Help with Leaking Star Sizer

[Texasflyboy]

Any low impact suggestions appreciated.

Here is the problem:



http://hgmould.gunloads.com/a/star.jpg


The lube (a semi-hard lube that melts about 140F) is leaking out all over the spring area. I've already broken down the part and the plunger/piston is leaking where it interfaces with the copper tube right at the arrow in the photo.

My guess is that either the plunger is undersize or the copper tube is oversize and I need a tighter fit.

My options are:

1. Have a larger plunger fabricated for a tighter fit.
2. Cut the existing piston for one or two o-rings

My other star does not leak like this so I am at a loss as to why this one leaks.

[deltaenterprizes]

Do you have a micrometer? Check the diameter of the plunger in the front and also in the back to see if it is worn, if not it is the sleeve and a bigger diameter plunger will need to be made and the sleeve reamed oversize to get it round again as when cylinders wear it is usually in an oval. You can also try lowering the temp if you are using a heater. I don't know if Magma does repairs,they may sell parts.
In order to make a good repair the inside diameter of the sleeve will need to be read to within .001" and the plunger will need to be within .0005'', not hard just time consuming. I have one doing the same thing I need to repair,when it gets warmer!

[Forester]

I bet Magma has parts they would sell to fix it. It does not appear to be a problem that would come from the housing itself being cracked. You probably just need the parts in that little assembly. That may be the lowest hassle solution.

Edited to add: is it possible the copper tube has developed a crack?

[Lloyd Smale]

ive replaced mine once and its due to be replaced again. Order the spring at the same time as they get wore faster then the piston.

[cajun shooter]

Magna for replacement parts. Very nice people to deal with and fast delivery.

[Lloyd Smale]

ill add too that if your ordering parts order the piston seal for the lube resevour screw too and change that will your at it. Those are about the only parts that wear on these and you should be about like new then.

[Texasflyboy]

I contacted Magma Engineering today. There are three design models of the Star Luber/Sizer according to them (for this part).

Design #1 was a sweated in place bronze sleeve that the piston rides in.

Design #2 was a sweated, and then a brass pin secured the sleeve in place. That is the model I own.

Design #3 is the current design by Magma, and the sleeve is threaded and held in place with a spanner set screw.

The good news is they will retro-fit the spanner style threaded sleeve. The bad news is that the cost of the mod is over $100.

A nice fellow on another board has offered to make a replacement. I'll see how it works.

According to Magma the hardest part is drilling out the blind brass pin that holds the sleeve in place. I have asked a friend to help out in drilling this pin out. To remove the old sleeve I am thinking heat and maybe threading the ID to accept a screw so we can pull it out. That's the plan anyway, we'll see how it works.

Updated Photo for those interested (http://members.cox.net/pobox596/A/star2.jpg)

[Lloyd Smale]

why dont you first try replacing the piston without changeing the sleave.

[Texasflyboy]

why dont you first try replacing the piston without changeing the sleave.

The piston isn't the problem. The piston OD measures .310" + .000", -.000" from end to end.

The sleeve ID measures .315" 3 O'clock to 9 o'clock, and .326" 12 O'clock to 6 O'clock. Given those ID measurements, I'm pretty sure a new sleeve is the cure.

A friendly machinist in ID is sending me a new bronze sleeve in the mail today with an ID of .311". We'll see how that works.

[686]

drill your sleve out just enugh to make round then bake a piston to fit.

[deltaenterprizes]

Ream the existing sleeve to make it round, and make a new piston to fit.

Be very careful heating aluminum, it has a low melting point and gives no warning like turning colors before it collapses! Been there done that.

Thanks on the info on the different types of instalation methods used for the pump housing it will aid me when I repair mine,one day!