Ttr 90 wont stay running and makes a ringing noise

i dont think you need a new carb but if you are already getting one this is fine you need to find out what jets are in it or you can get jet kits for your carb and change them yourself they come with instructions. with it running for a while just fine and then dies this sounds like you may have water in the gas or dirt in the carb bowl to check for dirt get a clean empty water botter clear one put the hose from bottom of carb in bottle and open the bleeder screw on the bottom of the carb bowl if there is dirt or water you will see it in the bottle empty the bowl then turn on the gas petcock let a bit more run through shut of petcock and close the bowl screw , if you see dirt then you should clean the carb remove and rebuild while you are doing this you can install larger jetting good luck

I would check the compression of the piston, the rings could be stuck and not have good compression. It should show 120 psi or more. Also can pull off the exhaust and look in the exhaust port to see the rings, piston, and cylinder walls. If the motor has a power valve make sure that is not gummed up or stuck. Mark C

sounds like your rings are shot, Prob only runs at high rpm & dies when gets lower and wont tick over, try kicking it over slowly with your foot can you feel the compreesion cycles , if not defo rings

Remove, dissemble and clean the carb. Check the rubber diaphragm for cracks, pinholes and poor seal at the gasket. Install a new spark plug, clean the air filter. The high idle is caused by a lean fuel mixture. Outside air is entering the mix. Look at the rubber "O" ring on the carb joint. Check for cracks and hardening of the ring. Your carb will have a plug or a hose at the front edge of the carb joint. Check the plug / hose and clip. Check for cracks in the plug / hose and hardening. Check the entire length of the hose if a hose is present. Please rate my answer. Thanks!

well it is normal for a four strokes exhuast to turn red your not suppose to let them idle for long periods of time. and the running problem is probably the carb i would take it off and clean it before doing anything else could save you money i had the same problem on a yz450f i took the carb off and cleaned it and problem was solved and also run 93 octane gas if your not already

Replace the fuel and air filter, replace the spark plug and make sure that the carb is lean, apart from a bit of adjustment on the mixture screws, that is all you can do short of cleaning exhaust ports and exhaust systems.

Piston rings may be sticking after sitting for so long. It may serve you well to remove the top end, paying special attention to the timing alignment as you do. Visually inspect the piston and rings. ensure the rings can move freely in their grooves. Look at the piston for signs of blow-by. A burned up surface of the piston that extends past the rings onto the skirts. You may simply re-ring this machine and it would solve your problem if you view these problems.

WOW>.. thats strange... anyway this sounds like a float level issue.. take it to a competent professional and he can clean and set the carb off the bike,

Because the timing is off. If the timing is too advanced, or too retarded, it will make your exhaust pipe cherry red.