455 won't run

[laynes69]

I've had my 455 rancher for a few years now. In that time I've cut maybe 10 cords with the saw. Last time I cut was maybe a couple of months ago. I went out to cut and the saw wouldn't start. I checked the plug and it's getting gas, checked the spark and it's there, but I'm only getting 90 psi at the cylinder. I don't know what to do, I've also pulled and checked the decompression valve. Any ideas?

 

[67 Mustang]

I've had my 455 rancher for a few years now. In that time I've cut maybe 10 cords with the saw. Last time I cut was maybe a couple of months ago. I went out to cut and the saw wouldn't start. I checked the plug and it's getting gas, checked the spark and it's there, but I'm only getting 90 psi at the cylinder. I don't know what to do, I've also pulled and checked the decompression valve. Any ideas?

Pull the muffler and check for scoring.

 

[fearofpavement]

Remove the plug and the muffler and take a look at the piston to check it for scoring. Doesn't sound good...

Have you tried a different spark plug?

 

[laynes69]

Pulled muffler, piston looks fine no scratches. It does look like the ring is stuck, it's inside the groove. Any way of freeing it without removal?

 

[fearofpavement]

The piston ring will be held inside the groove by the cylinder. push on it gently with the tip of a screwdriver or something similar to see if you can push it in slightly. Be very careful to not scratch or chip the piston while doing this. There should be a bit of spring action as you push in on the ring and it comes back out when you release pressure.

if the ring isn't "stuck" I would probably spray some wd-40 or something similar into the plug hole with the piston above the ports and let it soak for a bit to degunk things. Pull the engine over several times with the plug out before installing the plug and trying to start it again.

You do have spark?

 

[laynes69]

Yeah, I verified spark with a tester.

 

[jus2fat]

Bring the piston up above the ports and spray WD-40 or Liquid Wrench
into the plug hole and let sit overnight. Should free up the rings..!!

J2F

 

[laynes69]

I pressed on the ring and it did move a little. There's some carbon in the port. I'll have to go to the store, I don't have any wd40. Would 3 in 1 work?

 

[jus2fat]

I pressed on the ring and it did move a little. There's some carbon in the port. I'll have to go to the store, I don't have any wd40. Would 3 in 1 work?

3 in 1 is just light oil...like for sewing machines... get WD-40 or Liquid Wrench..!!

J2F

 

[CTYank]

Tell us in detail what you're doing to start the engine. All the settings.

Factory-recommended, ignoring compression release (and it works):
Purge carb diaphragm chamber of air by pressing elastomer bulb.
Set chain brake.
Pull out blue control to set "ON", fast idle and choke.
Pull starter until engine "pops."
Push in blue control, and crank again (fast-idle is still on.)

Engine should now run @ fast idle, without enrichment. Chain brake off, quickly.

I find that this procedure, or very close to it, is totally reliable for starting 455 engine.
Find no need for comp-release or chain brake.

Your compression test reading could easily be off, low without proper schrader valve at engine end.

 

[indiansprings]

Forget the WD-40, PB Blaster and other big box store "penetrants" and find you a source for "Kroil" "the oil that creeps", made by the KANO corp, I get mine thru Midway USA.com guns mithing supply. It's not cheap but works about 100 times better than anything else I've ever tried. Imho your issues are prolly going to run deeper than stuck rings.

 

[laynes69]

I don't use the chain brake to start or the decompression valve. I pump the bulb 2 or 3 times, put on choke and pull. It pops, I take it off choke pull and it's started. It always runs 2nd pull. What's a shrader valve? I just have a cheap compression tester from harbor freight. I know it was pulling over awfully easy when I was trying to start it. It's never not started.

 

[4xrpm4x]

Place the plug on the cylinder and see if it's a bright blueish spark. May not be enough spark to start. Check the flywheel for rust that would weaken the spark

 

[laynes69]

When I get a chance I'll get some penetrating oil and let it soak. There's very little rust on the flywheel. I was a machinist years ago and could feel where the ring is under the surface of the piston. Hopefully the ring isn't broke. I'll soak it and get back here, I don't want to tear it down if I don't have to. It upsets me, the saw looks new.

 

[4xrpm4x]

Personly I'd pull the cylinder to check. If it is broke you don't want it to grab a transfer or port and scar your p/c. How much easier was it to pull over? Are we talking incredibly easy. Or you think it's easier.

 

[laynes69]

Its no different than pulling with the decompression valve on. I cant pull just the cylinder, the saw has to be disassembled.

 

[3000 FPS]

Forget the Harbor freight compression gauge. I tried two of them and they both read low on an engine I new was good. I finaly got my money back. I would say that your compression is ok. Drain the fuel and try some fresh fuel. Remove the plug and see how wet it is afterwards.

 

[Chris-PA]

Forget the WD-40, PB Blaster and other big box store "penetrants" and find you a source for "Kroil" "the oil that creeps", made by the KANO corp, I get mine thru Midway USA.com guns mithing supply. It's not cheap but works about 100 times better than anything else I've ever tried. Imho your issues are prolly going to run deeper than stuck rings.

I did the Kroil thing for a long time - it was hard to get and expensive, and I eventually stopped bothering. I've found that if penetrating oil is gonna help, then Liquid Wrench works just as well. I even read some attempt to quantify that once (wish I had the link), and it pretty much confirmed that. Kroil is good, but not worth the hassle IMO.

There's only so much you can do with penetrating oil, although this would be a good job for it. Give it some time to do it's work.

 

[rmh3481]

Have you tried a teaspoon of mixed fuel poured directly through the carb down into the intake and then a couple pulls?

You cannot leave the fuel sit in these any more past a couple of days. I fixed a blower for a guy a couple weeks back that had the same symptoms. The zama carb needle was stuck and the unit would not pull fuel.

 

[nmurph]

I just did a 455 with stuck rings. When I got this motor, the local H dealership had already been in it one time. They replaced the piston (according to owner...the piston was OEM-not sure about the ring) and reassembled it with some type of liquid gasket. After I got it apart, I cleaned the ring and land well and the ring still stuck. I'm not totally convinced there wasn't a QC issue. I was hoping to just replace the rings. I broke the ring apart and tried to use it as a scraper. I sanded the ring thinner hoping to get it into the land. Even with some sanding (enough to get any carbon off), I never could get it to slip into the groove as it should. Anyway, I replaced the piston and away it went. I have run a couple of tanks through it since without a problem.

These motors are very simple to take apart. There are three bolts that hold the front and rear handles as a unit. Then remove the carb and muffler and the four bolts that hold the clamshell together, and you have it to its components. I replaced the crank seals and rubber gaskets that fit between the clamshell halves, and reassemble it without any type of liquid gasket.