Why does my 250cc suzuki quad have no compression with a new top end?

Hey Destry,
What makes you think its trying to run backwards...?? On a 4-stroke - this is odd!! .... I don't think a 4 stroke will run backwards!!.. (But, I have actually seen a two-cycle engine run backwards.... just retard the timing to zero).
1. Have you changed the spark plug?
2. Have you had the carb cleaned and set by a professional
3. Have you put in a new air filter.
4. Have you had the timing checked..(with a timing light)
If the engine actually runs backwards it will cause engine damage.. all the moving parts are designed, clearances are set, and fuel/air intake and cam timing are all designed for the engine to turn in one direction,,, when it does turn backwards, the valve train clearances are taken up and sometimes the valves will hit the pistons...(on a V-8 the cam chain controls all this..its "slack" only works correctly in one direction).. Please do 1 through 4 and repost with the results, Thank yoe

the exhaust and inlet valves will be moving if you rock the crank back and forward at TDC
this is called valve overlap and indicates that you are timing the valves on the exhaust stoke tdc and not the compression stroke tdc
turn the crank over till you get tdc again and see if the inlet and exhaust valves have clearance and the timing marks line up
timing is done only on no 1 piston TDC position compression stroke

This procedure is for 200 Kawasaki Prairie 400
1:on the flywheel cover, remove the pull starter asembley so you can turn the engine over by using a wrench. on that same side, remove the timing inspection plug. it will be on teh side of teh flywheel cover, and have a large flat blade screwdriver mark or allen hole you use to unscrew it.
2:with the inspection plug removed, slowley turn the engine untill you see a "F" and a line. from there, rotate the engine very slowley untill you see a "T." JUST after the "T" there is a line. you want the mark inside the inspection plug hole to line up with that line after the "T."
3: with the bottom end now timed, you will install the cam into the head. when you set the camshaft into the head, do so with the lobes pointing directly down. after the cam is installed, then install the cam sprocket and make sure the lines on it are directly left to right. the lines will end up lining up with the level surface of the cylinder head surface. ater you have installed the cam and sprocket, look again at the inspection hole in the flywheel cover to recheck that the bottom end is still on time.
4: once the cam is installed, and the sprocket is installed on it, you will see the lobes point down, and the cam sprocket lines are from side to side. then yo uwant to install teh cy;inder head cover.
5after the head cover is installed, install the cam chain tensioner, and slowley rotate the engine to ensure the valves and piston do not contact. USE HAND TOOLS TO ROTATE ENGINE, NOT ELECTRIC STARTER!! the electric starter will cause damage if the timing is off.

adj valves ? prolly why!

i would adj valves 1st and go from there. rings maybe stuck if it has sat a while w/o being started. run a compression test on it should have something at least. no compression doesnt sound right to me. if so rings stuck can be freed if so ,sometimes fixes it ,sometimes breaks it

go on youtube and look up the specific quad but usually you take off your timing cover on the head and put the notch to the top of the head and there should be a big flathead bolt thing to unscrew on the bottom end of your motor and un screw that and look for something that is carved in there like "TDC" "T" top dead center align it so they are both straight and make sure to loosen your chain that's usually on the head it should stick out or a bolt or some thing and take it off and that pretty much it

bad rings, bent valve, bad valve seat. make sure your oil pump is good once you figure out too.

It sounds like the camshaft is going flat. The exhaust lobe on the camshaft is the first to wear. Basically the exhaust isn't opening the entire duration it needs to expel the exhaust. This will cause the bogging issue. Polaris uses an overhead camshaft, which fortunately, makes it easier to replace. To check the camshaft:
1. Remove spark plug
2. Remove the large bolt on top of the recoil starter
3. Rotate the engine with the pull rope until the "T" mark on the flywheel is visible through the hole the bolt was removed from
4. Remove 8 screws on valve cover, fuel tank removal is not necessary but gives you more room
5. Remove 4 bolts from rocker arms, lift rocker arms off camshaft
6. Rotate engine again with pull rope to inspect camshaft. The center of the camshaft is the exhaust lobe, intake lobes are on the outsides of cam. The exhaust lobe should be about the same height as the intake lobes, and will be noticeably flat
To replace the camshaft:
1. Remove camshaft gear access cover on right side of engine
2. Rotate engine again until the "T" mark on flywheel is visible, 2 dots on the camshaft gear should be at the top of the gear and will be parallel to the mating surface of the valve cover
3. Locate the chain tensioner, 2 small bolts holding tensioner to cylinder and 1 large bolt in the center. Remove the large center bolt to remove tension. There will be a spring and pin inside tensioner so be careful not to let it fly out.
4. Remove screws holding gear to camshaft, leave the gear on the chain
5. On the left side of the engine, clamp the coolant hose going into the thermostat cover
6. Remove thermostat cover, some coolant will come out but is ok
7. There will be a round cover on left side of engine with 3 screws, remove that cover and pull the camshaft out through that hole.
8. Install new camshaft, make sure the automatic decompression lever does not come out while handling. Keep pressure on decompression lever and hold cam so that the little ball inside the cam is facing downwards, this will help to keep the lever inside the cam
9. Install cover on the left side
10. Install cam gear on camshaft
11. Remove exhaust rocker arm from the shaft and replace with a new exhaust rocker arm
12. Install spring, pin, and bolt in tensioner once the gear is in place
13. Install rocker arms, set valve clearance to .006 in for intake and exhaust
14. Reinstall covers and thermostat cover
15. Option B is to take it to a Polaris dealer to avoid the hassle of trying to do it yourself!
Hope this helps, if you need any more assistance let me know, Daniel

you might have gotten the cam timing off a bit? did you check the valve adjustments too?

it needs a set of rings and maybe a piston then it will be like new again