Husqvarna 55 a tale of woe

[Forrest Arnold]

Hello folks of aboristsite long time prowler first time poster. Anyways down to the problem I'm facing. So a while back I was given a 1996 husqvarna 55 by my dad. He didn't use it much and always took meticulous care of the saw so it was a total surprise to us when a visit to the saw doc determined that the piston was scorched. I was given the saw and stripped it down to see what the damage was. It wasn't bad I was able to salvage the cylinder. To my novice eyes it looked like an air leak caused the failure. I bought a meteor piston for it along with new gaskets a impulse grommet intake boot and replaced the carb bolts with stihl carb studs. Slapped her together and did a pressure and vacuum test. Held pressure and vacuum for 15 minutes give or take. Everything seemed to be progressing really smoothly until..... I decided to replace the carburetor since the old one had some junk in it. So trying to be thorough I found a factory walbro carburetor new in the box. Everything seems copacetic and as advertised. At this point I can almost smell the two stroke burning and hear the engine screaming so a fresh tank of gas is poured in and I give her a few pulls and a few more. Shes flooded no big deal pull the spark plug varify spark it's there pull the cord a few times to blow the gas out. Well gas just keeps on coming out, everytime the piston goes down it sucks in a whole bunch of gas. So I know there's an issue now this part might not be suitable for the feint of heart, anyways I put it back together and clamp the fuel line to get the fuel out of it, it pops once okay cool un-clamp it it starts but floods so I try it again hoping that the metering valve which is what I believed to be the issue would seat. Finally I decided to put the old carb on and see if the problem was still present. After getting all the gas cleared out it fired up and idled for a bit then stalled. Okay awesome some progress. At this point things go from me doing a little happy dance to soothing myself with beer. Here's what happened I needed to replace the muffler gasket and I figured while I'm in there I can check the piston to make sure everything's fine well I'm sure you guys can guess where this is going. Anyways I look into the port and low and behold there's some small scoring starting to develop well crap so at that point it became beer thirty. I went back out to the shop after a fair amount of cursing and pulled the cylinder off. The piston has some small scores and the cylinder either has been scored or has aluminium deposited on it. I know this has been a very long post hopefully some of you, the ones that made it this far will find some enjoyment reading of my tale of woe. Now to the meat and potatoes. I won't lie although I'm an equipment mechanic I am a total newbie when it comes to 2 strokes but I'm trying to learn. My question is where did I go wrong on this build I realize this is one of those questions that may not have answer. Did I miss the underlying issue with the saw in the first place? I felt I was very thorough when it came to doing the pressure and vac testing sprayed all the gasket surfaces the crank seals and the fact that it held pressure and vac for as long as it did would all seem to point to an air leak not being the issue. Could it have been damaged by the copious amount of fuel that it sucked down its throat hole or maybe when I pinched the line it leaned it out and scored it. I'm just trying to get to the bottom of this so that when I put a new piston (hopefully only a new piston) in it I don't have the same thing happen again. I'm open to any advise on the matter. Thank you guys hopefully at least one of you made it through this long winded post.

 

[Huskybill]

You need to clean out the aluminum material from the piston that’s welded itself to the cylinder walls. I use 600 grit sandpaper first and work it over the galling. The final approach is to use 1500 grit paper to finalize removing the aluminum. This usually doesn’t hurt the chrome plating. If the cylinder is really galled you need to replace it too.

 

[cuinrearview]

I don't see any indication that it ran long enough for anything to happen. I think where you dropped the ball was not being thorough enough cleaning and prepping during assembly. There are many reasons for scoring, so instead of searching for the needle let's see some pics of the haystack. Lots of pics of cylinder, piston, etc...

 

[HarleyT]

Yeah, The cleaned up cylinder has to look like new, as any imperfection will damage the new piston soon.
But all is just speculation without pics.

 

[motor head]

Every thing they said oh and don’t forget to rinse out the crank case thoroughly.I use fuel mix and do it several times to make sure it’s clean.

 

[Forrest Arnold]

Thanks for all the replies guys I thought I was had it clean but I might have dropped the ball in that department. I hot tanked the cylinder and then sprayed it down with brake clean. The crankcase cleanliness could be suspect there was a little grime in there I sprayed brake clean in there and wiped it clean. When I cleaned up the cylinder it looked good to me there were two areas that were a little questionable but nothing that would catch a nail. Maybe I'm just used to bigger engines where you can get away with more. As you can see it the pictures the damage just got started I'm sure if I'd kept on running it, it would have snowballed into a real mess in there. Thank you guys.

