The 034 Blues...crankshaft seals, bearings, or new carb?

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ReggieT

ReggieT

Member
Aug 13, 2015
99
Birmingham, AL
Hey Guys,

Listen straight to the point: I've gotten 3 different opinions ranging from 1 shops saying all you need is, "New or Rebuilt Carb" and 1 shop saying "crankshaft seals & the last shop saying you need "crankshaft bearings". o_O:rolleyes:

What is the best method for detecting shot crankshaft bearings and seals?
Is splitting the case the only method for repair?

I can handle the carb situation...I guess. :reading:
If I can't advance beyond my current chainsaw learning/repair curve...I might as well give up on chasing down all these 0lder series Stihl saws (044, 064,etc) altogether and perhaps cash in what I've got.

The Stihl shops in my area whine & dread to see me coming with them...and it's getting too freaking frustrating for me.


Thanks,
Reg
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What's the saw doing or not doing ?

I agree start with a leak down test. A pressure test to see if there are any leaks. Bad crank seals allow air into the lower end. This creates 2 problems for any 2 stroke. It effects the engines ability to draw in fuel and air so the saw runs poorly. No amount of carb tuning will make it right for any length of time. And the lower end air leak will cause the saw to run lean. Prematurely damaging it.

You can't test this by checking the saws compression because the leak is in the bottom end. Although I would still check the compression while I'm at it.

Bad lower end bearings can be a reality in a saw of this age. With the top end off you can check the play in the connecting rod bearing by trying to move the rod up and down. As for the main bearings while you have the top end off spin the lower end assembly. If the bearings are really shot you should be able to hear how noisy they are when your slowly spinning the crank shaft. If they are new bearings the assembly spins over much quieter.

Honestly do the leak test. If it holds air then I wouldn't worry about the lower end assembly. If it doesn't hold air then I would split the cases and rebuild the entire saw.

As for the Stihl shops whining etc if they are anything like the ones around me they know very little or have little interest in the saws. They just want to sell you a new saw.

Find a good pro saw shop or small engine mechanic. My local Jonsered shop works on so many Stihls because the local Sthil dealers are not as knowledgeable. The local Jonsered shop is a pro saw shop and would never whine about a customer coming in with an old saw needing work. They actually like that stuff. Find a better shop if possible
 
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I'm going to disagree a bit, because I don't think a leak-down or compression test is all that helpful. I mean, if it has low compression then you can be certain it needs a top-end rebuild in addition to whatever other problems need to be solved, but high compression doesn't always mean that the top end is okay, and regardless of the condition of the top end there are obviously other problems to be solved.

If I had no specialized tools, the first things I'd do to get a sense of the eventual repair bill would be to remove the starter cover (4 screws), clutch cover (2 bar nuts), clutch drum (one e-clip), spark plug, muffler cover (2 screws) and maybe the muffler body if it has an internal baffle. Then I'd look at the piston through the exhaust port, to see if it's scored, and I'd wiggle and rotate the crankshaft by hand (gripping it by the flywheel hub and the clutch end of the shaft itself) , feeling for any play or grittiness in the bearings. If the piston is scored, you need a top-end rebuild and also to figure out why it was scored. If you feel any play or grittiness in the crank bearings then the best-case scenario is that the case needs to be split and the bearings replaced. It's probably worth rebuilding the top end, if that's its biggest problem, but if it needs bearings too then I'd say it's now a parts saw. If both piston and bearings are okay then the situation isn't so bad and you can proceed to look for air and fuel problems.
 
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That's good points Jon.

I hardly ever work on saws anymore my regular runners are fairly new and havent needed anything. Yet. So I didn't think to check the obvious first which is looking for scoring on the piston. You can tell a lot by looking at the piston.

I'm no expert by any means. I can manage to rebuild a 2 stroke but never had formal training. Sorta just learned by tearing apart dirt bikes as a kid. I've always found leak tests to be reliable indicators of the engines seals and ability to hold air.
 
woodhog73 said:
I've always found leak tests to be reliable indicators of the engines seals and ability to hold air.
Click to expand...

