stihl 051

[martrix]

ok, ive done some more investigation, heres what ive found:
1)port for bar oil from the oil feed slot to pump is clear
2)pickup tube in oil tank has a rather friction lose fit on white teflon fitting(possible point for air entry,instead of drawing oil up??)
3)looking in tank(limited view) shows that the white teflon fitting doesnt have much oil in it
4)i can blow air through from the oil pickup through oil feed slot for bar when i rotate the clutch sleeve by hand aligning the d-shaft
5)rotating the clutch sleeve shows that the oil pump drive worm rotates

any ideas?

dave

Hi Dave, good to hear you're getting some results.

When I pulled out my oil pump to clean and inspect, I noticed that when I put it back I had to drive it home a little to make sure the holes on the pump lined up with the pick-up. I could see the holes lining up because I had the case split apart, but you shouldn't need to see these holes anyway, because you wont be able to get the cir clip on if its not pushed in far enough.

So, have you get the cir clip on properly, with it sitting in the groove?

Oil tank full?

Oil adjustment set to full?

Oil tank vent is operational?

Here are some picks of my oil pump and the pick-up body inside the case.

 

[djmercer1]

As Lake said, rebuild the carb.. easy and generally solves a lot of problems. It is also possible that your hard starting and smoking is bar oil. You probably need to address your o-ring problem.. it will be mighty difficult to get it to right right without doing that.

some more investigation has shown that i am infact leaking bar oil into the combustion chamber(about a teaspoon overnight). i already replaced the oring in the last couple of weeks. is there anything else that fails on the oil pump to allow oil to pass to the chamber, or did i use/damage a bad oring?

edit:
the cir clip is well seated, and ive toyed with the oil feed rate. i think that the pump is probably pumping oil(unless pickup tube is too loose on teflon connector) and it is bypassing to the cylinder.

 

[martrix]

As far as I know, the only way bar oil could get into the crankcase is either through the seal on the pump body, or through a leaking/bad crank case gasket.

A pressure test on the cylinder would probably tell you if the gasket is leaking.

What do you think Lakeside?

 

[djmercer1]

ok, since my compression test yielded a compression test result of 160psi, does this likely indicate that my issue lies in the shaft oring?

dave

 

[martrix]

I'm still a newbie to chainsaws, so anyone feel free to step in and correct me.

160 psi is good compression for the cylinder, but I don't think it can be used as a test for the crank case.

I think the crank case needs to be pressure tested through the impulse line.

 

[martrix]

OK, just looked at my manual.

To pressure test the crankcase, you need to remove the carb and the muffler. A special sealing flange with a nipple is then fixed on the cylinder over the inlet and outlet ports. The impulse line is then kinked together and air is pumped into the case up to 0.5 bar. If there are no leaks, it will hold the 0.5 bar.

If it doesn't, then you need to also do a vacuum test to determine if its the oil seals on the crank shaft.

I'm sure you could prep the saw, and then take it to a saw shop for them to test it.

A leaking crank case will make it hard to get the saw to idle and accelerate smoothly.

 

[djmercer1]

so, if i now have the saw idling ok, but just smoky would this indicate ok crank seals? i kinda suspect the oring i replaced on the pump shaft, not crank seals.

im thinking to pressure test ill use a piece of rubber mounted between the muffler and the exhaust port for a seal and make a plate with oring grove to mount where the carb block mounts for a pressure feed. if the case leaks throuhg to the oil reservoir i should see bubbles rising through bar oil and use a soapy spray on the crank seals, right? ive seen 0.5 bar(7psi) mentioned---is this the right amount of pressure to test with---i think i have a regulator from plant air thats that precise to use.

 

[djmercer1]

again looking deeper provides some ideas...

i took the oil pump out thinking the oring was bad, it was ok, but i think the rubber ring(#9 in image) is worn. i eliminated the pump shaft and housing by inserting the shaft(well oiled) and plugged the inlet/outlet of the pump with my fingers and pulled the shaft out. the vacuum produced inside the pump is enough to pull the shaft back into the housing with a 'good feeling' motion. the oring appears good and i checked the dimension and fit to the housing.

btw, matrix your pics help alot.

 

[Lakeside53]

yes matrix... GREAT PICS...

 

[martrix]

The easiest thing to probably do right now, is to just pull out your oil pump, clean it, and take some good close-up focused pics and post em. Use the Macro button on your camera if you have to.
I can remember what the condition of mine looked like, so I can compare it to that. If I think it looks worn, I will pull mine out and take some pics to compare, as my 051 is in pieces and the case is split apart.

It might pay to have a quick read through my rebuild thread here.

If everyone here thinks it looks good, then you either need to split open the case (big job for a newb, DAMHIKT) or pressure test the crankcase to get some more answers. If you do either yourself.....get a manual.

 

[djmercer1]

ok, ive got a couple of pics of my oil pump. the piston and pump housing seems ok to me. im pretty sure tha tmy leak is caused by the rubber ringthat seals the pump housing to the crank housing.

btw, i ordered a new sprocket for my saw and got the wrong one(i needed the spur type and i got the rim type). is possible to convert to the rim type from the spur type, whats involved?

 

[djmercer1]

bump...

 

[sthil10_fingers]

Im avidly watching as i have an old 050av that does the same just a bit slower