Cylinder/piston repair – Many questions, sorry so long.
First off – If I am being a PIA, asking too many questions in one post or whatever please let me know.
Secondly – Thanks in advance!
OK – My ole faithful saw has now become my project saw and my ‘learning more about saw engines’ saw. I have made reference to it in a few other posts I started (Search them if you want more background on what led me to this point)
The saw is a Husqvarna model 51, mfgs tag says 1997 if I remember correctly. I have replaced the saw with a 372xp so I can be down for a while as I work on the 51.
The conclusion of my dealer was that a cylinder/piston replacement was in order. Running a tank of straight gas led to the issue (It wasn’t me who filled the tank) and maybe water in the gas. The issue is poor performance under load, stalling, no starting when warm and general bad behavior. I do not think the saw is totally cooked, it still runs, just badly. Dealer said it would be too much money for him to do the repair and I may be better off, if so inclined, to do it myself. Dealer solution would be for new OEM cylinder/piston. I want to see if I can fix her up with a minimal, or zero, outlay of cash.
First off, I have never gotten this deep into a small engine before. I once removed the carb on the 51 and immediately put it back on. I forget why I removed it now. I do recall it being a PIA to get the choke and throttle linkages put back correctly.
OK – So on Sunday afternoon I decided to blindly dig in. I removed the bar and chain, spark plug, paw/muffler bracket, muffler, handle, I then loosened the 4 screws that hold the cylinder to the saw body. I was hoping I wouldn’t need to fully remove the carb. Well, out came the carb and the various plastic parts. Then out came the cylinder, the retaining pin on the piston and then the piston.
This all came apart without any hassles. I think I can get it back together without any issues. My workbench is loaded with parts.
The piston and cylinder do indeed seemed scored as my dealer said. My dealer also suggested (as some folks here also said) to try muriatic acid and emory cloth to clean up, and polish, the cyl and piston to see “if that does it”.
OK – At this point I have a few questions. (My primary questions are in Bold
Scoring
The cylinder and piston scoring appears to only be on the exhaust side. Does this tell me anything?
Compression testing
I think I know what compression means. I do not currently have a good way to test compression. Before I took everything apart I did put a finger over the spark plug hole and could feel pressure when pulling the started rope. I have also read about a leak down test. I do have an air compressor. Would a leak down test and a compression test effectively tell me the same thing? I could envision building a simple device to pressurize the cylinder, reading the pressure, and noting the drop over time. If I built such a device what would be a good starting pressure and how slow/fast would be a good indication of decent compression? Maybe the compression tester at HarborFreight for $5 would tell me, if after polishing, I was even in the ballpark. Should I just clean/polish the piston/cyl and re-assemble and have my dealer check compression?
Polishing cyl/piston
How does this even work? If there is a groove in my cyl wall and/or piston how will polish help with a compression issue? Polishing would remove material, not fill in any scoring, correct?
Cleaning
In retrospect I should have really cleaned the saw of dirt and grime BEFORE opening up the engine. I have a lot of gunk around the saw body and next to where the cylinder attaches. I have been careful not to get any gunk into the engine. I figure I should clean up things before putting the cylinder back on. Any suggestions on cleaning w/o contaminating the open engine?
Gaskets
I presume its good practice to replace the cylinder, exhaust and carb gaskets during re-assembly. Is this correct or can I re-use the old gaskets? How about liquid gaskets?
Cylinder and/or piston replacement and other parts
I am thinking that I may just go ahead and do the cleanup of the existing cyl/piston and put it all back together to see how things work. Good or bad plan? Are there any must replace parts, or good to replace, parts I should consider at this point? The cyl/piston after market parts are about $90+ on ebay. Piston only is about $30. I would love to just clean up things and have it work properly again w/o all new parts. BTW – The carb is newish and looks to be in perfect condition.
Piston Ring
Maybe just a new piston ring would be in order. $7 or so. It isnt obvious to me how the ring is removed. How is just a ring removed and replaced? Is that good insurance as part of my proposed polish and re-assemble to keep the cost down plan?
What I am missing?
When I put this all back together what do I need to consider? Side note - I once removed push rods on a 4 cylinder car engine; there was an alignment procedure that had to do with the position of the crankshaft in relation to the pushrods. I don’t remember exactly. Anyway, anything like this I need to consider when putting everything back together? Timing? (Not that I really know what that means or how to adjust it or if its even required)
OK – So I want to try and do this on the cheap, w/o parts if possible, and w/o spending money on test equipment. Am I doomed for failure? Is this post too long? Am I being a PIA? Suggested online reading? Sorry if I’m not using the correct terms, feel free to gently correct me, I’m learning.
