Diagnostics on a CRF450 that won’t start, summary of fuel and Carburetor operation and diagnostics 

Man i need help bad. I have a 04 crf450r. Runs great when it starts. But ive been chasing this hard start issue all over. Did valve clearances plug carb clean and coil. Nothing has helped. When i kick it will pop with each kick like it wants to fire but just isnt happening at the right time. I checked timing so many times i lost count. I even went couple teeth forward and back and its always the same situation. I need some guidance please.

I had a no start problem with a 03 CRF450R and rebuilding the carb and checking the valves revealed the problem. The valves were too tight and I went down the to smallest shim I had to get ,006 clearance and the carb was old and the gaskets were bad and jets were clogged. That and a quick oil change after a quick ride got a lot of black oil out of it. Runs pretty well now. 5 kicks maybe to start it up?

I would really appreciate your input, I have a 2004 Honda crf450r it only runs when you push start it or if you squirt fuel into the intake, it backfires when you kick it over. I cleaned the carb and everything so I’m not sure what to try next, thanks!

No comments or recommendations other than non-typical conditions would prompt me to pull the head and cylinder off and have a look, never hurts to have a look. If you can do this work it helps, check out some of my videos on top end disassembly

On a 03 KTM 450 after complete top end rebuild , cylinder re sleeve, new piston & new titanium valves and new adjustable accelerator pump with every thing tuned and running perfect. one day after a few months my muffler started melting my side plastic muffler cover, then a few days later the bike starts to lose power at higher RPM. Any ideas ? Thanks for any help on this. Carb is KEIHIN FCR-MX 39 Carb jets stock 170-40, in shop book 175-48 Jets In as of 03-22 - 178/50

Would this be the same carb as an 05 crf450x?

I have a question would really appreciate you input & help. I have a 2006 Honda 450R the carburetor in your video is identical. The Honda sat for about 2 years with the same fuel. I drained and refilled with fresh fuel. My quad would start only if adding some fuel in the intake run with mid to high throttle and shut down at an idle. I ordered a rebuild kit on amazon. Dis assembled cleaned all ports. Replaced true jets and seals supplied in the rebuild kit. After reinstalling the carb my Honda would not start. Not even with fuel sprayed in the intake. I ordered a replacement carb on line had the same results. I’m very surprised it will not even start for a moment. My next plan off attack is to check if the valves are too tight. Do you have any advise as too why i may have starting issues after rebuilding & replacing the carburetor?

The bike at the end is a 2002?