snapping and popping

[bigbad400]

2000 trx400 runs great in the throttle but when i get her open then let off the gass she pops and backfires it sounds like, i got a hole in the top of the airbox for better airflow i assume, i just baught it. i put a DG pipe on it, no jets done yet i wanted to figure out the popping. so what do we think is wrong here fellas.

[jrafter]

rejet it

[bartlettracing]

could be a few things .. make sure the exsaust isnt leaking.

A leak will cause poping ....

If it isnt leaking open the air/fuel screw up a good turn. this is located on the bottom side of the carb on the intake side in a recesed hole. best way is to lossen the carb and twist it to the side. I can do mine with a small bit out of a screw driver if I remove the engine breater tube and get my hands in there just right.

also alot of people raise the pilot jet upto a 42 .. this helps cold starting and the lean pop ....

ps. tape up the air hole in the box .. open air boxes wreck engines ...

unless your a pro racer you wont miss the added 1/4 hp ..

[drew416ex]

Most of the time its a lean pilot jet. And Open air boxes don't destroy engins, bad air filters do.

Originally posted by bartlettracing
ps. tape up the air hole in the box .. open air boxes wreck engines ...

unless your a pro racer you wont miss the added 1/4 hp ..

There is a bigger increase than that Its actually really decent just taking the lid off and rejetting for it. Why would it wreck engines? When I had a snorkel and closed air box lid and all I still got crap in my airbox. Tell me how open air boxes wreck engines? Its more of the filter and maintainance on the filter than opening up the airbox.

This is just removing the airbox lid not jetting at all. When you rejet it makes the curve smoother and there isnt a dip on the top end its more power all through the powerband

[krt400ex]

Originally posted by FoxHondaRider
There is a bigger increase than that Its actually really decent just taking the lid off and rejetting for it. Why would it wreck engines? When I had a snorkel and closed air box lid and all I still got crap in my airbox. Tell me how open air boxes wreck engines? Its more of the filter and maintainance on the filter than opening up the airbox.

they dont wreck engines...you just gotta clean your filter a little more often...no big deal and worth the extra ponies IMO. i have put well over 100 hrs since i opened up my airbox and that is on an engine that had 200 on it b4...with over 300 hrs on one build and my bike still runs fine...open airboxes dont destroy engines

Originally posted by krt400ex
they dont wreck engines...you just gotta clean your filter a little more often...no big deal and worth the extra ponies IMO. i have put well over 100 hrs since i opened up my airbox and that is on an engine that had 200 on it b4...with over 300 hrs on one build and my bike still runs fine...open airboxes dont destroy engines

exactly

[bigbad400]

yeah ive had a few quads and bu=ikes and never once did a hole or removed lid blow my motor, my blaster with 2700 in the motor alone is all open, its just got the k&n and the outerwears, mud sand nothing ever got in there. and its got the aluminum airbox and no holes in it to drain water out,
it will have as soon as im done riding at silver lake.

[bigbad400]

thanks thow guys, i got a few things to try out, the air screw sounds simple enough, if thats not it im gonna buy the power pack with the new k&n filter and a prefilter and the dynojet kit. also anyone with a set of decent nerf bars for sale?

[bartlettracing]

wow ..... for real ? foolishness running wild ...

I build race engines and have been building/racing for many years .

but of course your smarter than me. fine /ok ..

do a test your self .... I do not care at all what air filter you use ..

take your lid off and start your motor .... spray it with a garden hose .... what happens .... spits spudders quits .... WHY? it inguested the water... this is the same thing that happens when you crash though puddles/water ect ....

now remove the air filter and take a glass of water and mix some mudd/dirt into the water and make the water brown/dirty ....

now poor the muddy water into the airfilter and watch what comes out .. is the water clean now and look like new tap water again ? hmmmm NOPE ... looks like dirty water still ... Why because your filter sucks ! your filter is designed to filter large dry dusty air particals. not water .... all that dirty water you drive your quad through and hits your filter is ingested into your motor just like the test ... and thats a FACT jack ... class dismissed ...

