High Quality Chainsaw Bars Husqvarna Toys

Slug and jug clearance

countryhog

BTDT
Local time
1:51 AM
User ID
615
Joined
Jan 19, 2016
Messages
1,154
Reaction score
2,678
Location
NW Arkansas
Country flag
put new rings in craftsman 3.7 with LOW compression. All i can get now is 100 psi; bout what it was before replacing. Cant hardly start it but when i do compression is so low it wont idle and wont stay running at WOT. Dud all the normal stuff: carb, lines, filter, etc. even replaced coil with known good one since spark was nowhere hot enough. got couple of suspicions
Even thiugh both the slug and jug look good, no scoring, im wondering if clearance between them is too much. I checked new ring gap at bottom of ports and they were spot on.
Or - not sure if the jug is chrome or the piston. Either way, will that affect ring seating? Rings are ductile and are from greece
Gettin really frustrated here so all help is appreciated
 

mortalitool

aka Nick Stoeckel
Local time
2:51 AM
User ID
504
Joined
Jan 10, 2016
Messages
619
Reaction score
1,798
Location
Lexington, MN
Country flag
Do you have another compression tester to try? Could be that your comp tester is faulty.

Quick question: Does your comp tester have a schrader valve on it?
 

countryhog

BTDT
Local time
1:51 AM
User ID
615
Joined
Jan 19, 2016
Messages
1,154
Reaction score
2,678
Location
NW Arkansas
Country flag
Do you have another compression tester to try? Could be that your comp tester is faulty.

Quick question: Does your comp tester have a schrader valve on it?
Just the one. Got it from a reputable site member who swore by it. Yes it has a schraeder valve
 

Bigmac

Mastermind Approved!
Local time
11:51 PM
User ID
5937
Joined
Apr 19, 2018
Messages
5,430
Reaction score
37,464
Location
Oregon
Country flag
dose it “feel” low? What is the squish? Running a gasket? Have you tested the compression gage on one of your other “good” saws for a kind of baseline?
 

DrewUth

Too weird to live, too rare to die.
Local time
2:51 AM
User ID
762
Joined
Feb 3, 2016
Messages
199
Reaction score
469
Location
SJ
Country flag
To answer your question about rings- yes, rings meant for an unlined cylinder and a lined (plated) cylinder are different and will not seat properly if installed in the wrong type of cylinder.
 

countryhog

BTDT
Local time
1:51 AM
User ID
615
Joined
Jan 19, 2016
Messages
1,154
Reaction score
2,678
Location
NW Arkansas
Country flag
dose it “feel” low? What is the squish? Running a gasket? Have you tested the compression gage on one of your other “good” saws for a kind of baseline?
Has a distinct pressure feel at tdc. Running gasket. Didnt measure squish cause put it back to stock. Compression gage gives plausible. Results for known runners.
 

countryhog

BTDT
Local time
1:51 AM
User ID
615
Joined
Jan 19, 2016
Messages
1,154
Reaction score
2,678
Location
NW Arkansas
Country flag
To answer your question about rings- yes, rings meant for an unlined cylinder and a lined (plated) cylinder are different and will not seat properly if installed in the wrong type of cylinder.
Thanks. Now i get to research that
 

Chainsaw Jim

Con Artist LLC
Local time
11:51 PM
User ID
836
Joined
Feb 8, 2016
Messages
4,014
Reaction score
79
Location
Springfield Oregon
Wrong rings or not it should blow harder than 100. I'm thinking this saw was possibly a dud from the factory with too much squish area... maybe the wrong gasket was used. I'm doubting you overlooked bad spark plug threads, so checking squish to see if there is an immediate improvement might be a good start.
 

smokey7

Pinnacle OPE Member
Local time
2:51 AM
User ID
761
Joined
Feb 3, 2016
Messages
1,532
Reaction score
3,549
Location
Detroit
Country flag
What is the p&c clearance what is the squish? Also im fairly sure that is actually a Roper saw rebranded to craftsman and poulan. As such i dont think they had the plane bore with a plated piston. So as long as you bought rings by application not by size it shouldnt be a issue. Lastly if you got rings for a bare bore ie chrome faced or similar material will or can destroy the plating in a good bore rather quickly.
 

