LT 4000 Briggs engine problem

848 Views 3 Replies 3 Participants Last post by tbags4ever, Jul 13, 2009

tbags4ever

Discussion Starter · Jul 12, 2009

I recently got a LT4000 for free because the engine has a connecting rod issue. This tractor has the 19hp Briggs I/C Gold engine (model 42A707). The issue with the engine is that the connecting rod on one of the pistons works itself loose, resulting in a horrible knock. When I took off the access panel to look inside, I can see that there is some obvious wear on the crankshaft where the connecting rod has worked loose.

My friend who gave the tractor to me seems to think that the crankshaft must be slightly warped, which is causing the rod to loosen up. He had already replaced the connecting rod, and the same problem happened again.

Has anyone had this issue with their engine? Does this sound like an accurate diagnosis? Could it just be that he was not tightening the connecting rod to specs?

I'm ready to buy a new crankshaft, but those things are not cheap. Any help would be most appreciated! Thanks.

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davidg

· #2 · Jul 12, 2009

:Welcome1:

from the way you word your post i take it you are not real familiar with internal combustion engines. if the rod is "loose" and knocking then major repairs are required and you are taking the chance each time you crank it that it will come thru the block. you may already need to bore it out, replace the crank, or even just junk the engine.

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Walt 2002

· #3 · Jul 12, 2009

"My friend who gave the tractor to me seems to think that the crankshaft must be slightly warped,"
"? Does this sound like an accurate diagnosis?"

No.

"Could it just be that he was not tightening the connecting rod to specs? "

Could be PLUS, the rod journal on the crankshaft was probably scored and he didn't do anything about it. I have had several of these turned and used undersize connecting rods. I have not had any done for awhile but the shop I used was charging $45 to do both rod journals. You can also have these built up at some shops and turned back to std. That will be more expensive. IF you live around a medium size up community, there is likely to be a crankshaft turning shop in the area.

Walt Conner

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tbags4ever

Discussion Starter · #4 · Jul 13, 2009

Davidg, I know enough about engines to handle typical starting/running issues, but have not dealt much with crank, cam, piston, valve issues.

Walt 2002, I think you hit it on the head. I just need to study up on my terminology. Yes, there is scoring on the journal, and I should have known that this is enough to work the connecting rod loose. I will look for a shop that might be able to turn the journals. Otherwise I might go for a brand new crank.

Thanks for your help guys.

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