Rebuilding a Stihl 034, should I try it?

[cuinrearview]

Unless that oiler line is leaking I'd leave it all where it is. You can unbolt the oiler and kind of swing it out of the way to clean and check the seal for leaks if needbe

 

[dabills]

Unless that oiler line is leaking I'd leave it all where it is. You can unbolt the oiler and kind of swing it out of the way to clean and check the seal for leaks if needbe

You mean unbolt the oiler to check the oiler for leaks? This is not part of the vacuum test correct? If possible could you advise me of areas to look for leaks while performing vacuum/pressure test? Feel free to be very literal like you're talking to a 10 year old, lol

 

[cuinrearview]

I said that wrong. Basically, that oil line is a major PITA to assemble. It's pretty easy to destroy it taking it off of the oiler, so if you don't need to it's better to just leave it alone.

Once you get your mityvac and you pressure/vac test the assembly you'll only need to look for a leak if it doesn't hold one or both. Common leak points are: impulse hose, intake boot, crank seals, decomp valve(I don't think yours has one), spark plug, and cylinder base where it meets the crank case.

 

[huskihl]

You're gonna need the clutch on tight to seal off the worm gear bushing when doing your vacuum test

 

[dabills]

You're gonna need the clutch on tight to seal off the worm gear bushing when doing your vacuum test

I took the clutch off I was under the impression it needed to be off for the test. How will I see a leak if it's on there? Thanks

 

[huskihl]

I took the clutch off I was under the impression it needed to be off for the test. How will I see a leak if it's on there? Thanks

You could remove the springs and shoes from the clutch. Without it being tight, air can be pulled through between the crank and bushing while pulling vacuum

 

[SteveSr]

You're gonna need the clutch on tight to seal off the worm gear bushing when doing your vacuum test

I don't think so... This is an 034 NOT an 044 with the built in leak through the worm gear sleeve. I just pressure/vac tested my 034S without the oil pump (or clutch) even on the machine. I believe that the 034 crankshaft PTO stub is smaller hence the seal is directly on the shaft like little brother 026.

 

[huskihl]

I don't think so... This is an 034 NOT an 044 with the built in leak through the worm gear sleeve. I just pressure/vac tested my 034S without the oil pump (or clutch) even on the machine. I believe that the 034 crankshaft PTO stub is smaller hence the seal is directly on the shaft like little brother 026.

Could be. I just saw it in his pic and thought it had the same bushing like an 044

 

[Mad Professor]

You're gonna need the clutch on tight to seal off the worm gear bushing when doing your vacuum test

Nope. Same as 036. That is a new stihl seal on a 036 rebuild. New oil hose installed, Waiting to connect oil pump.

How does an 044 crank seal, seal on a bushing on the crankshaft??? If it did, how does bushing to crankshaft seal?

Maybe I'm missing something 044? I'm getting a couple of 044 freebies soon. Thinking about one of those 046/044 hybrids.....

 

[Mad Professor]

I don't think so... This is an 034 NOT an 044 with the built in leak through the worm gear sleeve. I just pressure/vac tested my 034S without the oil pump (or clutch) even on the machine. I believe that the 034 crankshaft PTO stub is smaller hence the seal is directly on the shaft like little brother 026.

Steve, educate me on this.

Built in vac leak?

Have not been inside 044/046 yet. Don't have any until next week.....FREE!

 

[BuckthornBonnie]

Steve, educate me on this.

Built in vac leak?

Have not been inside 044/046 yet. Don't have any until next week.....FREE!

044/ms440 utilize a different style worm gear bushing than 1125s. The 044 style bushing is stepped and the pto oil seal seals around it. Proper torque with the clutch is essential when pressure/vacuum testing. It can still leak (a bit) when things are torqued, so we pack it with grease and figure any tiny leaks can be tuned out. The bushings are known to crack as well.

046/ms460s do not utilize this bushing.

1125 bushings do not integrate with the seal. Instead, they sit on a washer that rides next to the seal (check your crank, there’s an obvious spot where this happens). The seal can therefore be tested without clutch torque on 1125s (034, 036, ms360).

 

[BuckthornBonnie]

The bushing on 044/440 is “sealed” by the seal and a tight fit around the crankshaft. It’s not the best design and used to utilize a tiny o-ring in the bushing. Stihl doesn’t call for the o-ring in updated notes... they would eventually fail anyway. Some guys still use o-rings, but I’ve built up a few just using grease and proper clutch torque.