Sounds like there's some confusion about the terminology here. A pressure/vac test is not at all the same as a "leak down" test. If you mean you'd seal off the impulse, intake and exhaust and perform pressure and vacuum tests to look for leaks, then I'd agree those would be helpful. But doing that requires some specialized tools, and it's not a "leak down" test.
 
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Jon1270 said:
Sounds like there's some confusion about the terminology here. A pressure/vac test is not at all the same as a "leak down" test. If you mean you'd seal off the impulse, intake and exhaust and perform pressure and vacuum tests to look for leaks, then I'd agree those would be helpful. But doing that requires some specialized tools, and it's not a "leak down" test.
Click to expand...

Ya that's what I mean. Seal off intake and exhaust and screw my pressure and vacuum pump into the spark plug hole.

I always called this a leak test. As in checking for air leaks. That's my lack of formal training lol :)

Anyways the kit for doing a pressure and vacuum test is fairly inexpensive
 
On the fuel supply side...
1. Tablespoon of fuel mix in carb throat and see if it runs strong for 5 secs - may take 10-15 pulls b/c will be a little flooded.
2. Try a similar new AM carb. You need one where impulse hole and intake diameter are the same. Small saws tend to be ~16mm intake diameter and large saws tend to be ~19.5mm intake diameter. Most all carbs are 31mm distance between 2 mount holes.

I don't have carb karma rebuilding old carbs like Tillotson HL, Walbro SDC, Zama C2S. They end up floody. I look for a new AM one that can be adapted. Eg: Latest project is a MAC 10-10A - I find a Husky 272 carb shows it to be a great runner and worthy of a NOS carb if price isn't too high. Or may fabricate throttle and choke rods for this carb.
 
I am just signing up to the tread. Lots of good stuff here.
I am still interested in what the "problem" is with the saw. Haven't heard that part yet.
 
Jon1270 said:
Sounds like there's some confusion about the terminology here. A pressure/vac test is not at all the same as a "leak down" test. If you mean you'd seal off the impulse, intake and exhaust and perform pressure and vacuum tests to look for leaks, then I'd agree those would be helpful. But doing that requires some specialized tools, and it's not a "leak down" test.
Click to expand...

What exactly is a leak down test then, as it applies to saws? That is always what I called that procedure.
 
maple1 said:
What exactly is a leak down test then, as it applies to saws? That is always what I called that procedure.
Click to expand...

I'm not going to link to it directly because I'm unsure of the local policy, you can find a multi-page AS discussion as the first hit for this Google search. Basically a "leak down" test is similar (in purpose, not method) to compression testing in that it quantifies the overall condition of the seal around the combustion chamber. It's used more on 4-stroke engines, which have additional potential sources of leakage such as head gaskets and valves. With 2-strokes that have no valves and single-piece cylinders it isn't all that useful, and it has nothing to do with the cylinder base gasket, crank seals, etc. I think Woodhog's referring to a pressure/vac test as a "leak test" is fine. It's when you start calling it a "leak down" test that it gets problematic, because that term means something specific and quite different.
 
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Jon that makes good sense.

In my dirt biking days I always purchased used bikes so that was generally the 1st thing I checked.

Since we are talking engines I'm going to throw out a question that may not have any good answer.

Let's say a 80 to 90 cc saw produces 6.5 hp. Or whatever but in that range. On a 2 stroke dirt bike ( which are all gone now they are all 4 strokes thanks to epa stuff) an 80cc motocross bike from the 1990s easily pumps out close to 20hp.

They are liquid cooled but that shouldn't effect HP. They have intake and exhaust port valves that automatically change the shape and size of the port ( to maximize low rpm, mid range, top high rpm) but saws don't need that they are meant to run wide open at top rpm.

So why does an 80cc 2 stroke saw produce barely 7hp when an 80cc 2 stroke motocross bike makes between 18 and 20 hp ??

Anyone ? A 2 strokes a 2 stroke. Simple air pump really with power on every stroke. High compression, lightweight internals, I don't get it ?
 
