I will try those suggestions Mark. I also plan to dispose of the fuel in that tank since I have no idea how old it is. This bike had trans issues and was never ridden.

I’m going to head out there shortly and place my thumb over the tube that the carb mounts to. I assume that I should feel a pulsation effect when cranking it over. Not sure how much I can do out there today. I wrenched my back yesterday and can hardly get up out of a chair….

Deleted my post as I'm wrong looking at parts pics. I thought the center & dis were one item disc bonded to the center but shows as two on parts list. As the piston goes down the dis. Should be covering the inlet pretty much. The splines are so coarse it'd either be cirrect orientation or very wrong I'd think. As piston rises from bdc the inlet should be open. Or am I thinking wrong. Just looked at yg1t lanscout & the center is part of the disc but all slides on a spacer with is pinned to the crank plus pin extends into the disc steel center. Learning as we go I am as have replaced a few of them on yg1 models that ripped the center out-- but that was in "63 haha.

Your pic looks good on my computer compared to phone. There would have to be a timing mark on the disc like a dot or indent & on the center. Plus the steel center is pinned to the shaft, so can't go wrong "i'm thinking". If no mark visible on the center then is it upsidedown.

The disc does have a double dot mark to ensure proper placement at TDC and yes the cutout starts closing off the inlet as soon as it rotates past TDC.

I didn’t mess with it much today but I did verify that the timing is good. I also verified that it is not puffing air out of the inlet when spinning it with the drill motor. I simply feel a slight pulsation as I expected.

Hope to get back at it tomorrow with fresh fuel, known good plug from my other JT. 

Sometimes you just gotta walk away and try another day. It fired up today with a tank full of fresh fuel and a different spark plug. It is heavily oiled at about 15:1 so it smokes like crazy. It did take a considerably long spin time with the drill motor but it finally started popping and then throttled up. It needs some fine tuning but that will have to wait because it's only 10F outside right now. As always, thanks for all your suggestions.



 

that bike sounds better than most bigger mx bikes. is that the stock exhaust.

No I found that pipe on eBay. I believe it is a custom made pipe. It was noted as fitting a JT but it didn’t. The seller offered to refund my money but I wanted that downswept pipe so I kept it and had a fabricator friend rework the head pipe to fit properly. I need to order a new squish gasket because I lost it during my rebuild. I had to modify the rear brake pedal and swap the kicker lever for one with an offset. So it was a lot effort and money to make that pipe work but I really like it.

Congratulations!!!!