

I would suggest trying out a smaller jet. is this true about the jet size? i've never heard that before. so the dynojets are lower the number the more gas it gives? so the klehn the higher the number the more gas it gives?

[jason43050]

Originally posted by Yellow250ex04
so the older models had 15 tooth front sprockets? yes 2004 and lower have 15 toothe sprockets....

[miller821]

I'd say drop a tooth on the front, cause like stated it gives better acceleration and its cheap.

[jsmith2232]

There is a chart on this site somewhere (i'll post it tomarrow when i get to work, it's on my computer there) I ran a full exhaust, k&n and rev box using a 146 dynojet that is equivelant to a 160 or 165 kehien, also when i built my motor before i had the 450 carb i was using a 170 dynojet, equivelant to a 190 kehien. both jets are the same scale, the higher the number the larger diameter hole for gas to go thru, but the dynojets are larger size for size then the kehein, also mukini has different size scale for thier jets. If you put in cam, i personally went with hotcam just because they were cheaper and didn't require hardened rockers or shipping the stock cam back as a core, and you don't need to bore or port and polish to do just a cam but i would suggest while youre in there to put in a higher compression piston probably 11.0:1 at a max if you still want to run pump premium gas any higher you will need race fuel. Je and Ross make great pistons, weisco are good to but are a bit heavier. Hope this helps a bit.

[jason43050]

Originally posted by jsmith2232
There is a chart on this site somewhere (i'll post it tomarrow when i get to work, it's on my computer there) I ran a full exhaust, k&n and rev box using a 146 dynojet that is equivelant to a 160 or 165 kehien, also when i built my motor before i had the 450 carb i was using a 170 dynojet, equivelant to a 190 kehien. both jets are the same scale, the higher the number the larger diameter hole for gas to go thru, but the dynojets are larger size for size then the kehein, also mukini has different size scale for thier jets. If you put in cam, i personally went with hotcam just because they were cheaper and didn't require hardened rockers or shipping the stock cam back as a core, and you don't need to bore or port and polish to do just a cam but i would suggest while youre in there to put in a higher compression piston probably 11.0:1 at a max if you still want to run pump premium gas any higher you will need race fuel. Je and Ross make great pistons, weisco are good to but are a bit heavier. Hope this helps a bit. so i have no mods done to my 2005 400 ex except i got a 150 dynojet in. it was a stock 148. so i should have went with a jet lower than 148 to give more gas?

[jsmith2232]

I just dug thru a bunch of old posts i did and copied the table of jet sizes to help you, i think you autta be about a 136 dynojet if you are running all stock. by getting more gas won't gain any performance unless you add more air to it.

http://www.mototuneusa.com/break_in_secrets.htm
Width------Kehein # -- DynoJets # -- Mikuni #
0,0350---- 92,5--------- 92----------- 86,3
0,0360---- 95----------- 94----------- 88,1
0,0370---- 97,5--------- 96----------- 90,0
0,0380---- 100---------- 98----------- 91,9
0,0390---- 102,5------- 100---------- 93,8
0,0400---- 105--------- 102---------- 95,6
0,0410---- 107,5------- 104---------- 97,5
0,0420---- 110--------- 106---------- 99,4
0,0430---- 112,5------- 108--------- 101,3
0,0440---- 115--------- 110--------- 103,1
0,0450---- 117,5------- 112--------- 105,0
0,0460---- 120--------- 114--------- 106,9
0,0470---- 122,5------- 116--------- 108,8
0,0480---- 125--------- 118--------- 110,6
0,0490---- 127,5------- 120--------- 112,5
0,0500---- 130--------- 122--------- 114,4
0,0510---- 132,5------- 124--------- 116,3
0,0520---- 135--------- 126--------- 118,1
0,0530---- 137,5------- 128--------- 120,0
0,0540---- 140--------- 130--------- 121,9
0,0550---- 142,5------- 132--------- 123,8
0,0560---- 145--------- 134--------- 125,6
0,0570---- 147,5------- 136--------- 127,5
0,0580---- 150--------- 138--------- 129,4
0,0590---- 152,5------- 140--------- 131,3
0,0600---- 155--------- 142--------- 133,1
0,0610---- 157,5------- 144--------- 135,0
0,0620---- 160--------- 146--------- 136,9
0,0630---- 162,5------- 148--------- 138,8
0,0640---- 165--------- 150--------- 140,6
0,0650---- 167,5------- 152--------- 142,5
0,0660---- 170--------- 154--------- 144,4
0,0670---- 172,5------- 156--------- 146,3
0,0680---- 175--------- 158--------- 148,1
0,0690---- 177,5------- 160--------- 150,0
0,0700---- 180--------- 162--------- 151,9
0,0710---- 182,5------- 164--------- 153,8
0,0720---- 185--------- 166--------- 155,6
0,0730---- 187,5------- 168--------- 157,5
0,0740---- 190--------- 170--------- 159,4
0,0750---- 192,5------- 172--------- 161,3
0,0760---- 195--------- 174--------- 163,1
0,0770---- 197,5------- 176--------- 165,0
0,0780---- 200--------- 178--------- 166,9
0,0790---- 202,5------- 180--------- 168,8
0,0800---- 205--------- 182--------- 170,6
0,0810---- 207,5------- 184--------- 172,5
0,0820---- 210--------- 186--------- 174,4
0,0830---- 212,5------- 188--------- 176,3
0,0840---- 215--------- 190--------- 178,1
0,0850---- 217,5------- 192--------- 180,0
0,0860---- 220--------- 194--------- 181,9
0,0870---- 222,5------- 196--------- 183,7
0,0880---- 225--------- 198--------- 185,6
0,0890---- 227,5------- 200--------- 187,5

