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Discussion Starter #1 (Edited)
Hey everyone, new member here but I've found plenty of good answers for issues with my 345 and 425AWS so I was hoping to get some assistance...
I am perplexed with the problem I'm having with my 425 that has developed after a successful summer of trouble free mowing. When starting the deck, the engine really struggles to get it started and will sometimes shut off completely. I'd say about 50/50 on if it will start the deck without shutting off. No matter whether it starts or not, the battery light comes on and the engine stutters quite a bit. Also, in thick grass it starts to bog down like it never did this summer. Basically, it is struggling under a previously easy load and I can't figure out why.
I verified that the blades spin freely by turning the shaft by hand. Tractor speed is normal at all times and I've verified both spark plugs are firing which were things I read that might be issues.
For reference, this mower uses a Kawasaki FD620D liquid cooled horizontal shaft connected to a trans-axle in the back running the shaft driven PTO.
Any ideas on what might be wrong would be greatly appreciated!
 

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I'm guessing that tractor has an electric PTO clutch. Does the battery light come on as soon as you engage the PTO or does it only come on after engine RPM falls below idle speed? The fist scenario would tell me your PTO clutch is drawing too much current, the second scenario is normal as the alternator output will be too low below idle and the light will come on to warn you. If it was mine I'd disconnect the mower from the PTO and try engaging the clutch, see if the battery light still comes on and how the engine responds.

EDIT: What I'd be looking for with that test is excessive current draw by the clutch. If you have a clamp-on ammeter then you could use that to measure the current, but I'm not sure what a normal value is for those. Certainly it should be less than the rated current output of your alternator. Is there a dedicated fuse for that circuit?
 

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Dixie had valid points on the electrical system, but your comment about bogging in heavy grass leads me down a different path.

First, check governor linkage and make sure it moves freely. If OK, next would be a fuel delivery problem: dirty strainer in tank, collapsing fuel line(s), inline filter, weak fuel pump, dirty carb. A last item may be the fuel itself. Do you use a fuel stabilizer like sea foam or stabil? Bob
 

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Discussion Starter #4
I'm guessing that tractor has an electric PTO clutch. Does the battery light come on as soon as you engage the PTO or does it only come on after engine RPM falls below idle speed? The fist scenario would tell me your PTO clutch is drawing too much current, the second scenario is normal as the alternator output will be too low below idle and the light will come on to warn you. If it was mine I'd disconnect the mower from the PTO and try engaging the clutch, see if the battery light still comes on and how the engine responds.

EDIT: What I'd be looking for with that test is excessive current draw by the clutch. If you have a clamp-on ammeter then you could use that to measure the current, but I'm not sure what a normal value is for those. Certainly it should be less than the rated current output of your alternator. Is there a dedicated fuse for that circuit?
I don't believe it is an electric clutch based on the gauge of wire going to the transaxle, but I follow your logic. The battery light comes on as the engine RPMs slow, which makes sense. I have tried without the deck and it starts the PTO with very little engine drain. This only happens with a load.
 

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Discussion Starter #5
Dixie had valid points on the electrical system, but your comment about bogging in heavy grass leads me down a different path.

First, check governor linkage and make sure it moves freely. If OK, next would be a fuel delivery problem: dirty strainer in tank, collapsing fuel line(s), inline filter, weak fuel pump, dirty carb. A last item may be the fuel itself. Do you use a fuel stabilizer like sea foam or stabil? Bob
We just rebuilt the carb near the end of the summer, but I'm not sure on the governor so I'll be sure to check that. Fuel filter looks clean, but I'll change that since I have one laying around. Fuel lines look good. I used sea foam before biting the bullet and cleaning the carb. I use 93oct fuel if that matters. Is the strainer the bag looking packet on the bottom of the fuel pump? It is dirty looking from what I remember when I cleaned out the tank the beginning of summer. I"ll have to check to see if that can be replaced.
 

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Dixie had valid points on the electrical system, but your comment about bogging in heavy grass leads me down a different path.
Whoops, I missed that key point! Yeah, that's probably not electrical...

This only happens with a load.
...as demonstrated here. So yeah I agree with md1600, check out the operation of the governor and yes, that bag-looking packet is called a filter sock and is commonly used on fuel pump inlets. Usually they're replaceable, the mesh is fastened to a plastic collar that just presses over a tit on the bottom of the pump.
 

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Hmmm, "rebuilt the carb near the end of the summer" and " starts to bog down like it never did this summer." Think perhaps they're related???

People have many definitions of "rebuilding a carb." NAPA, and I'm thinking many other auto parts stores, have a carb cleaner in a gallon bucket. Dismantle carb, put all metal parts in bucket, and soak overnight. Remove parts from bucket, spray with parts cleaner or carb cleaner. Any place that you can, put the small tube on the spray can into all of the holes and spray. Finally blow off with compressed air. I've got some old air nozzles that AREN'T OSHA approved and give me full 100 psi pressure. THIS is what you really need!

