Service & Maintenance Question
I have a 455 Rancher chainsaw that I've determined to...escalated
Service & Maintenance Question posted January 31, 2014 by Gary Wheeler
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Question:
I have a 455 Rancher chainsaw that I've determined to have stuck piston ring. The saw quit running while I was cutting after a couple hours of use and I couldn't get it re-started. Checked compression and found it at about 65psi after 6+ pulls. replaced the Decomp valve and tried a cylinder plug with no change to either. Thought I had ruined the top end with old ethanol mix fuel and have disassembled to determine for certain. The ring is definitely stuck and I have combustion deposits in the ring groove and on the piston below the ring. The cylinder "looks" good with the exception of two or three what appear to be "break-in" lines. I can even still see some of the original honing marks in the cylinder. I've run my finger around the cylinder and cannot feel any scoring, but it's cold in my shop and at my age, my sense of touch is not what it used to be even when my fingers are warm enough. I'm getting ready to order a piston and ring set and I'm wondering if I should re-examine the cylinder by some other method to look for scoring or should it be obvious. Also, some manufacturers no longer recommend glaze breaking or honing, what does Husqvarna recommend for installing a new piston and ring, should I hone the cylinder?
I've been running a richer oil mix than the recommended 50:1 and I assume that's the cause of the stuck ring. Thoughts?
Thanks for your time.
I've been running a richer oil mix than the recommended 50:1 and I assume that's the cause of the stuck ring. Thoughts?
Thanks for your time.
Answer
Gary,
First, To hone or Not to hone, here is what I have gleaned from reading a lot of Articles, Manufacturers info, Honing Product Info. , Websites , and both talking to one friend of mine who machines 2 cycle & 4 cycle cylinders, and to another friend of mine who owns an Authorized Chainsaw Repair store, and we all agree, “Don’t do it “.
Next, here is what I would suggest, thoroughly clean all the components, with both a chemical clean and then a soap and water clean (I use Dawn dish soap). Then Inspect all the components with a good bright light, and a mirror for inside the cylinder, outside and inside the piston. Look for any scratches, scrapes or scoring, If any of the parts are damaged then replace them. I also recommend aftermarket components, they very reasonably priced compared to OEM components, and I have never had any problems with them for the Model 455.
I am not sure why you are replacing the piston, but I have used “LMT” cleaner, (works great on carbon) and available at most big box stores, Farm and Tractor stores, and Automotive stores. I spray it on or fill a small container with it and let it soak, follow the directions on the can. After removing the ring, sometimes the ring breaks into pieces, I use a piece of the ring which is the exact size as the piston groove to clean out the groove, it works great. I also always replace the rings, I buy them for like $5.00 each. Just make sure they are the right size and fit the cylinder properly with the correct gap. Then some “White-scotch brite”, which is a very fine grade abrasive but really won’t leave scratches but polishes the piston, after about an hours work, I have an almost brand new piston. I do recommend replacing the piston bearing. I would also recommend a thorough inspection of the crank shaft, crankshaft bearing, and connecting rod, I have found problems with the crankshaft needle bearing.
After everything is really clean and Inspected, your ready for re-assembly. I make sure all the components are coated with a light coating of 2 cycle engine oil, inside the cylinder walls, inside and outside the piston, the piston groove, and piston ring, and the bearings. As I assemble the engine I use a lite smear of “Ultra black silicone sealant (follow directions on package) on all mating engine surfaces along with the cylinder gasket, again just a very lite coat. You definitely want to make sure you get a really good air tight seal of the engine. As I tighten up the cylinder bolts, and retorque them I check 2 – 3 times periodically that the crankshaft turns freely during the process.
I have never had a problem with Model 455 rebuilds, and only put it together one time (start to finish), and its done. All of my engines really run good, and maybe even better than brand new. Lol.
I Hope this information helps, but I don’t know If I really answered your question. If you have a specific question or I can be of help, just give me a shout.
PS. I am not a Husqvarna Representative or an Authorized Repair Center, just an experimental chainsaw person
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Gary,
One more thought, always use the proper fuel mixture, ie 50:1, More is not necessarily better.
Again, I hope the Info helps
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Karla,
I'm new at this forum and don't know how it works. Please see my additional questions posted below. thanks
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Wow! Thanks a bunch Karla. This is a great help. A few more quick questions if I could, 1) what do I torque the Crankcase bolts to? 2)where do I find the piston ring gap spec? and 3) I haven't examined the crankshaft closely, but on a quick glance it did appear to be a two piece shaft that comes apart at the crank pin journal. However, it seemed the crankshaft bearings were going to be in the way and they did not slide off easily. I have not taken the piston rod off the crankshaft yet and to examine the bearing, shaft and journal closely I'll need to do that. Are the crankshaft bearings pressed on? If so, any hints to removing them without damaging them? also, is there a spec on torque for the crank pin journal when I re-assemble it?
thanks again.
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Gary,
The torque range for the cylinder bolts are 9.6 - 11 ft-lbs, I would probably recommend around 10 ft-lbs (Mid range).
