2004 RMZ 250 Problems

Next on my list would be to perform a compression check and see if the compression is up to par.

Have you adjusted the fuel screw?
Have you adjusted the float height?
Have the valves been replaced?

Paw Paw

Has your 11yr old bike ever had a top-end done?

Get a leak down tester and an air compressor ... borrow one from somewhere or buy one (not that expensive)
You can use it to diagnose problems with the top end, and it will tell you exactly if the problem lies within the intake valves or the exhaust valves, or the piston/ring/bore.

I just had similar problems with my YZ450 and had to replace the intake valves because they were not sealing properly and were worn. The next time I do it, I will be getting the valve seats re-cut. A leak down tester will tell you for sure.

Sounds like it's definitely due for some top-end rejuvination then! Also, when you rebuilt the carb, did you replace the pilot jet with a new one, or clean the old one? The fuel screw will smooth things out, but the pilot is what feeds the idle circuit of the carb,...getting the idle screw adjusted properly with the fuel screw and proper pilot should make it "braap' with no hang-ups, or idle drop then climb situations, and definitely no stall. Either way, it's way past due for a top-end, LOL!

The bike is 11 years old and and you have ridden it for 8 of those year....That is just too long on the valves for that engine.
The valves need to be checked and most likely replaced and the seats cut or replaced. How many times have the valves been re-shimmed?
The float height effects the full range of the fuel delivery. Set too high and it will flood at low rpms. Set too low and you will run out of fuel at upper rpms.

Paw Paw

I'm surprised it has not scattered itself to bits yet. Those 04-05 Kawazuki's were real time bombs, with a fairly short fuse.

Hard to start, valves are probably sinking into the head. No amount of shimming is going to help.

With that much time on the bike I would inspect the cam chain along with the valves/

Part it out it is not worth fixing. The problem you have is that you have a 2004 rmz 250 which is the worst 250f ever produced besides the knock offs from pep boys. You'd be better off putting the money into something else my man! Good luck !

I've also owned my 04 RMZ since 2007 and it always started fine until recently I had issues as well. I did the valves and cleaned the carb which helped greatly but still was a pain to start. After messing with it for a while I found that I need to pull the hot start lever when it's cold. Ya I know that's weird but I guess it let's more air in the carb and I actually just flicker the hot start like a throttle for 30 seconds or so and once it's warmed up after riding a little it starts first or second kick. Maybe the float heights off and it's getting too much gas so it needs extra air but whatever the reason hey it works so I'm not complaining!

If you need the hot start lever when its cold,fuel is leaking into your engine when its just sitting. Sounds to me like your needle and seat are worn,and or your float level is not correct. Also check for clogged vent hoses. How many times have the valves been shimmed,if more than twice,your valves and or seats need to be replaced also. That engine was not very durable,and overheated very easy.

Thanks I appreciate the input. I did the valves only once since I have bought it in 06 or 07 but it was a raced by a pro GNCC rider ( unfortunately I forget the name ) so I'm assuming they did it at least once therefore it's safe to say it was done at least twice. I replaced all the needles including the float needle and the next thing I was gonna do was the valve seats. I didn't even think that the valve seats were related to the issue that I was having but now that you mention it that makes sense. I'll mess with the float height first and see if that helps. I know this belongs in a different thread but do you recommend Stainless valves or titanium? If I do the seats do I need to replace valves at same time even if they are in good condition (within spec)? I haven't put many hours on the bike cause I lived in shitty South Florida where there is no place to ride anymore plus I had health issues however I moved to CT this year where I have a MX track in the next town over and also found some nice trails close by so I'm gonna be testing the motor now that I'm riding more. I know everyone says these motors suck but since I'm a lighter rider (150 Ib) I love the fact that this bike is so light ( I think it's actually the lightest 250F ever). I've had good luck with it so far and I have basically every performance aftermarket part on the bike so the only time it overheats is when I'm stuck in tight technical single track and am mainly in first gear.