400ex + FRUSTRATION = giant molotov cocktail!

[400thacker]

I am so frustrated i want nothing more than to park my quad in a giant bon fire and watch it burn while indulging myself with a vast qaunity of budweiser and tequila. I have posted my problems and you guys have been a great help but once i learn something new to check, i check it and it's ok 9/10 times. never had an engine this hard to figure out.
maybe i will just torch the engine instead of the whole quad and then i can put a yamaha motor on it. i am so pissed at this point, i never want to own a 400ex again and prolly not a honda for that matter.

BTW i would never degrade a honda my installing yamaha anything. But i seriously want to watch it BURN STRAIGHT TO THE HELL IT CAME FROM!:grr:

[STUNTIN400EX]

I AM SORRY TO HEAR THAT! HONDA HAS BUILT A REPUTATION ON RELIABILITY! INSTEAD OF GETTING RID OF THE EX JUST BUY ANOTHER ENGINE.

[07trx400ex]

Keep in mind that you did not buy this new so you don't know what was done to it before you got your hands on it. Just a word of advice before writing off Honda.

Good Luck with getting the engine running !!!

Man I was the same way with my 400ex. Hated it for 3 years. Finaly sold the motor for $200 with every thing it uses and picked up a yz426 motor.

[400thacker]

this motor was running before and i stripped the head stud and replaced the cylinder and piston. seems like it's not in time but everything is where it is supposed to be according to the manual...can't figure it out and if i get another used engine i will de doint all this all over again. everything is pretty much new in this one, IDK what it is.

[tooney]

Hi,
Just a thought but if someone who owned the ex before you has fitted a Sparks advance key and you havent allowed for this when setting the timing you could be 6 degrees out,this could be possibly mean a tooth out on the valve timing??
Just a thought......:ermm:

[Grant Casey]

i wana do the exact same thing to my quad,,, put it on a fire and watch it burn,,,, while drinkng a rum

[frenimy]

Just a thought and mind you I haven't followed all your posts real close but is it possible you set TDC one the Exhaust stroke. I have done that before one a motor and it was a pain to diagnose. Just a thought.

[Hondamaster5505]

"i would never degrade a honda my installing yamaha anything"

That hurt my feelings:grr: lol.

Yamaha was always my favorite brand. I love their stuff, they're the most powerful, they have the best looking quads, and etc.
They have all been reliable too, never broke down on us.

By putting a yamaha engine in you'd be doing it a favor:p Not degrading it.

lol. Hondas are excellent, my second favorite, but yamaha will always be on top in my books.

[REPOMAN]

when you set TDC did you make sure you ONLY turned the crank counter clockwise?

[400thacker]

yup, only counter clockwise...correct me if i am wrong but dont they fire on 2 strokes? so will it matter if TDC is on the wrong stroke?

[elmer91]

i noticed that you are near northern KY, and i saw on craigslist the other day of a guy selling a 400ex engine. the guy is in Brookville Indiana.
http://cincinnati.craigslist.org/rvs/573708041.html

[TRXRacer1]

Originally posted by 400thacker
yup, only counter clockwise...correct me if i am wrong but dont they fire on 2 strokes? so will it matter if TDC is on the wrong stroke? It totally matters what stoke you have it on! This is a 4 stroke, not a 2 stroke. 4 strokes per fire hence the name. You could have the cam in upside down.

There was also a good suggestion about an advance key.

[400thacker]

i don't know jack about a sparks timing key...i know that my cylinder is TDC when the "T" lines up. how can you tell if the engine is TDC on exhaust or intake? WTF?
does it matter if the third mark on the cam gear is up or down? i didn't think that mattered either.
can i change one tooth either way of where it lines up to compensate for a sparks timing key? i dunno what to do

[TRXRacer1]

Originally posted by 400thacker
i don't know jack about a sparks timing key...i know that my cylinder is TDC when the "T" lines up. how can you tell if the engine is TDC on exhaust or intake? WTF?
does it matter if the third mark on the cam gear is up or down? i didn't think that mattered either.
can i change one tooth either way of where it lines up to compensate for a sparks timing key? i dunno what to do Chances are you don't have the advance key so I'd put that on hold for a sec. What you need to do is see what stroke you have it on or if you want just turn the cam 180 degrees and try again. You already have the marks lined up so take the tensioner out, unbolt the cam sprocket from the cam but don't take it off, turn the cam 180 degrees, bolt the sprocket back on, reinstall the tensioner, finish putting it together and give it a go.

