Engine Noise

[Firey400ex]

I have a 00 400ex, It runs great and has been well maintained. I was riding last weekend (not doing anything unusual) and when I came to a stop I noticed that my engine was making a bad vibration type sound. It gets louder when I rev it, and it does in in neutral and every gear. It kinda sounds like if you were sitting in the bed of a pickup truck and were holding on to one end of a chain and letting the other end drag on the ground. I adjusted the valves and replaced the timing chain tensioner. It still makes the exact same noise. It still has pleanty of power and idles fine, it just make an awful noise. Any ideas? It is driving me CRAZY and I'm afraid to ride it anymore until I fix it. :confused:

[JOEX]

This is mostly a guess.... thinking timing chain tensioner. Or it could be a loose bolt on the chassis somewhere, skid plate maybe...

Any mods done to the motor or quad in general?

[Aceman]

You replaced the tensioner, but have you looked at the actual timing chain? Maybe the chain is so slack even the tensioner can't keep it tight?

[JOEX]

Originally posted by Aceman
You replaced the tensioner, but have you looked at the actual timing chain? Maybe the chain is so slack even the tensioner can't keep it tight?
Need to get my eyes checked... I swear I read his post three times and didn't see the tensioner part:ermm: :confused: :chinese:

[pro-rider46]

Originally posted by JOEX
Need to get my eyes checked... I swear I read his post three times and didn't see the tensioner part:ermm: :confused: :chinese:

i do that too often...

[chipworkz]

Its hard to tell without being there, but since it is running fine I would also look for something loose. It could be almost anything so I have a little tip for you. It might sound strange but get a piece of wood, like a short piece of broom handle. Put it on you ear and touch the other end to various areas of the motor and chassis. The noise will get louder the closer you get to the cause. Kind of a backyard mechanics stethoscope. It really does work and I could tell which piston I burnt up in my Jeep engine before I pulled it apart. This trick goes back to your grandpas days. :D

[Firey400ex]

I don't have any mods except for a jet kit and sprockets.

I thought it might be the chain, but it started so abruptly. Everything was fine, then all of a sudden the noise started. Could that still be the chain? I figured it would take time to slowly stretch. How do I check the timing chain? The access hole where the tensioner goes in is so small and in a tight place.

I actually tried the broom handle trick (with an 9 inch 3/8 extension) and I can hear it best around the top of the motor, not so much in the crank case. .........if that helps any. Good tip!!

[Firey400ex]

Hey guys, thanks for the help diagnosing. I brought my quad to a local dealer. As soon as I find out what the problem is, I will post it!

[86 Quad R]

i bet it's either with the cam or the valve cover assembly....

[Firey400ex]

The owner of the shop said that it is the timeing chain. He is putting a new one on, and I get it back tomorrow. I really hope this fixes it :mad: . I will let you guys know tomorrow.

[Aceman]

Nailed it on post #3.:chinese:

[Firey400ex]

Wait......Wait......Wait Stop the bus. Shop owner tore the motor down and said it IS the cam!! Not cool at all.........this is really turnig out to be a pain in my *****. Does anybody know where the best place is to buy a stock replacement, or a Hotcam?

[ohsobad_chevy]

Buy the hotcam, get a stage 1, you wont be disappointed.

BTW: dealerships are the devil!!! lol j/k :D

[Firey400ex]

I bought the Hotcam stage one. Is it really that much better? What kind of difference did you notice?

It only costs 45 bucks more than a stock replacement, I figured I would go ahead and get it.

[Aceman]

Originally posted by Firey400ex
Wait......Wait......Wait Stop the bus. Shop owner tore the motor down and said it IS the cam!!

Well, I thought I nailed it on post #3.:mad:

[JOEX]

Originally posted by Firey400ex
Wait......Wait......Wait Stop the bus. Shop owner tore the motor down and said it IS the cam!! Not cool at all.........this is really turnig out to be a pain in my *****. Does anybody know where the best place is to buy a stock replacement, or a Hotcam?
What did they say was wrong with the cam? I find it kind of odd if the motor is still running strong the cam is bad. If the cam is bad i'd want to know what caused it to go bad, there could be some other underlining issue...

