I recently did a top end rebuild(piston, rings, cir-clips,this gasket set , new intake/exhaust valves, new valve stem seal), on my son's 2009 Suzuki LT-Z50. After reassembling and attempting to start, I discovered the starter wouldn't engage, even when bypassing the starter relay. So I got a new starter ordered. Anyways, I tried to pull start using the recoil starter and couldn't get it to fire. Spark is good, fuel is being delivered(I squirted oil/fuel mix in the cylinder to be 100% sure), however compression is at ~30psi. So some component is missing or backwards. I started with the valve clearance, which was off for both IN. and EX. but didn't seem to make any difference when corrected.

Are the intake/exhaust valves interchangeable/identical? I could not determine any differences between the two despite having different part numbers 12912-22G00 and 12911-22G00
Is there anything else I should check that would account for this massive lack of compression(should be 156 – 171 psi) before I tear down and inspect and reinstall rings? As you know, almost everything needs to come apart to get at the piston rings, so hoping for better alternative.
When tightening the exhaust nut to the stud, I noticed the nut continued to turn and never really tighten, but didn't think much of it and moved forward. Exhaust is still noticeably tight to the cylinder, the other nut was tightened to torque.
I only cleaned the nikasil lined cylinder with the green scratch pads and oil and then soap and water, then fresh coat of oil. There was no cross hatching present and the cylinder had some very slight discoloration from scoring but felt smooth. You could only notice imperfections under the right lighting. Measurements and bore were within service limits.
I really struggled installing the piston into the cylinder with the rings but finally got the job done. It is such a tiny bore and the rings are so brittle. I can't for the life of my find any resources or techniques for this engine install OR a ring compression tool for this tight of bore(36mm). I may try something homemade if the teardown has to happen.
Thanks in advance and let me know if any other info is needed.

This sounds just like a problem I had a few months back. I went the cheap route on piston and rings and ended up with lower compression than what I started with. Had the same problem getting piston/rings into cylinder. Finally got it in, but wouldn't start. Pulled it apart and one ring was basically stuck in the groove of the piston due to improper size. I spent the extra money and bought a Wiseco piston and rings and it went together easily and fired right up.

I went all OEM suzuki with parts, but not to say a ring is not sitting properly.
Did you use any tools to install the piston in the cylinder, to compress the rings? Do you recall your technique? I could hardly get my fingers in to compress the rings, the bore is tiny.
Thanks for the reply.

No tools. Just squeeze and push. Actually left the motor in the frame instead of taking it out like the first time. Hopefully someone else has another idea. Best of luck.

Almost all engines have a top side to the rings, are you sure you put them in the right way up? Also top and second rings are different, so again, did you get them right? I use the end of a small screwdriver to press the rings into the piston as I slide the cylinder over them, they usually go in at one side, so pressing down the other side of the ring whilst gently pressing the cylinder down, helps. There will be a difference between valves, if part numbers are. Take a look at the old valves, a different tulip shape to exhaust valve or dish in the face of the inlet perhaps? Did you grind the new valves in? If/when you take the head off again, get an insert fitted to the stud hole for the exhaust. It almost certainly won't hold, gas tight, with only one stud. Any motorcycle/car/lawnmower repairer should have M6 inserts and tools these days.

got it apart, confirmed rings are in the right location and letters "R" and "O" are facing up per the manual. Piston is facing the right direction.
sorry, I mispoke, I didn't mean valves, I meant is there a difference in the push rods that go to the cam rocker arms. The appear identical to me.
valves are sealing properly. I am not sure what you mean by grinding them in??
I did notice my spark plug whole is stripped which I will insert a helicoil. Not sure if that and the exhaust not sealing account for only a 30psi reading???
I am kinda scratching my head here.

Push rods are usually identical, but rods wear into the cam follower and rocker they have been mating with, so good practice is to mark which way up and where they came from. The exhaust won't affect compression, but a faulty plug hole may. While you have the top end apart, check the ring gap of the top piston ring with it in the cylinder, to make sure the bore isn't worn beyond specifications. Valves should seal on the seats, not sure how you know they are, but it is standard practice to grind them together with valve grinding paste when you are doing work on a cylinder head, to ensure they are gas tight.

You can basically do a leak down test, put air in the spark plug hole with piston in different positions. See if the air comes out the crank case, intake or exhaust. Or all 3. Back off the rockers if need be to verify the valves are closed.

Did you hone the cylinder?

Ring seating will raise compression but not that much. Or is the engine flooding? Too much fuel will wash down the cylinder walls and lower compression.

Like merryman said grinding them together, Most part stores still sell a valve lapping compound. Put a little on the valve seat face, install valve and spin. They make a tool, but I put a piece of vacuum hose in a cordless drill. Slip the hose over the stem and spin it that way because I am lazy.
Video gives a quick idea of what lapping is and does.

Sorry, but if you could lap valves in with a drill, why do you think mechanics have been lapping them in with suction cups for the last 120 years? It was found long ago that only a forwards and backwards motion would grind valves and seats properly. A magnification of the seat done with a drill will show a series of concentric rings rather than a smooth surface. Like sanding down a paint job in one direction only, it doesn't work.

In the service manual, it states to dump a small bit of gas in the exhaust and intake port with the valves and spring installed to see if the valves are sealing the gas. Mine did not leak any gas, so thats how I came to that conclusion, but I can certainly try lapping and grinding the valves and seat.
Good to know about the exhaust, that makes sense.
I did noticed I misread how to arrange the ring gaps for the oil rings. I had them all aligned with each other instead of spaced apart. The manual worded this very odd it took some googling to discover what was meant. I dont think that would be the problem as the 1st and 2nd ring would likely attribute to proper compression?????
The CAMSHAFT ASSEMBLY is difficult to hold in place before I can get the generator case on. I was able to Align the hole of the camshaft with the matching mark on the cam drive gear but the springs make the camshaft assembly want to pop off the drive gear. I am pretty sure it stayed in place but will have to think how I can ensure it is installed correctly.