 

[SteveSr]

Steve, educate me on this.

Built in vac leak?

Have not been inside 044/046 yet. Don't have any until next week.....FREE!

It has been several years since I rebuilt my 044 so all of this is from my failing memory! Looking at the 044 IPL the PTO seal seals between the oil pump worm bushing which installs directly over the crankshaft. It is advised to put some thick grease between the crank and the inside of the oil pump bushing to slow down any leak. When you see this design you'll shake your head and wonder why?

 

[dabills]

Ok I cranked it up to 7 psi and in 3 minutes it went down to just a tick above 6. Spraying bubble water but not seeing any bubbles. After 4 minutes it's still at 6. Is it supposed to not go down at all? What's my next step?

Edit: I tightened the hose barb down and now it only moved a tiny bit below 7 in a couple minutes, barely moved at all.

 

[SteveSr]

Ok I cranked it up to 7 psi and in 3 minutes it went down to just a tick above 6. Spraying bubble water but not seeing any bubbles. After 4 minutes it's still at 6. Is it supposed to not go down at all? What's my next step?

Edit: I tightened the hose barb down and now it only moved a tiny bit below 7 in a couple minutes, barely moved at all.

Flex the crankcase / tank mounts in all directions to try to elicit any intermittent leaks in the manifold and impulse hose. Also rotate and push/pull the crankshaft to look for seal related leaks.

Repeat procedure under vacuum. This is where you'll generally find weak/leaking seals. The object is to move all of the sealed joints around to force a leak in a weak/intermittent component.

 

[Nathan Graff]

Ok I cranked it up to 7 psi and in 3 minutes it went down to just a tick above 6. Spraying bubble water but not seeing any bubbles. After 4 minutes it's still at 6. Is it supposed to not go down at all? What's my next step?

Edit: I tightened the hose barb down and now it only moved a tiny bit below 7 in a couple minutes, barely moved at all.

You can lose some pressure due to the bike tube expanding. Rerun the test. Pump it back to 7, and see what happens.

 

[ken morgan]

want a boat anchor...then just do it!

 

[Mad Professor]

It has been several years since I rebuilt my 044 so all of this is from my failing memory! Looking at the 044 IPL the PTO seal seals between the oil pump worm bushing which installs directly over the crankshaft. It is advised to put some thick grease between the crank and the inside of the oil pump bushing to slow down any leak. When you see this design you'll shake your head and wonder why?

Thanks!!!

And that is another reason to love 038s!!!

Edit: will do another 038S --> 038m next this I learned has soured me to 044. May be 044 parts/saws on trading post near future

 

[drf255]

Sounds like you passed your vac and pressure test, at least to me. When you eventually get a saw with a leak, you’ll get the “aha” moment of what it’s like. The Stihl manual calls for a less stringent test than we all do. I can’t recall the actual number, but it’s something like 8mm of Hg for 60 seconds. Can just say, any saw I’ve had that acted like it had a leak (but still ran ok) couldn’t achieve any vacuum or dropped like a lead ballon in under 10 seconds.

And yes, the 044 has the sleeve that mates with the crank and larger than usual seal. If you grease it for vac testing it holds up fine, it will pop out if you pressure test without the clutch on to hold it in place. The 036 has a stepped crank with a washer and sleeve, the 046 has a Spring clip mounted to a groove on the crank for the worm gear to ride on.

IMHO, the 044 spacer/bushing is a dumb design. They didn’t carry it over to the 046 for some reason.

 

[dabills]

Sounds like you passed your vac and pressure test, at least to me. When you eventually get a saw with a leak, you’ll get the “aha” moment of what it’s like. The Stihl manual calls for a less stringent test than we all do. I can’t recall the actual number, but it’s something like 8mm of Hg for 60 seconds. Can just say, any saw I’ve had that acted like it had a leak (but still ran ok) couldn’t achieve any vacuum or dropped like a lead ballon in under 10 seconds.

I couldn't achieve any pressure at first, then I tightened the spark plug and voila, it held. I'm going to run both tests tonight and reef on all the components. Sounds like if it won't leak on it's own I'm supposed to help it