[wilkin250r]

I can only thing of a few reasons a camshaft would make a noise like that. One would be really REALLY loose rocker arms.

The only other way I could think to make a bunch of noise is the camshaft eating through the rockers arms, or vice versa. I could imagine this happening if you had a hardfaced camshaft (like Webcams) and didn't hardface the rockers, but I can't imagine this happening on a stock camshaft unless you had an oil-circulation problem.



If you have the option, get the old camshaft back and send us some pictures, I'm really interested in what/how it failed.

[Firey400ex]

Maybe the motor has not been running quite as strong, but I have not noticed a significant power loss.

First of all, I trust the guy who is fixing this for me. He is only charging me $100 labor to install the hotcam and timing chain. I bought the parts, so I know he is not marking them up.

He told me that there was some play at the end of the cam, and it has a blue spot from where the engine got hot at one point or another. He was describing this to me over the phone, so it it kind of hard to understand.

I will get the old cam and take some pics and post them on here for you guys who are interested. The quad should be ready Wednesday.

I am just ready for this nightmare to be over!!

[Firey400ex]

Okay friends. Help again. The part that was making the noise is the compression detent roller (right behind the flange on the cam). It has alot of play in it, and it is rattling like crazy. I have the cam inf ront of me right now.

MY QUESTION IS: The HOTCAM has NO DETENT ROLLER on it. my tech who is fixing it said to just go back to stock. Do I need an additional part for the Hotcam? Why isn't it on here? What is the deal?

[Firey400ex]

Is it cool to run the motor without the decompression mechanism? I called Hotcams and they said it is no problem. Then on the other hand, my tech said not to do it. Anyone had this same problem?

[Ruby Soho]

its fine

[Fenix169motox]

yeah i've had a hotcam in mine for about a year now and it starts up fine w/o the auto decompression thingy

[Firey400ex]

OH MY GOD!! My tech called me up today and said he has the new timing chain in, the new tensioner in, the new hot cam it, and the decompression pin and spring out. IT IS STILL MAKING THE SAME NOISE! He said he has had the piston out, head off, plug out and everything, and he has no idea what is making the noise. He aslo said he has adjusted the valves several times.

When it is cold and first cranked, the engine is quiet. As soon as it starts to get warm the noise starts (sounds like loose change vibrating on top of the engine) (gets lounder with higher revs).

PLEASE HELP! I am over $400 deep in this problem trying to get this noise fixed. I can't shell out anymore money.

[sc400ex_rider]

LOL those people arnt called tech's there called parts changers. he will get it right eventually. i wouldnt pay for all those parts he replaced.

[procircuit406ex]

My 400 does the same thing. I plan on rebuilding it this summer so I might find it then. Exact problem as you..no power loss but the sound kinda pisses me off...

[Firey400ex]

Have you still been driving it? How long has it been making the noise?

[procircuit406ex]

yeah ive been riding it..for about a year now

[Firey400ex]

Hey guys, what are the chances that a brand new timing chain with a new tensioner would rub on the guide rails and make noise. It does not seem possible to me, but I am seriously pulling my hair out over this problem.

Also, it there any way the timing chain guides could bend and the chain would rub? :eek2: :eek2:

I just went back and read EVERY thread on engine noises all the way back to 2001!! I will get this fixed one way or another!!

Procurcuit, it makes me feel a little better that you have been riding it for a while with the same problem and nothing has broken.

[procircuit406ex]

Yeah it started about ten minutes into the ride last March and nothing has happened yet...in the higher RPM's I would like to hear my bike instead of this noise though:mad:

[Firey400ex]

I'm not going another weekend without riding. If I can't figure out the problem by Saturday, then **** it. I will just ride it until it breaks. I will let you guys know what the problem is if I can find it.

[CSR400EX]

did he take the whole decompression mechanism off the cam?? and also, hotcams do make a litle noise, that is just the nature of them.

[86 Quad R]

at this point its hard to say what the problem is. kinda hard to diagnose without actually looking at it.

since the engine is an older one, it could be worn timing chain guide rails, piston to cylinder clearance and/or the valve cover/rocker arm assembly.

did the mechanic thoroughly inspect the rocker assembly? alot of parts up there and some of them could be out of spec.

