[BROESKY]

Hey new to the forum here. I just picked up an 04 400EX. Overall it's in great shape. It came with a K&N air filter and a slip on pipe. I'm just thoroughly going through it. I took the K&N off and replaced it with a new oem filter. Gave it a Rotella oil change. Had the carb off and took it to Honda for a cleaning. Cleaned the oil cooler. Everythng is back together. It starts good. When it runs and warms up i can here a pinging from the cylinder area. Its hard to pinpoint where its coming from. At first i thought it was maybe the header heat shield but when i put presher on it with my hand it doesn't go away. It's definately something in the cylinder area. I haven't checked the valve lash yet. Also when it runs it periodically misses a beat and stalls sometimes. Doesn't bog or anything when i crack the throttle but pops a little when i let off. Could it be a loose timing chain rattle thats also putting it out of time? Almost sounds like something in the head. I drained the tank and put fresh premium in it.

 

[BROESKY]

I also have no idea what it's got for jetting. I'm at 2490ft elevation. Only mods are a pro circuit slip on pipe. Stock filter with lid. Any help would be super appreciated. I run premium pump fuel in it.

 

[SlammedRanger]

I would adjust valves first. As that is a very likely cause of the ping you are hearing. Alot of times you can tell by how fast the noise is. Valves will be very fast. Timing chain slap will usually only happen at idle and go away when you get on the gas at all. Both are very common 400ex problems. But i will warn you. This motor ticks. Absolutely 100% no way to make it dead silent. As stupid as this may sound i always judge mine like this. If i can hear it with my helmet on i adjust them. Also if i hear the tick getting faster when riding around with my helmet on i know i really need to adjust. I also found torquing the adjutment nuts to 18 ft lbs like they say to do makes them last alot longer between adjustments.

Question number 2. Jetting. You will be good with a 150 main jet maybe 155 tops. But with your altitude you could almost get away with the stock main jet. As for the pilot jet. I would be changing that to a 40 or 42. They are lean on the pilot to meet emissions regulations. Put mixture around 1 1/2 to 2. And you should be good to go.

 

[BROESKY]

I would adjust valves first. As that is a very likely cause of the ping you are hearing. Alot of times you can tell by how fast the noise is. Valves will be very fast. Timing chain slap will usually only happen at idle and go away when you get on the gas at all. Both are very common 400ex problems. But i will warn you. This motor ticks. Absolutely 100% no way to make it dead silent. As stupid as this may sound i always judge mine like this. If i can hear it with my helmet on i adjust them. Also if i hear the tick getting faster when riding around with my helmet on i know i really need to adjust. I also found torquing the adjutment nuts to 18 ft lbs like they say to do makes them last alot longer between adjustments.

Question number 2. Jetting. You will be good with a 150 main jet maybe 155 tops. But with your altitude you could almost get away with the stock main jet. As for the pilot jet. I would be changing that to a 40 or 42. They are lean on the pilot to meet emissions regulations. Put mixture around 1 1/2 to 2. And you should be good to go.

Awesome thanks man! Super helpfull. I'll work on it today starting off with valve lashes. I guess its just the nature of the motors, my 420 i had was quiet.

 

[BROESKY]

What would you recommend for a jet kit, Dynojet? Some guy told me the jet numbers differ between jet manufacturers.

 

[wheeler]

Stick with Khien jets from Honda. Dyno jets do have different #s.


