Piston Seized today at Idle! Because of loose Head bolt?

[zwebx]

this is what your piston will look like on the exhaust side:

60 to 1 is like.... how do i put it..... from the bores perspective it would feel like dropping the soap in prison the first time

anyway... the reason it broke is because 60:1 is not enough oil... dont skimp on oil next time run somthing like 30:1 i personally run 25:1 but thats prolly because thats what i run in my rm125

 

[Deleted member 12676]

I agree. I'd never run the oil any leaner than 40:1
But the fact that you ran it at 40:1 and it seized means it's a jetting problem. Do you know how to correctly jet a carb?
Keep increasing the main jet size till top speed starts to lessen. Use micro drill bits to enlarge the main jet size.
Float height being too low can make it run lean. See my page at http://www.dragonfly75.com/motorbike/jetting.html

 

[crassius]

to get the piston out, try taking out all the barrel studs and turning the barrel

had a guy seize up one time after mixing fuel in a can, then grabbed the wrong fuel can to fill the tank

 

[Tanstaafl]

Ok so I took off the exhaust and intake manifold. The rings weren't caught in the ports like I expected. I sprayed more penetrating oil and smacked the piston with a hammer on a piece of wood. It did move, and it is down to about where half the hole where the pin goes through the piston/clips are. The rings are completely compressed so they didn't move out of place.

I haven't taken the engine off the bike yet. When I do I will try and knock the piston all the way out of the cylinder body because I will have a straight shot at it (bike bar won't be in the way). I hope I can get it out because the crank is moving, so I don't need a new bottom end. Any more ideas if I can't hammer it loose? I was wondering if I would have to cut through the cylinder block? If I can get it lower to where I can slide the pin out of the piston I can detach it from the crank shaft.

I am not that familiar with the small 2 stroke motors, but have had very extensive experience with large ones like Clarks, IR's and Cooper Bessemer 12 cyl 14"x14" (bore/stroke) engines powering integral gas compressors.

Piston seizures were most commonly caused by not fitting piston rings with sufficient end gap for expansion when reaching operating temperatures.

Does anyone check piston ring end gap on these bike drivers?

 

[Fabian]

I'm seeing all of the warning signs of a major f*&kup; not just the 60:1 oil fuel ratio, but the disassembly process as well.

I think your best option is to purchase a replacement engine because the rebuild process is going to be a complete catastrophe and that's just engine disassembly, where it's hard to f*&k things up any more than they are, as the engine is already trashed; burnt out from the inside and almost cooked to perfection all the way through; though just a little more cooking would have had the engine turn a nice golden crispy brown!

 

[Deleted member 12676]

Ring end gap on these engines is excessive, so that's not the problem.

 

[Pablo]

With the correct oil these engines can run all day, full throttle at 50:1. Not all oils are the same. If someone tells you this, they may not know what they are talking about. If you mix Amsoil Saber richer than 50:1 you will spluge oil out every orifice. Talk to people who have done this. They will tell you. Jaguar knows what he is talking about - you need to set your jet to match your oil ratio. If you run too oily, you can be in danger of running fuel lean.

The usual seizure of these engines is the ring gap roll pin coming out............are there actual pictures from 2011 of this engine?

 

[Fabian]

you need to set your jet to match your oil ratio. If you run too oily, you can be in danger of running fuel lean.

This above sentence is comprised of two parts and is correct, but the sentence needs to be reversed, because you can run an oil/fuel ratio, right up to the very ragged edge; walking a fine line between squeezing out the very last drop of maximum performance and that sickly sound of instantaneous engine seizure, so long as the carburettor is correctly jetted and the exhaust gas temperature is within acceptable limits, though engine life may be reduced when squeezing out that one last extra drop of performance with a pair of vice grips:

[sic retrorsum] If you run too oily, you can be in danger of running fuel lean. You need to set your jet to match your oil ratio.

 

[P.pocketscotcombo]

I would just buy a whole new motor...they're only about $80.00.

I've had that exact seize situation ,two options and actually the first,just simply replacing the engine can be as cheap as $45,tax and shipping total of 60 something if you shop around,I've found ebay quicker shipping better prices,Jeff Bozos has made enough spread the wealth oh and. 2ndly piston rings and cylinder kit is even cheaper,yes I've experienced the loose. Head bolts seize up,you've got to check before every ride during break in get an appropriate sized long handle Allen. Tool for easy head bolt tightening on the go!

 

[Wrench]

I've had that exact seize situation ,two options and actually the first,just simply replacing the engine can be as cheap as $45,tax and shipping total of 60 something if you shop around,I've found ebay quicker shipping better prices,Jeff Bozos has made enough spread the wealth oh and. 2ndly piston rings and cylinder kit is even cheaper,yes I've experienced the loose. Head bolts seize up,you've got to check before every ride during break in get an appropriate sized long handle Allen. Tool for easy head bolt tightening on the go!

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