timed and now a question

[dheavychevy38]

Ok i have timed my 440 and now when i turn over the motor the intake sucks and then pushes air out of it right after what gives denny?

[rideracelivemx7]

well.. in order for us to help you. you need to give us the best detail you can. are you even letting it crank crank crank or are you pressing it for a second so it can't complete the stroke. is it even all together? you sure you timings all correct and don't have the cam backwards. on the wrong stroke.

[Honda5]

make sure your timing marks are on. unlike rideracelivemx7 posted you can't have it 180 out it fires on both strokes.

[rideracelivemx7]

is that not what i said??

[GPracer2500]

Originally posted by rideracelivemx7
is that not what i said??

Not exactly. A "backwards" cam in a 400EX is kind of an oxymoron. Like Honda5 already mentioned, you can't really "....have the cam backwards. on the wrong stroke...", as you said. 180 degrees out of time just flip-flops the compression and exhaust strokes within the 720 degree cycle. The cam can't really be "backwards".

Ultimately, your idea about the source of the trouble is sound....just a bit sloppy with the details.



To the OP: check your cam timing again. I'd bet it's not right. Although it can't be exactly 180 degrees out of time, it certainly could be off by some other amount. That could easily create the symptoms you describe.

[dheavychevy38]

Thanks for the replys. I am a mechanic so no im not a complete dumb ***. I can't get the marks set perfect. Ok when looking through the hole on the case where you line up the line and the t i have that dead nuts on and when i go to set my cam i get the marks as close to horizontial with the head and yes i plan for the tensioner. My marks are either high on one side or low or wise a versu. The cam has two lines on it and the word out stamped in it.

[Honda5]

ok the next thing to check is that the keyway is not stripped. if you don't have a piston stop pot a screwdriver in the sparkplug hole (carefull not to bind it up) and make sure the piston is at TDC when the mark is on the "T"

[blaaze416]

^^when I replaced my cam and cam chain, I couldn't get the lines on the cam gear to line up perfectly horizontal with the head. It was slightly raised on one side. i tried this and that and this again to straighten it, then said buck it, and slapped it together. It fired right up and no problems since. I'm thinkin what the other guys are maybe concerned with is making sure your cam lobes are turned down, not up?

[dheavychevy38]

Thank you thats what i needed The piston is top dead center but when the word out is up on the cam the lobes point up. I will try it with them pointed down that would mean the it was 180 off Thanks Guys

[Honda5]

the piston is at TDC with the word "out" on top and on the bottomit goes up and down two times for each time the cam goes around once, you CAN'T be 180 out.

[blaaze416]

^^ maybe, maybe not...I really don't know. I do know my instructions read to make sure the lobes were pointing down. That's what I did, and she fired up and sounded great...so I'm sticking with that.

[Honda5]

I know this for sure I have built atleast 25 (not all mine )of them and still own 3 of them it is probably my favorite of all the quads I have owned.
the tech books tell you that because you need the cam lobes pointed that way for adjusting the valves.



this is my favorite 460ex (the wifes)

[blaaze416]

not to start a power struggle, but....anybody want a peanut butter and pickle sandwhich?

[gojk]

The above poster is correct. They tell you to put the lobes down so that you can adjust the valves once all is together. You can't adjust them properly when they are up, plus it would make the valve cover hard to put on since it would have to open a valve as you are putting it on.

The fact that the marks don't line up could mean that the cam chain is stretched. When mine was old and stretched it never lined up, got a new chain and it lines up perfectly now. Although it always ran fine when it didn't line up.