[Firey400ex]

What do you mean the "whole decompression mechanism"? I thought all it was is just sprind and plunger type thing. Is there more than that?

The shop opens on Tuesdays. I have been writing everything down that all you guys have suggested. I am taking the list to him tomorrow and we are going over everything from the motor mounts to the valve train. I WILL figure this out one way or another. Thanks for all your help!!

Please continue to give me suggestions if yall can think of anything else.

[X400EX]

Firey400ex,

I have a 2006 400ex with EXACTLY the same problem. I can't figure out what's wrong with it.

The noise started after I rebuilded it this summer after my tranny broke up.

I've installed this new stuff in it and it started to make this noise without any apparent reason :

- Hotcams
- 11:1 Wiseco Piston
- DID timming chain
- Sparks X-6

After I've rebuilded it, the sound started. I've tryed many times to adjust valves, even really tight... I've also completly rebuilded the motor another time cause I've broke the tranny again 2 weeks later. :mad:

I really can't figure out what's wrong. My 400ex works very well thought and gives great power.. Only that noise which pisses me off... I'd really like to fix that someday!

Thank you for your investigation in this problem.

[CSR400EX]

you should remove everything that i circled in the pic below, if he didnt, then you need to
http://i220.photobucket.com/albums/dd193/CSR400EX/decompressor.gif

[exrider12]

do you have a skid plate?

[John451]

I mean, I've never had the problem before, but I'd say that it might be some bearings somewhere in the engine. I think that it might be either the ones on the camshaft, or the crank (dont do that one unles you're completely sure) Also it could be an oblonger hole in one of the rockers. Look down the valve guide and make sure nothings in it or whatever. Idk, I'm usually the Dr. House of Dirtbikes and 4 wheelers, but you have me stumped on this one.

[Firey400ex]

No, I do not have a skidplate. I know they can rattle though.

The noise is FOR SURE in the top end. It sounds just like stretched timing chain, but it is not. I am stumped too guys. I was thinking about just saying f*** it and buying one of those brand new heads ff of ebay for $350, but I know this is just a stupid small problem and I can't put my finger on it.

I want to keep riding it, but the noise is VERY loud:eek2:

It has tons of power. If a deaf person rode it, he would think it was the best thing since sliced bread!

Thanks for the suggestions guys, I keep checking things as you tell me. Keep em coming, no suggestion is bad suggestion. We will get to the bottom of it eventually!!

[John451]

Haha, sry, I really cant tell what it is from just hearing about it. I'm sure I would be able to figure it out if I could work on it. It's just so hard to figure out when I can't hear it. It might be that when it warms up one of the heads warp a lil bit and that gives the rockers and or cam to wiggle. Because if they didn't mix the alloy enough and the didfferentn ores are just patchy they expand and contract at different heat points making it temporrarily warp. But I'm not too too sure. I can't believe noone knows how to fix that, out of the thhousands of 400's around noboddy's figured it out.

[Firey400ex]

I am replacing the valve cover/rocker arm assemply tomorrow. That should eliminate several things that can potentially make noise. I will keep yall updated.

If that dosn't fix it, I am going to post a video of it running, and maybe one of you prodegys will be able to identify it.

[JOEX]

This may be a long shot...

Has the quad been wrecked? Possibly a bent frame?

Since the valve cover is attached to the frame and the rocker assembly is attached to the valve cover it may be possible a tweak in the frame could affect the alignment of rocker assembly.

Maybe:p

[Ruby Soho]

Originally posted by JOEX
This may be a long shot...

Has the quad been wrecked? Possibly a bent frame?

Since the valve cover is attached to the frame and the rocker assembly is attached to the valve cover it may be possible a tweak in the frame could affect the alignment of rocker assembly.

Maybe:p

thats a good thought, i never would think of that

[X400EX]

Originally posted by Firey400ex
I am replacing the valve cover/rocker arm assemply tomorrow. That should eliminate several things that can potentially make noise. I will keep yall updated.

