mlhunter
Silver Member
Hi guys! Its been a couple of years since I've been on here and I now have 165 hours on my Pt425 with (EH72?) 25hp Robin/Subaru engine. Overall I've been satisfied with no problems. However, yesterday I encountered something new.
After using the brush cutter for about an hour to mow the remnants of a 1 acre food plot I started cleaning up some bramble choked paths with it. After several minutes of that I stopped to clear some junk out of my left front wheel and the motor rpm went way up! I dropped the throttle back to idle and it remained running near what would normally be full throttle! At that point I decided I'd better quit and put the tractor back on the trailer and went home with it.
Back at home, I studied the engine's throttle linkage and read the online Assembly/Disassembly and Parts manual to see what all is involved. Pulling the tractor's throttle lever back pulls the governor arm toward the carburetor and moves it to full throttle. It appears that the governor arm should pull against its restraining springs to govern how much thottle opening there is depending on the engine load. At rest with little or no load there is no movement of the governor arm to do that which seems to be why the rpms remain so high with little or no load. Nothing appears to be broke and all springs appear to be functioning normally.The governor arm is tight on the vertical shaft that goes down into the block where the governor mechanical parts are.
Right now it appears that I may have to remove the timing gears cover to get to those internal governor parts.
Naturally it couldn't happen at a worse time! I would like to hear from you guys that are familiar with these engines to determine if I'm on the right track and if there is anything else I should be looking at before I start pulling the hydraulics off the engine to to repair it.
After using the brush cutter for about an hour to mow the remnants of a 1 acre food plot I started cleaning up some bramble choked paths with it. After several minutes of that I stopped to clear some junk out of my left front wheel and the motor rpm went way up! I dropped the throttle back to idle and it remained running near what would normally be full throttle! At that point I decided I'd better quit and put the tractor back on the trailer and went home with it.
Back at home, I studied the engine's throttle linkage and read the online Assembly/Disassembly and Parts manual to see what all is involved. Pulling the tractor's throttle lever back pulls the governor arm toward the carburetor and moves it to full throttle. It appears that the governor arm should pull against its restraining springs to govern how much thottle opening there is depending on the engine load. At rest with little or no load there is no movement of the governor arm to do that which seems to be why the rpms remain so high with little or no load. Nothing appears to be broke and all springs appear to be functioning normally.The governor arm is tight on the vertical shaft that goes down into the block where the governor mechanical parts are.
Right now it appears that I may have to remove the timing gears cover to get to those internal governor parts.
Naturally it couldn't happen at a worse time! I would like to hear from you guys that are familiar with these engines to determine if I'm on the right track and if there is anything else I should be looking at before I start pulling the hydraulics off the engine to to repair it.