Richard,
I built my Jinma 304 from a crate unit and I can offer a few tips.
First and foremost, check every single nut and bolt for proper tightness. Then do it again in case you missed one. (grin) After all that, I later discovered that the bellhousing bolts were not properly tightened on mine at the factory so I had to split the tractor to fix that. I wouldn't have been able to discover that originally unless I had split the tractor, so I don't fault myself.
Use Loctite where appropriate. Tractors want to shake themselves apart if you let them.
The tie rod ends on Jinmas are adjustable - mine were loose and I didn't know they were adjustable so I had later problems. Check yours now and set them good and snug.
I recommend setting your wheels to the widest positions possible for better stability.
Check all electrical wiring points for proper grounding - the factory doesn't remove the paint before they screw the ground lugs down and they make poor contact. Re-do all of them using dielectric grease and you'll have fewer electrical problems down the road.
Take lots of time and care in setting the clutch correctly. The factory doesn't do this and it must be done. There are tutorials on how to do it on this and other tractor forums. Follow the directions and get it exactly right the first time. This is a critical item in assembly!
Drain ALL the fluids out of the tractor - every one. The factory fluids are junk. Flush all the systems, gear oil, engine oil, hydraulic fluid, injector pump and steering system with kerosene or diesel and refill with the proper US fluids. 15W40 engine oil, AW32 hydraulic fluid, 80W90 gear oil. The front drive takes gear oil, the injector pump takes motor oil, the steering takes hydraulic fluid. Do the radiator, too. Replace coolant with proper diesel-type coolant with SCAs, one that is rated for a wet-sleeve engine. (Uh, don't flush the cooling system with kerosene - use water, okay? grin)
If you don't have an adapter for loading your times with
ballast, might as well order one now. The more weight on the ground the better the traction.
That's what comes to mind right off - hopefully others will chime in with more ideas.
Rich