countryhog

BTDT
Local time
1:51 AM
User ID
615
Joined
Jan 19, 2016
Messages
1,154
Reaction score
2,678
Location
NW Arkansas
Country flag
What is the p&c clearance what is the squish? Also im fairly sure that is actually a Roper saw rebranded to craftsman and poulan. As such i dont think they had the plane bore with a plated piston. So as long as you bought rings by application not by size it shouldnt be a issue. Lastly if you got rings for a bare bore ie chrome faced or similar material will or can destroy the plating in a good bore rather quickly.
Really? How did you see this saw without me not knowing about it. Most definitely NOT a roper. Roper branded to craftsman as did poulan. Roper did not brand to poulan
Thanks for the ring tip
 
Last edited:

smokey7

Pinnacle OPE Member
Local time
2:51 AM
User ID
761
Joined
Feb 3, 2016
Messages
1,532
Reaction score
3,549
Location
Detroit
Country flag
My mistake. I read 3.7 and didnt think further on it. My apologies
 

countryhog

BTDT
Local time
1:51 AM
User ID
615
Joined
Jan 19, 2016
Messages
1,154
Reaction score
2,678
Location
NW Arkansas
Country flag
Correction. Ordered rings directly from sears parts plus from the parts diagram on their web site. So, rings are the right ones or sears shipping screwed up
 

countryhog

BTDT
Local time
1:51 AM
User ID
615
Joined
Jan 19, 2016
Messages
1,154
Reaction score
2,678
Location
NW Arkansas
Country flag
Finally got around to checking squish.
0.10”
WHAT?
Think i may have found the problem.
Tear down in order. Believe my base gasket material to be the issue. We’ll see
 

Bigmac

Mastermind Approved!
Local time
11:51 PM
User ID
5937
Joined
Apr 19, 2018
Messages
5,430
Reaction score
37,464
Location
Oregon
Country flag
Finally got around to checking squish.
0.10”
WHAT?
Think i may have found the problem.
Tear down in order. Believe my base gasket material to be the issue. We’ll see
That’s great you found it! Checking squish is always a good idea, It is amazing how much variance there is, on ms660 I have was .019 squish stock and another was .035 stock
 

countryhog

BTDT
Local time
1:51 AM
User ID
615
Joined
Jan 19, 2016
Messages
1,154
Reaction score
2,678
Location
NW Arkansas
Country flag
Reinstalled jug without gasket. Squish is now 0.05 (actually was 0.08 before; measured the solder wrong). Compression is now 130 psi. Still cant get this sucker to start. Even with a prime. Gonna try different carb. AGAIN. gonna make sure flywheel didnt shear key. After that im out of ideas. This thing really taking too much time. May end up in christmas thread
 

Bigmac

Mastermind Approved!
Local time
11:51 PM
User ID
5937
Joined
Apr 19, 2018
Messages
5,430
Reaction score
37,464
Location
Oregon
Country flag
Reinstalled jug without gasket. Squish is now 0.05 (actually was 0.08 before; measured the solder wrong). Compression is now 130 psi. Still cant get this sucker to start. Even with a prime. Gonna try different carb. AGAIN. gonna make sure flywheel didnt shear key. After that im out of ideas. This thing really taking too much time. May end up in christmas thread
That’s a nice bump in comp, it’s still a lot of squish, getting it down to .025 would probably give you another 25psi of compression! It must have been a poorly machined cylinder
 

Stump Shot

Disciple of Monkey's
GoldMember
Local time
1:51 AM
User ID
1377
Joined
Jun 5, 2016
Messages
30,974
Reaction score
193,744
Location
Northwoods of Wisconsin
Country flag
Reinstalled jug without gasket. Squish is now 0.05 (actually was 0.08 before; measured the solder wrong). Compression is now 130 psi. Still cant get this sucker to start. Even with a prime. Gonna try different carb. AGAIN. gonna make sure flywheel didnt shear key. After that im out of ideas. This thing really taking too much time. May end up in christmas thread

130PSI while not optimal, is enough for the engine to run. It should at least "Pop" with a prime and usually run for a couple seconds even with a completely dead carburetor. I would look into other areas such as a primary crankcase pressure test and a spark test.
 
Top