1978 ATC 90 no spark after rebuild

[turbowrenchhead]

After many hours of tedious work I went to start it. No spark. I adjust the points, check continuity, points working properly. I have power coming out of the magneto. I know the coil is a know good part. I replaced the switch with a new unit and I also replaced the wire harness. I sandblasted and painted the frame. So everything is painted with 5 to 6 coats plus clear. Does the coil need a good ground to the frame? Do the points control the ground side of the coil? The stator supplies voltage to the switch and the coil. How can the power go through the switch to the grounded greeen wire to the coil. Is their a resistor in the switch?
I'm just trying to understand how this circuit works. Does anyone have a factory diagram specific to my year and model? I have downloaded both of the manuals. The diagrams that are in those manuals do not match what is one my bike.

[atc350xer]

2 things come to mind... I was told you did have to have a good ground where the coil mounts, and on mine, under the clamp that holds the spark plug wire to the head, my wire was broken inside from bending on that little clamp for 30 years of spark plug changing/cleaning

[rdlsz24]

Did you have spark before the rebuild?

Rob

[shortline10]

Replace the points even if they look good and double check all the grounds . Do you have the ground lug on the harness bolted to the coil?

[turbowrenchhead]

I replace the points and the felt during the rebuild. And yes the bike ran fine before I tore it down.
I do not see a ground lug in the harness. There is a green wire that is soldered to a plate on the coil and I would assume that is the ground circuit. That green wire goes back to the switch.
I will check the continutiy of my ignition wire today and make sure that is good.
I'm going to clean the paint off at the rear motor mounts and where the coil bolts through and see what happens.

[turbowrenchhead]

I can't check the continuity of the ignition wire without damaging it. But I do have 12K ohms from the low tension wires to the ignition wire. I have proper resistance between the low tension wires as well. I cleaned the motor mounts and the mounts for the coil. I put it back together and still no spark. I'm at a loss. I'm going to pull the wire harness of my neighbors bike and swap it to see if I have it wired incorrectly.

[turbowrenchhead]

I checked the new ignition switch to make sure that it working. When its in the run postion its in a open state. So it must short the power to the ground side to stop ignition. Its starting to make a little more sense now. However I have tested everything I can and I still don't have an answer. I checked the orginal wire harness that is on my neighbors bike now and its wired the exact same way. Is it possible that ground path to the points has high resistance due to the paint thats on the engine?

[turbowrenchhead]

Here is the diagram that I drew up before I tore the bike down.

[turbowrenchhead]

I have spark now. The spark tester that I have does not work for the bike. I thought my tester was bad, but I tried it on my car and it works fine. So I may have had spark all along but it still doesn't fire.
I checked the keyway on the magneto compared to the magneto off the 83 110. The timing marks are off. I have a 83 crank/rod in the 90 and I'm using my stock stator and magneto. So I transfered the marks and retimed the chain. Still no luck. I checked to see when my valve was opening and closing compared to the piston travel and it was off. So I moved it two teeth counter clockwise. Now the valve is opening when it should but how do I know that its timed with the points. If it's timed on the oppisite stroke my plug will be firing on the exhaust stoke and not the compression stroke. Does the plug fire when the points open or does it fire when the points are closed?

[shortline10]

Timing is a pain in the butt sometimes so this is how I do it (very simple) . Remove the flywheel bolt , Point the flywheel key directly centered at the head and this makes the piston @ TDC , make sure the cam lobes are both pointing toward the block or it will be 180 out . make the cam sprocket dot point the same direction as the flywheel key toward the top head cap centered . Align the cam sprocket up with the cam and bolt it up and your done . Flywheel key and cam dot both pointing away from the block and its good to go and cant be off .

[turbowrenchhead]

Today I took a die grinder with an abrasive disc and cleaned all the paint at the motor mounts and the coil to the frame. I got .3 ohms after the procedure. I double checked the resistance of the coil. It met specs and the coil worked fine before the rebuild. Now I have spark. I had to take the plug out and ground it to a engine bolt and it had visuale spark. Still no start.
Then I checked the valves. I put a feeler into the chamber through the plug hole to feel where the piston is in relation to valve position. The exhaust valve was opening while the piston was in stroke 3 after ignition. Can't make any power if your fuel goes right out the exhaust. I pulled the cam and compared it to the orginal. The exhaust lobe was about 30 degrees retard from the orginal. So I put the orginal back in and checked the valves. Now the exhaust valve opens at bottom dead center and closes at the end of the stroke. I also found that the sleeve on the advancer pin was 180 degrees off. So my cam was on the oppisite side when the plug needed spark.
But still after these findings the engine stills does not start. I quit for the day because I'm frustrated beyond belief. Yesterday I fixed a 02 Jeep that the dealer couldn't figure out in about 10 minutes. But this 78 honda one cylinder is kicking my ass!

[turbowrenchhead]

Thanks for the advice I will do exactly that tomorrow and see if its correct or not. For tonight I'm done. I felt like pulling the rest of my hair out at the end of the day today.

[Grizzlypeg]

I wouldn't be surprised if it sparks on every upward stroke, both compression and exhaust. Does it have compression? We know it has spark. If so, have you tried priming it with a little gas and seeing if it fires up on the fuel you added?

[turbowrenchhead]

I did what shortline suggested and it was how it suppose to be. I took the cam out and then stamped it with an L to indicate lobes. It faces dirrectly towards the motor. So no problem there. I did a static timing procedure and the marks all lined up. I checked valve clearance. It was about 3 turns to tight. Way off. I adjusted it to .0025. The exhaust was just a tad to loose. When I pulled it then I could tell their was some compression there. I shot a little either in and it took off. Put the tank back on and hooked up the lines. I fired and ran. But its midnight here so I shut it off after 10-20 seconds. I took the new carb off because the cable is about an inch to long and I don't have the solder end to set it. I put a atc 110 carb on it that I put a rebuild kit into and then it didn't fire. Then the cord came out of the recoil. I'm done for the night.

[turbowrenchhead]

The restoration is a sucess. Its running quite well. It pulls a wheely no problem is 1st in high range. Before the bike had a hard time just getting going. You would have to hop off and give it a push. I will post some pics soon. I had to touch up the tank. It had sprung a leak.

[shortline10]

Did you get the Web cam to work ? So your running the 56mm rocky piston /atc110 cylinder , atc110 crank ? Now with a decent carb setup it should scream .
Congrats !!!!

[turbowrenchhead]

I doesn't run well with the web cam. I have to send it back. I was going to today but I got swamped with work. I have a new carb, waiting on the solder end so I can shorten up the cable.