I heard cleaning them ruins them !
McCulloch Chain Saws
- Thread starter Bruce Hopf
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I heard cleaning them ruins them !
One last ditch. Did you check the radial run out on the PTO side BH-108 bearing? If it's excessive you might be able to tune that out at speed but not at idle.
I did not actually measure the runout on either side, but based on Brian's prior recommendation I did try rocking the crankshaft while pressure and vacuum testing to see if it had any effect and it did not. In reality, I have had other saws with more perceptible movement on the PTO side that ran (and idled) just fine.
Mark
Mark
I am still saying an exorcism is in order.
No question on the carb. Other carbs from running saws have the same results.
No play in bearings.
Seals tight. Sprayed PTO seal while running. No change in RPM.
Pressure and vacuum test pass.
Points set properly, Timing checked.
Spark Plug ruled out.
Not sure if you changed out coil but this does not act like any coil problem I have ran into.
Spark seams to be correct.
Pulse circuit clear and no obvious leaks.
Intake with nes gaskets and isolators. I think Mark sprayed carb cleaner around the intake while runing without any RPM Change.
I think at one time it was said that the fuel line and filter were replaced.
I am out of ideas. Seams like every aspect has been covered.
Brian
No question on the carb. Other carbs from running saws have the same results.
No play in bearings.
Seals tight. Sprayed PTO seal while running. No change in RPM.
Pressure and vacuum test pass.
Points set properly, Timing checked.
Spark Plug ruled out.
Not sure if you changed out coil but this does not act like any coil problem I have ran into.
Spark seams to be correct.
Pulse circuit clear and no obvious leaks.
Intake with nes gaskets and isolators. I think Mark sprayed carb cleaner around the intake while runing without any RPM Change.
I think at one time it was said that the fuel line and filter were replaced.
I am out of ideas. Seams like every aspect has been covered.
Brian
I have tried changing the points (new points currently installed), different coil, and a different condenser. Nothing seems to help.
Mark
Mark
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I feel we have eliminated pretty much everything external. I think it is going to.boil down to something mechanical. Either a twisted crank causing a change in ignition timing (seems pretty unlikely) or the wrong piston (also seems kind of unlikely because I'm not one to install a blatantly different part without question) or a bent connecting rod changing the port timing (slightly more likely due to the damage on the original piston but still seems unlikely)
Either way, it's looking more and more like this saw is just going to be a really expensive shelf queen. If Mark cant figure it out I dont think anyone will.
Either way, it's looking more and more like this saw is just going to be a really expensive shelf queen. If Mark cant figure it out I dont think anyone will.
This is a very long shot, but could have someone have put the wrong flywheel on it somewhere along the line and it is one with the timing advanced far enough to allow it to start but not idle?
A very long shot.
Brian
A very long shot.
Brian
peter92
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It is possible to check the timing out using a DEGREE WHEEL , that way you not it right
Peter
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I believe Mark said he swapped the flywheel.
hseII
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Silly question, but are we certain this saw is a 7-10?
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Interesting angle. We've been so focused on the piston..., are we certain the piston involved has the correct cylinder? Mark sort of alluded to that already. Maybe the 69412/85240 piston is the one that should be used and we're missing the forest for the trees.
And it came to Kevin with problems and there was evidence that someone else had already been in the saw. Maybe the piston being replaced was the wrong one for the particular cylinder to begin with. I don't recall whether or not there was a tag number involved or any case identification to go by, but the carb box cover may not be original either.
And it came to Kevin with problems and there was evidence that someone else had already been in the saw. Maybe the piston being replaced was the wrong one for the particular cylinder to begin with. I don't recall whether or not there was a tag number involved or any case identification to go by, but the carb box cover may not be original either.
The model number on the tag in the saw says it is a 7-10 with a 10 prefix Serial number, the AF cover says 7-10 and the bore is right for a 7-10 at 2".
I did try a different flywheel with the same results. I also rechecked the timing using the McCulloch gauge, might be 1 or 1-1/2 degree advance, the point gap is dead on at 0.018".
I usually don't give up but this one has me thinking it's time to move on...
Mark
I did try a different flywheel with the same results. I also rechecked the timing using the McCulloch gauge, might be 1 or 1-1/2 degree advance, the point gap is dead on at 0.018".
I usually don't give up but this one has me thinking it's time to move on...
Mark
hseII
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So the Bore matches the questionable cylinder?
I guess that’s what I was trying to ask, although I didn’t choose the most straightforward way of asking that.
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Do you happen to have both a 7-10 and 6-10 cylinder handy in the attic for a porting comparison? It's about the only thing left that hasn't already been ruled out. I'm sure you don't want to tear down the saw again just to compare cylinders.
I spose it's out of warranty by now.....
Find a runner 7-10 Kevin and keep the lemon saw for parts. Its gotta be something up with that cylinder though maybe someone screwed up in the factory and the squish is miles away orr has someone tried to port it perhaps. . Maybe it never ran very well from new
Find a runner 7-10 Kevin and keep the lemon saw for parts. Its gotta be something up with that cylinder though maybe someone screwed up in the factory and the squish is miles away orr has someone tried to port it perhaps. . Maybe it never ran very well from new
Mark, this saw should be new at this point. Not much left of the motor it's self that is original to the saw or swapped from a running saw. I cannot think of anything that you have not either checked thoroughly or replaced or swapped with a running saw. Other than the question on the piston it seams like you have covered most every base. Other than maybe a hair line crack maybe in the cylinder which would be a really, really long shot? It's got 130 PSI compression which seems reasonable for a saw with new rings that have not seated in yet.
Brian
Brian
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That's just it, these saws do not come up around here which is why I bought this one from Mark. In three years of searching I only ever found 2 for sale. One of them the guy never returned my messages the other was priced at $700.
I hate to give up, I have a lot (for me anyway) of money into this saw.
Didn't realize (or recall) you actually got the saw from Mark. I now understand why he's going the extra mile(s) with it. Not many folks out there who'd go that distance.
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Yes, and I am in no way upset with Mark, it is very standup of him to do what he is doing. He never represented this saw as a runner, but rather an overall solid project saw which is exactly what it appeared to be, we never anticipated any of this.
Sincere apologies if my above statement appeared to cast aspersions for Kevin's difficulties with the saw. It was certainly not intended to by any means. I was simply attempting to point out the possibility that a previous owner (certainly not you!) may have created the problem by mismatching the piston with the cylinder since there was evidence that someone else had already worked on the saw. And as you pointed out, it obviously ran right somewhere along the line for quite some time before it became the current problem child.
