I picked up a JD LX255 at a great price but the guy was shady about what was wrong with it. I had to replace the head gasket and do a complete breakdown on the carb. At some point someone has tinkered with the linkages and it appeared that the carb had caught fire because the choke plate cap was melted and I had to put on a new choke kit.
I got it started and running, but it runs at dangerously high RPM. I have to move the throttle lever to the low throttle position to run it at the normal operating RPM. Moving the throttle lever up increases the RPM's significantly. I've also noticed a significant loss of engine power when the PTO is engaged.
The carb itself (Walbro) has two adjustment screws, a low idle on the top and a fuel mixture screw on the bottom right (in the picture). There are two adjustments on the linkage, what appears to be a low and high throttle limit. I've made minor adjustments to all of those adjustment screws just to see if anything changes and it did not.
Any suggestions would be appreciated.
There are two pictures of the linkage, one with the throttle in the high position and one in the low position.
#2
RoperGuy
Now when you say it revs dangerously high, it makes me think your governor is not set up properly, witch might also explain bogging after pto engagement.
What about the governor gear connecting rod that goes though the crankcase and connects to the L shaped linkage on the outside. I had that L shaped bracket off, does the position of the connecting rod matter when I attach the L shaped bracket? Would that cause this problem?
#5
RoperGuy
No just the outer linkage, I've had plenty of used/free machines where the previous owner had removed the carb and wouldn't run right after. I assume you know how to adjust the throttle cable and set air/fuel mixture.but I would suspect the unexpected when buying used. simple things like a return spring or linkage place meant can mean a lot. Is this an original carb for your make?
I have another LX255 in excellent condition so it gives me something to compare it to and the outer linkages appear to be set the same, I am wondering now about that governor gear connecting rod so I'll check with that tomorrow. The carb does appear to be the original OEM.
What about the governor gear connecting rod that goes though the crankcase and connects to the L shaped linkage on the outside. I had that L shaped bracket off, does the position of the connecting rod matter when I attach the L shaped bracket? Would that cause this problem?
Very good to know, thanks guys! I'll get to it as soon as we get home and I'll let you know if that solves the problem. Makes sense with the PTO issue, if it's already at max RPM's and I have it throttles down then the governor can't compensate with more RPM's when the PTO is engaged.
I thought that connecting rod would naturally rest in the "correct" position since the governor gear inside would be 'folded up' when the engine is not running. Not sure which way to turn the connecting rod before I re-tighten down the L shaped bracket to it but I'll just tinker with it and see if it makes a change.
I'm trying to attach photos. These are close ups of the connecting rod to the L bracket. The clean one is my mower, the dirty one is the one I'm working on. In mine the connecting rod is horizontal and the other is vertical. I'm feeling very good that's the problem. Can't wait to get home!
I adjusted the governor rod, it only rotates about 45 degrees, I had it all the way to the right so i turned it counterclockwise until it was horizontal to match the linkage on my other mower. Really didn't make any difference. I noticed that the plastic clip that holds the linkage rod that connects the top of the L bracket (and goes to the carb) was worn and had excess play in it. I replaced that clip and it helped. I can now idle it down very low but for normal operation I have to put the throttle lever at the halfway point. If I move it to full throttle it is dangerously high RPM. When I back the throttle down it does not want to respond so I have to manually push the L bracket back to reduce RPM's. It will then hold it at the lower RPM unless or until I increase the RPM with the throttle lever.
Could this be an issue with the internal governor gear or does this sound like a linkage adjustment issue?
I have drained the oil twice and I've not seen any plastic bits that might be a sign of a damaged governor gear.
When I engage the PTO I have to manually increase the throttle to compensate for the loss of power.
I took the engine off and opened it up. The governor gear cap had unseated. I put it back in place and closed it up. Hope to get the engine back on tomorrow and test it out.
#13
grumpyunk
Now you know why you got such a good deal. Follow the manual to make sure the governor arm allows full open throttle with all the slack taken out of the linkage. I would inspect the govern retainer very closely as it should not be able to come apart as yours did. The gizzards sure look nice and clean.
Remember that the governor is just fighting the spring that is connected to the throttle control. If the spring is under more tension (rabbit/fast) the governor has to work a bit more to close the throttle. If under low tension(idle) the governor has it easy to keep the throttle plate closed, or close to it. If there is excessive play in all the linkage, the governor will/can cause the speed to 'hunt' as things get out of 'synch', and the governor chases the throttle plate back and forth. A very narrow spring with hooks on both ends may be used to keep the slack out of the governor linkage, model and carb dependent.
tom
Great info Tom, thanks! Had it together yesterday and with a few adjustments to the linkage it is running and responding great. Hard to start initially but I may have weak gas, underpowered battery or worst case I need to clean the carb again but I'll work that out. It is idling great and running strong. I just rebuilt the deck and will put it back on today and then the real test, to make sure the engine compensates correctly when the PTO engages.
