400ex Wont start after new timing chain install

[Rhino0039]

Alright this is not my first rodeo with this bike I've raced it for years and rebuilt the top end time and time again and I have NO IDEA what has happened this time why it wont start. Ok this is the story I went riding the timing chain was getting really really loud I figured it was going to go anytime well the bike just stopped on me at one point after a weird noise well I get it in the shop the chain didnt break but the cam bolts were extremely loose and the chain was really streched. So I order a new heavy duty timing chain and new cam bolts I took the head off to make sure no bent valves or anything everything is fine... So I go about my business and put the new cam chain in and new cam bolts on the cam put it back together and everytime it sucks threw the exhaust when I go to start it..?? it sounds really weird It doesnt even sound like it wants to fire at all I have spark im gettin fuel and it has compression but is not firing at all just spins over and over I've never heard this before I've tried flipping the cam 180 degrees multiple times even tried to advance/retard it a tooth or so and I cant get anywhere still the same. I've tried replacing the cdi box with my buddys and it still wont start so PLEASE anyone any advice would help has this happened to anyone?????

[projectgoon1]

i would check these things if you havent :

pinched or clogged fuel tank vent hose

is your fuel still good

is your air filter clogged

check to see if your pilot screw is ajusted right

make an air leak in the intake manifold

or the valve decompressor could be malfunctioning

these are a few things i would check be cause a similar thing happed to me and it was a pinched vent hose on my fuel cap from when i was twisting my cap back on and it got bent

[Honda5]

flipping the cam 180 makes no difference they fire on both strokes. my guesses are

1) keyway stripped off (easy check with a screwdriver down the sparkplug hole)

2) bent valves, they have not been noticeable but bad enough to not run

3) using the wrong marks on the timing gear (not likely, sounds like you know what youm are doing).


but I really think it's the keyway... let me know what it is when you get it fixed.

[Rhino0039]

1) keyway stripped off (easy check with a screwdriver down the sparkplug hole)



My Keyway what do you mean? I'm almost positive the pistons turning over b/c its sucking in threw the exhaust

[Honda5]

if the keyway stripped the flywheel will be off and the timing mark will be in the wrong spot.

here is what to do;

pull the gas tank off then pull the sparkplug. put a screwdriver down in the hole then with a socket spin the motor (be careful the screwdriver doesn't bind) and make sure the piston is at it's highest point when the timing mark is at the "T" in the inspection hole.

I hope this helps, if not let me know and I'll try to explain better.

[Rhino0039]

[QUOTE]Originally posted by Honda5
[B]if the keyway stripped the flywheel will be off and the timing mark will be in the wrong spot.

Hopefully I'll get to mess with it tom. evening but are you talking about the sprocket on the end of the crank that runs the cam chain? I didnt know there was a key way on that if you are speaking of that

[rideracelivemx7]

lol no he's talking about a broken key in the flywheel. the woodruff key that holds the fly wheel on the crank. that actually might sound right I broke bthe woodruff key on a kodiak 400 that I was working on. it barley frigen ran but the key binded a little bit so the flywheel still moved but oh was it a weird sound. then go to the point were it has spark but didn't start up and I knew the timing was right. you mentioned you had a weird sound. that mighht be it. check it. just pulk off the cover and see if the flywheel moves. don't bother messing with inspection port. if the key did break there wouldn't be any damage. they piece of thekey can't escape. and only scaring will be there. there made to sever in half safley if they do go. well check that and let us know how it goes

[Rhino0039]

[QUOTE]Originally posted by Honda5
[B]if the keyway stripped the flywheel will be off and the timing mark will be in the wrong spot.

Sorry its been a couple days but I got to it last night I took the side cover off of the flywheel the key doesnt seem to be sheered it spins freely one way and locks up and spins the crank the other idk if that makes sense... well other words it seems to be working correctly as far as I know. Should I have taken the bolt out of the end of the flywheel to see?

[Honda5]

did you check to see if the timing mark on the flywheel and the piston are at top dead center at the same time? the key could be sheared off but you won't know unless you pull the flywheel.

[400exrider707]

You have more problems than a cam chain. If you were running the machine and it suddenly quit, but the cam chain wasn't broke, you have something else that went wrong. You need to find out what that was. Please explain the scenario a little better. You're lucky you caught that with loose cam sprocket bolts. That would have been a disaster. Are you sure the valves aren't bent? Try a leakdown test. I bet your cam chain was stretched so bad it jumped time and you may have bent valves. Have you ever replaced the cam chain tensioner?

[Rhino0039]

Originally posted by 400exrider707
You have more problems than a cam chain. If you were running the machine and it suddenly quit, but the cam chain wasn't broke, you have something else that went wrong. You need to find out what that was. Please explain the scenario a little better. You're lucky you caught that with loose cam sprocket bolts. That would have been a disaster. Are you sure the valves aren't bent? Try a leakdown test. I bet your cam chain was stretched so bad it jumped time and you may have bent valves. Have you ever replaced the cam chain tensioner?

