Okay, I have a 2002 4x4 250 Arctic cat. and just rebuilt the engine. New valves, valve seals, rings, gaskets, timing chain tensioner, and guard, everything basically.

Now, I can't get it started. Cranks though, with good compression...though not sure of the psi. When timing it, I pulled the plug on the left side of the block and found the "T" on the Crank. The piston was all the way up, assuming TDC! I lined it up with the arrow on the block. Once I did that I installed the cam, with the lopes down, and the lines on the end of the cam flush with the head at all times. I installed the timing chain and sprocket, making sure not to turn the cam, and to keep the two lines inline at all times. On the end of the came where the timing chain sprocket bolts two are these two lines and what seems to be the letter "D". Not sure what that is there for.

It cranks, and I do have spark when grounding the spark plug out. I thought I wasn't getting fuel, so I put a little in the sparkplug hole and it still wouln't start.

Does anyone know where I go from here. I'm mechanically inclined, as I'm a mechanic in the Army.

Not sure if the the CDI box is **** up or what. Any guidance would be much appreciated.

Thanks,
armyguy7776

 

Let me start by saying welcome to the forum and thankyou for serving in the armed forces.

I had a similar problem when I rebuilt the top end of my AC 400. I just can't remember how I installed the timing chain to compare it to how you did it. What I can tell you how I discovered my error.

I removed the access panels to the valve tappets as if I was going to adjust the valve clearence. I then, with the spark plug removed, pulled the hand starter rope slowly and watched the intake and exhaust valves. What I discovered for me was that I had the timing off. My exhaust valve was just closing on the compression stroke so it was all going into the exhaust.

If my memory is correct there are two marks on the cam, and the chain sprocket and the crank that have to all be lined up. I will have to look in my manual to see for sure. What I did was removed the head, loosened the can chain and turned the cam. I don't remember if I rotated it 90 or 180 degrees. But when I put it back together my problem was fixed.

Start by checking when the valves are open and closed and when it occurs in relation to where the piston is located. As you probably know it needs fuel, air, and spark at the correct time to run. From what you have said its not happening at the correct time. Also there are no timing adjustments, other than physically adjusting the timing chain. SO I am pretty sure your marks are not lined up in the proper order when you installed it.

SJ

 

The following directions come from my service manual for my 400. I am assuming that it is the same or similar for your 250.

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10. With the timing inspection plug removed and the chain held tight, rotate the crankshaft until the piston is at top-dead-center.
11. Install the rear cam chain tensioner guide into the cylinder head. Install the pivot cap screw and washer.
12. With the alignment pin installed in the camshaft and the cam lobes directed down (toward the piston), place the camshaft in position and verify that the timing mark on the magneto is visible through the inspection plug and that the timing marks on the camshaft sprocket are parallel with the valve cover mating surface.

?? NOTE: When the camshaft assembly is seated, make sure the alignment pin in the camshaft aligns with the smallest hole in the sprocket.

13. Loosely place the cam sprocket (with the recessed side facing the camshaft lobes) onto the camshaft and place it into position with the cam chain over the sprocket.
14. Place the C-ring into position in its groove in the cylinder head.
?? NOTE: At this point, oil the camshaft bearings, cam lobes, and the three seating journals on the cylinder.
?? NOTE: Note the position of the alignment marks on the end of the camshaft. They must be parallel with the valve cover mating surface. If rotating the camshaft is necessary for alignment, do not allow the chain and sprocket to rotate and be sure the cam lobes end up in the down position.

15. When the camshaft assembly is seated, ensure the following.
A. Piston still at top-dead-center.
B. Camshaft lobes directed down (toward the piston).
C. Camshaft alignment marks parallel to the valve cover mating surface.
D. Recessed side of the sprocket directed toward the cam lobes.
E. Camshaft alignment pin and sprocket alignment hole (smallest) are aligned.

If any of the above factors are not as stated, go back to step 10 and carefully proceed.

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I think from comparing this to the way you installed your parts your timing chain marks were not lined up. You should be able to easily double check the list on step 15. I will look in my complete manual and see if it is different for the 250.

Swampy