Thanks all!!!
First off – If I am being a PIA, asking too many questions in one post or whatever please let me know.
Secondly – Thanks in advance!
OK – My ole faithful saw has now become my project saw and my ‘learning more about saw engines’ saw. I have made reference to it in a few other posts I started (Search them if you want more background on what led me to this point)
The saw is a Husqvarna model 51, mfgs tag says 1997 if I remember correctly. I have replaced the saw with a 372xp so I can be down for a while as I work on the 51.
The conclusion of my dealer was that a cylinder/piston replacement was in order. Running a tank of straight gas led to the issue (It wasn’t me who filled the tank) and maybe water in the gas. The issue is poor performance under load, stalling, no starting when warm and general bad behavior. I do not think the saw is totally cooked, it still runs, just badly. Dealer said it would be too much money for him to do the repair and I may be better off, if so inclined, to do it myself. Dealer solution would be for new OEM cylinder/piston. I want to see if I can fix her up with a minimal, or zero, outlay of cash.
First off, I have never gotten this deep into a small engine before. I once removed the carb on the 51 and immediately put it back on. I forget why I removed it now. I do recall it being a PIA to get the choke and throttle linkages put back correctly.
OK – So on Sunday afternoon I decided to blindly dig in. I removed the bar and chain, spark plug, paw/muffler bracket, muffler, handle, I then loosened the 4 screws that hold the cylinder to the saw body. I was hoping I wouldn’t need to fully remove the carb. Well, out came the carb and the various plastic parts. Then out came the cylinder, the retaining pin on the piston and then the piston.
This all came apart without any hassles. I think I can get it back together without any issues. My workbench is loaded with parts.
The piston and cylinder do indeed seemed scored as my dealer said. My dealer also suggested (as some folks here also said) to try muriatic acid and emory cloth to clean up, and polish, the cyl and piston to see “if that does it”.
OK – At this point I have a few questions. (My primary questions are in Bold
Scoring
The cylinder and piston scoring appears to only be on the exhaust side. Does this tell me anything?
Compression testing
I think I know what compression means. I do not currently have a good way to test compression. Before I took everything apart I did put a finger over the spark plug hole and could feel pressure when pulling the started rope. I have also read about a leak down test. I do have an air compressor. Would a leak down test and a compression test effectively tell me the same thing? I could envision building a simple device to pressurize the cylinder, reading the pressure, and noting the drop over time. If I built such a device what would be a good starting pressure and how slow/fast would be a good indication of decent compression? Maybe the compression tester at HarborFreight for $5 would tell me, if after polishing, I was even in the ballpark. Should I just clean/polish the piston/cyl and re-assemble and have my dealer check compression?
Polishing cyl/piston
How does this even work? If there is a groove in my cyl wall and/or piston how will polish help with a compression issue? Polishing would remove material, not fill in any scoring, correct?
Cleaning
In retrospect I should have really cleaned the saw of dirt and grime BEFORE opening up the engine. I have a lot of gunk around the saw body and next to where the cylinder attaches. I have been careful not to get any gunk into the engine. I figure I should clean up things before putting the cylinder back on. Any suggestions on cleaning w/o contaminating the open engine?
Gaskets
I presume its good practice to replace the cylinder, exhaust and carb gaskets during re-assembly. Is this correct or can I re-use the old gaskets? How about liquid gaskets?
Cylinder and/or piston replacement and other parts
I am thinking that I may just go ahead and do the cleanup of the existing cyl/piston and put it all back together to see how things work. Good or bad plan? Are there any must replace parts, or good to replace, parts I should consider at this point? The cyl/piston after market parts are about $90+ on ebay. Piston only is about $30. I would love to just clean up things and have it work properly again w/o all new parts. BTW – The carb is newish and looks to be in perfect condition.
Piston Ring
Maybe just a new piston ring would be in order. $7 or so. It isnt obvious to me how the ring is removed. How is just a ring removed and replaced? Is that good insurance as part of my proposed polish and re-assemble to keep the cost down plan?
What I am missing?
When I put this all back together what do I need to consider? Side note - I once removed push rods on a 4 cylinder car engine; there was an alignment procedure that had to do with the position of the crankshaft in relation to the pushrods. I don’t remember exactly. Anyway, anything like this I need to consider when putting everything back together? Timing? (Not that I really know what that means or how to adjust it or if its even required)
OK – So I want to try and do this on the cheap, w/o parts if possible, and w/o spending money on test equipment. Am I doomed for failure? Is this post too long? Am I being a PIA? Suggested online reading? Sorry if I’m not using the correct terms, feel free to gently correct me, I’m learning.
Thanks all!!!