2004 Honda TRX 450 FM

[DLBeltran74 47]

Hello folks, I have a problem. I just rebuilt the top end on my 450 Foreman and I am not getting compression. I read in the book about some compression valve nut or some crap like that, but it doesn’t show me where it is. Can someone please post a picture showing me where it is? Also, no compression, I put the t at the hole and adjusted my valves. And still no compression. Am I suppose to rotate the engine one more time and line up the t and adjust my valves again then try a compression test. I read somewhere that it is engine is suppose to rotate twice on some stroke before adjusting the valves. Can someone help me out. First build and already annoyed!

[jeepwm69 7,751]

Did you get the timing marks on the cam lined up AND the T on the flywheel? 

[DLBeltran74 47]

I never went that far down into the motor. I bought it needing the top end. From the top everything on the inside looked to be in great condition. It switched into all the gears so I didn’t feel I need to go any further. 

[jeepwm69 7,751]

I haven't torn into a 450, but if you have a new cylinder, piston, rings on it and it has no compression it sounds like it's out of time.

 

@Fishfiles or @shadetree are the 450 experts.  Maybe one of them will chime in.

[DLBeltran74 47]

How do I know if it’s at tdc on the compression stroke? I have the T mark showing in the hole and the exhaust valve is tight and the intake valve is loose. Is that right? 

[Derf40 140]

on the compression stroke, both valves have to be closed or no compression

[Fishfiles 20,147]

Derf  is on  it ----   It sounds like you might have adjusted the valves on the wrong stroke , being one valve is tight and one loose -----pull the plug , stick your finger in the spark plug hole , tap the starter button till you fill compression start ,  then line the T mark up and both valves should be loose 

 

 

a valve could be stuck closed , did you do the head valve stem seals and lap the valves during this upper job  ? 

[shadetree 5,977]

i'll chime this in one more time. here is how i do my valves: i remove the rear pull starter, this gives me access to the rear cage, right behind this cage , stamped into the rear cover is a raised arrow. now i look on the cage, i am looking for a line that is stamped into the tang, this line, lines up with the raised arrow on the cover. now i remove the site plug for the timing mark, i'm looking for the T mark, once this is in the site hole, i now pull the rocker box off, yes..you have to remove the fuel tank to get to the rocker box. now i remove the spark plug, this makes it alot easier to turn the crank at the back on the pull starter wheel. you will need a 17mm socket to turn it. keep in mind, when i am doing a engine rebuild ?, i am also installing a new cam chain, this area also has timing marks that need to line up, but in your case, you are not doing a new cam chain install ?, so you can not make sure the cam chain sprocket is correct. so, once my two timing marks are lined up. now i turn my pull starter as if its cranking over, in this case, clock wise as if you are pull starting it. while i am doing this, i am watching my valves, spec the intake valve !. i do a full 360 degree turn with the pull starter and socket, i make sure my timing marks line back up, now here comes the trickey part..i turn the pull starter BACKWARDS !, slowly mind you !!, as i am doing this ?, i am watching the intake valve for movement, if i had the piston on TDC  ( top dead center ) on the compression stroke ?, then the intake valve SHOULD start to go down as i turn the crank backwards ?, if it does not ?, then this means i had the piston on TDC on the exhaust stroke !. have i lost you yet ?..lol. i'll make this simple. with the two timing marks lined up, watching the intake valve, as you turn the crank backwards , the intake valve will go down ( sooner or later anyway after a bit of turning ). if it does not go down ?, then go back clock wise, line up the line on the pull starter cage, now keep going all the way around until that line on the cage lines back up with the raised arrow on the rear cover..STOP !, now turn the crank backwards, as you do this..the intake valve will start to go down. when it does ?, STOP !, now turn the crank clock wise until you get that line lined up with the raised arrow, STOP !. now you are on TDC on the compression stroke. loosen the valve nuts, adjust the valves. put it all back together. this is how i've done it for years..and to this day, it have never failed me !.