Knocking sound under load

[StreetLegalEX]

Sorry to post this because I saw some topics about this but I couldn't find the answer.

Well I'll explain the situation.

My 400ex has been honed, has new piston, clutch.
Did a couple of tanks before being hard on her, so I think she has been broken in ok.

After a long ride (bout 200miles) I started noticing a rattle noise.
Noticed it when giving it full throttle when my revs were low.

Thought it was my key, slapping the plastic.

Thought that for a few weeks, till I removed the key.

So what is the case.
Engine runs fine in neutral, without any noise.

When I start riding I still hear no rattle. (half throttle)
But when I give it full throttle it makes this knocking noise. Keeps doing that until my revs get higher.

What could this be?

I run 98 octane fuel, on a standard bike so I think we can rule that one out.

Sounds like your clutch is going. :(

Also this thread might help you. ;)

http://www.exriders.com/vbb/showthread.php?s=&threadid=49179&highlight=knocking

[StreetLegalEX]

So maybe if I adjusted the clutch it would be gone?

Going to try that.

[Rip_Tear]

it might be nothing... Just in the back of your head, I always think something sounds wrong, I know its not good to just assume its okay, but unless your really worried, or its affecting preformance, I try not worry too much. I do keep an eye on stuff, but most of the time its just nothing.

[JD400exrider]

Check your skid plate if you have an aluminum one. Mine rattled for a while. Put some thin foam between frame and plate. No rattle. ;)

[StreetLegalEX]

No it's really coming from the engine, a loud, metal, knocking.
And it really only happens with throttle wide open, when I'm easier on the throttle it runs ok.

Also appears to be coming from the left side of the engine (where transmission etc, are).

if i was you i would pop off the left side case cover and check it out and make sure everything looks a-ok

[Rip_Tear]

Originally posted by nacsracer27
if i was you i would pop off the left side case cover and check it out and make sure everything looks a-ok

Definately a good idea!

[DEAL]

Mine used to do it under load , it turned out to be my chain slapping my skidplate.

[Stevie-D]

or your engine could end up like mine. it was tickin under load like yours...then after i let off after pinnin it, it would make a whirrin sound, this is after it burnt enough oil to fuel a barge for a month. then it wouldnt start, then it went to the shop, where im still waitin for them to look at it...


just dont want you to do the stupid thing i did by ignoring it:rolleyes:

[Scott-300ex]

how did you gear your 400 for the street?

and how fast does it go?

do you have a spedometer?

[Evan400ex]

I have that same knocking noise in my 400ex,...and it is pretty much brand new still. It sounds like valve clatter to me.

[StreetLegalEX]

Well my Ex has standard gearing for the streets (15 front dont know about the back) will hit about 120km/h.

About the sound, I kind of ignored it, but its still there and i am beginning to worry.

Actually it's more like a metallic noise, scratching.

I thought about my piston rings....please tell me this is not the case. What are the symptons of bad piston rings? Because I didn't lose any power and it actually runs fine apart from the noise. Starts up on first punch of the starter button, idles nice, revs nice in neutral, only under load the noise is making me crazy!

What do you guys think?

[SGA]

Knocking under a heavy load sometimes means a lower rod bearing. It is a deep knocking sound. That is rare on a 400ex though.
A piston pin will tap at idle, then be silent under load.

Valve clatter is a lighter sound, makes a good clatter when it happens. Have you adjusted you valves since your rebuild?

[StreetLegalEX]

Well, problem solved. The guy I bought my quad from appears to be a real dumbass.

Here's the list.

- Cilinder bolts were NOT tight (could be loosened by hand!)
- The bolts that hold the sprocket on the camshaft were also loose
- My timing was off
- Some gaskets were missing, others used twice and not original Honda
- Head gasket was blown
- 3 out of 4 screwthreads have been wasted, so now I can't securely tighten my valve-head anymore

List is actually even longer than this.

Anyways got most of the above fixed and it runs like a charm now. Still have minor oil leaks from valve-head though...

[StreetLegalEX]

Well, quad ran good for a few weeks, now I have BLOWN MY HEAD GASKET again!!!!!!!!!!

The dude that repaired the quad said he didn't get it. He changed all bolts and gaskets, torqued everything down to spec etc. He also checked if the cilinder was flat.

What can be the problem here? My quad is still at stock bore (although cilinder has been honed+new piston) and all gaskets were premium Honda....(the guy who fixed it did about 30 other xr400 type blocks without any problems...)