2007 400ex issues

[midnightride42]

I picked up a 2007 400ex with the valve broken and melted on the piston. The head was damaged right by the valve hole.

I picked up a 2002 head and valve cover.

I took the jug and go it bored and honed out to a 416 higher compression piston. Wiseco piston.

I replaced the piston, and put everything back together.

I made sure the lobes were facing down when installing the stage 2 Hotcam, with the mark on T on the flywheel side.

Now when I start it up, It will not start.

if you lower the choke arm and apply the gas you get a popping sound in the air box. and puffs of somke out the slip on pipe.

things I've done:

-new battery.
--new plug.
---checked connections.
----re did the timing 4 times onces with flipping the cam with the lobes facing up.
-----I'm getting fuel.
------I'm getting spark. (put the plug on the frame and I can see a good constant arc.
--------took the plug out and put a rod down in the whole and put the T mark back on, it is Top Dead Center when the mark is at T.

If you put a socket on the bolt on the flywheel you can turn it freely...so it isn't binding up or anything.

I'm really lost now.

Does anyone know if the valve cover could be different in the 2007 vs a 2002? Wasn't sure if the parts in the valve cover have different clearance etc that would cause my issues of not starting up the bike.

Like I said it just turn over, but wont start up. If you hold the gas lever in with choke all the way up you can feel a ticking in the gas lever and hear in the carb. at times it puffs big circles out of the slip on and you can hear popping sounds in the air box...sometimes it's really loud.

Thoughts, suggestion.....
Thanks.

[RoadRage77]

When you say you did your timing, After you found you're T mark you did make sure the timing marks on the cam gear are set correctly,Right? There is 3 marks on the gear... 2 marks are 180 degrees from each other and they run parallel with cylinder and the other mark faces upward. ( hopfully you have a book easier to see then explain)...
Hmm.. key on ? Cut off switch on the bars is in the middle? not to the left or right??
How about the compression release in the head. ( its a little plunger with a spring)..
What kind of carb are you using ? is it cleaned out ?

Is the plug wet( getting fuel to it ) ????

Umm.. let us know.. we'll try to go from there... by the way.. did you check your fuse?

I just went thru a big problem like this on my friends bike, come to find out it would not start cause they flipped the bike, and a wire up by the starter swith/headlight switch on the handlebars is messed up.

[midnightride42]

It has the stock carb.
Plmug has fuel on it when I pull it.
The compression spring is not there.

As for the cam, I made sure the lobes on the cam were facing down and and the marks were lined up with the head.


Beginning to think maybe the valves on the 02 head are bad because of the backfiring/pooping sound in the airbox.

I made sure the key is on the ON spot, and the kill switch is centered. I'm getting spark so I ruled out the switch.

Anyone else have thought suggestions?

[jasonwayne222]

check ur valve clearances, do a search for the specs its a real quick and easy thing to do and it will solve ur question on the geometry of the valve cover.

And if you want to check to see if ur valves are bad just take off the head and fill the intake and exhaust ports with fuel and watch the valves and see if it leaks. if it does get some lapping compound and lapp them in until they dont leak.

also u need to find out why it had a valve hit the piston. I had this happen to me once when i left out one of the cam stops. the bearings came off the came and made the valves open wrong.
U dont want this to happen again if it happened before.

Take off ur carb and hit the throttle. it should shoot a stream of fuel about a foot in the air. if it is then the main circuit should be good. it could still have a clogged pilot if it wont idle. take the jets out and clean them. run some wire through them or whatever u got to do.

and u dont need the decompression mech. for the cam u have.

[hondaracing_13]

Did you check out the 02 head before you installed it.

[midnightride42]

Cam stops? You talking about the little things where the decompression spring sits in/under?

[jasonwayne222]

no, there are two dowl pins that are on the outside of each of the cam bearings. they keep the bearings from walking off the cam. just being sandwhiched by the valve covers are not enough to keep the bearings on. trust me I know.

They are easy to spot and make sure they are there.