exhaust sucking not blowing...

[quadgod440ex]

ok guys i just got my cylinder and piston back from the machine shop i got a wiseco .40 over 11.1 comp piston , also got a new hot cam stage 2 , and a crf timing chain , once i put everything back together i had it on TDC and the cam lobes were facing down , the exhaust is sucking my hand in a blowin out the intake , i was reading and i found out the cam could be 180 degrees out , but im on TDC and the lobes are down , i now read that it has to be on a certain stroke , i tryed to do a search but im not finding what im looking for , can someone describe to me what im doin wrong here ? i know this has probley been asked alot i tryed to search but im just not getting the answers im lookin for . thanks alot ill be waiting

[44oEX]

well you put the exhaust on the wrong side. it goes on the front.

sorry I had to say it lol

but seriously if your on TDC ( the T mark on the flywheel).

and the lobes are facing down then you should be good.

The thing about the right stroke is that when you take it apart you have to be on the compression stroke. but when you reasemble you don't have to worry about that.

double check the timming and the cam lobes. vavle free play. ....

thats all I can think of

[F-16Guy]

I think you hooked your battery up backwards.:D :blah: Seriously, I'm not sure how that's possible, aside from the engine turning over the wrong direction.

[44oEX]

if you hook the battery the wrong way the starter will turn the wrong way BUT the one way clutch on the flyweel will just free wheel and not ingage. so you can't turn the motor backwards

[Fortman_400]

your timing is 180 off, because it may be opening and closing the valves at the time u want it to but when u put it back together u prolly weren't on the compression stroke so it was sparking on the exaust stroke instead of the compression, which means it burnt the fuel and threw it out the intake valves during the intake stroke.

[44oEX]

well you can't be 180 off. cause the motor sparks every rotation. so it sparks 2 time in a cycle ( 4 stroke ) so the motor doesn't know when it compression and when it's exhaust stroke. it's the cam that decided.

[F-16Guy]

Originally posted by 44oEX
well you can't be 180 off. cause the motor sparks every rotation. so it sparks 2 time in a cycle ( 4 stroke ) so the motor doesn't know when it compression and when it's exhaust stroke. it's the cam that decided.
Absolutely. It may be possible that your valves are so tight that they never close all the way, allowing things to suck and blow ( :blah: ) when they shouldn't.

[BlackRaptor]

Foreman is right, the engine follows a four-step combustion sequence every stroke. 1.Intake (Piston is going down to suck fuel in) 2. Compression(Piston is coming up to squish the atomizied fuel) 3. Combustion (SPARK, Piston going down from the combustion)4. Exhaust. (piston is coming up to force the exhaust out)Hence the name 4 stroke. So No it doesn't fire 2 times a cycle. So it fires every other time the piston comes up. When the piston comes up to force out the exhaust there is no spark, then it goes back down to suck in fuel.

[sampleez]

yes it actually does fire every rotation, because the trigger is on the flywheel and the flywheel turns two times in one cycle.
and check the valves. when i powdercoated my valve cover on my old 400ex, i had to take out the rockers and when i re-assembled them, they were soo tight that the valves weren't closing all the way, and it wouldn't crank. once i loosened them to spec, she fired right up.

[400EXracer74]

i think that kid meant the battery thing as a joke and you jsut ruined it haha, but that is good to know.

[44oEX]

sorry to ruin the joke :D

[Jay300ex]

Are you trying to run the motor or are you observing this by turning it by hand? If its by hand it sounds like your turning it the wrong way, which would mean the piston is going down on exhaust (wrong) and going up on intake (wrong).

I dont think the cam can be in backwards considering one side of it mounts a timing gear (which is timed to the crank VIA timing marks) and that gear has a cavity in the cylinder and head to operate in. So a cam in backwards seems unlikely.

If your piston is at TDC when you are installing the cam with the lobes facing down, then thats means there is no actuation at the rockers, that would be TDC COMPRESSION (valves are closed) This is where you would set your valve timing.

