Abby’s Guide > Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) > Discussions > Small engine re-ring
Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions |
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trouts2
Location: Marlboro MA
Joined: Dec 8, 2007
Points: 1328
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Small engine re-ring
Original Message May 18, 2011 12:20 pm |
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Homelite 20042A, 25cc It was a problem getting the ring in because the bottom of the bore flares out. You can't use a ring compressor. I put the top of the piston in the bore then tried pushing the ring in with the tip of a pick. In the process the ring broke. What's the way to do it? Where should the ring gap go? Is it centered on the longest section of uninterrupted wall? The crank weight has 11 degrees stamped on it. How is the timing set? I have not taken off the flywheel and assume it only goes in one way but not sure. There is no key shown on the exploded view.
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trouts2
Location: Marlboro MA
Joined: Dec 8, 2007
Points: 1328
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Re: Small engine re-ring
Reply #7 May 19, 2011 8:13 am |
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Borat: Have you got it running? Not yet, it needs at least a ring and gaskets >>Generally, there is an arrow embossed on the piston crown No arrow or mark on the piston. Maybe it’s not fussy on these models. ? Which way does the dowel usually face? Friiy & niper99, The compression on this was 70psi which I would think ok for a start and run. I don’t think there is any compression release on these. What’s a ballpark psi for these? The sump area cover gasket was torn and the cylinder gasket in bad shape. I’m not sure if those were ok before and ripped during disassembly. One of the screw bosses fell off when the cylinder was unscrewed. There are only three screws holding the cylinder down, one broken so only two. There are threads left on the boss so might be enough for grip. Maybe the boss area could be clamped and glued in place.
Broken boss lower left.
Broken boss lower left
The crank is on roller bearings which was a surprise.
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trouts2
Location: Marlboro MA
Joined: Dec 8, 2007
Points: 1328
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Re: Small engine re-ring
Reply #10 May 20, 2011 9:14 am |
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Borat and niper99, >>>Do you have the piece of the boss that was broken off? I do. there’s only a tiny amount of surface to weld to and very difficult or impossible to get at the back sides for welding. I might try JB weld. The surfaces are clean, rough (good surface for gluing) and fits back in it’s spot very well. The surfaces are small though. Possibly JB welding it in place then using a bolt through the crank piece and bolt with a washer on the broken section head side might work. The washers could grab the remaining ½ not broken section on the head side. Even if the weld broke the washer would hold the broken head section in place and hold down the head to the block section. Thanks for the Durafix reference. I watched many videos on aluminum welding. I never knew that repairs could be done with a small torch. Very interesting stuff. Poking around YouTube I found stitch pins and a few other methods of repairing cracks in cast blocks I never heard of before i.e., locking pins, tapered, screw-in, and stitch. I'll probalby give the aluminum welding a try on some scraps.
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trouts2
Location: Marlboro MA
Joined: Dec 8, 2007
Points: 1328
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Re: Small engine re-ring
Reply #12 May 21, 2011 7:50 am |
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Bill_H, They are the same type of rods. I think what you said was if you aluminum welded (low temp braze) around a bolt then the bolt can be backed out as the weld filler will not stick to the bolt. Just getting familiar with the terms but I think that is due to the wetting action which is the bonding (wetting) of the filler to the welded stock. The temp of the steel bolt would be higher so no wetting (sticking). The bolt could be welded around and backed out. There were a few videos of making a threaded stud. A puddle of filler was melted onto an aluminim piece and a nut placed on top. The inside of the nut was then filled with filler and when cooled the nut backed off the filler making a threaded stud on the piece. Possibly an experienced person could build up the broken ear with or without a bolt inplace. If without then the hole could be drilled and tapped or run a nut and bolt through. One interesting video had a block put in a oven to get it to 200 degrees then reparing a crack.
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trouts2
Location: Marlboro MA
Joined: Dec 8, 2007
Points: 1328
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Re: Small engine re-ring
Reply #13 May 27, 2011 10:44 am |
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Bill_H, I picked up some alumaweld rods at HF but have not tried to use them yet. Borat, The broken ear on the head was glued with JB Weld. I let it dry for a several days then tried pushing hard up and down on the ear it's holding. That's impressive as the two glue surfaces on the ear are very small. I think it will hold the screw torque and probably be ok when vibrating under load.
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trouts2
Location: Marlboro MA
Joined: Dec 8, 2007
Points: 1328
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Re: Small engine re-ring
Reply #16 Jun 17, 2011 9:56 am |
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The ring came in and installed. On screwing on the head the glued ear broke off. The ear section contained half of a screw position. I think the mate of the ear to the rest of the head ok but when screwing in the screw the ear broke. It went in with resistance. There was probably glue in the thread area and caused too much pressure on the ear. The other head screws were put in and the section by the ear covered with glue along with a large section of head to crank. Glue now runs from the head through what’s left of the screw hole over to the crank section. The glue section then is massive and covers the head and crankcase area. It starts and runs so if the glue and the other screws hold the head in place it should be a viable engine. I’ve got a trimmer with the same engine so will probably swap them and keep the original as a spare. The engine had very low compression and now gets 120psi. The purpose of messing with the engine was just to get experience with two strokes.
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