want inexpensive performance

[05trx400exridr]

i got a new 05 400ex early this year, my first quad. its completely stock other than cutting the spark arrestor and reducer off of the end cap for the muffler. im looking for more top speed without loosing torque and i want to keep my reliability too. what are some of the less-expensive mods i can make to my 4 wheeler?

[04TRX400EX]

Huh :huh Wanting more top speed without sacrificing low-end torque isn't going to come cheap. The easy and effective way to gain top speed is to change the front sprocket. You have an '05 so your's comes with a 14 tooth front sprocket. Changing it to a 15 tooth (which was stock for 1999-2004 model years) will give you about 8-10mph and lower 5th gear rpm's, but you will lose some torque. I just did the opposite on my '04 because I wanted more torque for exiting the corners at the MX track, but it sucks for trail/desert riding. I had no top-end!! Other than that, you have to do a bore kit and cam to gain more top speed while retaining, if not increasing your low-end power.

[Wheelie]

http://www.exriders.com/vbb/showthread.php?s=&threadid=243661

This should help you out.

[bwamos]

Easiest way to get more top speed without affecting the power characteristics is to get your rpm limit increased.

[idontknowwhoiam]

i took my tip off and ran it for a day and thought it sounded like crap...ya it was WAY louder but it sounded like junk to me i ended up puttin it all back to normal

[Wheelie]

A rev box won't improve the top speed on a stock engine. A stock engine can't pull 5th to the stock 9100rpm rev limit, let alone a higher one.

Increase the power output of the engine, and the engines ability to make HP at the higher RPMS. This will increase the top speed with the stock gearing and the stock rev box.

[bwamos]

ehh... I've never had a problem getting a stock 400ex to hit the rev limiter on dirt or hardpack, and I weigh 196.

In the sand or mud maybe.. but anywhere else in a long straight line it hit's the rev limit pretty easily. (of course if "I" wanted to go in a long straight line, I'd drive my car.. lol)

More HP isn't going to get you any faster. It will just get you there faster.

But, I do agree it isn't the best solution. Just the cheapest.

Slip-on, filter, cam, rejet is almost always the best bang for the buck on power. But power doesn't equal top speed.

[swva400ex]

mine when it was stock would not pull 5 to the limiter. now with the work done and a rev box it want pull 5 to the limiter. might just be mine. idk

[ZSNOW]

whats the best slip on i can get for my z400


sry for the off topic

[ohsobad_chevy]

Originally posted by ZSNOW
whats the best slip on i can get for my z400


sry for the off topic

OMG...this topic has been beat to death...click the search button at the top and please dont steal other peoples threads, at least make a new one!! :rolleyes: :rolleyes:

[Kansas400ex]

have you thought about a port and polish job and a cam slip on, lighter flywheel i know that the lightening of a flywheel will only make it rev out faster but still it a performance mod.

[krt400ex]

Originally posted by bwamos
ehh... I've never had a problem getting a stock 400ex to hit the rev limiter on dirt or hardpack, and I weigh 196.

In the sand or mud maybe.. but anywhere else in a long straight line it hit's the rev limit pretty easily. (of course if "I" wanted to go in a long straight line, I'd drive my car.. lol)

More HP isn't going to get you any faster. It will just get you there faster.

But, I do agree it isn't the best solution. Just the cheapest.

Slip-on, filter, cam, rejet is almost always the best bang for the buck on power. But power doesn't equal top speed.

i weigh 180 and i can't get mine to hit the rev limiter in 5th. mines stock. this is on hardpack. how do u do it

[Wheelie]

When my engine was stock, w/a slip-on, filter, removed airbox lid, and no choke, it wouldn't pull the rev limiter in 5th with 15/38 gearing.

After I built the engine, it has no problem hitting the rev limiter in 5th w/the same 15/38 gearing. The machine now has a higher top speed as well.

A stock 400ex will do about 65. A little bit of math will tell you that at 9100rpm a stock geared EX is capable of about 75.

[05trx400exridr]

would removing my choke get me any more top speed, and would i need to alter my airbox lid? also i live in iowa, so would it be easy enough to re-install for the winter?

[Wheelie]

I don't think removing the choke would give you a better top speed, if it didn't it wouldn't be noticable. When I removed mine, I noticed better throttle response and little bit more power. If you're careful removing it, it won't be difficult to re-install it for cold weather.

Simply remove the airbox lid and re-jet to compensate for the added airflow.

[plkmonster2]

I hit the rev limiter with my 99, stock gearing, minimal mods, and 22 inch paddles. It did 81 MPH with a tail wind. Hit around 70 with no wind.

[ohsobad_chevy]

Originally posted by plkmonster2
I hit the rev limiter with my 99, stock gearing, minimal mods, and 22 inch paddles. It did 81 MPH with a tail wind. Hit around 70 with no wind.

How did you clock this??? :o

[plkmonster2]

Used a gps... I don't know what else would work..

