Deere 1420 front deck mower question about engine

[Volvoman]

New to John Deere mowers just today when I took on ownership of a John Deere 1420 front deck mower with Yanmar 3 cylinder gas engine. 737 hours from new. Seems to be in real nice shape, definitely not abused in any way. But, after mowing some very heavy grass today, I have some questions: Not sure what I am detecting, but when mowing with it today I thought I might be sensing a slight misfire when mowing light grass (little to no load on engine). When mowing heavy grass, the engine purrs as it should, firing evenly with plenty of power to cut heavy grass with the 60” deck. Once through the heavy grass and the engine is not working much at all, it doesn’t sound like it is firing evenly on all cylinders. Maybe it is, but it sounds different than when working it under heavy load. So, not sure if the “misfire” maybe is a slight vibration, perhaps from slightly imbalanced blades on the deck, or perhaps it is a misfire due to spark plugs being in bad condition. Under no load, low idle sounds good. Not perfectly smooth, but quite good. At high idle, no load it runs perfectly.
So, tomorrow morning, the blades will be removed for sharpening and balancing. After that, will pull the plugs for inspection. Anyone here with experience running a Yanmar 3 cylinder gas have any thoughts as to what I may be detecting?
Vvm

 

[Volvoman]

Okay, so time for an update. What sounded like a misfire was not what is going on. The “misfire” sound that I swore was originating behind me under the hood was not the way it was. Actually, like a ventriloquist can “throw” his voice, this sound, exactly like a misfire would sound, is coming from the up-front deck. Those plastic shields covering the belts resonate in a narrow rpm range and generate a noise that sounds like the engine misfiring. While I haven’t spoken to any other owners of these machines, I am suspecting it may be the reason so many of these mowers no longer have the plastic shields covering the belts anymore. The shields resonate like a drum skin. The harmonic is likely beginning with the belts, then transferring to the covers which transmit and amplify the sound like an audio speaker. That’s what I was hearing. Sounds like an engine misfiring. Maybe more so due to my wearing ear muff silencers. So, mystery solved. Wish I’d figured it out before going through the spark plugs, wires, etc.
Vvm

 

[beddy85]

Just recently sold my 1420 with 840hrs. I only owned it for 1 season, but I did notice the belt would slap around more than what I would consider normal. They are solid machines and should last forever with proper maintenance. I would make sure the belt is good and tight.

 

[Volvoman]

Did you notice anything problematic about the 1420? Just curious that you sold after one season, maybe due to problems?

 

[beddy85]

Did you notice anything problematic about the 1420? Just curious that you sold after one season, maybe due to problems?

I didnt have any problems with it. I bought it from a local older gentleman that bought it new. It was a solid machine. Had an air ride seat and awd. The reason I sold it was cuz it was because it was because any attachment I wanted for it was too far out of my budget. I would not hesitate to own one again. I ended up with a front mount grasshopper and find its more comfortable for me vs having a steering wheel. Just make sure you keep the radiator clean and you'll be good for a very long time. Also, make sure you keep the toe adjusted so you dont wear your rear wheels out so fast.

 

[Volvoman]

Good to know. Thanks. Did you find the awd to chew up the turf when turning sharp?

 

[beddy85]

Good to know. Thanks. Did you find the awd to chew up the turf when turning sharp?

I noticed it a little bit if I'd try to whip it around too fast. Does yours have awd?

 

[Volvoman]

No, it doesn’t. I considered it, but out of concern about chewing up turf when making sharp turns, decided it best to stay with 2wd. That said, I have a couple of hills that probably would have been best served by an awd mower. Always tradeoffs to make.

 

[beddy85]

No, it doesn’t. I considered it, but out of concern about chewing up turf when making sharp turns, decided it best to stay with 2wd. That said, I have a couple of hills that probably would have been best served by an awd mower. Always tradeoffs to make.

Yes, actually the awd on those work pretty good.

 

[Richandtd]

I have an 07 1545 with the 72” flex deck and I have 6 belts on the deck. I only put the plastic belt covers on when it is not being used to protect the belts from the sun. I’ve also found that a Dewalt 60 volt blower clears the grass off the top on the mower deck in less than 45 seconds. This is a beast of a mowing machine. I keep it in 2 wheel drive unless I need 4 wheel Traction. This is real easy on the diesel which makes me smile. My field of green what ever grew there looks like a lawn after I cut. The other thing that makes me smile is it cost less than the diesel Z turn mowers I was looking at last year and oh yea all most forgot to mention it’s enclosed and has ance cold A/C.