Discussion in 'Chainsaw Stickies' started by WesternSaw, Jun 21, 2008.
On the cylinder
This is a photo of a cylinder with " CAST " into it boost port, notice opening on the left side of the cylinder opposite the exhaust port. Must be cast in at time of casting cylinder can not be machined in. The boost port is opposite of the exhaust port or behind the coil. Notice the thicker side of the cylinder for the boost port.
The port to properly feed this Boost port must be cast into the base casing at time of original casting. Normally there inst enough material to "Machine" the feed port into the flywheel side of the casting on engines not designed from scratch for the boost port. That is the reason for the cut in the base of the cylinder wall in the above photo.
I will add photos to this post shortly from my Phone of a non boost port P41 cylinder and a side view of the P45 Cylinder showing bulge behind the Mag that is necessary when casting in a boost port.
On or about page 650 of this thread there is an excellent video showing the difference in two Jugs from I believe 60 series saws, one boosted and the other with out. Either way the boost port must be planned for and in the casting of the cylinder, there isn't enough material there to " MACHINE " one in.
Notice in the above photo, the cylinder has no boost port, this is a P41 cylinder. Also the lack of material for one.
Also see the flywheel side of the base casting of the engine built using P45 parts. There is a large boost feed port Cast not machined into the base half.
The above photo clearly shows the boost port bulge behind the coil that is fed from the feed port in the base of the other photo.
I believe the piston used for the "boost port" cylinders is different in the pin boss area as well.
Wow some good info there. Thank you for sharing that! So I went and picked up the p39 today. pulled exhaust and the p/c look perfect, that has me excited! the only issues with the saw are the chain brake not engaging, and apparently it leaks bar oil pretty bad. I threw some fresh mix in it and it fired and ran like a champ. Here's to hoping I can sort out the bar oil leak and the brake!
hey guys. On this p39 I picked up, the chain brake doesnt engage. When I move the hand guard back and forth I can see that the band is expanding and contracting. But it's not contacting tight enough to touch the clutch. Is there some way to adjust the tension on the band?
I am not sure but I think you need to remove the band and the spring and then you need to turn the spring around the band in a bit to just the tension hope you understand what I am saying
If I understand you, there is tooth (or similar) on the brake band located inside the spring itself, turning the spring effectively shortens the entire length of the assembly?
If I'm correct it looks like a right-hand thread (righty tighty).
The MSgt in me requires I recommend you remove the Phillips head screw, then the entire assembly.
I probably would not reinstall the assembly. One of the requirements for my FarmSaw (new late 1979 0r early 1980) was no chain brake. I have been chainsaw nibbled a few times but a chain brake would/did not prevent any of them!
So essentially your saying the band itself has "threads" cut into the end that match the profile of the spring? I will take a closer look tomorrow. Thanks
I'm sorry I'm not familiar with "Msgt". To clarify your are suggesting it is better to not have the entire chain brake assembly on the saw? I'm not sure I follow.
I believe Lou was referring to the Master Sergeant rank he achieved while in the military. I believe he might have even learned a thing or two about mechanical things while there
Thanks for your service Lou!
I am not familiar with tensioning any chain brake. I was restating what I think chainmaster said, more as a question for him than a how for you.
IMO it will be near impossible to retention the brake assembly with it installed. If I were to try, my understanding is correct, and I wanted a chain brake; I would remove, adjust, then reinstall and test the brake assembly for proper tension.
I am a retired USAF MSgt (20 years 2 months and 27 days, not that I kept track).
I have not at the time of this posting ever needed/used a chain-brake. You are the only one that can determine whether you do or not. As I said I have 3 (I think) chainsaw nibbles and NO chain-break would have prevented any of them. A little more attention to what I was doing on my part would have! I have two nibbles above my left knee. I got in the habit of resting the bar of my Farmsaw against my lower thigh after completing a cut. I know better! The third and last is my upper left thigh, I had a 24" bar on my 359 Husqvarna and leaned into the saw. Again a moment's inattention was the cause. None of my nibbles was so severe it required a doctor or stitches.
Good luck with your saw, my Pioneer is the best I've operated to date.
@ paul hill;
I was drafted in 1973 and enlisted in the Air Force 24 hours before my report by date. I thoroughly enjoyed fixing aircraft, especially those others tried and failed to do. I made Master Sergeant at 13 years (on my sleeve). The last 7 years were difficult, they don't allow MSgts to fix aircraft. Cracking the whip was not something I enjoyed. Trying to keep the BS fairly shared amongst other specialties made me very popular with my subordinates but despised by my superiors. Probably why I retired an E7.
I'd do it again but would not have made E7 so quickly!
I was typing when you posted. Thanks.
I understand now. Sorry, I meant no disrespect. None of my other saws have a chain brake. I certainly subscribe to the same school of thought. Accidents a prevented by the operator not the tool. I guess I figured if it's there might as well have it operational. I'll pull it apart soon and see if it can be corected. If not so be it! Thanks for clarifying lou, I appreciate you taking time to respond.
I didn't note any disrespect.
Both my Husqvarnas have chain brakes. Every time they trip it is the absolute most inopportune time possible.
I must apologize; tact is not something the AF taught me and when an aircraft and a pilot's life hang in the balance I got very good at using few words and a subordinate's feelings weren't any consideration. Only that my instruction/technical data was understood and followed.
I most often cut my hinge with a plunge cut and two horizontal cuts, as long as you don't use the upper half of the bar nose kickbacks are extremely rare. Even the few times they happened that wonderful chain brake didn't trip. I suspect it is only there to limit liability for the chainsaw manufacturers.
Again I wish you luck no matter what you decide.
From what l remember here on the brake Band the projections would wear off. lts probable that is the cause of failure. l would remove Spring and band as Chainmaster has suggested look in this area.
Hope you can see in the pic the end of spring.
Thanks, Beavers; it is more complex than I envisioned.
Something else to consider, brake bands can wear. Replace the band if worn less than 20% thickness at the point of heaviest wear.
Find a spot on your band that has no wear and do your first primary measurements from their.
Note: The Brake bands are subjected to a lot of wear during usage. The band does not have to be broken apart to not work
Thanks guys. I will take the calipers out and measure before I tear it apart. I do have another question though. The saw pumps oil while idling.is that normal? I'd have thought it would only oil once rpm's picked up. Even with the adjustment closed as far as possible.
These pioneers all oil while idling. Unlike some modern saws where the worm gear that drives the pump is driven off the clutch drum, these have the worm gear tightly fit onto the crank, so if the motor is running then the oil pump is pumping. The worm gear position is important so before you pull it make a note of how far on the crank it is located.
The best "home made" tool for removing the oiler worm gear is a pipe fitting (1/2" or 3/4" NPT I think....) and a puller. Someone on here will have a good photo. Others have successfully pried the gears off, but they are very very fragile.
Perfect. I'm not even going to touch the oiler if that's how its suposed to be. Thank you very much for clarifying that.
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