I buttoned up my JT motor today and it manually shifts thru all the gears so I’m pretty sure my shifting issue was the damaged boss on the shift drum stopper. And I swapped out the hollow shift drum for the solid shift drum. That should eliminate the stopper pin problem which ultimately caused the damage to the boss.

And the new bearings resolved the slop I had at the flywheel. I had a hard time inserting the bearings with the heat / freeze method. They just wouldn’t drop in like all the videos I’ve watched. So I made a bearing puller and it worked fine. My son had the TUSK crank tool which pulled the crank into the bearings perfectly.

Tomorrow it goes back in the frame!

HELP!

I installed my freshly rebuilt JT engine into the frame and fully reassembled all the peripheral stuff. I added extra 2-stroke oil to the fuel tank because this is a new piston and rings on a lightly honed original bore. The only reason I have new piston and rings is due to my boneheadedness with a rattle gun had cracked one of the skirts….. the original was good…. $200 mistake.

I installed all new bearings, seals, and gaskets all around using all Yamaha parts. $300 with shipping. The original crank bearings were shot and the flywheel side had noticeable slop. The crank journals are fine and showed no signs of spinning in the bearing race.

The compression is just shy of 120 psi. I have good spark. Fuel is flowing to the carb and the plug is wet. IT WILL NOT RUN!!! It doesn’t even pop at all. I verified the rotory valve is timed correctly as per service bulletin 256. I verified the piston is installed correctly with the arrow pointing at the exhaust. I doubt the timing is off because the stator is not slotted. So it bolts down exactly as it was and I did not touch the points or condenser. It won’t even pop with a shot of starting fluid right up its throat!

What could I have done wrong with this build? What am I missing?

I should be shot at dawn for even thinking it but did you leave the crank seals out. Doesn't make sense. Is the stator mounted 180- out. Is it just flooded & needs full throttle & a push down the driveway. Not a long reach plug & the piston smacking the gap shut. I've run out of stupid thoughts but don't have any good ideas at the moment sorry.

All new crank seals in place and carefully installed.
The crank seal on the rotory valve side is actually pressed into the rotory valve cover which I thought was odd, but that’s how it is.
Stator is mounted correctly due to the rubber grommet that is permanently stuck on the wire and fits into the case notch.
Plug is correct and properly gapped.
I spun the crank by the flywheel nut with drill motor for a good length of time while holding the throttle wide open.
I'm thinking it has to be related to the rotory valve, but I did it by the book.
 

...was putting together a CT1 the other day and forgot whether I put yamabond on the section between crank and trans. 

I’m good there as well. I specifically recall going around ALL the mating surfaces of the case joints including that wall between the crank and the trans.

But that was a great suggestion.

I built this motor using the cases from another JT motor due to the damaged stopper boss at the shift drum stopper pin. So this stator plate is bolted into a different side case this time. I doubt that the mounting holes for the stator plate would be clocked slightly different from one case to the another. But I will check timing tomorrow.

If this link works i stopped it at 9.37 after failing trying to stop it with pin in view but looks like the valve could easily be flipped. But regardless i'd still expect something, backfire or flames out the carb--i dunno--something. I guess if flipped it'd blow out instead of suck but--!!.


 

If plug is wet and you have good compression and spark, it should at least pop.

If rotary valve is not right, they tend to blow a noticeable amount of air back out of the carb when cranking

My suggestion after checking timing is use a spark plug out of a known good running engine. 

It could also be flooded now after the start attempts or maybe the float was stuck initially and flooded the engine?  I've had that happen.  If plug is still wet but it doesn't fire, shut off the fuel supply and try to clear the flood.

Edit:
added link showing valve placement.
imgur.com/a/xo4cUaZ

I have the rotary valve placed over the splined insert correctly. The side closest to the crank has a raised hub and it is not flat like the side opposite the crank.

I watched that same video before I reassembled my motor but I was apprehensive about it when I saw him press the crank into the bearings by pushing on the opposing end of the crank instead of pulling the crank into the bearing. I’m sure many people do it that way but I would be the guy who ruins the crankshaft.