1989 YZ250.....Starts within 3 kicks. Idle seems to not be a perfect "purrr" but doesn't stall out. Pops a little here and there. It seems to be starving for power so I thought maybe putting around in the yard it needed opened up. I took it down the road and 1st gear is a good 2 second delay before it "grabs". 2nd gear about the same, maybe 1.5 seconds and 3rd gear maybe 1/2 second before she takes off.
So to mimic the sound it's like burrrrrrrrrr (2 seconds) then WAAAAAAAAAAAAA. Once you get it there the power is incredible. Front end wants to lift up in 3rd gear. But it takes a bit to get there.
Is this a power valve issue or a jetting issue? Another note, I'm getting a ton of oil splatter where the fatty meets the silencer. Perhaps the gas the guy dumped in before was too rich? Book says something like 25:1.
Could be rich. Could be Lean. Could be powervalve. Could even be an airleak... the joys of old bikes!
Start by pulling the carb and recording the settings. Check against the stock jetting specs in the manual.
If the manual states 25:1, then that is what the standard jetting will be set for. However you can run up to 40:1, even 50:1 safely depending on oil, and obviously jetting properly to suit.
I run my 1989 RM250 on 40:1 with 0 issues and very little spooge for reference.
On another note.....fresh oil change in the crank with a new gasket that evidently isn't doing whatbits supposed to do. Is this a sign the coolant and oil is mixing?
The delay sounds more like a PV issue. That's the way hot ported bikes would act in the 70's, before PV's. With the exhaust porting timing always being high you have to wait for it to, "get on the pipe". The PV give you some low port timing to pull you through the lower rpm ranges.
Hard to tell from the picture about the oil / coolant thing. If it's leaking out the top, then there's a good likelihood there is coolant flooding the cases. Simply look in the radiator to see if you are losing coolant and drain the oil to see if it's got coolant in it.
Sounds like you had the side case off, so there's a possibility that you have got something jacked up and you have both a stuck PV and a coolant leak.
And I'm not sure what oil you're running, but I doubt there's any reason for you to need to run more than 40:1 premix, regardless of what the book says.
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