Need More Top End!!

[BlackDevil]

Recently bought an 07 black 400ex. Added a yoshi rs-3 carbon full system, k&n, no lid, dynojet kit, new needle, 3rd notch, 170 main, 3.5 turns as the directions stated, renthal r3-2 gold 0-ring chain, renthal 15/38 sprockets. so here is my problem

Before the sprockets it ran 67 with no lid, and 70 with the lid but was breakin up slightly though 4th and 5th top end. got the new sprocket set up for top end which is amazing but im not even close to hittin the rev limiter. im beatin a lot of stuff now that i wasnt but im not gettin the top end I need. I called dynojet and they said i needed a bigger main so i ordered a 175. the yoshi exhaust claims w/o the spark arrestor to run a 178.

Could my main jet be too small causing it to not turn up on top like it should???

that was a lot but i need to get this fixed!!
Any help is much appreciated.

[Kaleigh]

thats breakin up? is it happening when you're at WOT at the top of the RPM band.. if so that means your rich.. if you want more top end.. drop some teeth in the rear sprocket or at to the front..

I think its for ever 1 front tooth=3 or 4 teeth in the back..

maybe some taller and lighter tires..

if you keep the lid on.. you might want to drop to 165..

but for speed.. you're going to have to do gearing and raise you RPM up some..

[idro]

taller tire?

[PismoLocal]

Stage 2 hot cam will give you tons of top end.

[Kaleigh]

Originally posted by idro
taller tire?

yea.. taller tires will give you top speed..

[idro]

Originally posted by Kaleigh
yea.. taller tires will give you top speed..
ya i know, i didnt see you had already posted that. my bad dude

[BlackDevil]

Originally posted by Kaleigh
thats breakin up? is it happening when you're at WOT at the top of the RPM band.. if so that means your rich.. if you want more top end.. drop some teeth in the rear sprocket or at to the front..

I think its for ever 1 front tooth=3 or 4 teeth in the back..

maybe some taller and lighter tires..

if you keep the lid on.. you might want to drop to 165..

but for speed.. you're going to have to do gearing and raise you RPM up some..


I did about 20 test runs today. Started out with the set up i had above. ran 72.4. Went to 180 which i know is way to big but it was a starting point. it was slower. went to 160 then 165 then 175, back to 170. changed my mixture screw from 3.5 to 2.5. moved the needle down to the 4th notch, up to the second, then to the 5th. I noticed it was breaking up on the 5th so i put everything back the way I had it from the start. 170, 3rd notch and 3.5 turns. seems to be all im gonna get out of it for now. Of all the different things i did i was b/t 68 and 72.

The low end is amazing, 1st, 2nd and 3rd are real powerfull. After that its a turd. i used a gearing calc i found on here and it says i should be runnin 75. who knows.

And I have already changed the sprockets, stock is 14/39, im runnin 15/38.

20" rear tires and I dont want any bigger really.

guess im gonna have to do some internal work???

Any other suggestions are appreciated

[BlackDevil]

Originally posted by PismoLocal
Stage 2 hot cam will give you tons of top end.


I read that a stage 2 is for a built motor

[Kaleigh]

there really isnt that much you can do in the internals to make more top speed.. you will also have to either drop some teeth in the rear or go to a 16 in the front.. or add more RPM with a rev box..

[PismoLocal]

IMHO The reason your probably not hitting 75 is horse power. Just because your bike is geared to top out at 75 doens't mean you have enough power to get it there.

There is nothing you can do to your motors internals to make it have a higher top speed. Adding performance parts just get you to the top speed faster. The Top speed is completely regulated by gear ratios(sprockets) and tire size. If you bought a 16 tooth front sprocket and 37 tooth rear and you didnt beef up your motor at all, your quad would probably top out at around the same MPH as it goes right now because you wouldn't have enough Horse power to pull that gearing.

[Kaleigh]

What are you using to do your speed test.. Speedo. GPS or a Pace Car/truck/bike

[vett_09]

Originally posted by PismoLocal
IMHO The reason your probably not hitting 75 is horse power. Just because your bike is geared to top out at 75 doens't mean you have enough power to get it there.

There is nothing you can do to your motors internals to make it have a higher top speed. Adding performance parts just get you to the top speed faster. The Top speed is completely regulated by gear ratios(sprockets) and tire size. If you bought a 16 tooth front sprocket and 37 tooth rear and you didnt beef up your motor at all, your quad would probably top out at around the same MPH as it goes right now because you wouldn't have enough Horse power to pull that gearing.

He's exactly right. If you run taller gearing, you need a motor that can pull taller gearing. Installing a cam is a start, and you'll notice a difference. But to get the most of your gearing changes, you should look into bore kits or at least a high compression piston.

[troutman561]

Remember those gearing calculators dont take into account for things like your weight and wind resistance and all that.. so 70ish sounds about right....

[PismoLocal]

Originally posted by vett_09
He's exactly right. If you run taller gearing, you need a motor that can pull taller gearing. Installing a cam is a start, and you'll notice a difference. But to get the most of your gearing changes, you should look into bore kits or at least a high compression piston.
I mentioned the stage 2 because I noticed a significant power increase in the upper rpm range after I installed it on my 400ex.

[exrider2001red]

heres a question why do you want top end i know topspeed sounds good at first but after a while youll want bottom end again i know i bought my bike second hand and all i know that is on it are the mods listed in my sig but i think theres more cause ive clocked it 3 diff times at 79-81mph and everyone says thats not possible with my mods but the radar gps and a truck speedo cant all be lying but ya now i want bottom end and lots of it its way more fun