Engine shutter when engaging pto: My 322 has (what I consider) a high idle speed, 2000 rpm. If I engage pto at idle, engine stalls, period. !/3 throttle, maybe stalls, but definitely shudders. 1/2 throttle, engine slows for a few seconds, maybe 2-3, and then normal. Try different throttle settings to eliminate shudder. Bob
 

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Hm.
Sounds like when our conquest was only running on one cylinder. When you tested for spark, was the engine hot? Sometimes coils and diodes intermintently fail when they are hot. Run the engine until it is at operating temp, and then disconnect one of the spark plug wires, if the engine dies, it is only running on that cylinder. Do this to both sides, one at a time.
 

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NAPA, and I'm thinking many other auto parts stores, have a carb cleaner in a gallon bucket. Dismantle carb, put all metal parts in bucket, and soak overnight. Remove parts from bucket, spray with parts cleaner or carb cleaner. Any place that you can, put the small tube on the spray can into all of the holes and spray. Finally blow off with compressed air. I've got some old air nozzles that AREN'T OSHA approved and give me full 100 psi pressure. THIS is what you really need!
Agreed. That's the best way to clean a carb BUT the new stuff doesn't work as good as what was sold several years ago. Probably the granola-eaters trying to save the world again. Lol. I found this out when I put both carburetors from my boat in a brand new bucket of the stuff and it... sorta worked. Nothing like the old school version! OSHA approved air nozzles? What are those? :) I do have a few of them as they're good for moving a high volume of air due to the venturi provided by the holes in the sides, but I have a couple old school ones as well for when I need high pressure!

Engine shutter when engaging pto: My 322 has (what I consider) a high idle speed, 2000 rpm. If I engage pto at idle, engine stalls, period. !/3 throttle, maybe stalls, but definitely shudders. 1/2 throttle, engine slows for a few seconds, maybe 2-3, and then normal. Try different throttle settings to eliminate shudder. Bob
My 332 (diesel) will do this too, it does best just under 1/2 throttle for PTO engagement with the mower. I can do it at idle without stalling as long as I'm not in tall grass, but it does almost stall.
 

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I had some Permatex (I believe) carb back in the late 60's/early 70's. The carbs actually sparkled when you took them out. It would remove anything and everything from the carb! It would also remove your skins, hence the "need" to take if off the market!

OSHA approved air nozzles: Again! back in the 70's OSHA said full pressure air nozzles are dangerous and can inflict personal injuries. I agree IF improperly used! OSHA then ruled that an air nozzle cannot produce more than 35 psi. The company I worked for scrapped all of their nozzles (about 3 of which I "happened" to end up with!) and bought new "approved" nozzles. We "modified" a couple of the approved nozzles, but eventually the manufacturers also modified the nozzles so they couldn't be "field modified" to give full pressure!!

BTW, a ball valve attached to your air line WILL give you full flow @ max pressure! A piece of 3/16" tubing on the end helps direct the flow. Bob
 

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Discussion Starter #11
Hmmm, "rebuilt the carb near the end of the summer" and " starts to bog down like it never did this summer." Think perhaps they're related???

People have many definitions of "rebuilding a carb." NAPA, and I'm thinking many other auto parts stores, have a carb cleaner in a gallon bucket. Dismantle carb, put all metal parts in bucket, and soak overnight. Remove parts from bucket, spray with parts cleaner or carb cleaner. Any place that you can, put the small tube on the spray can into all of the holes and spray. Finally blow off with compressed air. I've got some old air nozzles that AREN'T OSHA approved and give me full 100 psi pressure. THIS is what you really need!

Engine shutter when engaging pto: My 322 has (what I consider) a high idle speed, 2000 rpm. If I engage pto at idle, engine stalls, period. !/3 throttle, maybe stalls, but definitely shudders. 1/2 throttle, engine slows for a few seconds, maybe 2-3, and then normal. Try different throttle settings to eliminate shudder. Bob
I believe you're right about them being related. The carb was completely disassembled and jets were completely cleared out of debris (there was quite a bit). This was done because it was running really rough. Since then, the engine has ran better than ever at every throttle level. The lack of power
I have tried at various throttle levels. 1/3 engine shuts off, 1/2 it "might" start, 2/3 it'll start pretty smoothly. It's always started without issue at 1/2 until this summer.
I've ordered a tank filter, but for now I'm going to run it for a few minutes without that filter to test these ideas.
I'm really appreciating the advice everyone!
 

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Discussion Starter #12
Hm.
Sounds like when our conquest was only running on one cylinder. When you tested for spark, was the engine hot? Sometimes coils and diodes intermintently fail when they are hot. Run the engine until it is at operating temp, and then disconnect one of the spark plug wires, if the engine dies, it is only running on that cylinder. Do this to both sides, one at a time.
It was hot and I tried starting the deck before and after. Definitely a change of power no matter which side I disconnected.
I wish it was the spark plugs because that was my gut feeling, but what everyone here has said definitely has me sniffing the fuel system for problems.
 