I did put my cam in on the wrong stroke so I took the inspection covers off the valves, took my plug out of the head and grounded it, bumped the starter a couple times and looked to see if the spark was firing with the valves open or closed. It was firing when they were open...... no good, I had to turn the cam. I'm guessing there is a better way but maybe you can use this method to see before you tear it apart.

[400thacker]

thanks alot...i will give that a try with the valves and spark thing. i have switched the cam like that before and it didn't work but maybe it is the cam gear upside down? does it matter?

[TRXRacer1]

Originally posted by 400thacker
thanks alot...i will give that a try with the valves and spark thing. i have switched the cam like that before and it didn't work but maybe it is the cam gear upside down? does it matter? If you followed the book and set the marks on cam sprocket with TDC then you will be fine no matter if it was on the compression stroke or not.

[the Z Man]

You may want to make sure your cam decompression is either in or out, if you took out the little spring, you have to make sure you remove the part on the cam, it will not run this way..

[416exfreak]

Originally posted by 400thacker
i don't know jack about a sparks timing key...i know that my cylinder is TDC when the "T" lines up. how can you tell if the engine is TDC on exhaust or intake? WTF?
does it matter if the third mark on the cam gear is up or down? i didn't think that mattered either.
can i change one tooth either way of where it lines up to compensate for a sparks timing key? i dunno what to do


All 4 valves will be loose when its on the right stroke.

Check to see if it has the advance timing key too.

[416exfreak]

Originally posted by TRXRacer1
If you followed the book and set the marks on cam sprocket with TDC then you will be fine no matter if it was on the compression stroke or not.

If it wasnt on the compression stroke and the wrong valves were open, then it wouldnt run or either it would run like arse.

Explain to me how it wouldnt matter please?

[TRXRacer1]

Here's a pic from when I did mine. Notice how all the lobes are facing down. This is how it should look at TDC on the compression stroke. This will do like freak said and allow all the rocker arms to be loose.

Maybe you already mentioned it but what are you setting the valve clearance at?

http://miltechsolutions.tripod.com/offroad/wata/400ex%20rebuild/416ex-asslube.jpg

[TRXRacer1]

Originally posted by 416exfreak
If it wasnt on the compression stroke and the wrong valves were open, then it wouldnt run or either it would run like arse.

Explain to me how it wouldnt matter please? He was asking if the cam sprocket could be upside down and that's what I was commenting on. If the horizontal lines were lined up correctly to TDC then it would not matter if he set the cam sprocket on the compression stroke or not. If he has to turn his cam 180 degrees he does not need to turn the sprocket too. I'm not sure if I'm getting the point across but simply put the cam sprocket can't be upside down. it doesn't matter as long as the cam is in the correct position.

[416exfreak]

Oh, my bad.

I thought you meant that it wouldnt matter if the cam was facing the right way on the compession stroke.:ermm:

[xcracer416]

heres the deal, if you checked compression and it was good, and you know your getting GOOD fuel to the engine its got to be the timing. there are three marks on your cam gear, two straight across from each other and one in the middle. the two on each side line up with the horizontal plain of your head with the mark in the middle straight up at the top of the gear. Make sure your flywheel is on the "T" line in the side cover hole and your cam lobes down. put your sprocket on the cam lightly snug the two cam bolts. then compress your tensioner and tighten tensioner up. release the screw driver and recheck your marks they should be perfectly lined up. if they are then tighten your cam bolts up to the sprocket and reinstall your valve cover and adjust valves to I think its .004 intake and .005 exhaust but you might want someone to verify. If you done this step by step and have compression and fuel the enine should run. What spark plug and brand are you running by the way? Have you gaped your plug correctly? oh yeah before you bolt the head cover back on make sure you put a few drops of oil on your cam journals and lobes.