The gap is checked by pushing the piston ring by itself up into the cylinder maybe about an inch of the way up. The piston can be used to ensure that the ring is square or an equal distance into the cylinder. using a feeler gauge the gap should be about 1 mm or less. (See attached picture file)
I have not found an easy way to assemble and dissassemble the crankshaft, so if the crankshaft bearing is bad then I just replace the crankshaft. I usually clean the bearing up by a good chemical soaking and spray with carb cleaner or brake cleaner, etc, after cleaning the bearing a good oiling with some 2 cycle engine oil, then I give the connecting rod a few good manual spins, to make sure it turns freely on the crankshaft if you have a bad needle in the bearing you will know right away, it feels like a flat spot as you rotate the connecting rod on the crank.
Again, I hope this helps.
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Gary,
One additional story, I had a model 455 that I took apart not too long ago, and one of the needles came out of the crank bearing which is an amazing feat in itself, but to make matters worse the piece of needle found its way up the fuel transfer channel of the cylinder and came out at the top of the cylinder wall, which was also amazing and then the needle embedded itself into the cylinder wall and pinned the piston to the cylinder wall. The piston was siezed to the wall of the cylinder by the broken needle. The rings were actually fine, I obviously had to replace the cylinder and the piston in that case. But I guess at 13000 rpms, anything can happen. Lol.
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Thanks Karla,
All great information and will be very helpful in getting my saw running again. Thanks
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Gary,
Glad I could help, and if you need any additional Info just give me a shout.
Also here is a link to some aftermarket components for the Model 455, they are brand new parts, and I have been very happy with my purchases from them, and great shipping too.
http://www.ebay.com/sch/barrydm/m.html?_nkw=&_armrs=1&_from=&_ipg=25&_trksid=p3984.m1439.l2654
I hope this helps
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Cool. Thanks again.
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Karla and others,
I could not obtain LMT cleaner locally so on the advice of an aviation mechanic I bumped into, I soaked the piston in denatured alcohol. It seems to have softened the carbon deposits sufficiently and I should be able to get it clean. However, I have been unable to get the piston ring to budge. I tried moving it both side to side (around the piston in the groove) and up and down between the ring lands of the groove without the slightest movement. I've also examined it very closely several times and cannot see any indication of a gap at all. The closest thing I've found is a semi-circle notch in both the ring and groove that are aligned on one side of the piston. There seems to be some kind of "pin" or something in the hole created by the alignment and I can get the tip of a dental pick all around the "pin". I've also used the dental pick to remove the carbon from the between the ring and the top land in the groove and still cannot get the ring to slide up to the land at all. It almost seems as if the ring is some how machined into the groove and is not removable. Have any of you seen anything like this? My saw was manufactured in 2011, is this some kind of new design of the piston and ring? I've attached a picture of the piston that shows the "hole" and "pin" I've described. Any hints on getting the ring removed and replaced? If I can't get the ring out, I guess I'll just replace the piston and ring. Any hints?
Thanks Gary Wheeler
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By the way, the picture gives the appearance of a line that might be thought to be the gap adjacent to the "hole", however, that line is just in the picture and is not on the actual part.
thanks
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Gary,
Nope, Looking at the picture that is a regular piston and ring in the groove, so it definitely will come out of there. The piston from what I can see looks really pretty good, and you should be able to clean it up, but you will have to be able to remove the ring, it seems to have a lot of carbon in there too.
I don't think the denatured alcohol will work, but I do know that some of the chainsaw mechanics use a 50/50 mix of acetone (which you should be able to find in a hardware store or paint supply store) and brake fluid oil ( automotive store). I have never used it personnally, but some of the other mechanics even put into a spray bottle and use it for cleaning up the inside of cylinders, and anything that has carbon in it.
I would be careful with the pick that you don't scratch the land above the ring.
Also, the pin in the piston groove is to stop the ring from rotating in the groove and also to make sure that the ends of the ring are arranged in the piston so the ends will not align with either the intake or exhaust port in the cylinder, and when its not stuck with carbon it moves very freely. If you notice where the pin is, directly below it in the ring (referring to your picture) there is a split in the ring, if you can get a small jewelers screwdriver ( a good size one is the blade is no wider than the groove) and start at the split to try and pry it up. But I would definitely soak it first for a few hours, and the using a very small screwdriver lifting the split ends.
I hope this helps.
PS. The ring may break into several pieces by the time you get it out of the groove, save the pieces they make great groove scrapers to get the rest of the carbon out of the groove, after you get the ring removed.
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Thanks Karla,
I'll keep working on it then. When I examine the piston closely in good light, I cannot see the split in the ring you saw in the picture. I saw it in the picture also and assumed it was just a shadow in a bad photograph, but I'll try the screw driver procedure you mentioned. I have found a source I can order the LMT cleaner form and I'll probably just do that and try to get this thing done. I've got four large cherry trees laying in my yard that I have to get up before the weather warms up and I have to start working on mowers instead of my own chainsaw. :)
Thanks again.
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