I’ve owned my 2000 400EX about a month now. Got it bone stock with only issues (I thought) was leaking carb and toasted rear axle bearings. I’m still not familiar with good brands and ones to stay always from. I ordered a complete carb for 48$ and complete axle bearing carrier for 35$ off eBay.
I also ordered an uni filter, hmf performance full exhaust and a DynoJet kit+42 piliot jet.
With everything installed I was very happy with it except gearing so I dropped from 15/38 to 14/39 with a new gold oring chain, all from primary drive. I knew they are cheap but I wanted to test the gearing before I dropped cash on nice gears.
Hmf’s head pipe is a different shape and my clutch cable was laying on it so I went and got some of those spark plug heat sleeve things for it but it’s still making the cable stick after a hard ride and cool down.
With the new carb, I put in the DynoJet needle to same length as stock. 170 main, 42 piliot, and about 2.5 turns out on the idle screw. It won’t start with out choke and even after warm has a weird idle. Sometimes it idles high, other times it barely idles and dies, usually high then starts to drop until it dies. It doesn’t pop through the exhaust on deceleration but I noticed about the first 1” of the head pipe starting to turn orange when riding at night. It doesn’t bog or blow black smoke so I think I’m pretty close on the jetting
And here’s the big one that I’m all butthurt about lol. I rode for about 2 hours Saturday, moderately hard on it and it did great, no issues. Sunday I took it to my dads, he went first and babied it 1st through 3rd. Came back, shut it off, we talked for a few minutes. I got on, started fine and I ripped on it 1st-3rd, when I let off he said it shot a flame out the exhaust and a few seconds later it died when idling. When I started it back up, it sounded like it had something rattling/slapping in the engine, not the trans for sure. It was low on power and every time it made that slapping sound, maybe timing chain?, it would miss, catch it’s self and repeat. Throttle made it worse. Full on oil, no metal on the dipstick, not hot. Drove the truck to it and pushed it up the ramps.... when I got home I checked the valves, they weren’t loose so I pulled the cover, no rocker arm damage, cam looks good but I’m not sure how the timing chain should look/feel. I was thinking about ordering a stage one hotcams since I’m already that deep and it includes a chain but I don’t want to rip the clutch cover off if I don’t have to.
Sorry for the long post, I’ve been procrastinating making an account here