Oh, and the ignition system fires every 360º, Intake and exhaust. Do the procedure again but turn yours valve adjusters all the way out until the cam gear is tight and the cam chain is tensioned. ALWAYS TURN YOUR MOTOR OVER BY HAND

[quadgod440ex]

im tryin to get the quad to run , this is how i do it , i turn the motor over by hand until i get to the T then i check to see if all the rockers have alittle play in them (which means compression stroke i was told) then i put the cam lobes facing down with the 1 notch up and the 2 notches align with the head , then i tighten down the timing chain tensnor , then check the valves should be i think 6 exhaust and 5 intake ?? then i try to start it and get nothing .... it sounds like it has compression , what should the compression be if i did a compression test ? if my timing was out 180 degrees wouldnt i not be getting spark? im stumped i really wanted to go riding this weekend.

[shamisc]

Double check your cam valve lash reccomendations. 5 on the intake seems like too much, but IDK. I don't think this is your problem though. You may have some bent valves not letting your comb. chamber seal off during compression.:confused:

[cals400ex]

make sure your headers aren't leaking air where they connect to the head. make sure both air boots are on tight and neither are cracked. look close, those cracks are hard to see. what ignition box you running? you will want to richen up the slow jet and the mixture screw so your not lean either. .005 intake and .006 exhaust is the correct lash. just make sure your not too tight, this can cause starting problems. i assume the timing chain tensioner is in place too and functioning properly by not sticking?

[quadgod440ex]

im running a white brother cdi , the valve lash is perfect , why would i have bent valves ? i just took the motor apart for a rebuild i never bent any valves , if the timing was out 180 degree would i be getting spark or no ? Damnit this is pissing me off.

[44oEX]

the timming can't be 180 off. so don't worry about that.

are you just turning it by hand or did you try to start it with the starter?

[beak7707]

Yes it will still spark if it is out of time just to answer your question. Thats what I would check, are you sure it is sparking and getting gas?

[quadgod440ex]

im positive the bike is getting gas and spark . im stumped never had this problem before.

[Fortman_400]

make sure ur valves are seating all the way and be sure the timing is correct

[beak7707]

So now you are trying to start the quad with the starter and it just wont start, or what is going on? Did you take the plug and stick it on the clylinder or something to make sure spark is there? I'm just asking because you were asking about spark a couple post up. If you have been cranking on it is the plug wet when you pull it out?

[quadgod440ex]

i took the plug out of the cylinder and it was alittle wet but didnt look soaked or anything , then i put a new plug in it and held it onto the head before i put it back in and the motor had spark , then i put it back in and it just wont start.

[44oEX]

well this is just a idea. But I did have trouble before to get a new motor to start.

What I do when a new motor won't start is hook it up to a car battery, so it turn over faster. make it turn over until it starts. then run it for a couple minute to let everything seal like it should and then it will start like it normaly does.

it really work good

[Jay300ex]

Commonly valves bend when the camshaft is improperly timed to the crankshaft, this is why you should always turn your motor over by hand to make sure everything rotates and clears. Double check your valve train by simply having the rocker covers off and turning the engine over (counter clockwise). Start looking when your valves open after your intake valve closes the piston should be returning to TDC for the compression stroke. Basically just make sure they are opening when they are suppose to in relation to your piston position. If thats all good then you take the systematic approach:

1. Compression check - Leak down test (is there a sound mechanical condition)

2. Check Spark - You might have spark, but is it occuring when its suppose to? Use a timing light (if this is normally wrong it will fire, but run bad and after fire/back fire)

3. Are you getting fuel.

If there is an intake air leak preventing it from running you can find that by spraying a little carb cleaner or starter fluid at your intake boots and stuff.

[cals400ex]

put the stock ignition box on with a new plug and see if that helps

[400exrider707]

Originally posted by cals400ex
put the stock ignition box on with a new plug and see if that helps

Yeah I would try that too. Also if you put the cam in with the lobes down on TDC then it can not be out of time by 180 degrees, at most you could be off like one tooth or something.

[Fortman_400]

well first things first, are ya turning it over by hand or by the starter,, cuz pretty much the only thing i can think of is by hand turning it backwards, other than that it should run

[shamisc]

Originally posted by Fortman_400
well first things first, are ya turning it over by hand or by the starter,, cuz pretty much the only thing i can think of is by hand turning it backwards, other than that it should run

I thought he might be turning it clockwise too.

[quadgod440ex]

no im tryin to start the quad with the ignition , im gonna try the stock cdi and see what happens.

[shamisc]

That sounds like a good starting point.;) I HATE aftermarket CDI's!!:mad:

[44oEX]

man try to start it hooked up to a car battery. it will start I todl you I have had that problem before of not starting a new motor. a bigger battery will start it. at least try it and let us know