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Breaking Bad (engine)

Minimac

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1265
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central Fl & CNY
I broke the 250 in my Morphous, so I did the next logical thing- put a 400 from a Majesty in it, which the factory should have done. Now it's time to break open the 250 and see what went wrong, and possibly repair it. Any tips or gotch yas for opening that puppy up? How to go about splitting the cases? The engine is in a box in the garage...
 

wentwest

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You have great freedom to mess around, because the engine is already broken.

What did it do to lead to the "broken" diagnosis?
 

Minimac

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Engine would start and run, then within a minute, would quit-similar to the old 2stroke 'soft seize'. Then wouldn't turn over (locked up?) or start. Fuel, coolant, oil and electrical systems, battery, etc., all check out fine. A few hours later, it would crank, start, then quit. Nothing on the self diagnostics, either. There isn't any scraping (rings), or knocking noises, and no metal when I drained the oil, but I suspect an issue with the crank or rod bearings. The shop manual doesn't say too much on splitting the cases.
 

wentwest

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It's hard to believe it seized because of heat because it stalled in a minute. I was thinking fuel, but you said it wouldn't crank until a few hours later. Maybe some sort of blocked oil passage? I once bought a non-running Honda Elite that I finally found had a piece of gasket that had been part of the crankcase seal broken off and floated to a place where it blocked the pickup for the oil pump. Even though the engine had oil the pump couldn't pump it. I replaced the piston and cylinder and it ran just fine.
 

Minimac

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As I wrote, I have the service (shop) manual, and it isn't much help for splitting the cases. Hopefully, I'll get started on it next weekend and won't break anything.
 

psykown

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My bad I missed that lol Are you having trouble getting the case physically apart? Ive found on the bigger engines bolts like to hide behind the oil pump, also on the ones I've split there is some RTV used in a few spots which can make it difficult to seperate the cases even after all the bolts are out


Also there is always one more bolt left holding the cases together......always :lol3
 

matty

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England Scotish border
Engine would start and run, then within a minute, would quit-similar to the old 2stroke 'soft seize'. Then wouldn't turn over (locked up?) or start. Fuel, coolant, oil and electrical systems, battery, etc., all check out fine. A few hours later, it would crank, start, then quit. Nothing on the self diagnostics, either. There isn't any scraping (rings), or knocking noises, and no metal when I drained the oil, but I suspect an issue with the crank or rod bearings. The shop manual doesn't say too much on splitting the cases.
Reading what you posted Its hard to Imagine the engine has a Hydro Lock issue ( Head gasket head coolant to cylinder leak) And the electrics ok But wont turn over.
Now by wont turn over / Like 2 troke soft sieze ... do you mean it physicaly was solid or just not Turning over on starter? Was it trying to throw it over or just Clicking? Did you try to turn motor by hand when it was in its locked state, like A socket on the crank nut etc etc. ?
As for splitting cases ... Go easy top end might be all you need, and perhaps not that.
 

Minimac

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central Fl & CNY
The starter engaged fine, the engine would not turn over. It acted as though it was seized. After about fifteen minutes, the engine would turn over fine, maybe run then "seize" again. I didn't want to risk anymore damage, so I parked it until I can get time to see what the issue is.
 

matty

Border raider.
Joined
Feb 8, 2022
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139
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265
Location
England Scotish border
The starter engaged fine, the engine would not turn over. It acted as though it was seized. After about fifteen minutes, the engine would turn over fine, maybe run then "seize" again. I didn't want to risk anymore damage, so I parked it until I can get time to see what the issue is.
I would say it was hydro locked but it sounds from your wording not to quite fit the norm for this. its not a trans issue is it? I would imagine if it were a sieze of some kind i would imagine you would see other aspects show like slap or smoking etc. No folow up issues with your motor swap points to it being in the engine trans, but i think it would be more defined if it were a siezing issue in top end crank etc.
 

Minimac

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It's now the middle of September, and once again, life got in the way. The poor 250 is stuffed in a corner of the garage, awaiting my return to the north next May. I guess I'll have lots of time to search and try to figure out a plan of attack. In the meantime I have a Helix and Reflex to ride and play with.
 

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