Slapping noise in the top end? Wth?

[400exhotwire]

im troubleshooting my girlfriends 400ex for her. we are having issues with a "slapping" like noise almost in the top end.

it occurs consistantly, about every 1 second roughly. REGARDLESS of rpm, the noise stays consistant. slap.. slap.... slap... you can let it idle, or rev it up, same consistancy.

what could possibly be moving at the same speed, regardless of engine rpm? her valves are in spec, oil is fresh, power is fine, no smoke, no leaks, nothing to help me..

mods; lid off, 11:1 piston, hmf slip-on.

[400exhotwire]

i took a video of it, kinda hard to hear it, but you can make it out.

i listened closer, it is NOT as consistant as i thought. however, it does not fluctuate with rpm range.. it will change pace at idle sometimes.

i cant think of what this would be. obviously its a moving part, but if its hitting/out of spec, it should be consistant with something i'd think?

let me know if i should upload the video. someone told me they do this with aftermarket cams and the decompression pin removed? this bike has a stock cam.

[nakomis0]

Hey does it sound like this!
http://www.youtube.com/watch?v=-AMoU17xU5Y

If it does thats a cam chain tensioner.

[fordman125]

hope that works out better for you than it did me every one told me i was nuts and didn't hear anything so i just keep riding till it died turns out there was no oil going to the time end and now my head and the rest of the top end are toast:mad:

[400exhotwire]

so what was your issue to cause failure?

my noise sounds like i was tapping a wrench against the case gently? ill upload the video sometime tonight.

[MtnEX]

I've had a noise too... for over a year now...

Mine's random sounding though... and seems to crop right after a fresh oil change.

http://www.youtube.com/watch?v=Ep3pi9K-Fn0


I don't know if it's the cam chain getting closer to the service limit or something to do with the decompressor mechanism in the head.... but I figure one of the two...

[400exhotwire]

listen close to my video. its kinda hard to pick it out, but i can hear it. its a "slap" noise. after thinking about it, i guess it could be the chain rolling over at idle with slack, and ocassionally hitting a guide hard enough to make it slap the case internally?

it would explain why its never a consistant slapping.

http://www.youtube.com/watch?v=o7Tr2S4c8AY

closest sound i can relay for you to listen for, is like someone tapping a 1/2" wrench against the case. its not a fast tapping like out of spec valves, p-v clearance, ect.

[MtnEX]

Seems like all 3 of us have a little different sound.
But it's hard to tell.


I think it would be a bit easier to pick out your noise if your idle speed wasn't so high and if you didn't have the whistler intake...

[MtnEX]

Wait a minute... after several tries... I think I hear it... like every second or half second...

[400exhotwire]

Originally posted by MtnEX
Wait a minute... after several tries... I think I hear it... like every second or half second...

yep thats it. its a fairly faint sound, i think its linked to the tensioner.

i forget on the 400ex, are they auto tensioners or manual? we put on a new timing chain for her about 2 rides ago. perhaps it stretched and it didn't tension properly?

im going to tinker with it later and see how the tensioner looks.

[mmbintn]

The tensioner is an auto tensioner, it will keep tension on the chain as long as it can. So, if thats it, either it is worn out or the chain is bad already. I suspect the tensioner would be bad before a new chain though.

[MtnEX]

It's pretty easy to check the operation of the automatic tensioner. Take it out and have at it.



On a side note, does anyone know what the chain positioning is supposed to look like when you look down at it from the top?

I was able to get a good look through the right intake valve cap opening.

[MtnEX]

Originally posted by 400exhotwire
yep thats it. its a fairly faint sound, i think its linked to the tensioner.

i forget on the 400ex, are they auto tensioners or manual? we put on a new timing chain for her about 2 rides ago. perhaps it stretched and it didn't tension properly?

im going to tinker with it later and see how the tensioner looks.

Did you ever pull out the tensioner?

Did it work?

If it did, when you went to put it back in with it fully extended out... how far away was it from where it needed to mount?...

(before you realized it had to be retracted to get back in)



Also, for what it is worth, finally after a whole year, I have came to the final confirmed conclusion that my engine noise is the decompressor.

I've had several professionals tell me so, but only 2 actually had an explanation for it... this last one being the better of the two... and that coupled with re-doing my carb makes me understand now.

There is nothing wrong with mine... obviously since it's been doing it a YEAR... but specifically because my carb settings are causing it to come and go.

My carb has not been right since I had the work done... and what is going on is an idle fluctuation that the engine goes through that gets my decompressor tapping.

[storms400ex]

my decompresser makes noise sometimes too, there was a thread awhile back on how to take that piece out, i would if i knew where that thread is

[Honda#4]

I think all you guys have a faulty cam chain tensioner, i've never heard of a decompresser making noise like what I heard on them videos.

[400exhotwire]

we got a new tensioner, was not the issue. took it to honda and the decompressor is sticking i guess. my girlfriend took it in and he diagnosed it to that.

[MtnEX]

They'll up your idle RPM and charge you $100 :blah:

[Firemedic552]

Originally posted by 400exhotwire
listen close to my video. its kinda hard to pick it out, but i can hear it. its a "slap" noise. after thinking about it, i guess it could be the chain rolling over at idle with slack, and ocassionally hitting a guide hard enough to make it slap the case internally?

it would explain why its never a consistant slapping.

http://www.youtube.com/watch?v=o7Tr2S4c8AY

closest sound i can relay for you to listen for, is like someone tapping a 1/2" wrench against the case. its not a fast tapping like out of spec valves, p-v clearance, ect.
mine sounds very similar.

[MtnEX]

How did it all turn out?