MS260 Giving me fits!!!!

Okie294life

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I’m working on rebuilding a MS 260 replaced seals, p&c and all the critical rubber. Intake and fuel line. Idles like garbage….it still acts like it’s getting an air leak somewhere I don’t understand it. Carb is the only thing I haven’t touched. I’ve got a pressure tester but haven’t tried that yet. Only thing I noticed when I tightened a couple of the head bolts they could have had a little dirt or grease in the threads on the saw, but I used new bolts. Used acetone and tried to get them as clean as possible. I’m kinda stumped because I don’t want to start tuning on something that I’m not 100% sure about. I’ve ran it a couple times and torqued the head bolts and they seem to stay consistent.
 

cscltd

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2 pieces of Duct tape stuck together also also works and bolts will make their own holes for vac test
 

Okie294life

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You don't need anything other than some inner tube sandwiched between the cylinder/exhaust & carb/intake. You can even get fancy & use a .22 case to punch holes in it for the bolts
That’s kinda what I was thinking had some of that spoke rubber laying around for bicycle tires but can’t find it. I also have a hole puncher around somewhere also. Never thought about using a .22 case that’s mixing fun with more fun. Have to see if I got any ammo laying around. I got the threaded insert for the spark plug to hook up the airline so should be good with just a couple pieces of rubber
 

Okie294life

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Unless the carb is known good you need to clean and rebuild it so you can rule that out.
I’ll probably do that and just inspect it. May have a bad diaphragm or clogged LS jet, or screen. It’s got some low speed bog and is making the tale tale grunt/snort when you rev it up, like it’s choking for gas. Hard to explain but sure you guys know what I’m talking about.
 
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That’s kinda what I was thinking had some of that spoke rubber laying around for bicycle tires but can’t find it. I also have a hole puncher around somewhere also. Never thought about using a .22 case that’s mixing fun with more fun. Have to see if I got any ammo laying around. I got the threaded insert for the spark plug to hook up the airline so should be good with just a couple pieces of rubber
Motorcycle shop will give you old tubes for free
 

Okie294life

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One more question I tried the duct tape idea I’m putting pressure through the spark plug hole blocking between the carb and saw body, also blocking between the muffler and cylinder. Still not holding pressure do I need to block the impulse line and fuel line also?
 

MFV

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I rebuilt mine and then found this in the carb. Also I didn’t use a cut up can and ruined one of the seals when I installed it fixed those 2 things and all good
 

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Okie294life

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I rebuilt mine and then found this in the carb. Also I didn’t use a cut up can and ruined one of the seals when I installed it fixed those 2 things and all good
I’m still digging used a cut up plastic bottle to install seals they look awesome still can’t get it to hold pressure probably end up ordering some block off plates if I can’t figure this out. Been spraying soapy water everywhere no clue.
 

SteveSr

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I’m still digging used a cut up plastic bottle to install seals they look awesome still can’t get it to hold pressure probably end up ordering some block off plates if I can’t figure this out. Been spraying soapy water everywhere no clue.
These are known to leak at the FW crank seal. pull the FW, pressurize the saw (5-7psi) and spray with soapy water... or dump in a bucket of water. leaks will be immediately apparent! Just follow the bubbles!
 

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That’s kinda what I was thinking had some of that spoke rubber laying around for bicycle tires but can’t find it. I also have a hole puncher around somewhere also. Never thought about using a .22 case that’s mixing fun with more fun. Have to see if I got any ammo laying around. I got the threaded insert for the spark plug to hook up the airline so should be good with just a couple pieces of rubber
Be sure to only use spent shells... Don't just to pull a projectile & dump the powder or you'll be in for a surprise when the primer goes pop
 

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