Width------Keihin # -- DynoJets # -- Mikuni #
0.0350---- 92.5--------- 92-----------86.3
0.0360---- 95----------- 94-----------88.1
0.0370---- 97.5--------- 96-----------90.0
0.0380---- 100---------- 98-----------91.9
0.0390---- 102.5------- 100---------- 93.8
0.0400---- 105--------- 102---------- 95.6
0.0410---- 107.5------- 104---------- 97.5
0.0420---- 110--------- 106---------- 99.4
0.0430---- 112.5------- 108--------- 101.3
0.0440---- 115--------- 110--------- 103.1
0.0450---- 117.5------- 112--------- 105.0
0.0460---- 120--------- 114--------- 106.9
0.0470---- 122.5------- 116--------- 108.8
0.0480---- 125--------- 118--------- 110.6
0.0490---- 127.5------- 120--------- 112.5
0.0500---- 130--------- 122--------- 114.4
0.0510---- 132.5------- 124--------- 116.3
0.0520---- 135--------- 126--------- 118.1
0.0530---- 137.5------- 128--------- 120.0
0.0540---- 140--------- 130--------- 121.9
0.0550---- 142.5------- 132--------- 123.8
0.0560---- 145--------- 134--------- 125.6
0.0570---- 147.5------- 136--------- 127.5
0.0580---- 150--------- 138--------- 129.4
0.0590---- 152.5------- 140--------- 131.3
0.0600---- 155--------- 142--------- 133.1
0.0610---- 157.5------- 144--------- 135.0
0.0620---- 160--------- 146--------- 136.9
0.0630---- 162.5------- 148--------- 138.8
0.0640---- 165--------- 150--------- 140.6
0.0650---- 167.5------- 152--------- 142.5
0.0660---- 170--------- 154--------- 144.4
0.0670---- 172.5------- 156--------- 146.3
0.0680---- 175--------- 158--------- 148.1
0.0690---- 177.5------- 160--------- 150.0
0.0700---- 180--------- 162--------- 151.9
0.0710---- 182.5------- 164--------- 153.8
0.0720---- 185--------- 166--------- 155.6
0.0730---- 187.5------- 168--------- 157.5
0.0740---- 190--------- 170--------- 159.4
0.0750---- 192.5------- 172--------- 161.3
0.0760---- 195--------- 174--------- 163.1
0.0770---- 197.5------- 176--------- 165.0
0.0780---- 200--------- 178--------- 166.9
0.0790---- 202.5------- 180--------- 168.8
0.0800---- 205--------- 182--------- 170.6
0.0810---- 207.5------- 184--------- 172.5
0.0820---- 210--------- 186--------- 174.4
0.0830---- 212.5------- 188--------- 176.3
0.0840---- 215--------- 190--------- 178.1
0.0850---- 217.5------- 192--------- 180.0
0.0860---- 220--------- 194--------- 181.9
0.0870---- 222.5------- 196--------- 183.7
0.0880---- 225--------- 198--------- 185.6
0.0890---- 227.5------- 200--------- 187.5


Thats compliments of Redracer....

 

[BROESKY]

You guys are awesome. One more question. Is it recommended to change out the timing chain on these after so many hours? Are they known to snap or is it even something i should worry about? Thanks again.

 

[SlammedRanger]

I agree with wheeler 100%^^^^^

As for timing chain. Yes they are well known to stretch. Never seen one snap before. Have seen them skip time from being so stretched. And what will happen is the tensioner will be out of adjustment room and the slack in the chain will slap or knock. Eventually it will ruin the chain guides also. But the fix for the is to put a crf450 timing chain into it. It requires zero modification. Full drop in and never stretch another chain. Its 2 plates thicker but still fits in the guides no problem.

 

[BROESKY]

I agree with wheeler 100%^^^^^

As for timing chain. Yes they are well known to stretch. Never seen one snap before. Have seen them skip time from being so stretched. And what will happen is the tensioner will be out of adjustment room and the slack in the chain will slap or knock. Eventually it will ruin the chain guides also. But the fix for the is to put a crf450 timing chain into it. It requires zero modification. Full drop in and never stretch another chain. Its 2 plates thicker but still fits in the guides no problem.

I like that, deffinately going to go the crf450 chain way. Picked up the 400ex service manual today from Honda. Was able to get the valve and clutch cover off today. I guess it would probably be wise to replace the guides and tensioner too?

 

[SlammedRanger]

Honestly i am still running my oem tensioner and guides in my quad. And im far from easy on it. If the guides arent showing excessive wear and the tensioner still functions i would leave them alone. Thats just my opinion.

 

[BROESKY]

Thanks again for the help everyone! Going to order gaskets and crf450 chain today. I might take off the head too just to check cylinder and replace head gasket for a piece of mind everything is ok.

 

[SlammedRanger]

Be careful with doing that. Make sure you get a good mls headgasket cometic or oem. And be sure to un torque in many slow steps. The heads can warp. I always get them decked anytime they are removed just to be sure im good. And your welcome! Always glad to help!

