header weld question???

[biggun132]

what welds on the header are yall grinding? will this be about the same as a aftermarket exhaust besides the diameter of the pipe?

[dalejiw25]

The welds on the inside of the header pipes closest to the motor. if you look inside you'll see the terrible welds in there restricting the flow. Won't be near as good as aftermarket ,but it helps.

[slightlybent47]

The header is welded from the inside and there is a bead of weld that can be ground down.
It's not as good as a larger pipe but unless you have a built motor I realy dont think a head pipe will make that much defrance.
It's an easy mod and it wont hurt anything just don't take out to much.

If you have some time go for it.

[biggun132]

yea i know it wont be the same... but with just a stock motor i am thinking i will just save myself some money and just do a slip on. im thinking of going with a HMF. i have the airbox lid off with the outerware lid thing on there. what kind of jetting should i go with?

[slightlybent47]

Not sure on the jetting but you are stock so jetting my not be necessary.
The head pipe mod can't hurt.
A slip on pipe won’t do much by itself. But if you plan on doing more in the future then you can start there.
If you plan on doing more mods later then it would be better to wait till you can do it all at the same time.
That way you will feel the gains all at once.

[ksnell]

my buddy ground his out has his air box lid cut up slip on muffler and a sparks timing key and he is running a 190 jet, also has 42 pilot with the choke taken off and it halls butt

[rob_990]

Originally posted by ksnell
my buddy ground his out has his air box lid cut up slip on muffler and a sparks timing key and he is running a 190 jet, also has 42 pilot with the choke taken off and it halls butt

190!:huh

[ksnell]

yea i got a 185 in mine and the spark plug is white thinking about trying a 190. the sparks key will be here friday so maybe saturday i can play around with it.

[sprayedgt]

X2 190! I have a FULL Yoshimura exhaust, UNI, removed choke, and Sparks advance key and jetted @ 152 main perfectly. IMO that sounds like a huge main for your mods. I know each bike is different, but had no idea different by that much.

[ksnell]

we also have the air box lids off. hes runnning a uni and i have a k&n with prefilter also we r in north louisiana idk if that makes a difference or not

[dariusld]

If you can pull 5th gear and not sputter thats great. But 190 sounds way to big to me also.:eek2:

[bigbad400]

yeah 190 is huge i have an 11:1 440 and i have a 170 in mine i think or 175 maybe. i dont remember them well they have numbers so i dont need to. but thats big for a stock motor for sure, unless your at like 6-7000 feet or something. i think you need to look into your jetting more your plug could be white from pilot running lean too, your needle is prolly on like the lowest setting meaning its restricting and your main really dont need to be that big. the needle tapers into the main to release it out little as you open the trottle, if its in too far it will act like your main is too small. the ideal spot for the needle clip is in the middle or one up from there. i would look into it and make sure thats not the problem.

never know it could just be how yours runs. good luck.

[TRXRacer1]

Something is wrong if a 190 is working.

[biggun132]

yea i second that. ive got a 150 in there right now with a suppertrap slip on. and mine runs kinda good i think its a little lean when i pulled the lid i gotta do a plug check and make sure.

[biggun132]

the HMF website says to run a 165/170 for their slip on. that was based on a 900ft alt.

[Red400EXGuy]

I think i'll give this mod a try with freeing up the flow through the header...do you use a dremel to simply grind the welds down or is there a different way other members have tried??

[ksnell]

Originally posted by biggun132
the HMF website says to run a 165/170 for their slip on. that was based on a 900ft alt.
that with just there slip on so wouldnt a full exhaust or grounded header plus no air box lid put you at 180/190 i may be looking at it differently idk always open to learn new things

and a side not r all jet numbers the same for different brands? that could be the issue

ex guy i would think a dremel would be the perfect tool for the job good luck

[dankbud42o]

ex guy i would think a dremel would be the perfect tool for the job good luck

it works but takes a long *** time, its wicked loud and u go thru quite a few grinder bits....but it works!! lol

[sprayedgt]

Originally posted by ksnell
that with just there slip on so wouldnt a full exhaust or grounded header plus no air box lid put you at 180/190 i may be looking at it differently idk always open to learn new things

and a side not r all jet numbers the same for different brands? that could be the issue

ex guy i would think a dremel would be the perfect tool for the job good luck

A 190 Keihin is about a 170 Dyno Jet or a 160 Mikuni. A 190 DJ is about 215 Keihin and god knows what size Mikuni. I would say the most it would be is right around a 160 Keihin. Maybe you just looked at it wrong and mistook the "6" for a "9"?

[TRXRacer1]

Link to a conversion chart:

http://www.jetsrus.com/FAQ_mikuni_vs_dynojet_vs_keihin_sizes.htm

[ksnell]

definately a 185 in mine and 190 in his they could just be like you said keihin and equivilant to like 165/170

[tri5ron]

Originally posted by TRXRacer1
Something is wrong if a 190 is working. X2,
if it is a 190 Kiehen,.. and you are seeing a white sparkplug,...

my guess is you have a huge airleak somewhere around the intake boot between the carb and the head.

I have a stock piston and cam, with a full Big Gun race series system, Sparks key, and PERFECTLY tuned 450r carb. (straight off the dyno)..
and I am running a 162 Kiehen main, at nearly sea level.

[400ex28]

I ran a 150 in mine with no lid, full exhaust, fully built engine. I tried a 160 a long time ago and it wouldn't even run on that lol. 190 sounds outrageous.

[ksnell]

its prolly some off the wall brand they came from a local atv supply place around my house. im disagreeing with anyone but i know what numbers are on the sides of them. and it will absolutely not run with the airbox lid on so maybe they r like a 170 who know i try and find some keihin jets and play around with that:confused:

[TRXRacer1]

Originally posted by ksnell
its prolly some off the wall brand they came from a local atv supply place around my house. im disagreeing with anyone but i know what numbers are on the sides of them. and it will absolutely not run with the airbox lid on so maybe they r like a 170 who know i try and find some keihin jets and play around with that:confused: I think we're just trying to let you know that you've got a potential issue here. If I were you I'd start by taking the intake off the head. check the o-ring and if it looks fine lube it up and re-install it. I'll never put one of those back on dry. See what happens it's free and easy.

[biggun132]

what kind of jets are yall running? to be using the 150's and 155's? what kind of jets does hmf use?