I have a Kawi FD501V twin cylinder liquid cooled on a JD LX279. I've had to replace a number of things, to include the carb. It was running very rough and the jets were seized inside and I ruined the jets getting them out so I replaced the carb. I've replaced the voltage regulator that was bad (not charging). New PTO also. Engine RPM's were not an issue before.
Now when I engage the PTO it drops about 1000 rpm. It will also struggle when going uphill, the governor is not compensating. I have reset the governor correctly. I'm afraid I may have stretched the governor spring slightly during the carb replacement.
Could a weak governor spring be the cause of the governor not compensating for the power draw and causing the RPM's to drop? Is there anything else I should be looking at?
Yes
The speed is a tug of war between the governor which is trying to close the throttle & the governor spring which is trying to hold the throttle open .
Pull the governor arm to open the throttle slowly with you finger
If you feel the arm pulling against your finger and it gets stronger the faster the engine is reving then the governor is working properly
the governor is built onto the cam, it uses large ball bearings in a flyweight system. the part that spaces the balls is made out of plastic, it locks onto the cam with 2 small tabs, if they break off the governor will work but with a long delay.
I have another LX279 that I use regularly. I swapped the governor springs and there is no change. The mower runs excellent, starts easy and idles good up and down. It has no issues until you engage the PTO or drive it up an incline and then the RPM's drop significantly. What else could the issue be?
the governor is built onto the cam, it uses large ball bearings in a flyweight system. the part that spaces the balls is made out of plastic, it locks onto the cam with 2 small tabs, if they break off the governor will work but with a long delay.
What is the top no load speed? Service manual say 3550. Did you take the throttle control plate loose or off? If you did and did not put it back exactly where it came off it will effect the top no load speed. Changing the spring would have no effect if this is the case.
I did have to take the throttle plate off when removing the carb. When I put it back on I adjusted the plate to roughly 3600 rpm and tightened it well. The plate has not moved and it holds the correct rpm at high throttle, until I engage the PTO or travel up an incline, then rpm's drop to about 2400.
Have you done a cylinder balance test? Start it up and pull one plug at a time and watch the drop in rpms and if it dies on one cylinder the other one is dead. 1000 rpms is a big drop with both cylinders firing but not just firing on one.
May not be a spark issue very carefully feel the exhaust pipe going into the muffler if one is not firing it will be cool but be careful not to burn yourself.
Just thought of this we have a hand held lazier heat gun will give it a try next time I have one running on one cylinder. You can also check for spark with a hand held tac no tac reading no spark.
The mower runs excellent, starts easy and idles good up and down. It has no issues until you engage the PTO or drive it up an incline and then the RPM's drop significantly.
Blades could be dull.
Valves out of spec.
Engine overheating.
Improper oil.
Governor and or throttle springs messed up.
Dirty engine block and cooling fins.
Cutting too much grass at one pass.
Cutting wet grass.
Dirty air filter.
Dirty fuel tank.
Deck is clogged with grass.
Spindle bearing/s going bad.
PTO going south.
Valve adjustment check.
Tire pressure too low.
Improper belt/s installed.
Idler pulley bearings going bad.
Belt routing improper.
Blades installed upside down.
Water in the fuel.
Weak spark.
Once again, the rpm's drop when I engage the PTO or when going up an incline (with the PTO off) so I'm pretty sure I can rule out anything with the PTO or the deck. And I doubt low tire pressure is an issue.
That shows the governor is working as it should so either the arm has slipped on the shaft or the spring is not pulling hard enough against the arm to over power the governor.
Spring can be stretched or n the wrong place or the throttle cable is not on the right place , the outer can slip under the clip which is very common .
To set the cable loosen the cable clip & se the throttle control to wide open.
On a throttle only system pull the outer back as far as it will go & tighten the clamp
On a combined throttle/choke cable pull it back till the choke closes fully then tighten the clamp , now back off the control lever to the full speed detent and check the choke is fully open, if not adjust the cable till it just does open fully
Had an LX279 for 14 years never had any real trouble from it, used non ethanol gas in it the whole time, had one problem later on with it when you engaged the PTO the motor pulled way down, replaced the battery because the light on the dash would flicker as the rpms would drop, after the battery was replaced no more problems ever, don't know what deck your using, mine was a 6 blade piranha deck (44")
Unplug one spark plug wire at a time so engine is running on 1 cylinder. If you have a dead cylinder you probably have a valve problem. Most likely exhaust valve.
May not be a spark issue very carefully feel the exhaust pipe going into the muffler if one is not firing it will be cool but be careful not to burn yourself.
Yea touch an exhaust pipe that might be 400F+ degrees. Can you say BBQ human? Basically HLW49 are you nuts? Third degree burns are not fun at all.
Just tested a Briggs here that I having a problem with and one side is running at 700+ degrees F and the other only at 125F. I finally narrow its problem so it should fixed next week. Just had other things to do today. Like 4 Stihl trimmers.
One side is running way lean the other so lean it not even firing.
Since we have no exact model no. could not look up exact engine. I would assume it is a single bore carb. If it were a two bore carb. I would say one side of the carb. may not functioning as it should. This could be the problem on the Briggs Star Tech is working on.
Responding to several suggestions: it has a brand new 550cca battery. I used a laser temp gauge, both exhaust pipes got up over 700 degrees. The engine model # as stated in the original post is a FD501V, single bore carb. Update: I have two LX279's so I did an engine swap today. The good engine worked fine on te mower with the problems, so that rules out the deck, belts, pulleys, battery, etc. The problem is isolated to the engine.
Among the many things I had replaced on this mower was the Ignitor/CDI control module. One cylinder was not firing and the diagnoses led to the CDI. I purchased an aftermarket CDI but it corrected the issue and both cylinders were firing correctly. Could the CDI cause the drop.in RPM's under load?
Update: I cracked the case to check the governor. Governor appeared fine. Spent $40 on sump and crankshaft gaskets and put it back together and it's running fine, not dropping rpm's. The only thing I can guess is that something in the governor linkage was in a bind.
Now for the the bad news. This engine has been fighting me all the way. Fix one issue and another occurs.
Gas is leaking out of the overflow on top of the carb when it is running and under load. It runs fine, just excessive fuel. I'm at a loss! Any suggestions?
