Had some bad luck this weekend _YM1700

[SailorBob]

I encountered a problem with my newly rebuilt engine (7 hours). I was mowing along and heard an awful racket coming from the engine. I immediately shut it down. I removed the valve cover and the problem was obvious. The valve spring for the #1 exaust valve had broken in two. Needless to say I was totally disgusted..

After cooling off a while with the assistance of an adult beverage I decided to pull the head and see how bad the damage was. I believe that I got lucky. I found all of the broken and loose pieces. The push rod was lying off to the side. The valve remained in the head. You can see a mark on in the carbon on the top of the piston but no damage. There was no damage to the piston or cylinder liner.

This morning I took the head to the machine shop and the guys looked at it and said that it looks fine. They are going to replace the spring and check the seat. The machine shop guy says that he has seen this before. It was probably a defective spring...just rotten luck. He also said that it just takes a tiny nick on the spring to cause them to break.

I am getting way too familiar with the guts of this engine. I was amazed how quickly I had the head off. Of course I still bagged and labled all of my parts just like I did the first time. I will drain the oil and change the filter just in case there are some small bits in there. It might be good thing I put the magnets on the oil filter. With a little luck I should be back in business this weekend.

 

[Box]

Sorry to hear about your bad luck. I hope it all works out this time around.

 

[rock2610D]

Not sure I have ever heard of a new valve spring breaking like this. Old ones maybe but I would cover all my bases and inspect all of the springs. Not sure if this could cause the issue but if you have a decompression mechinisum could it case this issue if it were out of adjustment??

I would bet you also retorqued the head after 1st install. Did you re-gap the valves after? Mine got really tight (zero gap) after retorque. I had to re-gap all the valves.

Hope everything works out

 

[MJPetersen]

I am getting way too familiar with the guts of this engine. I was amazed how quickly I had the head off.

I do not mind doing a job once, but really hate to return to it again and again. I had a Ford pickup with a 302 that I felt like needed a zipper for the front of the engine.

Maybe this is it and you will not have to tear it down again in your lifetime. Then again, maybe you are getting to like it so much that you will want to start your own part time business of engine overhaul.

Mike

 

[SailorBob]

Not sure I have ever heard of a new valve spring breaking like this. Old ones maybe but I would cover all my bases and inspect all of the springs. Not sure if this could cause the issue but if you have a decompression mechinisum could it case this issue if it were out of adjustment??

I would bet you also retorqued the head after 1st install. Did you re-gap the valves after? Mine got really tight (zero gap) after retorque. I had to re-gap all the valves.

Hope everything works out

I don't see how the decompression lever could have done it since the valves that are pushed down by the lever were fine.

Yes, I did retorque the head and readjust the valves. It is possible that I messed that up but, it was running fine and sounded good. I am just going to chalk it up to bad luck. I hope the tractor does not turn out to be a lemon like a Saab I used to have. (Talk about and expensive peice of junk!)

If I have any more bad luck with this tractor I may have to call a priest to perform and exorcism on this tractor .

 

[sandman2234]

Well, it could have been worse!!!
Hopefully it will run again, soon and cheaply!
David from jax

 

[SailorBob]

Well, it could have been worse!!!
Hopefully it will run again, soon and cheaply!
David from jax

I got it back together this weekend. It runs good too. All I had to replace was a valve spring, and valve stem seal, changed the oil and filter. I also took to head to the machine shop and and had them check it out. They found nothing wrong but a dinged stem seal. So, they just put the new spring and seal back in. (Did not charge me anything either ).

I guess I got lucky. Only time will tell whether or not my problems are over. I am just keeping my fingers crossed.

 

[svcguy]

Simply put, things happen. The message from all of this is you now know (and have shared with a number of others) that dealing with and taking care of major work is not beyond the scope of the average tractor owner. It's all about having the jam to get in there and get your hands greasy. Seems to me you've done very well. Congratulations.

 

[Underwaterdog]

I briefly looked over your previous post and don't see anything related to the tappet adjustment. You may already know this but just in case you don't.....
From my previous days rebuilding gas burners, broken springs are often caused by some kind of binding. I have seen valve springs break because of insufficient or no valve tappet clearance. I'm not sure what engine is in your YM1700, but my american book shows the smaller 2T's 73 & 75 need a .008" gap. The larger ones,2T84A and 2TR20A take a .006" gap cold. Valve tappet clearance should be checked after assembly the cylinder head and approximately every 300 hours of operation.