Yep brand new cam chain tensioner and brand new HD chain and I got new bolts for the cam sprocket and locktighted them this time. I have no idea I was in the bottom end nothing looked out of the ordinary tho its getting everything it needs to start but wont? I held a piece of paper up to the intake it sucks it in and the exhaust pushes a little out isnt as strong I dont think..? but it wont even think about starting just turns over and over and over doesnt even pop

[400exrider707]

Originally posted by Rhino0039
Yep brand new cam chain tensioner and brand new HD chain and I got new bolts for the cam sprocket and locktighted them this time. I have no idea I was in the bottom end nothing looked out of the ordinary tho its getting everything it needs to start but wont? I held a piece of paper up to the intake it sucks it in and the exhaust pushes a little out isnt as strong I dont think..? but it wont even think about starting just turns over and over and over doesnt even pop


Lets get back to basics then.

Spark
Compression
Fuel
Air

I'm guessing fuel and air are covered

You need to do a compression test, or better yet a leakdown test.

Check for spark as well, it's simple enough.


What cam chain did you get?

[Rhino0039]

One thing I havent checked is compression test I dont have the equipment gunna have to get it from a buddy but I'm getting fuel carbs clean as a whistle and its got spark checkd that a hundered times I've rebuilt this motor alot and this is just blowing my mind ive never heard it sound like this not ever even once pop wanting to start. The cam chain I have is the heavy duty version its really wide its got like 4-3 links wide

[Honda5]

in your first post you said it is sucking through the exhaust. that means the crank and cam timing do not match that is the only way it will suck through the exhaust, other then a bent valve.

[400exrider707]

Originally posted by Honda5
in your first post you said it is sucking through the exhaust. that means the crank and cam timing do not match that is the only way it will suck through the exhaust, other then a bent valve.

400ex can be off of time, but it can NOT be 180 degrees out. It's impossible.

I asked what cam chain you got because you can use a CRF450 chain, which is probably what was sold to you anyways at a huge markup. They're only $35 from service honda.

How old is the current setup (piston/valves). Whens the last itme it was rebuilt?

Did you have the head off of the machine this last time? What cam are you using? Stock? Did the dowel and spring fall out of it?

When I put my 400ex back to stock and put the stock cam in, it would turn over and over and over and wouldn't start without that dowel and pin in there, otherwise the decompression mechanism just holds the valve open.

[justin1022]

Originally posted by 400exrider707
400ex can be off of time, but it can NOT be 180 degrees out. It's impossible.

I asked what cam chain you got because you can use a CRF450 chain, which is probably what was sold to you anyways at a huge markup. They're only $35 from service honda.

How old is the current setup (piston/valves). Whens the last itme it was rebuilt?

Did you have the head off of the machine this last time? What cam are you using? Stock? Did the dowel and spring fall out of it?

When I put my 400ex back to stock and put the stock cam in, it would turn over and over and over and wouldn't start without that dowel and pin in there, otherwise the decompression mechanism just holds the valve open.


screw the decompression just pul that crap out of there it is eather not closing when its supost to or seazing up you dont need it anyway.. its got electric start as far as i new the only reason i would want a decompression is for kicking. and if you rebuilt your quad lots you probly have a after market cam exetra.. and most aftermarker cams dont have the loub to push the doul in and thats weird.. i got told you can run without the doul and spring.. i am doing a rebuild on mine and and trying to figure out if you can pull all that junk out its what im going to do if i can i jsut got told to pull the doul and pin and it will still run..

[400exrider707]

Originally posted by justin1022
screw the decompression just pul that crap out of there it is eather not closing when its supost to or seazing up you dont need it anyway.. its got electric start as far as i new the only reason i would want a decompression is for kicking. and if you rebuilt your quad lots you probly have a after market cam exetra.. and most aftermarker cams dont have the loub to push the doul in and thats weird.. i got told you can run without the doul and spring.. i am doing a rebuild on mine and and trying to figure out if you can pull all that junk out its what im going to do if i can i jsut got told to pull the doul and pin and it will still run..


If you have the decompression mechanism (its not a lobe on the cam) on the stock cam, you need the dowel and pin. This mechanism is NOT on the aftermarket cams, though it can be pressed off the old cam and pressed on the new one. When installing an aftermarket cam (without the mechanism there) you must removed the dowel and spring out of the head, otherwise it's going to take out your motor. Yes all 400ex's have electric start, unless you've converted it to kick. Honda put it in there so they must have thought it was a good idea for one reason or another. You dont need it though as proven by many with aftermarket cams.

[justin1022]

Originally posted by 400exrider707
If you have the decompression mechanism (its not a lobe on the cam) on the stock cam, you need the dowel and pin. This mechanism is NOT on the aftermarket cams, though it can be pressed off the old cam and pressed on the new one. When installing an aftermarket cam (without the mechanism there) you must removed the dowel and spring out of the head, otherwise it's going to take out your motor. Yes all 400ex's have electric start, unless you've converted it to kick. Honda put it in there so they must have thought it was a good idea for one reason or another. You dont need it though as proven by many with aftermarket cams.

yea well you see this is my story i am doing a rebuild and i got a 440 kit and all and a heavy duty timing chain but wile i was stripping my quad befire to see if my stock rings were shot i somehow lost the spring for the doul in the proccess so can i just pull the doul out and run it like that? or do i need to remove the hole decompression set up? and i got stage 2 hot cam so i havent ben using that decompression for a wile now.

do what? you need some hooked on phonics. we cant read what ure saying:rolleyes: :huh

[justin1022]

Originally posted by hondarider661
do what? you need some hooked on phonics. we cant read what ure saying:rolleyes: :huh

ha sorry, ok i bassicly just asked if i can run my quad without the doul and spring or do i need to pull the hole decompression. because i lost my spring and dont use it anyway because i have a aftermarket cam..