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Run's better with the air box cover off

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Why does my bike run better with the side cover off ?

Too rich mid/top is strong low end was so so until I remover the cover.

Stock carb 150MJ / 22.5SJ 3 turns out on A/F

FMF power 4 and power bomb header

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3x3 mod done main jettng is good very strong pull to top end. With cover off bottom/mid and top are very strong. With cover on low or cruse is so..so mid / top is strong.

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3x3 mod done main jettng is good very strong pull to top end. With cover off bottom/mid and top are very strong. With cover on low or cruse is so..so mid / top is strong.

Sound rich.

How high are you?

Do you have a jet kit?

If so which one?

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Sound rich.

How high are you?

Do you have a jet kit?

If so which one?

300 ft.

yes

JD

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300 ft.

yes

JD

What needle setting?...If it's on Blue clip 4 ,try it on #3 with side cover on...

Install a 160mj and see how it runs...150mj is too lean for your set up..especially with the colder weather....

being rich on the needle can be compensating for a lean main...

BTW..Sometimes running with the side cover off can give the illusion of better performance because of the increased induction noise...

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What needle setting?...If it's on Blue clip 4 ,try it on #3 with side cover on...

Install a 160mj and see how it runs...150mj is too lean for your set up..especially with the colder weather....

being rich on the needle can be compensating for a lean main...

BTW..Sometimes running with the side cover off can give the illusion of better performance because of the increased induction noise...

Just moved it from #4 to #3 side cover on and it had a slight mid sumble at cruse. Put it back to #4 with cover off and it ran very good at low,mid,top and cruse... Illusion I don't know. I'll try it again but it sure seems to run smoother with it off. Will try a 160MJ next but I think its running rich as my plug color before I removed the cover was black.:lol:

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OK..Recommend setting for JD jet kit with open pipe ,3x3 at near sea level is

#160 main jet

jd blue

clip 4

22.5 pilot jet with extended screw or 25 pilot jet with stock screw

2.75 turns

Are you sure the 3x3 opening is 3"x 3".?...air filter clean?

Is your PC4 corked?

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How does one check to see what the main jet is set at, the bike I just picked up has a K&N filter, full yoshi Ti system, hot cams, and a JD Jet kit.

This weekend I am doing some basic maintenance... oil/filter change, new plug, reset the suspension for my weight, and a good cleaning

I was going to do the 3x3 mod while i was in there, do you think i will need to change the jetting again? I am at sea level right

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How does one check to see what the main jet is set at, the bike I just picked up has a K&N filter, full yoshi Ti system, hot cams, and a JD Jet kit.

This weekend I am doing some basic maintenance... oil/filter change, new plug, reset the suspension for my weight, and a good cleaning

I was going to do the 3x3 mod while i was in there, do you think i will need to change the jetting again? I am at sea level right

Welcome aboard, you will have to open it up and look.

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300 ft.

yes

JD

150 main at 300 feet, your lean. Should be using a 160 main & blue needle

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FWIW:

California 2003 DR-Z400S, wouldn't run when I bought it

Performed 3x3 airbox mod

Replaced the air filter

Replaced the carb with less grungy used identical Mikuni CV

Installed extended fuel screw

I am in the San Francisco Bay Area, home altitude about 400 feet

Re-jeted carb with JD kit: blue needle, clip in 3rd position, #155 main jet, #25 pilot jet, fuel screw 2.75 turns out

She runs great. Always starts in one second or less, even when ice cold. I'll pull the tank in a few hundred miles and check the spark plug just to be sure

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How does one check to see what the main jet is set at, the bike I just picked up has a K&N filter, full yoshi Ti system, hot cams, and a JD Jet kit.

.

This weekend I am doing some basic maintenance... oil/filter change, new plug, reset the suspension for my weight, and a good cleaning

I was going to do the 3x3 mod while i was in there, do you think i will need to change the jetting again? I am at sea level right

Welcome to TT...:) and congrats on your new bike..Got pics.?

It's odd that the PO didn't do the 3x3 when he added the good bits..Perhaps he is telling you stories about the JD jet kit.:banghead:

You will need to check what the current jetting is...the stock needle will have no clip adjustment....

Access to the main jet is a pain in the butt with the stock mikuni..Carb/Float Bowl removal is required..

There lays another reason to upgrade to an Fcr, (here it's just a matter of undoing the cap in the centre of the bowl and using a 6mm socket to remove mj) ...Needle access is from the top on both types of carbs...http://shop.thumpertalk.com/ProductDetails.asp?ProductCode=INT_KEIHIN_DRZFCRMX

While your doing the maintenance thing it would be worthwhile to do a valve clearance check...http://www.thumpertalk.com/forum/showthread.php?t=813179

Has it got an MCCT?.. definitely a smart investment...:lol:

Edited by CraigoDRZ400sm

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Welcome to TT...:banghead: and congrats on your new bike..Got pics.?

It's odd that the PO didn't do the 3x3 when he added the good bits..Perhaps he is telling you stories about the JD jet kit.:cheers:

You will need to check what the current jetting is...the stock needle will have no clip adjustment....

Access to the main jet is a pain in the butt with the stock mikuni..Carb/Float Bowl removal is required..

There lays another reason to upgrade to an Fcr, (here it's just a matter of undoing the cap in the centre of the bowl and using a 6mm socket to remove mj) ...Needle access is from the top on both types of carbs...http://shop.thumpertalk.com/ProductDetails.asp?ProductCode=INT_KEIHIN_DRZFCRMX

While your doing the maintenance thing it would be worthwhile to do a valve clearance check...http://www.thumpertalk.com/forum/showthread.php?t=813179

Has it got an MCCT?.. definitely a smart investment...:lol:

Sorry to the OP to thread jack, I will make my own thread tomorrow, I will be ordering the FCR 39 from Eddie while he is doing his holiday special, the bike does not have the MCCT, i will read up and order one, as for right not I think i will just cut the 3x3 hole and if it seems to run weird throw some gorilla tape on it until the new carb comes in

The jet kit on the bike is actually the Dyno Jet kit, and only has 6k miles, do u think the values need to be checked and adjusted already?

If so i will stop by my local dealer and pick up a feeler gauge and maybe the hotcams shim kit if need be.

This website has so much info, so thanks to everyone for helping the community :)

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I am guessing since the hotcams were installed, which was when the bike had 0 miles on it lol so 6180 miles ago, i will grab some feeler gauges and check them out this winter as well

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150 main at 300 feet, your lean. Should be using a 160 main & blue needle

Correct me if i am wrong but, if I am lean would it not run leaner with the air box cover off? It should be missing or have a surge of some sort with it off. Why does it run better with it off ? My low,mid,top and cruse is way better with the cover off.

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Correct me if i am wrong but, if I am lean would it not run leaner with the air box cover off? It should be missing or have a surge of some sort with it off. Why does it run better with it off ? My low,mid,top and cruse is way better with the cover off.

Your are correct, it will run leaner with the air box cover off. Some thing is odd with your bike. At sea leavel or your 300 feet you should need at least 155 mian or 160 with the JD kit. I am at 2500 feet and run 155 main blue needle and with the side cover off it with sputter, to lean.

Do you have a big bore in your bike? That would cause it to suck more fuel out of a small jet.

Are you sure you it's a JD ket?

At 300 feet with your set up and a 150 jet it should be lean.

Bottom line, if it runs better with the cover off than use that as your gide for your bikes jetting needs.:lol:

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