Loctite 620 would seal the metal to metal outer ring of an oil seal to the seal bore, with the engine under vac the green will be drawn in to any gaps.
Pioneer 620 - Won't rev up clean to full throttle
- Thread starter cdahl383
- Start date
Help Support Arborist Forum:
cdahl383
ArboristSite Operative
Well it’s got a new seal now. I’ll check it tomorrow and see if it has any leaks.
So that leak wouldn’t cause a problem then? I figured since I found it I might as well fix it.
What’s your take on what the issue is? Carb related still?
I might try popping the Welch plugs off to see if there’s any crud in there.
What about that felt filter in the sediment bowl? Maybe I could remove that just to see if that’s restricting fuel flow?
It really does sound like it’s starving for fuel though. If it had an air leak wouldn’t it just run like that forever? It dies out like it ran out of fuel.
cdahl383
ArboristSite Operative
I’ll keep that in mind for the future.
Is the felt filter in the sediment bowl a new one or older used possibly hardened or partially blocked?. We replaced them every time we removed the glass for cleaning, about once a month back when those saws were our main tools in the woods. I think they came in a bag of 25 from our local dealer.
cdahl383
ArboristSite Operative
It’s the old one that came with the saw. I soaked it in chem dip but maybe it’s just too far gone? I couldn’t find any online at the time so I just left it.
I could remove it temporarily just to see if it makes any difference. I’ve got a new filter in the tank so that should stop most of the crud from getting through.
Sounds like a problem I had on my boat. It idled fine and was ok at low speed but any high and it starved. Fuel filter in the carb was clogged - happened very suddenly. By all means, get that felt out and try it.
I noticed in the video, when you loosened the fuel cap to see if that was causing fuel starvation, you tightened in right back up. You might want to try that again with leaving the cap loose for a few minutes. it takes a little while for the carb to recover the fuel volume under the diaphragm after it's been seriously depleted.
cdahl383
ArboristSite Operative
Ok I’ll keep that in mind. Not sure if I’ll get to mess with it today, maybe tomorrow.
cdahl383
ArboristSite Operative
Installed the new clutch side crank seal on Friday evening since I found it had a small leak between the seal bore and the outer edge of the seal. This time I put some motoseal around the outer edge of the seal before I tapped it in. I also added a small layer of motoseal around the outer edge crevice with a small pick, then smeared it around to smooth it out. Brought the saw inside to cure over the weekend at room temperature since I knew I'd be busy anyway.
Brought the saw back out to the garage today (my wife will be happy now) and did another pressure test. This one was much better. Sprayed soapy water around the crank seal while I had 7psi pumped up into the engine. No bubbles at all anywhere. Looks like it's a perfect seal now.
Watched the Mityvac gauge and it barely lost any pressure this time. After a minute it lost around 0.5psi and by two minutes it was still a little above 6psi (starting pressure was 7psi). There might be a very small leak elsewhere, but I don't think that's going to cause any problems at this point. I'm going to call it good, reassemble the rest of the saw, and move on to other things.
I think I'm going to double check my fuel line routing in the tank. I'm thinking maybe the rubber line I used was kind of stiff, so by bending it to route the filter way at the other end of the tank, it could be lifting the filter up out of the fuel perhaps if it's not completely full. I might just pull that line off and get some larger tygon line that's more flexible and try that. I can always put the rubber line back on if it doesn't make a difference.
I'll remove the felt filter from the sediment bowl and see if that makes any difference as well.
If none of that helps, I may try popping off the welch plugs in the carburetor just to rule that out too.
I took the fuel cap apart and it looks like it's clean and assembled properly per the parts diagram I have. But I'll try unscrewing that as well when it's running to see if that makes a difference.
Beyond that, I think the fuel system is pretty much covered. I'd really like to get my hands on a spare HL22A carb though just to rule out that mine isn't goofed up somehow.
If none of that helps, I may have to just move on to the ignition system. Perhaps the condenser is causing weak spark once it's warmed up? Coil going bad?
At this point, all I can do is just make a list of things to try, and then start marking them off one by one as I do them. At some point, I'll find the issue. Hopefully I find it sometime this year though haha!
Here's a quick video I made earlier today when I did another pressure test to check the new seal I installed:
Brought the saw back out to the garage today (my wife will be happy now) and did another pressure test. This one was much better. Sprayed soapy water around the crank seal while I had 7psi pumped up into the engine. No bubbles at all anywhere. Looks like it's a perfect seal now.