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Your last check tells me you're hittin' all both cylinders! I'm still going on the assumption that when you need more power, the governor is opening the throttle plate (??) but there just isn't enough fuel for the engine to respond. Keep checking, keep asking, we'll get it! Bob
 

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Your last check tells me you're hittin' all both cylinders! I'm still going on the assumption that when you need more power, the governor is opening the throttle plate (??) but there just isn't enough fuel for the engine to respond. Keep checking, keep asking, we'll get it! Bob
Alright so I finally had some time tonight and changed both the in-line fuel filter and the one in the tank attached to the pump. Still struggled a little to start the deck but the engine wasn’t warmed up all the way. Once it started it seemed to run at more consistent RPMs, however I don’t have any thick grass to test the load on. After I warmed it up it was able to start the deck with minimal effort.
I did inspect the governor movement while adjusting the throttle and it didn’t look right to me. First of all there is a pin hole in the shaft that looks like it should have something (r-clip or linkage arm) in it but there is nothing. So it looks like the governor/throttle arm is just slid onto the governor shaft and moves very very slightly when the throttle is brought up. I’m not as familiar with governor articulation so maybe someone can chime in on that.
I attempted to adjust the governor shaft on the arm as described in someone else's post taken from the repair manual but it seemed to make the tractor run much worse. I shut down and loosened the bolt on the governor arm so it would go back to the previous position. It seems to run about the same as before adjusting the governor.
 

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My 425 with a 60" deck has a similar condition When I got the tractor it had around 1,000 hours on the engine and it had been rebuilt because of the typical cam gear failure. You have to start the engine and let it warm up some before engaging the deck or it will die. The colder it is outside the longer you need to let it warm up. Even after it's up to operating temperature the engine will still stutter and drag down a little when you engage it. Overall power seems fine, but don't really have anything to compare it to. It will chug thought some pretty tall and thick grass before the engine starts to bog down. Guess I've never messed with it as it hasn't been a huge deal, but do need to check on the governor operation.
 

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I think you have the answer when you said " I have tried without the deck and it starts the PTO with very little engine drain". Disconnect the deck and recheck spindles and EVERYTHING that powers the blades....idlers included.
 

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Discussion Starter #17 (Edited)
Try different throttle settings to eliminate shudder. Bob
Bob, you were right on it with this comment!
I wanted to update everyone after fighting with this for over half the winter...Below is what I have done up to this point:
  • Change tank fuel filter
  • Change inline fuel filter
  • Adjusted governor shaft to arm
  • Changed spark plugs and verified they are both firing independently
  • Cleaned mower deck thoroughly and verified all pulleys and idlers spin freely
  • Replaced the governor spring and throttle spring on the control panel
I had my Dad come look at it since I had exhausted all ideas in my mind...he believed (based on his 6th sense) that the engine wasn't developing enough RPMs at full throttle to work correctly. This is funny because he doesn't even own a 425, he has a late model 345!
So we borrowed a tachometer and measured the RPMs at idle and full throttle while consulting the service manual I dug up online.....
Sure enough, it was only developing ~3200 RPMs at full throttle which is low compared to the ~3600 described in the service manual. We adjusted the throttle control panel and the throttle cable up to spec and it starts the deck with ease. I don't have high grass to test at the moment but I can tell when accelerating from full stop that we are back in business.
Thank you for all the help and hopefully anyone else who has this problem can learn from my blunders 🚜
 

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Welcome to the forum, it is helpful when asking an engine question if you specify what engine you have. I think that is suggested in the Forum guide lines. There are engine people who may not recognize what engine you have by model numbers of the machine. By the way, I am not experienced with the engine you apparently have but the difference between 3200 rpm and 3600 rpm should not make the substantial difference you seem to indicate.

Walt Conner
 

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Welcome to the forum, it is helpful when asking an engine question if you specify what engine you have. I think that is suggested in the Forum guide lines. There are engine people who may not recognize what engine you have by model numbers of the machine. By the way, I am not experienced with the engine you apparently have but the difference between 3200 rpm and 3600 rpm should not make the substantial difference you seem to indicate.

Walt Conner
Ah, good point. It is a FD620D and I'll update the original post for reference.
I see your point with the RPM difference. I did quite a bit of cutting and driving yesterday and it responds very differently to accelerating, starting the deck, and bearing a load.
Also, in my reading, I have noticed many people complaining of engine stalling when starting a 60" deck using this same engine and mower. Considering some people are able to use a 60" without issue makes me think this adjustment is important to the output of the machine, and a throttle panel slightly out of spec could cause power loss problems more widespread than folks may realize.
 
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