If that dosn't fix it, I am going to post a video of it running, and maybe one of you prodegys will be able to identify it.

Alright, can't wait to know if it's gonna fix it or not!

Good thought JOEX, I've noticed my big cover bolt lil hard to put there, but never wrecked that quad so I don't think that my frame is really bent.

[JOEX]

Originally posted by Ruby Soho
thats a good thought, i never would think of that
Quite some time ago someone else mentioned this theory in relation to valvetrain noise but there wasn't any follow up:ermm:

[chipworkz]

Here is another thought. You might want to check the valves and valve springs. If you have a bent valve or a bad valve spring (Broken or just weak), that could cause some noise. If for some reason the valve spring has become weak, it may look fine but not return the valve fast enough. There isn't any pops or backfiring through the Carburetor or exhaust is there? Since you say it has tons of power is a long shot but what the hey.:p

[John451]

The frame theory's a good thought but if that were the problem he problably would have remembered cuz it takes alot to bend thhe frame unless u hit an extremely sweet spot. Like I said and one of the other people. Check the valves, springs, and the valve guide. You may even want to take a pipe cleaner or a gun cleaning rod with one of the fuzzy screw on ends and run it through a few times that should help even if its not the problem. But ya sounds like an oblonged hole in one of the rocker arms. Ill bet you have it.

[Firey400ex]

Thats a good suggestion about the frame. I have never wrecked it, but my buddy who I bought it from hit a tree hard enough to bend the DG front bumper and break a weld on the LF lower a-arm. That was about three years ago though. The noise just started. The engine is quiet when first cranked, then starts the clatter right when it begins to get warm. There are no pops from the carb.

I will check the frame where the valve cover atttches. That is a great idea. I know that the metal expands when it gets hot, it may just move enough to couse a noise. I will get a pry bar and apply pressure to different angles of the head/valve cover and see it I can get it to quiet down.

I will keep you guys informed. Thanks again for all the help!

[Firey400ex]

<object width="425" height="350"><param name="movie" value="http://www.youtube.com/v/Jut9schi2Do"></param><embed src="http://www.youtube.com/v/Jut9schi2Do" type="application/x-shockwave-flash" width="425" height="350"></embed></object>

Test.......did this work, or do I need to post a YouTube link?

[Firey400ex]

http://www.youtube.com/watch?v=Jut9schi2Do

Listen to it. The sound is real loud towards the end of the clip. Help me!!

It has new HotCam, timing chain, tensioner, and valve cover/rocker assembly.

The valves are perfect, they are not the noise.

Excuse the jacked up looking exhaust, I was messing with the spark arrester and all the bolts were cross threaded and broke.

Let me know what yall think it is!

[X400EX]

BUMP!

Hope someone can figure it how just by the sound.. I'd like to get that thing fixed too!

Firey400ex : Just to let you know, I've been riding for 1 year with that sound, making me crazy.

[Firey400ex]

Man, I'm glad to hear that somebody else has the same prablem, and it is cool to ride it. The bike still hauls *****!!!!

[d kelley]

That sounds like an excessive piston to cylinder wall clearance problem. This noise will generally increase over time and won't affect performance to much. It is caused by the piston skirt actually collapsing or getting smaller than when new. Your mechanic should have checked this when the engine was apart. It should not cause you any problems other than the noise and likely will not harm anything in your engine any further other than the cylinder wall needing to be bored oversize which it most likely needs now anyway.

[John451]

UUHHH!!! I wish I didn't watch that because now I'm worried about mine. My 300ex has been makin that noise. AHH! Ill have to check next time. It might also just be how the spark arrestor pipes sound. I have an fmf spark arrestor with the plates. I also stripped all the bolts. I'll check tomorow and see if it really is makin the noise or if I just talked myself into thinking there was a noise. I think mine's more of a valve noise tho.

[Firey400ex]

Slowly you guys are making me feel better about this noise. I tend to freak out when I hear something unusual...........I guess it's a good thing because some can be fatal if left alone.

Thanks for the reply D Kelley! What you said really makes sense. The last thing my mechanic said was that he thought it was either piston slap or the the rod. A rod and crank is super expensive, so I'm glad you think it is just the piston.