[GW_400ex]

Ok i am going to go down one tooth in my front sprocket and make it a 14, and i belive i will be goin with the Stage 1 Hot Cam. when i do this what else should i do? i really do not want to bore it out right now. someone mentioned about goin to a high compression piston, but if i do that don't it have to be bored?

[swva400ex]

no i dont have to bore with a high comp. piston. the dome of the piston i higher. its like it says, it raises the comp. by leaving less space in the chamber.i could tell a small gain on the low end with the piston.like i said it was small

[GW_400ex]

well i know for sure that im going with Stage 1 Hot cam because it will just go right in with out modification, i might do a High Comp piston not sure yet though. The reason i am lookin for more power in the rear end is for when i come out of turns i can instantly be spinning the tires and enough to clear the jumps.

[jsmith2232]

To give you an idea of the torque that you will get, I've got the 416 in my sig but with all the mods listed and with out the 450 carb i could still pull wheelies sitting down in 5th gear just by hitting the gas.

[Groundworx]

Originally posted by GW_400ex
well i know for sure that im going with Stage 1 Hot cam because it will just go right in with out modification, i might do a High Comp piston not sure yet though. The reason i am lookin for more power in the rear end is for when i come out of turns i can instantly be spinning the tires and enough to clear the jumps.

My 01 has pretty much the same mods as yours, but with a 11:1 piston. That piston makes a hell of a difference. I am probably going to cam mine as well.

[krt400ex]

Originally posted by GW_400ex
its a 2001 400 ex, k&n oil and air filter, slip on E-series white bros pipe, not jetted yet. But i am also lookin to get ride of the slip on to go with pro sercuit full exhaust system.

Also if i get a cam do i have to bore and jet it ? what all has to be done with a cam ? and what is the best brand i been lookin on post on here and i see weisco is good.

jet it first before u do anyhting. if ur bike is jetted lean(which urs prolly is) the bottom end is the first thing u will lose. happened to me with the 300

[MAD450r]

I find the 400ex has was too much bottom end stock. I just may be use to my 450r now, but im ready to put a 16 tooth front sproket on mine. I run 155 k mj and 42 pilot. every turn I come out of I have to lean forward to let the rear tires break loose or the front end comes up.

I mean stock I could leave the line in second without slipping hte clutch at all. Now with piston and stage 2 hot cam I can leave the line in 3rd. I give every around my riding area a tough time beating my 416ex. I mean we hit the road to go to another riding area and they all smoke me. When on a track its a different story.

Now my R is a bit low on lowend but it makes up for it from mid to top so I just need to clutch more and keep the R's up.

Practice that and you'll find you didn't need to build a 400 for lowend you need to add topend in my opinion.

[jordan_m6]

the hi comp. piston and the stage 1 is a great combo. It would be perfect if combined with a +1 1/4'' swing arm to keep the front end down it you like to hammer it out of corners.

[troutman561]

I'd say go with a 13t, I have that on my 05' and I like the way it came out..

Before replacing the cam, I'd get it properly jetted, play around the with sprockets, and don't forget to put some airholes in your air box lid. (and either put some screen over the airholes, or run a pre-filter over that K&N)

Try that, and see if you need pull more before messing with Honda Reliability.

[GW_400ex]

Alright, thanks for the help guys i will get it rejetted cause it is burnin a little rich, and i forgot about puting holes in the lid on the air box. how big should they be or does it not matter?

[Def-e-nition]

Originally posted by jason43050
so i have no mods done to my 2005 400 ex except i got a 150 dynojet in. it was a stock 148. so i should have went with a jet lower than 148 to give more gas?

Jason . hi .

NO .
What the guys are saying , is that the standard Keihin Jet you had in the bike before you ran out and bought a dynojet kit , was numbered 148 . Thats the standard one .

