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| Fitting a piston to Blaxland Pup |
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Message |
    
Michael
Member
Username: mdm01
Post Number: 4
Registered: 11-2011
| | Posted on Monday, January 23, 2012 - 05:38 pm: | 
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Hi, I purchased a Blaxland pup X model engine off ebay recently, the engine was very stiff to turn over so thinking it was seized I removed the cylinder and piston. Upon inspection the bore, piston and rings look OK, I think it was hard to turn over due to the bore being dry.
I have some questions that I hope someone can help me with, firstly is there any special technique for refitting the piston, I have purchased a standard ring compressor. Also, I have read on this website that the cylinder base gasket should be a certain thickness, can anyone tell me the thickness of the gasket material I should use?
Looking forward to your feedback.
Best regards Michael |
Greg Y
Senior Member
Username: gregoryan
Post Number: 91
Registered: 09-2004
| | Posted on Monday, January 23, 2012 - 07:24 pm: |
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I have heard of tight pistons; because they had been fitted without the rings being end-gapped! If you're brave and careful enough to take the rings off the piston, you could then try the rings up the bore to see that they all have at least some end gap.? Also try piston up the bore Without the rings on to see if and where it is tight. I had a Simplex 3Hp that had a warped barrel due to expanding concretions in the waterjacket.[ Warning; do not put piston up barrel by it's self with rings on, as the top ring can pop out into the larger diameter combustion chamber - locking the piston up there!!]
I used a piston ring compressor once on a Simplex twin. once i got the first piston up the barrel i realised that the ring compressor was caught there around the con rod, unless the big end was undone. These are ok for multi-cylinders with removable sumps, where the pistons with their rods enter from the top of the barrels.
THe Blaxland cylinders have a large lead-in taper to help the rings squash in without a compressor, using a bit of rotation [before you get as far as the ports]. |
Michael
Member
Username: mdm01
Post Number: 5
Registered: 11-2011
| | Posted on Monday, January 23, 2012 - 10:17 pm: |
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Thanks for your response Greg, the water galleries are corroded and there is a crack in the cylinder under where the water pump mounting flange is, so maybe the bore is warped. I will try your suggestion with the rings and piston. I also noticed that each ring has a small cutout at the open end to locate with a lug in the piston groove. It's going to be really hard to stop the rings moving out of the required locations when reinstalling. So the lead in taper you mention, if I compress each ring with my fingers as I feed it in, will this be sufficient enough to get the piston and rings back into the cylinder?
Thanks again Michael |
Greg Y
Senior Member
Username: gregoryan
Post Number: 92
Registered: 09-2004
| | Posted on Tuesday, January 24, 2012 - 02:36 pm: |
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THe ring alignment pins are no trouble, you should be able to just use your fingers to start rings into the taper. If the piston only goes in some of the way - but the rings fit seperately;now that you mention that crack, you may have distortion. I have relieved the water jackets before by drilling 4/ 10mm holes above the water cavity, then using a long 8mm masonry bitt to drill out the concretions, the drill doesn't cut the iron [ but be careful where it's cracked, then tap threads into the holes and stop them with glued grubb screws. This method may be controversial/ too daring/ too technical, but if is the most likely way of saving your engine,,,,,,? |
Michael
Member
Username: mdm01
Post Number: 6
Registered: 11-2011
| | Posted on Wednesday, January 25, 2012 - 07:49 pm: |
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I just removed the rings from the piston and tried the piston in the bore and it won't go in very far at all so it looks like you are spot on with the warped bore. Looks like I need to put the word out for a good second hand cylinder for an X Pup. I bought this engine for a spare, I have a Master Pup going strong in my boat, so no rush until something crops up. The X Pup came complete so $360 was still a good buy. |
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