 

[BROESKY]

Thanks yeah i did go around about 5 times in a star pattern loosening all the bolts. I decided to take it a step further becuase i wanted to know the condition of the rod so i took the cylinder off to. i made a video if you guys can just check it out and let me know what you think.

 

[BROESKY]

Con rod wobble is not even an 1/8" of an inch. Con rod small end does have a bit of discoloration but and i cant feel any scoring when i put my finger in it.

 

[BROESKY]

Yeah so nevermind. I got the cases apart today. Just going to give it a full rebuild. The one crank bearing had play in it also. Cant believe my Honda dealership in town wants 680 bucks for a crank! I believe i seen one on service Hondas site for 300 and some. I think i'll stick with oem, heard mixed reviews on wiseco and hotrods.

 

[SlammedRanger]

If there is no up and down play the bearings are good. Wobble is 100% normal. But while you are doing what you are i would have a valve job done for sure. And have new valve seals put in. You will have to take the cylinder and piston to a engine machine shop to see if the walls measure with-in spec. There is a max piston to wall clearance spec in your manual.

 

[BROESKY]

If there is no up and down play the bearings are good. Wobble is 100% normal. But while you are doing what you are i would have a valve job done for sure. And have new valve seals put in. You will have to take the cylinder and piston to a engine machine shop to see if the walls measure with-in spec. There is a max piston to wall clearance spec in your manual.

At first i wanted to buy a new one but Honda don't make sport quads anymore so i figure i'll rebuild the motor in this one and keep it for a long time. I'll shine the cases up and everything and maker brand new again. Can a guy take some scotchbrite and just polish up the light scuffing on that piston if it measures in spec? Dont mean to ask so many questions lol. Are these cylinders nikasel coated, can the be honed again without worrying about coating? Some of this stuff my manual doesn't mention.

 

[wheeler]

If your looking for a shop to do any machining like valve job ect, I can dig up the receipt of the place I used. They were priced reasonable, did great work all with a quick turn around time. They are on the NW of Edmonton though... LMK

 

[SlammedRanger]

Dont even worry about asking to many questions. There is no such thing. That is what this site is for. I wouldnt worry about putting a used piston back in as long as there arent any deep scores or signs of seizure it will be perfectly fine. But i would bet with the age of the machine the cylinder will not measure good enough to not require atleast a small over bore. No the cylinders are not coated. Just standard steel sleeves. They can be bored to a max of a 88mm safely. But they make 85.5-86 and 87 mm pistons for them aswell. And compression bumps from 10:1 10.5:1 11:1 12:1 13:1. Lots of aftermarket options. I will list them in order of best IMO to worst. JE-CP-WISECO-VERTEX-NAMURA. These are the reputable brand names out there. But plenty of other cheap-o ones. No matter what you do. Do not trust any machine shop that says they dont need the piston for cylinder boring. They do not know what they are doing if they say they dont. If they do know what they are doing they will measure the piston and make the cylinder match it perfectly. There are always tolerances that even the piston manufacturers are to stay within. And those tiny differences are what make a huge difference.

 

[BROESKY]

Dont even worry about asking to many questions. There is no such thing. That is what this site is for. I wouldnt worry about putting a used piston back in as long as there arent any deep scores or signs of seizure it will be perfectly fine. But i would bet with the age of the machine the cylinder will not measure good enough to not require atleast a small over bore. No the cylinders are not coated. Just standard steel sleeves. They can be bored to a max of a 88mm safely. But they make 85.5-86 and 87 mm pistons for them aswell. And compression bumps from 10:1 10.5:1 11:1 12:1 13:1. Lots of aftermarket options. I will list them in order of best IMO to worst. JE-CP-WISECO-VERTEX-NAMURA. These are the reputable brand names out there. But plenty of other cheap-o ones. No matter what you do. Do not trust any machine shop that says they dont need the piston for cylinder boring. They do not know what they are doing if they say they dont. If they do know what they are doing they will measure the piston and make the cylinder match it perfectly. There are always tolerances that even the piston manufacturers are to stay within. And those tiny differences are what make a huge difference.

Awesome help man. It's my first time rebuilding a motor but having fun doing it. Anything else i'll be sure to post questions. Just going to get everything cleaned up and miked, and see what i need for parts.