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amc 250 problems fitting barrel

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amc 250 problems fitting barrel

Post  stephenhopleyWS9 on Tue May 29, 2018 7:18 pm

I have just received the bottom engine back after having the big end refurbished on the AMC 250 engine . I have had the bore honed and purchased a new standard piston and rings. The rings are sized to the bore but I cannot get the barrel onto the piston. I have purchased a sealey ring compressor to no avail.
has anyone had the same problem and if so how was it overcome

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Re: amc 250 problems fitting barrel

Post  Cruiser79 on Tue May 29, 2018 8:38 pm

I'd recommend fitting the rings in the bore and checking the end gaps aren't too tight
minimum gap is .010""
maximum gap is .025"

The barrel should have a chamfer on the base of the bore to aid squeezing the rings into their grooves while you fit the barrel. Its usually just a case of easing the two together and squeezing in the rings with your fingers to help things along. Ring compressors wont come into play on this type of engine build. A healthy covering of two stroke oil on the rings/piston and bore wouldn't go astray to help assembly but not necessarily needed

Mind me asking where you were able to find a new piston?
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Cruiser79

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Enginr

Post  kerabo on Tue May 29, 2018 8:55 pm

stephenhopleyWS9 wrote:I have just received the bottom engine back after having the big end refurbished on the AMC 250 engine . I have had the bore honed and purchased a new standard piston and rings. The rings are sized to the bore but I cannot get the barrel onto the piston. I have purchased a sealey ring compressor to no avail.
has anyone had the same problem and if so how was it overcome

Stephen
PM me your email I will send you something

Ken
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kerabo

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AMC engine - piston/cylinder

Post  FB vincent on Wed May 30, 2018 2:37 pm

This is a scary subject. One false move and you break the piston rings.

Contrary to what Cruiser 79 suggests, I would advise the use of a piston ring clamp. I would also recommend that this is a two person job, one to hold the cylinder, and the other to manipulate the rings into the bore.

I presume you have checked the fit of the bare piston, and separately the rings(s), into the bore.

The cylinder must be exactly in the correct line to avoid the rings fouling one of the many ports.

Yes, lots of lubrication before you start. If one of the very thin rings rides up over it's retaining pin, you will have a disaster. You need both the clamp to prevent the rings revolving, plus nimble fingers to ease the rings into the chamfer and ensure that the cylinder is not tilted.  

Good luck.

(From one who has refitted his 20T cylinder many times and learnt the hard way.....................)

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Re: amc 250 problems fitting barrel

Post  stephenhopleyWS9 on Wed May 30, 2018 4:57 pm

having been up most of the night attempting to replace the barrel,having broke a ring last weel I was not confident to say the least.
I then removed the piston and was able to locate this in the barrel with the rings, It was a bit tricky to replace the pin in the small end and fit the circlips but was achieved.
The piston moves up and down freely so I can only hope all is well. No doubt I will find out when I attempt to start it.
I dont see any way of knowing that all is well but would have thought that any problem with the rings would stop the free movement of the piston but we will see.
It is a lot of years since I have worked on a motorcycle but dont remember anytyhing this difficult.
If all is not well it will go for spares and put it down to experience.
Thanks for all the advice
steve

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Fitting barrel

Post  kerabo on Wed May 30, 2018 5:09 pm

You will normally feel or hear it if you snap a ring. You do need to be carefull on these above most other engines as it has the grooved transfer port as well.
Look in the exhaust and the inlet and maybe have a gentle poke to see if one feels loose.
Regards Ken
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Re: amc 250 problems fitting barrel

Post  stephenhopleyWS9 on Wed May 30, 2018 5:18 pm

Thanks again. I dont see or feel anything loose but who knows I never expected this when I took it on,There is no real way of knowing if anything is not right
steve

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Re: amc 250 problems fitting barrel

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