Watched the Mityvac gauge and it barely lost any pressure this time. After a minute it lost around 0.5psi and by two minutes it was still a little above 6psi (starting pressure was 7psi). There might be a very small leak elsewhere, but I don't think that's going to cause any problems at this point. I'm going to call it good, reassemble the rest of the saw, and move on to other things.
I think I'm going to double check my fuel line routing in the tank. I'm thinking maybe the rubber line I used was kind of stiff, so by bending it to route the filter way at the other end of the tank, it could be lifting the filter up out of the fuel perhaps if it's not completely full. I might just pull that line off and get some larger tygon line that's more flexible and try that. I can always put the rubber line back on if it doesn't make a difference.
I'll remove the felt filter from the sediment bowl and see if that makes any difference as well.
If none of that helps, I may try popping off the welch plugs in the carburetor just to rule that out too.
I took the fuel cap apart and it looks like it's clean and assembled properly per the parts diagram I have. But I'll try unscrewing that as well when it's running to see if that makes a difference.
Beyond that, I think the fuel system is pretty much covered. I'd really like to get my hands on a spare HL22A carb though just to rule out that mine isn't goofed up somehow.
If none of that helps, I may have to just move on to the ignition system. Perhaps the condenser is causing weak spark once it's warmed up? Coil going bad?
At this point, all I can do is just make a list of things to try, and then start marking them off one by one as I do them. At some point, I'll find the issue. Hopefully I find it sometime this year though haha!
Here's a quick video I made earlier today when I did another pressure test to check the new seal I installed:
cdahl383
ArboristSite Operative
Put the saw back together again. Here's what I did today to see if anything would change:
1.) Removed felt filter from sediment bowl
2.) Replaced rubber fuel lines with more flexible tygon fuel lines (thought maybe the rubber line was kinked in the tank)
3.) Started the saw with the fuel cap on and then fuel cap off
4.) Blew compressed air through the impulse hole into the cylinder
No change. Does the exact same thing each time. It starts up, runs well for a bit, even revs up to full throttle, idles well. I made some adjustments to the low speed screw and it changed how the saw idled. Got it set to where it idles the highest and then turned it out just a little more to add a little more fuel.
Runs for a couple minutes then starts to run funny, bogs down, idles rough, and craps out. Let it sit for a few minutes, it'll fire back up again and then do the same exact thing. Sounds like it's running out of fuel.
So in summary:
1.) Felt filter was not a restriction
2.) Fuel line must not have been kinked
3.) Fuel cap must be venting okay
At this point I think I've just about exhausted all the potential issues with the fuel system. It also has no air leaks as I verified earlier today with the pressure test.
To recap what's been done/tested so far:
- the saw has new crank seals
- no air leaks (passed pressure/vacuum test)
- has spark inside and outside the cylinder
- points have been cleaned and gapped to .020"
- 145psi compression both cold and hot
- brand new fuel lines and fuel filter
- fresh premix fuel in tank
- new spark plug gapped to .025"
- carburetor has been rebuilt with a new Tillotson carb kit (new filter, new gaskets, new diaphragms, new needle/seat, new o-rings on needles
- carburetor has been cleaned thoroughly multiple times including using chem dip, carb cleaner, compressed air, and ultrasonic cleaner, all new gaskets around intake manifold and exhaust
- removed felt filter in sediment bowl with no change
- unscrewed fuel tank cap with no change
- replaced sediment bowl gasket that was previously leaking with no change
- replaced needle/seat with captured needle/hooked metering arm to ensure needle is opening/closing properly
- adjusted L and H speed screws on carb to best running until after a few minutes the engine runs rough and dies
My next steps are:
1.) Remove carburetor again and pull both low and high speed welch plugs, clean, and replace with new welch plugs
2.) Move on to the ignition system (replace condenser, points, coil, plug wire)
Anything else I may have missed?
1.) Removed felt filter from sediment bowl
2.) Replaced rubber fuel lines with more flexible tygon fuel lines (thought maybe the rubber line was kinked in the tank)
3.) Started the saw with the fuel cap on and then fuel cap off
4.) Blew compressed air through the impulse hole into the cylinder
No change. Does the exact same thing each time. It starts up, runs well for a bit, even revs up to full throttle, idles well. I made some adjustments to the low speed screw and it changed how the saw idled. Got it set to where it idles the highest and then turned it out just a little more to add a little more fuel.
Runs for a couple minutes then starts to run funny, bogs down, idles rough, and craps out. Let it sit for a few minutes, it'll fire back up again and then do the same exact thing. Sounds like it's running out of fuel.
So in summary:
1.) Felt filter was not a restriction
2.) Fuel line must not have been kinked
3.) Fuel cap must be venting okay
At this point I think I've just about exhausted all the potential issues with the fuel system. It also has no air leaks as I verified earlier today with the pressure test.
