Why one Stock 400 has more power ?

[spincr4hire]

My buddy and I went riding Saturday. We both have stock 400's other than his has Renthal bars and I have Razr tires. He wanted to ride mine and get a feel for the Razr's because he was thinking of getting a set. His 400 has considerably more power,and his bike is 5 months older (both are 2001's). Both had the oil changed and air filters cleaned about the same time. Whats going on ?
Its almost like his bike has an aftermarket pipe on it as compared to mine.

[Mity Mo]

Is there a tire size difference between yous? Other than that it is hard to tell what it might have been. That is pretty strange but I dont doubt it for a second. Mo:confused:

[spincr4hire]

My front tires are actually lighter than his, I've got the 21x7x10 4-ply's on douglas black labels... which are as light or lighter than the factory 22x7x10. I'm sure my rears are lighter or as light. It feels like he's got at least 1.5 to 2 more horses.

[lil'redrocket]

check your throttle adjustment I think its supposed to have like 3/16 play in it you may have too much play

lilred is on the money today,,,,yeah almost all 400ex come from the factory with the throttle adjustment all the way out,,so you might be only getting 75% of the motors power,,check into that..I know mine was all loosy goosy,,

[spincr4hire]

So just adjust it in on the thumb throttle ?

What you need to do is adjust the slack connector right at the throttle housing. Pull the rubber boot back and adjust so the throttle has very little play. You might wanna have the key around so you can have the quad running for testing,,YOU DO NOT WANT TO OVER ADJUST. test it out before doing any riding,,comprede'. The owners manual has a page on proper slack in throttle cable..

[Tommy 17]

also try to take off the head pipe and look at the welds... i heard that some have bigger welds and cut down on the air that goes out of the motor... its just a thought...

[harebounder]

Bro it has to be more than 1 or 2 horse you would not be able to tell why don't you two drag race. Then switch machine to compare each others riding abilitys. Maybe its in your head.

[shockwave67]

Are your Razor tires shorter than stock? If so thats the MPH difference from lower gear ratio. If not,Switch bikes and look for the same results.
NO two machines are identical,There will always be slight variances such as better combustion sealing from rings or looser valves or tighter chain. Dont let it worry you. Check your throttle and valves and tune up if tire size is different. If you want to blow him away without him knowing it, put a 16 sprocket on the front,grind your case saver a little to put it and the guard back on and then you will put four bikes on him top end.:D

[coryatver]

20 inch razr's are closer to 22 inches

My cousin has a 99 400ex and his buddy had a brand new 2000.They brought them over to my house.Because I have about 600 acres to ride on.(not mine but have permission)Anyhow my cousins had a K&N filter and dynojet kit and his buddies was stock.His buddy beat him everytime.No matter if they switch or not.

My 300ex has beat every warrior and 300ex.As well as a piped and camed 250x.Some bikes just run better than others.


Not sure why but they do.



86 trx250r
97 300ex

[RAPTORAZ]

Two words: Production Tolerances.

[Pro400EXC]

Yah, my friend has a 2001 400ex and so do Ibut, he had his for 3 months and I had mine for about a yr.

Well my friend Mike (I swear he is Barry Hawk Jr in the woods,he is soooo fast,but he doesn't have the aggressiveness to race tough) and my 400 is ragged out(ridin real hard) and my Buddy Mike says my 400ex has more power it feels like. My friend and I have the same pipes and Jetting, he just has a air filter and Razr 20's on the rear, and also a twist throttle, so why does my 400 have more power?

[spincr4hire]

20" Razrs are the same as the 20" Ohtsu's, I set
them side by side when I first got them, they are lighter with the douglas black labels as compared to factory, if anything. My buddy agrees that his is has more pep, its not in my head. I'm not worried about top end speed or outrunning him, I was just curious as to why his had more low end. If anything I could get a 14 tooth front, I guess for more low end.

Interesting Post Topic.
(seriously) When my 400EX was new and still stock, I kept up with and passed lightly modded 400EX's. It was definitely faster than other stock 400EXs...all my friends noticed this.

Even after all the mods I have done, my 416 easily beats my friends with 406's, 430's and 440's...go figure...I can't explain this.



(hmm, wait a minute, I just noticed "Twin-Turbo" written on the side of my engine case.....heheheh....kidding....LOL)

I don't know if this is a valid reason, but while I was installing my White Brothers E Series pipe and on my 400EX I read the details on the Dyno Chart provided. They mentioned that the stock jetting on the 400EX they conducted this particular Dyno test on was a 155 MJ. It also stated that they have seen stock jetting on TRX400's range from 142 through 148.

I know the manuals state a 148 stock MJ but I would imagine White Bros see's a lot of stock machines and would have no real motive to state false details like these on their dyno charts.

I wonder if for some reason, the factory jetting is not all that standard. I would suspect that a machine with a 142MJ would perform different than a machine with a 155MJ stock.

If they are re-jetting to get the motors to all run smooth, than there is obviously other issues they are compensating for. RAPTORAZ mention production tolerances and that’s where I would place my money.

Has anyone noticed that there machine had something other than a 148 stock main jet?

[harebounder]

They prolly had that main jet in their dyno chart because at the altitude and air temp they were at they had the best results with that pipe on there. Now i am not sure what i have for a main jet because when i bought my 400 it hade the white bros on it with a k@n filter power kit installed. I have no problems with it starting and that is even in under 20 degree temps but you do have a good point. That one might have a different mj in it would effect performance in two different machines. You would notice throttle response between the two machine hense being one feels more powerful than the other.

[kaneman23]

Another thing to consider is body weight. Are you lighter or heavier then him. My bro has a 01 EX and I have a 00' and both are stock except I have ITP holeshots, Renthal Bars, and AC Nerfbars. His is slightly faster maybe 1/2 to 1 quad faster everytime we race. We both weigh about 220lbs put I think my tires and Nerfs are just a little bit heavier and that is why his is slightly faster....