John451, I wonder what the deal is with those bolts in the muffler breaking? It must be a common problem. All three snapped with little warning. I kinda like the way it sounds though.........even though it looks totally ghetto.

[CSR400EX]

it could be piston slap, but when my 440 got done, it made that noise from day 1 even with a new crank, CRF timing chain, new timing chain tensioner, valve job, and new stage 2 cam. your bike sounded just like mine even when freshly rebuilt. hmmmmm....

[wilkin250r]

What's your valve lash set at?

[Firey400ex]

.004 intake and .005 exhaust. I have tested it at .003 and .004, and at .005 and .006. It is definitely quieter at Honda's specs. Even with the Hot Cam.

What do you think It should be at?

[Firey400ex]

FYI........for those of you who read this thread. I rode the **** out of the bike today for about 5 hours and it did great. The noise is still there, but I am happy with the performance.

Oh yeah...........The HOTCAM ROCKS!!!!! It no longer has that "flat spot" at the end of the gears where it stops pulling.

[wilkin250r]

0.004" and 0.005" sounds about right, I don't have any different recommendations. You did set the lash while the engine was cold, right? NOT while the engine was warm?

[John451]

Originally posted by Firey400ex
Slowly you guys are making me feel better about this noise. I tend to freak out when I hear something unusual...........I guess it's a good thing because some can be fatal if left alone.

Thanks for the reply D Kelley! What you said really makes sense. The last thing my mechanic said was that he thought it was either piston slap or the the rod. A rod and crank is super expensive, so I'm glad you think it is just the piston.

John451, I wonder what the deal is with those bolts in the muffler breaking? It must be a common problem. All three snapped with little warning. I kinda like the way it sounds though.........even though it looks totally ghetto.

Yeah, I have the fmf spark arrestor one with the oval disks. I mean it sounds cool but i could have done a better job makin a new way to put them on. I put the screws in from the inside and the disks then the back plate and nuts. So now its gona be annoying to add disks. But it holds. Sounds cool but not too throaty : / might geta white bros. What does the spark arrestor do for the bike anyways?

[bartlettracing]

clean the screen in the oil tank .... the topend might be starving for oil .....

[Firey400ex]

I pulled the oil hose where it flows into the head, and it was sqirting everywhere, so I think it has good flow. Where is the oil screen? I should check it anyway. I have never done it before. Do they get clogged easily?

The spark arrestor keeps the tailpipe from shooting fire...........I think.

[HondaEXrider22]

I have a similar problem. Only at idle though. Sounds like a chain is being slapped on the side of the motor. I havent had any decrease in power or anything, and it hasnt progressed, so I am just riding.

[mikecancu812]

I think the motor sounds good. It sounds just like my Cannondale.

[John451]

Ohhh, does yours have the plates that supposidly increase hp? And if it does have you changed it and noticed a difference?

[ohsobad_chevy]

My 400's valves were pretty noisy and with hotcams, even louder, but judging from the video, the noise was definately louder than normal. I hope you get this thing figured out, man and please let us know what the fix was.

[X400EX]

I just watched the video.

:eek: :eek:



I got the same, exact noise. Same, same thing.

My 400ex started to make that noise after I've rebuilt it.

Only difference is the new stuff there :

- Wiseco 11:1
- Hot Cams Stage II
- Did timming Chain
- X-6
- Uni

That's all the mods I've done and it has been knocking since that time. I've adjusted the valves so many times, even very tight without any difference. It would only go well cold and then hot, the noise is back again.

I hope so much that someone can figure it out! Doesn't seems to affect the motor since I'm riding it like that since last summer, but that sound is silly.

[procircuit406ex]

Did you ever find out what it was?

[Misfit400ex]

hmm mine has a sound kinda like this too, i thought it was the aluminum air ducts vibrating since i bought it with them on there, and it sounds like vibraiting aluminum. ill get a video of mine posted tomorrow. i'd like to know what the noise is myself... seems alot of us have the same problem..

