400ex engine noise.

[ben300]

So in regards to my previous thread, i had my 400 rebuilt. 11:1 wiseco, stg2 hot came, crf timing chain, new valve-train. it runs, and runs good. But it makes a weird noise. not im not talking about the valve tick (which got louder from the stg 2 came. which i expected). its making a weird knock noise from the bottom end.

at first i though it might either be a rod bearing or or a crank bearing, but it 1) doesnt do with when its cold, only after it warms up, and 2) if it was a crank or a rod bearing, i would expect it to get a lot worse as the motor climbed through the RPM's but it doesnt. i cant hear the noise anymore once its on the throttle.

i embedded a video i took of the motor running. the noise that i feel as a knock is not as loud in person as it is in the video (taken with a galaxy note 3). I dont know if this noise was there before and its louder now because of the more aggressive cam? or it was there and now im just over analyzing any small noise cause i just rebuilt this. My builder checked the crank and doesnt think it was bad and thinks it cause of the more aggressive cam and because the jetting was lean.

anyone else ever hear a noise like this?

thanks for any input you guys can give me

[CJM]

Yep, I had a similar sound awhile back.

Turns out the cam was moving around in the head because oneof the dowel pins had had trouble going in and I had persuaded it slightly. Well turns out the hole was slightly out of round and the pin came out. Cam was rocking all around in there. Timing chain was also ruined and kinked like crazy. Id pull the valve cover and verify everything is good first.

I also had a wicked vibration develop before or during the same time, quad would vibrate so much your hands would hurt after awhile. Crank was def on its way out.

[ben300]

Yep, I had a similar sound awhile back.

Turns out the cam was moving around in the head because oneof the dowel pins had had trouble going in and I had persuaded it slightly. Well turns out the hole was slightly out of round and the pin came out. Cam was rocking all around in there. Timing chain was also ruined and kinked like crazy. Id pull the valve cover and verify everything is good first.

I also had a wicked vibration develop before or during the same time, quad would vibrate so much your hands would hurt after awhile. Crank was def on its way out.

so what did you do to check it mark? or how long did it take you to find out? and like cam was literally walking balk in forth in the cam journals? this sound doesnt come from the head though. it comes from the crank. but i can truly determine where at in the crank case it is coming from.

[CJM]

Well the thing was I figured it was something related to going swimming in a lake with my 400 so I said F it and let it go ben. When I finally dug into it about 3 months later (it sat most of the winter) and found the timing chain bad and so forth. The cam was basically walking int he journals but surprisingly it didnt do any damage to anything. You could see slightly where the one pin had come out on that side and the cam made very minute marks but they were deep or bad.

I too though that it was the bottom end, did the old screwdriver trick and found it in the head however. Noises can be deceiving ya know.

Does it vibrate at all? Clearances were all good when assembled? Did you put it together or someone else? Crank bearings checked/seemed fine?

I suppose overall I coulda looked into it earlier, but I didnt really care since I was mostly riding my 450.

[LxMxL97]

My 400 made a similar noise I just thought it was another special trait the came along with the 400ex motors

[ben300]

Well the thing was I figured it was something related to going swimming in a lake with my 400 so I said F it and let it go ben. When I finally dug into it about 3 months later (it sat most of the winter) and found the timing chain bad and so forth. The cam was basically walking int he journals but surprisingly it didnt do any damage to anything. You could see slightly where the one pin had come out on that side and the cam made very minute marks but they were deep or bad.

I too though that it was the bottom end, did the old screwdriver trick and found it in the head however. Noises can be deceiving ya know.

Does it vibrate at all? Clearances were all good when assembled? Did you put it together or someone else? Crank bearings checked/seemed fine?

I suppose overall I coulda looked into it earlier, but I didnt really care since I was mostly riding my 450.

well i had someone else build the motor for me this time due to the cold and my lack of a heated garage. but the guys that built it are knowledgeable and have been building MX motors for awhile so.

theres no vibration that i can tell of. i figured if it was a crank bearing, it'd be vibrating like a CR500 ro another big bore 2smoke. and the noise is not noticable as soon as you give it any RPM's past idle. When you start giving hte motor gas, all you can hear is the motor and the cam tick from the more aggressive came.

been talking with the guys that did the motor. one of them is gonna look at it this weekend. we're wondering if it has anythign to do with the CRF cam chain being wider than the stock 400ex cam chain. we're also wondering if it has anything ot do wiht the break in period on the cam. The hot cam instructions state that it requires 30 mins of actual "ride" tiem break in time. i may have about 20 minutes total on the motor since its been put back together.

the other idea we had is it may have somethign to do with teh cam chain tensioner since we didnt replace it during the build.

either way, this weekend im gonna tear the head off and inspect teh cam/cam chain/cam journals/head dowels and see what i can come up with.

[ben300]

My 400 made a similar noise I just thought it was another special trait the came along with the 400ex motors

ever have any problems from it?


see thats what i thought. i dont know if its been a noise thats always been a part of it and im just now noticing it and being a hypocondriac lol..or if its something new.

[2001400exrida]

nothing on that vid sounds out of normal to me. I can't really hear it over the pipe though. the tick is louder than i like, i know everybody says these things tick ,but both my 400's i've been able to make quieter than what i'm hearing in your video. Many times when people say the tick is normal, there's often cases where it's adtually a tick from something like the cam chain, or the dowels like CJM mentioned. I would make sure your tensioner is working as well. What fuel are you running with the 11:1? You might want to consider going up to a higher octane if you're getting detonation it will knock.

[LxMxL97]

ever have any problems from it?


see thats what i thought. i dont know if its been a noise thats always been a part of it and im just now noticing it and being a hypocondriac lol..or if its something new.

I only had the motor for about 35-40hrs of total ride time but it ran great and pulled strong never had a problem I say pull the valve cover since it's very easy check the dowels make sure they are there but I wouldn't go any deeper in the motor I would just run it how it is

[ben300]

nothing on that vid sounds out of normal to me. I can't really hear it over the pipe though. the tick is louder than i like, i know everybody says these things tick ,but both my 400's i've been able to make quieter than what i'm hearing in your video. Many times when people say the tick is normal, there's often cases where it's adtually a tick from something like the cam chain, or the dowels like CJM mentioned. I would make sure your tensioner is working as well. What fuel are you running with the 11:1? You might want to consider going up to a higher octane if you're getting detonation it will knock.

ya, the tick is a little loud, but i attribute that to three things 1)crf cam chain, 2) the stage 2 cam, and 3) the valves need to be readjusted after break in (which i planned on doing)


im gonna check the tensioner and the dowl pins. liek i said. the knock or the "boop boop boop boop" as my buddy calls it doesnt get louder, adn its actually louder in the video than it is in real life.



and as for fuel. when i initially fired it up, i was running some bad gas and i believe i was having some detonation. yesterday i drained the tank completely and put in a mixuture of 2.5 gallons of vp 110 and sunnoco 93 (both sold at a gas station owned by guys that run big block mods). i calculated it gives me in the ball park of 102 octane which i feel confident running at 11:1 compression.

my builder says he wants me to see what it sounds like with a larger pilot jet in it and that it might be to lean. it probably was. i ahve not changed jetting yet and am running a 40 pilot.

so its like, if i can find anything in the head, do i do what LxMxL97 says and just not worry bout it till something actually happens? which something may never happen?