Originally posted by bartlettracing
wow ..... for real ? foolishness running wild ...

I build race engines and have been building/racing for many years .

but of course your smarter than me. fine /ok ..

do a test your self .... I do not care at all what air filter you use ..

take your lid off and start your motor .... spray it with a garden hose .... what happens .... spits spudders quits .... WHY? it inguested the water... this is the same thing that happens when you crash though puddles/water ect ....

now remove the air filter and take a glass of water and mix some mudd/dirt into the water and make the water brown/dirty ....

now poor the muddy water into the airfilter and watch what comes out .. is the water clean now and look like new tap water again ? hmmmm NOPE ... looks like dirty water still ... Why because your filter sucks ! your filter is designed to filter large dry dusty air particals. not water .... all that dirty water you drive your quad through and hits your filter is ingested into your motor just like the test ... and thats a FACT jack ... class dismissed ...

your lucky to find water where i live. tons of sand on top of limestone filters everything and water sinks into the ground. so water in the airbox... not worried one bit

[400exrider_88]

Originally posted by FoxHondaRider
This is just removing the airbox lid not jetting at all. When you rejet it makes the curve smoother and there isnt a dip on the top end its more power all through the powerband

out of curiosity, where did u find that chart?

Originally posted by 400exrider_88
out of curiosity, where did u find that chart?

GTT

[drew416ex]

Originally posted by bartlettracing
wow ..... for real ? foolishness running wild ...

I build race engines and have been building/racing for many years .

but of course your smarter than me. fine /ok ..

do a test your self .... I do not care at all what air filter you use ..

take your lid off and start your motor .... spray it with a garden hose .... what happens .... spits spudders quits .... WHY? it inguested the water... this is the same thing that happens when you crash though puddles/water ect ....

now remove the air filter and take a glass of water and mix some mudd/dirt into the water and make the water brown/dirty ....

now poor the muddy water into the airfilter and watch what comes out .. is the water clean now and look like new tap water again ? hmmmm NOPE ... looks like dirty water still ... Why because your filter sucks ! your filter is designed to filter large dry dusty air particals. not water .... all that dirty water you drive your quad through and hits your filter is ingested into your motor just like the test ... and thats a FACT jack ... class dismissed ...

Just curious, who said anything about getting water in it? Maybe I missed that. I ride mx so Im not going splashing around in water so i dont have that problem with my open box.

[krt400ex]

Originally posted by bartlettracing
wow ..... for real ? foolishness running wild ...

I build race engines and have been building/racing for many years .

but of course your smarter than me. fine /ok ..

do a test your self .... I do not care at all what air filter you use ..

take your lid off and start your motor .... spray it with a garden hose .... what happens .... spits spudders quits .... WHY? it inguested the water... this is the same thing that happens when you crash though puddles/water ect ....

now remove the air filter and take a glass of water and mix some mudd/dirt into the water and make the water brown/dirty ....

now poor the muddy water into the airfilter and watch what comes out .. is the water clean now and look like new tap water again ? hmmmm NOPE ... looks like dirty water still ... Why because your filter sucks ! your filter is designed to filter large dry dusty air particals. not water .... all that dirty water you drive your quad through and hits your filter is ingested into your motor just like the test ... and thats a FACT jack ... class dismissed ...


lmao...i dont friggin care if you have been building race engines. i popped 6 holes in the top of my lid towards the front (too keep water out...it tends to splash the back of the lid), and i rarely ever get water in my airbox. i do lots of mud riding and its all good. the other thing is that...your airfilter is made to filter out ALL the dirt particales...not just the big ones. if you have a properly maintained and oiled filter(as i do) you will have no problems with dirt. my riding area, if it isnt sopping wet, is so dry that you cant breathe....and i never have dirt sucked into my engine...i would know if it was too because it would have left some residue in the intake for me to see when i clean my filter out...lol