won't start; valve seals?

[bbender85]

so we picked up another 400 recently and ran it good for the first time this weekend. ran all day saturday, then went to start it sunday and it won't start.

- kill switch isn't activated (lol)
- has spark
- gets fuel
- checked the valves at TDC and all have the right lash (so i assume the timing didn't jump?)

i did notice this:

with the valve caps off and slowly turning the crank manually, i hear alot of "seeping" on the compression stroke, coming from the right side intake valve; do you think we dropped a valve seal? would this make it not start? what else could it be?

[honda400ex2003]

if it dropped a valve it would not start for sure. but you cant drop a valve seal. it could be wore out but it should still run. Check your plug for oil on it and see. that would be the second best way to tell or do a leak down test on it to see. even a compression test could tell you. worn valve seals cause oil to drip down on the piston causing smoke on initial startup and during hard acceleration. otherwise I can t help any more than that. steve

[bbender85]

ok, i didnt know if the seal could fail at once; i know they wear, and the symptoms of wear that you mentioned, but the run-one-day, not-the-next made me wonder if it was possible, considering the "seep". thanks for the response.

[honda400ex2003]

hey no prob bro maybe someone else knows more about it. sounds like something in the valvetrain though. The only way to tell if you dropped a valve is to open er up and that is not just a hop skip and just as i am sure you know. I will think about this a bit more and see what I can come up with. steve

[Sanddraging28]

any chance that the what you hear is coming from the head gasket????

if it dropped a valve you know know it for sure!!!!!
the valve seals would not cause it not to start.

check the cam timing. open the side ports and put the motor on TDC and make sure all the rockers have some wiggle.
i would check the compression and go from there

[honda400ex2003]

could be a blown headgasket as sand said, or even an exhaust leak possibly. did you have the plug out or in when the noise was heard? steve

[bbender85]

check the cam timing. open the side ports and put the motor on TDC and make sure all the rockers have some wiggle.


- checked the valves at TDC and all have the right lash (so i assume the timing didn't jump?)


i am going to try to get ahold of a compression tester and go from there.



did you have the plug out or in when the noise was heard?

lol, plug was in.


thanks again

[honda400ex2003]

Sounds good LOL just figured I would throw that one out there. LOL, good luck, steve

[bbender85]

so i just popped the valve cover off:

on the compression stroke that "hissing" comes from the timing chain side... i am thinking the head gasket is junk somewheres around there. just talked to a buddy with a compression tester, so hopefully i can get ahold of it this weekend. :(