Multi Gauge speed not reading

[roadrunner]

Could someone describe best way to troubleshoot speed reading low or not at all. Seems to most of the time read 4mph. I would assume I need to clean a plugged speedo pressure tube. How best to do that and where to start?

thanks

John

[jb123]

if you have it hooked up at the motor, use a small drillbit by hand and try to clear it that way, or air pressure downwards as the motor tubes get clogged much.