[Scott.Boyd]

I picked up a 1987 LT250 4WD to go with the collection of broken I have. Last guy said his kid was riding it and it came to a halt. If he let it sit he could start it again. He only had the rope pull working. Prior to this it ran fine with no issues.

I got it home and fixed the electric start. Added a qt of oil. Gave it a go and it will fire but before it will get up and idling (a few seconds) it does appear to tighten up and the starter really starts working to turn it over. When it sputtered it seemed clean, no oil smoke. Can barely budge it with the rope pull. Let it sit and it loosens up. Crank it with the plug out and it doesn't seem to tighten up. Any thoughts?

 

[ToyFord]

Just a guess, is the exhaust valve not opening? Also, have you tried using the compression release while pull starting?

 

[Scott.Boyd]

So playing around some more, it is getting tighter. Even with the plug out it is staying tight, even after sitting. Looking in the cylinder via plug hole no signs of piston/cylinder issues.

I'm thinking lower rod bearing. Anyone else had other seizing events? Looking for simple stuff before I tear into case splitting.

It still rope pulls, but just barely.

 

[A5g7]

Drain your oil and put in some diesel and pull the rope a couple times with the spark plug out and drain the diesel and put a little of oil in it then drain it and put new oil in and try that

 

[A5g7]

My grandpa taught me that trick on mine and it worked

 

[justsomeoldguy]

Drain your oil and put in some diesel and pull the rope a couple times with the spark plug out and drain the diesel and put a little of oil in it then drain it and put new oil in and try that

That sounds worth a try. And check for 'glitter' in the diesel when you drain it.

 

[Koslaw]

Sounds like a lower rod bearing to me as well. Take a coffee filter and pour the old oil through it and see if you find anything "interesting" in it. If you have it freed up and you pull the plug or plug wire and allow it to keep cranking without firing does it start to lock up too?

 

[Scott.Boyd]

I put it aside to think on it. But yes, the more I turn it over, the tighter it gets. Pretty much too tight to keep going, much worse and it will be seized.

My thoughts are to pull the top end and see if that makes a difference. If it does, well we know which half. If it's still tight, I guess out of the frame and start stripping it until I find the subcomponent that failed.

While dreading it, my suspicion is lower rod bearing. Thanks for the thoughts.

 

[Koslaw]

Hopefully with the top end off you can rotate it and when it starts to lock up you should be able to tell if the connecting rod is hard to move by hand. At least that way you will know if thats the cause. I don't remember but if its a crank bearing rather than the connecting rod bearing, you might be able to remove the bearing without having to split the case completely.

 

[Scott.Boyd]

There is hope, wishful thinking, and reality. From what I've seen in the Suzuki shop manual, if it's the lower rod bearing, case splitting and lots of transmission bits to keep in order will be inevitable.

 

[Scott.Boyd]

I've only turned it forward with the rope pull or electric start. It's not likely a hunk of something broke loose. It doesn't rotate free and then tighten, it's constantly tight regardless of piston position at this point, so something has decided to introduce a constant source of friction. Could be camshaft, something in the clutch, case bearing supporting the crank. So many things. We'll know someday when I get the time to tear into it. I'm fortunate to have the workspace and the tools.

 

[Scott.Boyd]

Some amazing packaging in these designs.

 

[Koslaw]

That's a pretty nice setup. I just have a 1 bay garage to work out of hah. If it makes you feel any better I completely took apart and rebuilt one of these engines for my senior year of high school end of the year shop project. Somehow I was able to figure it out and made it work again. That was about 12 years ago now though. I figure if I could do it in HS anyone who is mechanically inclined amd has the right tools can do it. I do remember the flywheel being a huge pain to get off the shaft, as well as getting the inner case to split open.

 

[A5g7]

Nice work area I just have a dirt yard