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So started mowing this morning with my GT235 that has the Briggs engine. Something went snap and the whole tractor started vibrating like crazy. Turned off the blades, still vibrating. I can still start it, and it will still move so the drive belt is intact. What broke? Did I lose one of the two pistons? I did have to drive it a short distance to get back to the garage, but couldn’t tell you if it had less power or not. Thanks in advance.
 

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You will need to look things over good. It could be a drive component, belt tensioner, many other things too. Hopefully the Briggs is fine.
 

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With it still vibrating with the blades off, that limits the areas of concern to things that are always spinning (obviously).

If the transmission's belt is always engaged, that's something to look at, something like the tranny cooling fan somehow going way out-of-balance (like losing a bunch of fins).

A broken connecting rod would be a concern, for me. If you didn't hear terrible noises from the engine after the "snap", that's probably encouraging. You could remove one spark plug (I'd pull both wires), and either turn the engine by hand, or briefly engage the starter. See how it sounds when you're only compressing 1 cylinder. Then reinstall that plug, and remove the other one. If it turns more easily & faster on one cylinder, that piston may not be moving, and could have a broken connecting rod (or a valve that's staying open, etc). If the plug hole is above the piston (likely), you could also stick something like a pencil down through the hole, until it touches the piston, then turn the flywheel by hand. That will tell you whether the piston is moving.
 

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So started mowing this morning with my GT235 that has the Briggs engine. Something went snap and the whole tractor started vibrating like crazy. Turned off the blades, still vibrating. I can still start it, and it will still move so the drive belt is intact. What broke? Did I lose one of the two pistons? I did have to drive it a short distance to get back to the garage, but couldn’t tell you if it had less power or not. Thanks in advance.
Does the engine run smoothly or rough and irregular? You should be able to tell the difference between one and both cylinders firing, especially under load when moving it.

It could be as simple as the transmission belt splitting; enough is intact to keep spinning the tranny so you can move it, but the split 'tail' of the belt is slapping everything in its path, such as the rotation stop of the PTO clutch (directly under the engine), or something at the transmission or idler pulley. Drop the deck and look under the machine first. That transmission belt lasts about two years before it goes south, or about 200 hours. I've been through three of them at 550 hours on mine.

If it isn't the belt, then start looking at the engine, like RedOctobyr mentioned. Pull both spark plugs, take a pencil and put it down one spark plug hole at a time, then turn the engine by hand, using the flywheel screen of the crankshaft at the top of the engine. If the pencil gets pushed back, you have a moving piston, of it doesn't get pushed back, you've likely got a broken connecting rod. A stuck valve won't keep it from running, but it will miss and be down on power. A broken connecting rod usually causes catastrophic damage from the piece still connected to the crankshaft slinging around and breaking stuff like the engine case. If you were fortunate (?) enough that the rod broke close to the crank, it might not be enough of a piece to hit stuff inside the engine. but a rod usually breaks at a thinner end than a thicker one. The B&S engine is generally a robust and trouble-free engine, as long as the maintenance hasn't been ignored.
 

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The first thing I would look at is the PTO clutch. If the bolt is still tight then I would look at pulling a plug wire one at a time to see if you have a dead cyl.
 

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Discussion Starter #6
Thanks all. I will try the suggestions as soon as I have time and report back what I find.
 

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I think it would be a good idea to make sure everything is mechanically sound before starting the engine again, so do that first by checking that the pistons are moving correctly as stated above. After that you will have to just start checking things off the list of possible causes.
 

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I think it would be a good idea to make sure everything is mechanically sound before starting the engine again, so do that first by checking that the pistons are moving correctly as stated above.
Agreed. If the engine internals are fine, then there's no big risk to starting the engine. But if you *did* break a connecting rod, it's possible that the next engine start could destroy something.

If it were me, I'd check piston operating turning the flywheel by hand, before starting it again. If it turns out you're just being overly-cautious, that's OK, it only costs you a few minutes :)
 

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Definitely ^^^^ Better safe than sorry. Even though it ran after the vibration started, if something happens to shift to the wrong place on the next startup it could grenade the rest of the engine. If you don't already have a hole in the block, better not to create one! Hopefully you just have a faulty ignition issue causing one cylinder not to fire or something similar.
 

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Again, thanks to everyone who has posted up. Did some checking on my own, and had to take it in to my local JD dealer. They didnt break down the whole engine but did determine that a connecting rod broke. They said they could take it down further for an additional charge to determine if it broke at the piston or crank shaft, but that if it was the crank they could not get that part anymore. Service guy basically said unless I was handy enough to tear the engine down myself, it was probably better to cut my losses.

So, anyone looking for a used GT235 for parts? :)

Any recommendations on a replacement unit? I know I dont want any of the big box store models. I guess the X350 is around the same level as the GT235, but the service guy said they also have an S240 48" that while has the frame of the e series, it comes with the x series deck. I am also somewhat interested in the Ryobi electric rider. I am not completely against used, but my last 2 JD's were used and I have not had the greatest luck. First one was a big box store model, the transmission was toast. Luckily I was able to rebuild that by replacing the pumps in the K46 and added the synthetic oil to it. But once I got it running ok, I felt my yard required a better built JD, so that is how I ended up with the GT235. It has been a great mower for the most part, this is the first real problem it has had in the 4 years I have been running it aside from the plastics cracking and falling apart.