To recap what's been done/tested so far:
- the saw has new crank seals
- no air leaks (passed pressure/vacuum test)
- has spark inside and outside the cylinder
- points have been cleaned and gapped to .020"
- 145psi compression both cold and hot
- brand new fuel lines and fuel filter
- fresh premix fuel in tank
- new spark plug gapped to .025"
- carburetor has been rebuilt with a new Tillotson carb kit (new filter, new gaskets, new diaphragms, new needle/seat, new o-rings on needles
- carburetor has been cleaned thoroughly multiple times including using chem dip, carb cleaner, compressed air, and ultrasonic cleaner, all new gaskets around intake manifold and exhaust
- removed felt filter in sediment bowl with no change
- unscrewed fuel tank cap with no change
- replaced sediment bowl gasket that was previously leaking with no change
- replaced needle/seat with captured needle/hooked metering arm to ensure needle is opening/closing properly
- adjusted L and H speed screws on carb to best running until after a few minutes the engine runs rough and dies
My next steps are:
1.) Remove carburetor again and pull both low and high speed welch plugs, clean, and replace with new welch plugs
2.) Move on to the ignition system (replace condenser, points, coil, plug wire)
Anything else I may have missed?
Looks like you have everything covered. One other thing I do on the vac/pressure test - if I see a drop, I pinch off the line going to the gauge. If it still drops, you have a leak in the gauge or the tubing.
Helped a friend today work on a sandcast poulan. Had good spark, apparently, but ran poorly, had to hold the trigger wide open and it barely ran. Let go and it would die. Spitting unburned fuel out of the exhaust. Turned out to be a bad condenser. After that was fixed, had trouble with tuning, not wanting to idle. That turned out to be a bad gasket for the reed valve plate and possibly a poor fuel filter. Remember, these things are 60 years old. Take nothing for granted.
Should add, when it was running poorly with a bad condenser, one in a while it would pick up speed and sound normal, but drop out again. Electrical problems are funny that way.
WoodmanSr
ArboristSite Member
Agree with this recommendation. Weak spark can't keep up with fuel load & can be confused as carb issue.
Assume you've followed others work. Samish Saw covers 2 quick looks at 620 Condenser & Carb rebuild.
As previously stated here, I've used Sig-01 Ignition Chip on Homelite. Samish did a clever trick of poking the chip terminal put thru gutted point grommet. Nice job!
Also, I can't erase my visual question on an earlier post.
Your post #124, Feb 24th; disassembled carb bits look correct, but #125 post.. what is the image of black plastic metering lever. Hopefully just some needle leak test setup. That needle lever seems weird / incorrect.
Edit (update) -- found the offset bracket CPM-01 chip shown by Samish. Less common than Sig-01 (Rotary 9334) or BM-11 versions.
... Ebay item#
163612007933
from Midwest Group LLC
... ... Amazon item#: CYC3701260805462
I think he was plugging one of the ports in diaphragm chamber while blowing through the needles.
cdahl383
ArboristSite Operative
Cool, I'll keep that in mind. I guess it could be a small leak from the Mityvac itself. Either way, that small of a leak is not causing the issue, but I hear what you're saying.
cdahl383
ArboristSite Operative
I see. I sure hope it's just ignition related. I would love to replace the condenser and fire it up and have it run properly.
cdahl383
ArboristSite Operative
That's how mine sounds. The idle fluctuates and my first instinct was to think that was related to an air leak or fuel starvation issue. But if the spark is inconsistent/intermittent, that would cause it to run funny as well.
Can't say for sure until you try it. Just relating an experience from yesterday. On an old saw, everything is suspect.
cdahl383
ArboristSite Operative
Hopefully that's all it is, some sort of ignition issue with the condenser or coil.
I'll check those videos out later on.
That was just a grommet I found that I jammed into that slot where the metering lever goes so I could blast carb cleaner/compressed air into the high speed channel. It was just a temporary block off. If I didn't block that area off, the carb cleaner/air would just shoot straight through into the metering chamber area and not be forced up through the channel into the carb throat. I was able to use that to force the carb cleaner up into the venturi, and then I could verify it was not blocked when I forced compressed air through there and saw the carb cleaner shoot up into the carb throat. It was just for testing purposes.
The metering lever I'm using now is the type with the hook on it so it connects to the needle to move it both up and down.
I'll see if I can get the saw running properly with the parts I have right now. It should run find with the points if everything else is good. Maybe I'll upgrade at a later time.
Hoping to work on the saw on Friday or over the weekend.
