I'm starting to accept the bitter reality that my PM 270 may need crank seals... I can't seem to get a tune at WOT. For the first 3 - 4 seconds at WOT it has a good little 4-stroke blurble, but then the blurble goes away, RPMs pick up a little and it seems like it's slightly lean (no audible 4-stroking) after 5 - 6 seconds. It's also a little slow to return to idle. Not like a bad leak, but like a seal starting to go... I think....
A few questions for someone like CBFarmall that knows these saws intimately...
- Does anyone have part numbers for bearings and seals?
- just how bad is replacing seals? Splitting the case? Should I expect to need new gaskets?
My old Canadien may be one step closer to a wall hanger, I rebuilt the carb and can't seem to get a consistent tune on the top end. But it idles like a dream, I'm just out of options it seems.
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Red electrical tape where it was rubbing on the housing a little.What's up with that plug wire?
I'm pretty good at tuning saws but this has me stumped.... yeah it starts great and will sit and idle perfectly, great throttle response and power in a cut. But when I try WOT out of the cut, I get a few seconds of 4-stroking and then it smooths out and revs slightly. If I go much richer it starts to get lazy and smokey off idle.I'll get the seal numbers, they're common. Main bearings are 6203c3 on both sides. I would recommend changing them because PM and IEL both used shielded bearings. Most of the time, after 60 some years, these bearings are rough turning or seizing up. Changing them requires pulling the cylinder, piston and rod, pulling the ignition and flywheel case off and knocking the crank out. Use heat when installing the bearings. The flywheel side has a lip over the seal meaning you have to install the seal before the before the bearing and the case half must always be pulled to change the seal. When you do this you'll know how rough the bearings are.
Expect to make gaskets. They are not out there. Be very careful with the fiber head gasket. Recoat with copper sealant.
That said, you it idles like a dream? Bad seals generally reveal themselves here first. I'd be looking at the fuel lines or diaphragm lever height first. Otherwise, start tearing it apart.
The old girl is manual oiler only, it's a very early 270.Does that saw have an auto oiler? It is impulse driven. If the diaphragm is torn, could be your problem?
All the diaphragms are brand new, and the kit came with a new lever, needle and seat assembly, I opted to leave the originals as they are different and looked good. I could certainly try swapping to the new parts if I can't sort my tuning issue...Have you changed the carb parts? That is an old style lever and it looks like it has seen some miles. Definitely get the modern kit. Carb diaphragms don't last forever.
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