 

[Forrest Arnold]

Sorry guys somehow I posted the pictures twice. I learned it is hard to get good pictures of the cylinder bore. One other thing I forgot to mention is about the prep on the cylinder for clean up. I used muriatic acid and 800 grit sandpaper to get the heavy galling off the cylinder walls. After that I went to 1500 grit wet sand and finished it off with 2000 wet. When I was finished it looked like a new cylinder except for 2 spots below the intake port. They are low spots so not galled aluminum you could run a razor blade flat across them and it wouldn't catch.

 

[Jacob J.]

Your piston looks fine and can go back into service. I would find a better cylinder though. There's spots of missing plating below the exhaust port and those areas will continue to chew up your new piston if you keep running it that way.

 

[HarleyT]

Yeah, buff it all off real good, and put it back together, but make sure it is well lubed, since you used brake cleaner.

 

[HarleyT]

Is it plating missing?

If it is, yeah, find another cylinder, there are plenty around.

 

[Forrest Arnold]

Okay yeah I rubbed the bore down with 2 stroke oil and soaked the piston before reassembly. I think you guys might be right on the missing plating I'm not used to cylinders with only a thin hard plating. I guess I'm going to have to try and source a cylinder that's in better shape and just polish the piston out. This time I will make darn sure that I get all the crud out of the lower end. I guess I can chalk this up to a learning experiance. Any advise on good places to find a replacement cylinder? I'm really hoping that I can figure this 55 out so that I feel confident enough to rebuild my 288xp. I wanted to get some experience on a cheaper saw before I take the plunge on the 288.

 

[Ted Jenkins]

I bought three 460 a while ago and have been very impressed by them. What you did not mention was cleaning out the carburetor. Yes the cylinder looks like metal scrap. If there is a slight chip in the plating on the cylinder I throw them away. Yes I have replated some of them and worked fine, but it is way too much a problem to not replace them. Saws have to have the carbs cleaned constantly if under certain conditions such as exposure to saw dust or water in fuel. One of my 460 which is about 10 years old have never had the carb off. It has had clean fuel little to no water exposure so it runs superb. There is no way to being an expert until you have some failure. Thanks

 

[Forrest Arnold]

I didn't mention the cleaning of the carb because I had bought a new replacement carburetor for it. However the new carburetor which is a walbro has an issue with it in the metering circuit I think that was causing the saw to pull in so much fuel it was pouring out the exhaust. Upon inspection of the new carburetor it looks like there is a defect which causes the hi speed needle to not be able to limit fuel. This is just a theory all I know is the needle when bottomed out sticks way out unlike the needle on the old carburetor. So I put the old carburetor back on to see if the over fueling problem went away and it did so it was pretty safe to assume that the new carburetor was a problem. I knew the original carburetor needed a rebuild on it and when I'd taken it apart before I decided that a new carburetor was the best option I had found that the screen in the carburetor was filthy. You guys are awesome and very knowledgable I really appreciate the help I have received thus far. Looks like its unanimous that I will have to find a new cylinder for this saw.

 

[SteveSr]

I didn't mention the cleaning of the carb because I had bought a new replacement carburetor for it. However the new carburetor which is a walbro has an issue with it in the metering circuit I think that was causing the saw to pull in so much fuel it was pouring out the exhaust. Upon inspection of the new carburetor it looks like there is a defect which causes the hi speed needle to not be able to limit fuel. This is just a theory all I know is the needle when bottomed out sticks way out unlike the needle on the old carburetor. So I put the old carburetor back on to see if the over fueling problem went away and it did so it was pretty safe to assume that the new carburetor was a problem. I knew the original carburetor needed a rebuild on it and when I'd taken it apart before I decided that a new carburetor was the best option I had found that the screen in the carburetor was filthy. You guys are awesome and very knowledgable I really appreciate the help I have received thus far. Looks like its unanimous that I will have to find a new cylinder for this saw.

While you're at it check the new carb to see if it holds 7-10 PSI at the fuel inlet. If it doesn't you have found your flooding issue.

 

[Forrest Arnold]

Okay tested the new carburetor it will not hold any pressure at all. The old carburetor holds pressure with no issues. So that being the case what should I look for in the new carburetor that would cause it not to hold pressure?

 

[cuinrearview]

The spring, metering lever, and needle.

 

[Forrest Arnold]

Okay gotcha that's basically what I was thinking. I'm not sure what's up with the hi speed needle on the carburetor something seems funky but maybe it's just a different design. Low needle turned out 1.5 turns hi needle bottomed out. On my other carburetor both needles at 1.5ish give or take are protruding the same amount.

 

[HarleyT]

He is talking about the needle/lever under the cover/diaphram with 4 screws.

 

[HarleyT]

Like this one......

 

[Saw Fixr]

On your fifth picture down, is the piston ring locating pin pointing directly back towards the intake opening of the cylinder?