80 DT85 only high RPM for 15 minutes

[speed]

I loose my high RPM after about 15 minutes.I know it's got a high and low section in the ignition but where? CDI? I have a 87 DT85 parts motor,if it is the CDI will it work on my 1980. Again it run smooth when this happens just no full throttle,about 3000 rpm.water pump seems to be working fine ,no over heating.

 

[speed]

Re: 80 DT85 only high RPM for 15 minutes

Been reading other forums ,and even though water comes out in big stream,and no alarm, could it still be overheating? One person suggested changing head gasket on the older DT85 with newer version.Is there any way to over ride rev limiter to see if over heating is possibly my problem?

 

[99yam40]

Re: 80 DT85 only high RPM for 15 minutes

Does your alarm work? Test it. Most motors have a temperature switch that grounds to the block when they hit a high temp.
You need to make sure it works before you can tell if it is comeing in and preventing you from destoying your motor.
A motor can overheat if the thermostat does not open and let the water flow through the motor passages.Pull it and test in a pot of hot water to see if it opens and at what temp it does open and close