Hi all got old Yamaha rt2 this thing is real pain. First got cylinder bored out new top
end then it wouldn't run. Key way was shared off replaced bike started but won't rev up.
Did leak down test it was good been through carb many times. Bike runs a little better with choke on. Please help thank in advance

Have you checked for the exhaust being plugged?

unhook the fuel line from the carburetor or petcock and turn the petcock to on and RES to make sure enough fuel is coming out. It should be flying out. Also check to make sure your flywheel is tight and your in time as well i just had my flywheel come loose on my DT250 because i forgot to snug the thing up so it would idle great but not rev up hardly at all!

I have done both of your suggestions already ..lots of gas coming out the new petcock and the flywheel is tight

hhmmmm its possible your decompression release is stuck open those tend to get gummed up have you checked that yet?

No that's something I never thought of I'll try that tomorrow. If the exhaust were plugged why would bike run better with choke on?

If that dont work out it might be the air mixture screw setting or the needle height setting. I have an RT3 that's giving me all sorts of problems that im gonna have to take to someone or start a thread on. Arent those things fun to kick over! the kick back is VICIOUS to say the least i had an x-ray done back in July because i thought i broke my ankle from it kicking me back! i couldn't walk on it for nearly a week.

Yes my first thought is exhaust too, but only reason the choke would help is if the choke jet in the bowl cavity was blocked so opening the choke just ads air leaning it off a bit--but that stretching the imagination a little so probably not that. Carb small Oring is important as drowns it but wouldn't improve with choke. Need an audio of it really please. So far as exhaust goes there's a restrictive swirly thing deep in the tail bit--can see it looking in unless it's been removed, in which case it'd be rowdy [noisy] 'as'. If it was 'that' restricted you could [to prove a point] reduce the main jet by heaps just for a stationary rev, but maybe only something i'd do lol. Decompressor won't affect it revving out even if you held it open & will just take the sharp edge of the exhaust note. Some motors have them open all the time, think one year of RD400 & our AG175's about "76. Anyway--!!.

They love shearing keys of which you've found, but make sure it hasn't done it again. Gotta be super tight & held solid to get a solid feel on the socket. There's a pic of mine somewhere on here with the holding tool resting on the footrest & engaged in the slots so nothing moves at all. I'll admit i overtighten mine but the crank is damaged from someone else's undertightening.

I did leak down test yesterday it held 8psi for 5minutes no problem. Then started back up it revs up on it's own with no choke