[airman88]

Holy **** Mine does the same thing, it has been doin it for a LONG time and it still has a **** load of power,
i got
JE 10.8:1 87mm 416
hotcams stage 1

i always thought of it being the rocker arms, my brother had the same problem with his and he put a new rocker assembly on it and it still did it, so i didn't even bother with mine, but here is the sound clip


http://www.youtube.com/watch?v=LZNJuFI-7Co

[Misfit400ex]

its hard to hear over the aftermarket exhaust. i got a stock pipe on mine, you can hear it better i think because of that on the video. ill make it tomorrow.

[Misfit400ex]

aparently its a common 400ex noise, the phantom ping. lol... if a strange noise that doesnt effect performance at all is the 400ex's big problem.. then thats cool with me.. at least it isnt like the warrior, and have the motor mount be perpetually breaking..

[Firey400ex]

Yeah Airman and Misfit...........we all got the noise going on. After a few more opinions and a few weekends of HARD riding, I think it is the wrist pin bushing or bearing (whichever it has). ..............It still runs great though. I was thinking about replacing the piston and wrist pin, but I don't want to get machine work and all the other stuff done. I don't want to spend more money trying to fix a noise that dosn't effect performance.

Does your noise get a bit louder when you have been riding for a while and the engine is real hot?

Does anybody know if it is possible to replace piston, rings, and wrist pin without getting the block machined?

[Firey400ex]

Oh yeah, I just ordered a HMF exhaust because I heard it is loud as ****. I'm hoping it will cover up the tick sound :p :macho

[John451]

Well you can pick up a cylinder honer for about $15-20 and just hone it andd keep it the same bore. If there's a small engine repair shop around they will do it for 10cents a stroke and they should do 100-150 200 if its bad. So that's 10-20 bucks. If u do that u should get an 11:1 high comp piston just to make you're quad even more amazing. It adds more power than the pipe and it's the same price as the stock piston. Runs about $80. That's a sweet idea with the pipe lol. I'm taking my silencer off and runnig a pipe out. It sounds awesome with it haha. I stood 3' behind it and each powerstroke felt like someoe was punching me in the chest.

[Firey400ex]

So..........let me make sure I have this straight. I can buy a honer and hone the cylinder myself, then just drop in a new piston, rings and wrist pin?..........no machine work necessary? Have you done this? It seems like I've heard before, that I needed to get it bored out if I'm putting a new piston in.

If you are sure it is cool to do it that way, I will definitely get started on that pretty quick. It sounds like a good inexpensive fix.

Oh yeah, what brand piston did you use?

[Firey400ex]

So..........let me make sure I have this straight. I can buy a honer and hone the cylinder myself, then just drop in a new piston, rings and wrist pin?..........no machine work necessary? Have you done this? It seems like I've heard before, that I needed to get it bored out if I'm putting a new piston in.

If you are sure it is cool to do it that way, I will definitely get started on that pretty quick. It sounds like a good inexpensive fix.

Oh yeah, what brand piston did you use?

[Misfit400ex]

http://www.youtube.com/watch?v=tNLxslSxHok

[John451]

Well when my engine blew I just honed it and put a new ring in. But since the crown's knocking. you'll need a piston too. You'll have to check the old one and see if its been bored already so you get the right fitting one. And you might want to talk to the guy who did the work on it and ask him about the high comp. 11:1 piston to see if it will work with everything else and if there will be any compression ignition (when the gas ignites from compression then the spark goes after) if the head was shaved it might not work right. But usually weisco makes it. They're on ebay for around $80 with ring, pin, and circlips.

When I rebuilt my dirtbike I only did the hone and ring and it worked great. It went from barely any compression because of blowby but after it was makin great contact and was like I had just bored it. But that was because it was a 1 ring and the cylinder walls had tiny scratches. Just look and see if there's alot of damage. Since the crown was slapping it might have a little damage.

[Firey400ex]

From what you said, and from what I have found through researching all this, the engine removal and rebuild does not look hard at all. It is on my list to be the next project.

In the mean time, I drained the oil last night and replaced it with 20w50 to see if it would quiet down. It didn't seem to hurt it any. Also, there were tiny tiny tiny pieces of metal in my old oil. I'm talking Very tiny. I could barely see them. Is that normal?