Dynojet uses different numbers , for e.g a 136 Dynojet is the smae size as a Keihin 148 . So by installing a 150 main jet , from dynojet - your bike is going to be running wayyyy too rich . Understand ? Go back to the dynojet instructions , and follow them , please . It will show you at what altitude you can put in what size jet .
if you are at the coast : try a 142 , or a 146Dynojet .Once you run a pipe : remove the Lid , and bump up the dynojet to a 170 .

Its as big as it will go , but if you folow the instructions you should have good success . I have found the dynojet kits to like to run the bikes a bit rich . This is simply to play it safe , as a lean engine is a Dead engine . But running too rich , washes away oil off the sleeve , and this might mark the skirt (meaning that the oil that was suposed to be there , was washed away from running the bike too rich ) .This makes Quad owners angry , and engine shops happy ..

Run rich to be safe , I.e , follow the dynojet instructions . I also like experimenting , but it is dangerous to do so .142 or 146 will be fine if you are not running anything after-market .

Hope I've helped you .

I agree 100% with the 450 R guy - my quad wants to head north for the winter as soon as you hit the throttle hard . I find the nose terribly light , and adding more torque only seems to make matters worse for when you are trying to pull away at greased-lightning speed . very frustrating !! I cant keep the nose down , so from a standstill the z just pulls off and away from me . At a rolling start I dont suffer from the nose climbing so high , and my power is easier to control . Someone has suggested i NOT use the low-down torque of the engine from pull-away , but instead wind the throttle and drop the clutch : my only question is that if the Rear wheels bite - we all know I will either have to back off fast , or b: ill be on my back . On tar .

[jason43050]

Originally posted by Def-e-nition
Jason . hi .

NO .
What the guys are saying , is that the standard Keihin Jet you had in the bike before you ran out and bought a dynojet kit , was numbered 148 . Thats the standard one .

Dynojet uses different numbers , for e.g a 136 Dynojet is the smae size as a Keihin 148 . So by installing a 150 main jet , from dynojet - your bike is going to be running wayyyy too rich . Understand ? Go back to the dynojet instructions , and follow them , please . It will show you at what altitude you can put in what size jet .
if you are at the coast : try a 142 , or a 146Dynojet .Once you run a pipe : remove the Lid , and bump up the dynojet to a 170 .

Its as big as it will go , but if you folow the instructions you should have good success . I have found the dynojet kits to like to run the bikes a bit rich . This is simply to play it safe , as a lean engine is a Dead engine . But running too rich , washes away oil off the sleeve , and this might mark the skirt (meaning that the oil that was suposed to be there , was washed away from running the bike too rich ) .This makes Quad owners angry , and engine shops happy ..

Run rich to be safe , I.e , follow the dynojet instructions . I also like experimenting , but it is dangerous to do so .142 or 146 will be fine if you are not running anything after-market .

Hope I've helped you .

I agree 100% with the 450 R guy - my quad wants to head north for the winter as soon as you hit the throttle hard . I find the nose terribly light , and adding more torque only seems to make matters worse for when you are trying to pull away at greased-lightning speed . very frustrating !! I cant keep the nose down , so from a standstill the z just pulls off and away from me . At a rolling start I dont suffer from the nose climbing so high , and my power is easier to control . Someone has suggested i NOT use the low-down torque of the engine from pull-away , but instead wind the throttle and drop the clutch : my only question is that if the Rear wheels bite - we all know I will either have to back off fast , or b: ill be on my back . On tar . thank you man. i put a 138 jet in and it runs like a raging beast now. before it would bog out on me when i get near a top of a hill. i put a 13 toothe sprocket on too o my gosh the difference is enourmous! instead of being inbetween gears on a track i ride on i can stay in 2nd instead of switching from 2nd to 1st all the time! thanks again!:D

[krt400ex]

I agree 100% with the 450 R guy - my quad wants to head north for the winter as soon as you hit the throttle hard . I find the nose terribly light , and adding more torque only seems to make matters worse for when you are trying to pull away at greased-lightning speed . very frustrating !! I cant keep the nose down , so from a standstill the z just pulls off and away from me . At a rolling start I dont suffer from the nose climbing so high , and my power is easier to control . Someone has suggested i NOT use the low-down torque of the engine from pull-away , but instead wind the throttle and drop the clutch : my only question is that if the Rear wheels bite - we all know I will either have to back off fast , or b: ill be on my back . On tar . [/B][/QUOTE]




if u race on pevement then don't dump the clutch or else u will be on ur back. but u can put it in 2nd, rev the engine all the way out and feather the clutch. i do it all the time. takes some practice to get it right when ur on the pavement, but it is very effective. if ur on dirt, put it in 2nd, rev it all the way out, sit foward(sometimes over the handlebars), and dump the clutch. u will get some tire spin, but that's a good thing