So any recommendation as to what I should or shouldnt look at would be great. I have a 1 acre lot, about 1/3 of it is wooded and is not maintained. The rest is zoysia grass. Front yard is a large hill, average grade, nothing difficult to mow really, but I think it is steep enough that over the years it would kill the cheaper trannys. I do have a fair a mount of trees and landscaping to maneuver around, so something that steers well is key. The most attachments I would use on it will be a cart, no need for any blowers, blades, buckets, etc. I do prefer to mulch instead of bag, so having it do that as well as possible is another plus.
 

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Discussion Starter #13
I can't believe that somebody with VW in their name has to ask about troubleshooting. hahahhahaha just funning
Heard that... be awhile since I have had a VW to work on unfortunately!
 

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Again, thanks to everyone who has posted up. Did some checking on my own, and had to take it in to my local JD dealer. They didnt break down the whole engine but did determine that a connecting rod broke. They said they could take it down further for an additional charge to determine if it broke at the piston or crank shaft, but that if it was the crank they could not get that part anymore. Service guy basically said unless I was handy enough to tear the engine down myself, it was probably better to cut my losses.

So, anyone looking for a used GT235 for parts? :)

Any recommendations on a replacement unit? I know I dont want any of the big box store models. I guess the X350 is around the same level as the GT235, but the service guy said they also have an S240 48" that while has the frame of the e series, it comes with the x series deck. I am also somewhat interested in the Ryobi electric rider. I am not completely against used, but my last 2 JD's were used and I have not had the greatest luck. First one was a big box store model, the transmission was toast. Luckily I was able to rebuild that by replacing the pumps in the K46 and added the synthetic oil to it. But once I got it running ok, I felt my yard required a better built JD, so that is how I ended up with the GT235. It has been a great mower for the most part, this is the first real problem it has had in the 4 years I have been running it aside from the plastics cracking and falling apart.

So any recommendation as to what I should or shouldnt look at would be great. I have a 1 acre lot, about 1/3 of it is wooded and is not maintained. The rest is zoysia grass. Front yard is a large hill, average grade, nothing difficult to mow really, but I think it is steep enough that over the years it would kill the cheaper trannys. I do have a fair a mount of trees and landscaping to maneuver around, so something that steers well is key. The most attachments I would use on it will be a cart, no need for any blowers, blades, buckets, etc. I do prefer to mulch instead of bag, so having it do that as well as possible is another plus.
I’m finding that a Zero Turn is the lowest cost way to mow and maybe pull a small lightly loaded cart (not towing around loads of gravel or dirt). It will likely require a more robust/heavier unit for the slope. 48” of 54” would likely be best, but it will take some practice to use it well. Otherwise, I would recommend a John Deere X380 or X390. Used can be okay if you keep the hours under 400. Lower is always better. You need to see them in person to know how used they are. All five machines I’ve bought used came out okay with some service and fixing.

Then if you have time, it could be good to keep the GT235 for an experience with a son, daughter, grandson, granddaughter, neighbor kid, ... you get the idea. I still remember replacing the connecting rod in a push mower when I was maybe early teens. Never hurts to understand how things come apart or go back together.
 

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I just saw that B&S motor for $500 on eBay. It came out of a GT 235 and the seller said it will run on the pallet. That would be my first option if the deck and tranny are still good. That is a great tractor.
 

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Discussion Starter #16
I just saw that B&S motor for $500 on eBay. It came out of a GT 235 and the seller said it will run on the pallet. That would be my first option if the deck and tranny are still good. That is a great tractor.
Do you happen to have a link to that motor?
 

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I just checked and it is gone. But you can keep rechecking for a B&S 350777 and maybe one will appear. There is also a Kawa FH580V that will fit your model also. Good luck.
 

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+1 on looking for a replacement motor with the kaw or Briggs either can be found. Your gt235 is much more tractor(k71) than a new x350(k46) youd have to jump up in series and there not cheap. It all depends on what you want to spend.
 

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Front yard is a large hill, average grade, nothing difficult to mow really, but I think it is steep enough that over the years it would kill the cheaper trannys. I do have a fair a mount of trees and landscaping to maneuver around, so something that steers well is key. The most attachments I would use on it will be a cart, no need for any blowers, blades, buckets, etc. I do prefer to mulch instead of bag, so having it do that as well as possible is another plus.
With the hill/trans challenge then you're definitely not in the ballpark of an S240 or X350 (K46 trans). In the X300 series, you'd at least want a model with power steering to get a bigger K57 (X370)/K58 (X390,X394) trans that will let you easily change the fluid. To get up to a K72 trans that's comparable to the GT235, you're looking at X500-series models.
 
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