[Wheelie]

cough: cough:

81mph :rolleyes: :rolleyes:

[ohsobad_chevy]

Originally posted by plkmonster2
Used a gps... I don't know what else would work..
I think you got a miss read, pal.
Stock 400 will do 70 and thats giving it a little bit. My buddy was beside me in his vet, I was doing exactly 67 MPH. It was on a drag strip, so don't think I ride on the road!! :cool:

[plkmonster2]

I had 22inch paddles and a tailwind. I did 3 runs on the wet beach. It was 80, 81, and 80. Tailwidn probably was 20-30mph gusts. Without any wind it would do 70, at sea level.

[oldskoolex400]

got mine up to 76 once then 78 later on in the day with 20 in rears stock rev box and 15t front

[Over-land 450r]

put a 440 kit filter and exhaust.

[plkmonster2]

Sorry that I got off topic. I meant to mention a pipe and a filter is a good upgrade for about 250. If you have 500-600 I'd look into a high compression piston and a cam to go with the other two. Another step up would be a 406 or 416 then head work.

[400exrider707]

Originally posted by Wheelie
A little bit of math will tell you that at 9100rpm a stock geared EX is capable of about 75.

The gearing calculator shows exactly 67mph for a 400ex up to 04.

[ohsobad_chevy]

Originally posted by 400exrider707
The gearing calculator shows exactly 67mph for a 400ex up to 04.

Yup, wind has nothing to do with it!! Your gearing will only let you go so fast...then you have to have the horse power to push it all the way there. But if you had stickers on your quad, you could do 90 mph...HAHAHAHA...damn kids!! :rolleyes:

[-copyguy-]

With an aftermarket rev limiter and 22's he MIGHT be able to get it to 86.4....not saying he did...just that it's possible...

[plkmonster2]

Originally posted by ohsobad_chevy
Yup, wind has nothing to do with it!! Your gearing will only let you go so fast...then you have to have the horse power to push it all the way there. But if you had stickers on your quad, you could do 90 mph...HAHAHAHA...damn kids!! :rolleyes:

?? Kids?? Wind has nothing to do with what? Maybe your theoretical top speed. You need horsepower to overcome the wind resistance. A stock 400 has the re limiter set at 9100 or 9200, I have to look. With 22's, and at 9200rpm, a 400 does 84, according to the calculator. Yeah, with wind resistance, my 400, or a stock one would never hit this speed, maybe only 67 or so When I was in the tail wind, I had an approximate wind speed of 50 or so. Much less than a 67 MPH wind. My ground speed was 81. The gearing calculator only goes up to 8250. Maybe you should have looked at that first. Maybe that is the Average Rpm that a 400 will hit in top gear.

[ohsobad_chevy]

LOL...Just cause some guy made that program, it is accurate?? Do you believe everything that you see on the internet?? :ermm:

[swva400ex]

Originally posted by ohsobad_chevy
LOL...Just cause some guy made that program, it is accurate?? Do you believe everything that you see on the internet?? :ermm:




i here ya on that. everything you read is true, common on man, didnt they teach you that in school.lol

havent really seen to many engines push horsepower to the rev.

[-copyguy-]

that program has been referred to more than once by users of this site. Why don't you sit down with a calculator and check his math? :p

Also, I didn't say it was probable that those speeds were reached, I said it was maybe possible...maybe

[plkmonster2]

The calculator is actually pretty accurate. It uses the true gear ratios of the 400. When you type in the engine speed, and tire size, it will show you how fast it can go, at that rpm. Your quad may not go that fast, but if the engien could rev that high, it should be close.

Originally posted by plkmonster2
The calculator is actually pretty accurate. It uses the true gear ratios of the 400. When you type in the engine speed, and tire size, it will show you how fast it can go, at that rpm. Your quad may not go that fast, but if the engien could rev that high, it should be close.


30mph in 1st gear :huh


i dont think so

[Dannys440]

Thats true IF it could hit that rpm but 99% of the time,it wont. Guessing, mine i can feel it pull till about(guessing by sound)8350RPM,after that it flat lines. If it would pull the full Rpm it would be faster.


Out of these 3, the 99 I have hit the Rev limit on it one time.And that was due to wheel spin in 3rd.


03 - full fmf exahust,jetted,rev box,no lid,16 tooth front,20" ground busters

99 - 14 tooth front,no lid,big gun header W/cobra can,jetted,18" turf tamers

04 - 440 kit,15tooth front, no lid,jetted,20"shreader xc

[ohsobad_chevy]

Originally posted by Kickstarts_Suck
30mph in 1st gear :huh


i dont think so

Thats kinda what I was thinking!! I think that calculator is a little off.... :o

[-copyguy-]

depends...you got a 99-04 with 15/38 gearing or a 05-06 with 14/39 gearing...BIG difference.

[ohsobad_chevy]

Well, I gotta 2004 with the 15 tooth front...There is no way it will reach 30 mph in first...no way what so ever!!! :cool:

[-copyguy-]

with 22's? Plus, it's theoretical...just because a calculation says it's possible, that doesn't mean it's probable... I also put an aftermarket CDI into the calculator at redline...

It was a lot of what ifs to show that the calculations support his theory...