[416exfreak]

The valve lash on the stock cam is .10 intake and .12 exhaust.

According to my OEM manual.:)

[the Z Man]

Don't forget the decompression...

[xcracer416]

Originally posted by 416exfreak
The valve lash on the stock cam is .10 intake and .12 exhaust.

According to my OEM manual.:)

thanks for the verification. I was way off on that. I havent adjusted a 400 in awhile.

hmmm...my manual has .004 intake and .00 5 exhaust as stated previously

[CSR400EX]

this is a way to tell if you got it 180 out. put the timing mark on the flywheel at TDC. take off your valve cover, and your cam lobes should be pointing down like in the pic on the second page, if they are pointing up, its 180 out

[TRXRacer1]

Originally posted by CSR400EX
this is a way to tell if you got it 180 out. put the timing mark on the flywheel at TDC. take off your valve cover, and your cam lobes should be pointing down like in the pic on the second page, if they are pointing up, its 180 out There are 2 strokes where the piston will be at TDC. This won't tell you which stroke you're on.

[tooney]

At risk of being shot down in flames for my ignorance as I understand it the 400ex has a wasted spark ignition,meaning it fires on both cycles of the engine,ignition and exhaust.
As long as the cam timing marks and crank timing marks are set inline it wouldnt be the end of the world if the cam had been installed with the lobes facing up when the valve cover was being installed,it would just have meant that as you were tightening the valve cover down you would have also been pushing down 2 of the valves.
If everything lines up correctly and you are sure there is no advance key then we need to be looking elsewhere.
Are you certain the tappets adjusted CORRECTLY??

[TRXRacer1]

Originally posted by tooney
At risk of being shot down in flames for my ignorance as I understand it the 400ex has a wasted spark ignition,meaning it fires on both cycles of the engine,ignition and exhaust.
As long as the cam timing marks and crank timing marks are set inline it wouldnt be the end of the world if the cam had been installed with the lobes facing up when the valve cover was being installed,it would just have meant that as you were tightening the valve cover down you would have also been pushing down 2 of the valves.
If everything lines up correctly and you are sure there is no advance key then we need to be looking elsewhere.
Are you certain the tappets adjusted CORRECTLY?? If the lobes were installed up you'd bend the valves right out of it.

[400thacker]

i don't have them adjusted yet because i want to get everything else squared away. i don't have the right size filler gauges. they feel like they are where they should be when the valves are closed though. i know they are all closing all the way.

WTF - the engine will not run WITH a decompressor on the CAM BUT WITHOUT the spring and pin in the head? this may be my problem all along. i thought that the spring and pin just kept it from working at all just making it harder to start without the exhaist valve slightly open.

[JOEX]

Originally posted by speedyquad
hmmm...my manual has .004 intake and .00 5 exhaust as stated previously
.004in & .005in

OR

.10mm & .12mm

[the Z Man]

WTF - the engine will not run WITH a decompressor on the CAM BUT WITHOUT the spring and pin in the head? this may be my problem all along. i thought that the spring and pin just kept it from working at all just making it harder to start without the exhaist valve slightly open. [/B][/QUOTE]

If the lobe is still on the cam it is decompressing the motor and will not start, you need to either have the pin and spring in there or all of it removed (lobe too) This happened to me...

[the Z Man]

pm's are full paypal is bobcatorjo@aol.com 5 bucks should be plenty, Z.

[400thacker]

thanks. i just took the decompressor off my TC cam and i am going to try that tomorrow. hopefully that will fix it. with that spring you are sending me i will also be able to run my stock cam if i want to! THANKS ALOT FOR THE HELP EVERYONE!

this site is a blessing to say the least. I pay for internet just for this site! LOL

hopefully I wont have to set it a blaze now. I will keep everyone posted!

Originally posted by JOEX
.004in & .005in

OR

.10mm & .12mm
after i posted and left the site, i got to thinking that was the case...

[the Z Man]

Parts are on the way, Z.

[atv_man2007]

your cdi box being bad or something simple like your sub wire its a single wire by your left foot if your on the atv runs to the bottom of your motor just a thought seems like everyone else is trying to help also but only takes a sec to give the wire a little shake and try to start it.