mad murdock
ArboristSite Guru
That is a looker there 1-52! How do you like the forester bar? I have never tried one. Are they solid, or laminated?
The unofficial Mac 10-10 thread
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mad murdock
ArboristSite Guru
10-10 piston cyl clearance??
A friend of mine is rebuilding a Promac 10-10 for his dad for fathers day. He is going all out and trying the best he can to make it a "new" saw. It is shaping up nicely. he ordered a new piston and rings, PN 69210, and it looks real good. It has about a .0010"(ten thousanths) interference between the size of the piston, compared to the size of the cylinder. you can still see a lot of the factory cross hatching in the cylinder, i don't think the saw was used heavily. It apparently caught on fire by the original owner, due to a fuel leak either at the tank parting line, or bad fuel line. Either way, it was not burned bad, he has all the metal pieces cleaned and repainted, the main bearings and seals replaced, and is trying to final fit the piston/cylinder. The cylinder has a slight reverse choke, and the piston appears to be milled so it is slightly smaller at the top end than it is at the skirt end. Recommendations for correcting the fit issues? What is the proper piston to cyl clearance? just hone till you get the proper clearance? Thanks for the input!!
A friend of mine is rebuilding a Promac 10-10 for his dad for fathers day. He is going all out and trying the best he can to make it a "new" saw. It is shaping up nicely. he ordered a new piston and rings, PN 69210, and it looks real good. It has about a .0010"(ten thousanths) interference between the size of the piston, compared to the size of the cylinder. you can still see a lot of the factory cross hatching in the cylinder, i don't think the saw was used heavily. It apparently caught on fire by the original owner, due to a fuel leak either at the tank parting line, or bad fuel line. Either way, it was not burned bad, he has all the metal pieces cleaned and repainted, the main bearings and seals replaced, and is trying to final fit the piston/cylinder. The cylinder has a slight reverse choke, and the piston appears to be milled so it is slightly smaller at the top end than it is at the skirt end. Recommendations for correcting the fit issues? What is the proper piston to cyl clearance? just hone till you get the proper clearance? Thanks for the input!!
machinisttx
Addicted to ArboristSite
.010" is ten thousandths. .001" is one thousandth. Round objects are generally not millled to shape, but turned on a lathe.* The piston should not be an interference fit with the bore, assuming it's the correct size piston and not a .010" or .020" over replacement. Both the bore and the piston need to be measured to make sure they are the correct size. It's possible that an oversize piston made it into box for a standard size one, or someone shipped the wrong one altogether, etc.. Always measure before doing anything else.
* I'm a machinist by trade. Not trying to bust your chops or anything. :smile2:
mad murdock
ArboristSite Guru
No offense taken. Thanks for the reply. That is what I was trying to say, I know that there should be a slip fit between the piston and cyl. I was wondering what the specs were supposed to be, and advise on if it would be advisable to turn the piston and adjust cyl bore by precision honing to get proper fit? Is the PN piston I posted the right one for standard size? I should have used better terminology on my prior post, I feel a bit embarrassed as I am an aircraft mechanic by trade
machinisttx
Addicted to ArboristSite
Standard bore is 1.75" on all 10-10 models except for the 10-10S, which had a 1.812" bore. The acresinternet.com site has the bore/stroke listed for lots of different saws. The IPL that I'm looking at shows the 69210 part # to be a .020" oversize piston assembly. It shows part # 69212 to be the standard size piston assembly.
If cross hatching is still prominent, I would, at most, install new rings on the old piston and reinstall it. That's assuming the old piston is not damaged in some way that precludes doing so. I doubt new rings are even needed since it sounds like the old ones probably didn't even have time to seat well before it caught fire. 62814 is the part number for new standard size rings on the IPL I have up.
If cross hatching is still prominent, I would, at most, install new rings on the old piston and reinstall it. That's assuming the old piston is not damaged in some way that precludes doing so. I doubt new rings are even needed since it sounds like the old ones probably didn't even have time to seat well before it caught fire. 62814 is the part number for new standard size rings on the IPL I have up.
mad murdock
ArboristSite Guru
Thank you sir! Good info. I will pass it on. Makes sense that the piston is the way it is now. I know that McC on some models used letter designations to denote different fits on piston cyl combinations (A,B, or C). No such markings on these parts. There is some light scuffing on the original piston skirt, I will pass the info on, so he can get the saw going. What is ring end gap supposed to be?
machinisttx
Addicted to ArboristSite
.006" to .017" according to the service manual. That's checked with the ring in the bore, just above the exhaust port.
mad murdock
ArboristSite Guru
Good Saroyan rep sent! Thanks a lot!
Clearance between the piston and the bore should be around 0.003 and 0.005". Ring end gap for 10 series is hard to measure since the piston has pins to keep the rings from rotating but if you try to measure end gap like a non-pinned ring you will not get accurate results.
Pistons are generally not round and smaller at the top; both conditions are by design so that the piston becomes round and uniform diameter when up to operating temperature.
Mark
Pistons are generally not round and smaller at the top; both conditions are by design so that the piston becomes round and uniform diameter when up to operating temperature.
Mark
machinisttx
Addicted to ArboristSite
That makes sense. There is more material to expand/contract at the ring end than there is at the skirt.
I found a very nice 2-10G recently, with regular 28" bar and Original bow bar. Built in 1964, complete with owner's manual.
The owner told me that the Mac dealer switched the bullfrog carb with a regular Tillotson soon after he purchased it (starting problems).
It's a nice runner now ; it's quite rare to find a bow bar on this side of the atlantic, so I am pretty happy with this one.
The owner told me that the Mac dealer switched the bullfrog carb with a regular Tillotson soon after he purchased it (starting problems).
It's a nice runner now ; it's quite rare to find a bow bar on this side of the atlantic, so I am pretty happy with this one.
Nice bow saw. :msp_thumbup::msp_thumbup: Now get you a guard, be careful and enjoy it. Ron
Very neat saw Roland, do be careful if you cut with it without a guard on the top of the bow or you may develop a leak.
Show us a couple of photos in side the air box to see how they fit the cube under the hood.
Mark
Show us a couple of photos in side the air box to see how they fit the cube under the hood.
Mark
mad murdock
ArboristSite Guru
My friend has a promac 10-10 he is restoring for his dad for fathers day. He is at an impass with the project, he needs a PN 69212 std size piston, with PN 62814 std rings, he has a PN 69210 .020" O-sized piston and rings he can trade someone, or if anyone knows where to go to get the correct match for his Std Cyl. Thanks!!
mad murdock
mad murdock
Warped5
WingNut
Does he require NOS parts?
mad murdock
ArboristSite Guru
technically no, but he is wanting to make the saw as "new" like as possible, including commisioning new decals and a complete strip and repaint of a saw that was already decent, before he took it all apart. When he is done the saw will be totally remanufactured. He is doing it up right. I will get some pics of it to post when he gets it done.
Hi Mark, don't really know which guide you mean and how it can cause a leak ; please enlighten me.
I knew I had that one comin...
That looks like they changed the bottom half of the fuel tank as the carburetor bolts right up.
Here is a shot inside the 5-10 I received with more home spun adapter to fit the cube carburetor to a saw originally fit with a flat back type carburetor.
Mark
Here is a shot inside the 5-10 I received with more home spun adapter to fit the cube carburetor to a saw originally fit with a flat back type carburetor.
Mark
Eccentric
Mister Wizard
Mark's referring to the aluminum guard that goes over the chain on the top rail of that bow bar. Protects your body from the chain. Getting cut makes you leak...
