My stock 61x engine threw a rod. Why did this happen?

streetroc

streetroc

Location
Georgia
All stock single carb 701 in my '95 FX1. It was running great and I was just cruising along at about 25mph then it suddenly locked up and that was it. The machine shop said that it looked like lack of lubrication. I'm certain that I mixed the gas correctly though. Why did this happen? Do I have another problem somewhere else that I need to address before I put my replacement engine in?

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Harbor

Harbor

Location
Stockton
If your running pre mix, lack of oil is probably not Issue. It does shows signs of heat so you’d suspect that.

I had a similar failure on a buddies ski few years back and on my wife’s ski. The bearing started failing well before the lock up, creating the heat signature, we just didn’t realize It until it was too late. It was just age and over due for a tear down...I rebuilt both and they are still running stong.
 
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E350

E350

Site Supporter
Location
Sacramento Delta
Same 1995 FX-1 here.
Should streetrpcl85350 have (and me now) tear down a perfectly runinng engine?
And do what?
From the Service Manual, it looks like there are roller bearings in the piston (wrist) pin. So I guess they are replaceable.
But the crank assembly doesn't look like it is user rebuildable? Is it?
If not who do you recommend to send it out to?
And is just best to run it until it breaks and then repair it?
I am getting better at working on these things, but I have no idea what to do until something breaks.
 
streetroc

streetroc

Location
Georgia
E350 said:
Same 1995 FX-1 here.
Should streetrpcl85350 have (and me now) tear down a perfectly runinng engine?
And do what?
From the Service Manual, it looks like there are roller bearings in the piston (wrist) pin. So I guess they are replaceable.
But the crank assembly doesn't look like it is user rebuildable? Is it?
If not who do you recommend to send it out to?
And is just best to run it until it breaks and then repair it?
I am getting better at working on these things, but I have no idea what to do until something breaks.
Click to expand...

I don't think they are rebuildable. It looks like they are pressed together from the factory. A new crank assembly is about $650 but so is a replacement engine online. I just pulled the 61X engine out of my old square nose to drop it in as a replacement. My FX1 is in such incredibly good factory condition that I want to keep it all original if I can
 
E350

E350

Site Supporter
Location
Sacramento Delta
Harbor said:
If your running pre mix, lack of oil is probably not Issue. It does shows signs of heat so you’d suspect that.

I had a similar failure on a buddies ski few years back and on my wife’s ski. The bearing started failing well before the lock up, creating the heat signature, we just didn’t realize It until it was too late. It was just age and over due for a tear down...I rebuilt both and they are still running stong.
Click to expand...

@Harbor talk to us buddy. How do I rebuild the cranks in our 1995 FX-1 and 1994 SN SJ?

Links would be appreciated if you have a rebuild thread...
 
Harbor

Harbor

Location
Stockton
E350 said:
@Harbor talk to us buddy. How do I rebuild the cranks in our 1995 FX-1 and 1994 SN SJ?

Links would be appreciated if you have a rebuild thread...
Click to expand...

It’s not something you’ll be doing yourself. It presses together and may need web replacement and rods, in addition to the bearings and a key way weld repair. You’d need a press and v blocks, fixtures for the press, web indexing and a dial indicator set up to true it after assembly. You can send it out for a rebuild or buy a replacement from Jetmaniac or watcon or one of the other vendors... competitive crankshaft does rebuilds as well as others..
 
Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
streetroc said:
I don't think they are rebuildable. It looks like they are pressed together from the factory. A new crank assembly is about $650 but so is a replacement engine online. I just pulled the 61X engine out of my old square nose to drop it in as a replacement. My FX1 is in such incredibly good factory condition that I want to keep it all original if I can
Click to expand...
Any crank can be rebuilt. Just depends on cost vs return. You can probably find a crank for less money
 
E350

E350

Site Supporter
Location
Sacramento Delta
@Harbor I have a press. I don't have the type of V blocks which would hold the crank true for measuring with a dial gauge. And I don't know what other fixtures I would need. I can buy a magnetic dial indicator, but I would have no idea how to true the crank if it was out of round. I have used a great CNC precision machine shop in Sacramento called Langills https://langills.com/ They can likely do anything I ask of them.

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@Big Kahuna what did you determine about your crank. Is is true or not?

But, if the crank is out of specification, the Yamaha Service Manual says, just replace it.

So, then the question is:

1. Drive it until it breaks?

or

2. Replace it every 25 years or so, just for good measure?

What do you guys recommend?

@Harbor I may be a little like you, but probably with fewer skills. Everything I have (including my body) is used. Everything will break eventually. I am up for fixing something myself because, I figure, all it can do is break anyway. . .
 
Harbor

Harbor

Location
Stockton
Here’s some info... you could search out more on your own. But Like @Quinc mentioned, and I agree, it’s not really worth it unless your going into business or own a shop and have that type of work to sell..

You could get a boring bar and hone And dial bore gauge and micrometer for $3000 plus and bore your own cylinder too. Again it doesn’t make a lot of sense.....

https://www.google.com/shopping/pro...rds=epd:8446293384011466324,cdl:1,prmr:1,cs:1

https://www.ebay.com/p/1837061517?i...FPw4viXDeoxbAKU8xW7zUxgrTCjTxOBAaAgvDEALw_wcB
 
E350

E350

Site Supporter
Location
Sacramento Delta
@Harbor understood, accepted and agreed.

So, then the question remains:

1. Drive it until it breaks?

or

2. Replace it every 25 years or so, just for good measure?

@Big Kahuna wait a minute, the V blocks which came with my H.F. 2-ton press will work if your oak will work.
 
Harbor

Harbor

Location
Stockton
E350 said:
@Harbor understood, accepted and agreed.

So, then the question remains:

1. Drive it until it breaks?

or

2. Replace it every 25 years or so, just for good measure?

@Big Kahuna wait a minute, the V blocks which came with my H.F. 2-ton press will work if your oak will work.
Click to expand...

So the answer is not one size fits all....

For the weekend warrior/rec rider with a stock boat to one with all the bolt on’s, I’d wait till it develops some symptoms that warrant an internal inspection of some kind....
 
E350

E350

Site Supporter
Location
Sacramento Delta
Just a question on how to perform measurement two in the above page from the Service Manual:

"2. Measure
Small end free play
Use a dial gauge"

Are you measuring the wobble from the small end left to right?

So do you set the dial gauge at zero with the small end all the way to the left,
and then push the small end towards the dial gauge to the right,
and that is your measurement?
 
Harbor

Harbor

Location
Stockton
E350 said:
Just a question on how to perform measurement two in the above page from the Service Manual:

"2. Measure
Small end free play
Use a dial gauge"

Are you measuring the wobble from the small end left to right?

So do you set the dial gauge at zero with the small end all the way to the left,
and then push the small end towards the dial gauge to the right,
and that is your measurement?
Click to expand...

Yes but move the crank, Have your gauge set with enough plunger retracted into gauge to pick up the movement in both directions
 
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