piston ring insertion under cylinder

[Alvin]

Hi All,

Has anyone ever changed piston rings with pistons still with conrods on crankshaft. Meaning pistons and new rings entering via underside of cylinders, using a ring compressor. Reason to avoid access via crankcase cover and limited access to bigends. Any advice either way, please.

[MoominPapa]

Hi All,

Has anyone ever changed piston rings with pistons still with conrods on crankshaft. Meaning pistons and new rings entering via underside of cylinders, using a ring compressor. Reason to avoid access via crankcase cover and limited access to bigends. Any advice either way, please.

 

I don't see how that will work: when both big and little ends are connected the rings won't emerge below the cylinder even at BDC. If you're not going to disconnect the big ends then you'll have to remove the gudgeon pins, but I don't think the pistons emerge far enough from the bottom of the bores at BDC to do that either.

 

MP.

[RLWP]

I don't see how that will work: when both big and little ends are connected the rings won't emerge below the cylinder even at BDC. If you're not going to disconnect the big ends then you'll have to remove the gudgeon pins, but I don't think the pistons emerge far enough from the bottom of the bores at BDC to do that either.

 

MP.

 

I guess that the engine has separate cylinders that can be lifted up leaving the pistons and rods behind.

 

Richard

[MoominPapa]

I guess that the engine has separate cylinders that can be lifted up leaving the pistons and rods behind.

 

Richard

D'Oh, of course! Sorry.

 

MP.

[RLWP]

D'Oh, of course! Sorry.

 

MP.

 

's OK. I went through the same mental process myself.

 

Richard

[denboy]

yes it can be done but is a bugger to do, if you cant get the compressor out once you slide the block down very little clearance to do it

[Albion]

Hi All,

Has anyone ever changed piston rings with pistons still with conrods on crankshaft. Meaning pistons and new rings entering via underside of cylinders, using a ring compressor. Reason to avoid access via crankcase cover and limited access to bigends. Any advice either way, please.

 

I don't think that I would choose to do it that way personally. Hefting a great lump of cylinder around while delicately trying to deal with compressor and rings can't be easy. It can be tricky enough to do from the top (depending on the quality of your ring compressor) and could be a nightmare from the other direction.

Roger

[Arnot]

Hi All,

Has anyone ever changed piston rings with pistons still with conrods on crankshaft. Meaning pistons and new rings entering via underside of cylinders, using a ring compressor. Reason to avoid access via crankcase cover and limited access to bigends. Any advice either way, please.

 

Yes but it's fiddly. Make sure that the piston is at TDC and lock the crankshaft somehow (I used a chock of wood through the starter aperture) then you have to work each ring into the bore very carefully while someone else takes the weight of the barrel so it never drops on to the next ring. Make sure there is plenty of lubrication on the rings and the bores. I use Graphogen a colloidal graphite, it makes the engine smoke like hell when it first starts but seems to do the job.

 

It is however a process fraught with risk...

 

Good luck!

 

Regards

 

Arnot

[bobtom]

Hi I agree with Arnot "it is a process fraught with risk" but, if you are CAREFULL it can be done. On my SR2 (in a previous life), the "pots" had a chamfer at the bottom that helped the rings to ease into the pot. With a friend holding the pot, and using 2 pieces of stick to squeeze the ring closed, I managed it. I re-iterate Arnots point though - BE VERY CAREFUL. Good luck Tom

[NB Esk]

If you need to try it this way, you may be able to compress the rings individually, using cable ties.

 

Trouble is, you'll want to keep raising the cylinders to check you didn't break any...

[Timleech]

If you need to try it this way, you may be able to compress the rings individually, using cable ties.

 

You can probably do it with your fingers. Try not to cut yourself, though.

The barrels are really not very heavy, that's not an issue.

Try doing the same with a Gardner 4LK, four pistons into a single waterccoled block. That's fiddly

 

Tim

[Biggles]

Hello Alvin

 

PistonBroke got there first. I was going to suggest cable ties. I would be locking the pistons in place squarely with blocks of wood between the block and either side of the bottom of the piston.

[BEngo]

Hi All,

Has anyone ever changed piston rings with pistons still with conrods on crankshaft. Meaning pistons and new rings entering via underside of cylinders, using a ring compressor. Reason to avoid access via crankcase cover and limited access to bigends. Any advice either way, please.

 

This is how Kelvin J/K pistons go in every time. No need to remove the cylinders, or heads both of which are quite hard work compared with taking off the side doors. Bit of a fiddle to move the crank webs out of the way at the right stage, but once you have the knack both pistons can be out and back in under half an hour- provided you don't drop the big end nuts into the sump of course. The bottom of the liners is tapered and the rings are compressed as the pistons slip in.

 

N