[Misfit400ex]

metal in oil is never good. ever. it'd be like saying "oh yea i have little tiny bearly noticable FLESH EATING BACTERIA in my blood stream, should i be worried?"

[John451]

Well the metal isnt too good but it's not too bad. You ca still ride it but in the next 3 or 4 years it may need something. One of mine was spittin teeth out, like 1/2" pieces. Still works fine after 3 years.

[Firey400ex]

Thats good news. The specs were so small that I could only see them if I shined a flashlight on the oil. The 20w50 did pretty well on my ride today, so I think I will continue to use it.

Also, the flesh eating bacteria in my blood dosn't seem to get any worse, so maybe my bike will be okay :blah: Ha ha.....kidding.

[John451]

Lol. yeah that's normal if that's what it takes to see it. all of em get that. I'd only start to get worried if the pieces get to be like teeth AND the gears get choppy when it skips the missing one. you can feel it at that point.

[GPracer2500]

Maybe it's just me but I am not hearing whatever you guys are hearing. I just listened to those three youtube clips and they all sounded pretty "normal" to me. Maybe the exhaust sounds are suppressing the troublesome noise in the vids [shrug]. I was expecting to hear a real racket and I didn't hear it. More like this....

http://www.youtube.com/watch?v=xoRR8EHn_5E&feature=related


My old 400 wasn't exactly the quietest engine around. I originally had a WB regrind on rockers that may or may not have been hardwelded. The cam and rockers eventually failed. Obviously any problem like this would have been discovered by now.

http://i34.photobucket.com/albums/d133/gpracer2500/400EX%20cam%20rockers/P3100076Medium.jpg

http://i34.photobucket.com/albums/d133/gpracer2500/400EX%20cam%20rockers/P3100075Medium.jpg

Old oil, hot temps, tight valves, and hard running where all likely contributing factors. The last hour or so it was run like that it made one hellva racket. It couldn't have been mistaken for normal. Much more like the vid I linked to above than anything I heard in those other videos. I replaced that top end with a barely used HotCams and a used rocker cover and rockers (in good condition, previously used with a stock cam).

Before the original setup wore out I don't recall there being excessive clatter. I never thought of it as quiet though. The hotcams setup was louder, I'm pretty sure. It did have a bit of a tick to it. But it was fine.

$0.02

[edit: the clip I posted was not my bike--just some random clip I found on Youtube]

[Firey400ex]

Good post man! thanks for the reply. I have replaced my cam and rocker cover already. When fully warmed up my motor is almost as loud as yours in the clip. I think it is partially because of my Hotcam, and partially because my wrist pin is wearing out.

I need to post another video of my quad after I have driven it for an hour or so.

[greyghost400ex]

man u guys just saved alot of long nights without sleep my 400ex is making the same sound its not to loud but only makes the rattle ab 1/2 to 3/4 throttle only started about 2 weeks ago and my 400 is a 2004. no lack in performance. but a pain in the *** because i know its there. i change the oil to 20/50 and its not as bad but still there did the valves still there :mad: i have 440 kit hot cams 11:1 piston and stroker . i agree with some of u guys phatom 400ex noise. ive had the motor work done for ab 3 years now.. think we should boycott? haha :devil: anyway thanks for the info fellas saved me alot of money!!!!

[airman88]

on a good note i just replaced my cam chain, sliders and tensioner, went with crf chain... no noise... purrs like a kitten, smoothest it has ever ran since i bought it....

[91trx250]

well I'm no quad expert or anything but the two things that come to my mind when i seen that video was earthier one of your rocker arms are warped from the heat..probably the side that had the blue spot on the cam...OR pull your spark plug and see if the tip of the plug looks like its getting it

[ryanhood1983]

So its the cam chain and or tentioner..

[John451]

Well, there's alot of things it could be. The worst thing that it could be is the piston skirt knocking on the cylinder walls.
What I would do is take the valve cover off and look down the camchain slot in the cylinder with a flashlite and see if you see any signs of the chain slapping it. If it's not that then it's problably the rockers.

[steve181]

Its a honda motor

Eventually they will all sound like this <_<