Wish I could answer that, but it's outside my range of expertise. What RPM do dirt bikes typically operate at? I'm wondering whether it has to do with saws having to be optimized for power over a range of RPM's because they're direct drive, whereas a bike has a transmission and can be optimized for a relatively narrow power band.
 
As for exhaust sure that does play into it but an extra 75 percent or more power just from a bigger pipe and expansion chamber ? I hear ya but there's got to be more to it.

I don't recall max rpm on an 80cc dirt bike but it's in the 12,000 to 14,000 range. The bikes actually got a much broader powerband so it is easier to ride than all top end power. That's why they engineered port valves into them that open or close to change the port dimensions at certain rpm. But at full open throttle those are wide open just like big ports on a saw.

What's funny is the EPA pretty much is the reason 2 stroke bikes no longer exhist. Yet auto tune or mtronic stuff never made it's way to the dirt bikes. Many many many times would be riding trails with friends and their bikes would be smoking like nothing I've ever seen and I'd tell them it's running way to rich ! Auto tune would have cured my friends rich running blubbery bikes I suppose lol

So I'm still scratching my head.

Doesnt matter really but I'd sure like for my 70cc saw to be cranking out 12 to 15 HP or a ms660 to be cranking out 20hp. That would change how we all cut our wood !! :) Actually under this rational my 50cc saw would be like at 8 to 10hp so I guess there would be no need for anything bigger
 
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If I suspect crank seal leakage I used to block off the carb & exhaust ports, pressurize the case with a few pounds of pressure and drop it into a bucket of water and watch for bubbles. Pull the tanks & handles first.
 
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NateB said:
The first thing you should do is state what is wrong with your saw.
Click to expand...
NateB...really all I know is that it came to me as a "box of parts" with the disclaimer it needs a "bearings, seals, and a carb"...never bothered to assemble it cause I'm lost on that sorta stuff...I just ran straight to some shops.
The pic's I posted was after a couple of shop visits...it never cranked at all for me or them.
Last guy said he "hated!" this saw more than his 1st wife!
WHATEVER!<>
That's being straight-up..;em

PS...I just found my old notes of what the 1st Stihl Tech said it needed..he also stated it did not need bearings.
1.) New Carb/Carb Kit 2.) Clutch Drum Tooth Sprocket Kit 3.) Rewind Starter Pawl Kit 4.) New Air Filter
This all he stated it needed to be great runner.
Thanks
 
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woodhog73 said:
What's the saw doing or not doing ?

I agree start with a leak down test. A pressure test to see if there are any leaks. Bad crank seals allow air into the lower end. This creates 2 problems for any 2 stroke. It effects the engines ability to draw in fuel and air so the saw runs poorly. No amount of carb tuning will make it right for any length of time. And the lower end air leak will cause the saw to run lean. Prematurely damaging it.

You can't test this by checking the saws compression because the leak is in the bottom end. Although I would still check the compression while I'm at it.

Bad lower end bearings can be a reality in a saw of this age. With the top end off you can check the play in the connecting rod bearing by trying to move the rod up and down. As for the main bearings while you have the top end off spin the lower end assembly. If the bearings are really shot you should be able to hear how noisy they are when your slowly spinning the crank shaft. If they are new bearings the assembly spins over much quieter.

Honestly do the leak test. If it holds air then I wouldn't worry about the lower end assembly. If it doesn't hold air then I would split the cases and rebuild the entire saw.

As for the Stihl shops whining etc if they are anything like the ones around me they know very little or have little interest in the saws. They just want to sell you a new saw.

Find a good pro saw shop or small engine mechanic. My local Jonsered shop works on so many Stihls because the local Sthil dealers are not as knowledgeable. The local Jonsered shop is a pro saw shop and would never whine about a customer coming in with an old saw needing work. They actually like that stuff. Find a better shop if possible
Click to expand...
Good Stuff...Thanks!
 
ReggieT said:
PS...I just found my old notes of what the 1st Stihl Tech said it needed..he also stated it did not need bearings.
1.) New Carb/Carb Kit 2.) Clutch Drum Tooth Sprocket Kit 3.) Rewind Starter Pawl Kit 4.) New Air Filter
This all he stated it needed to be great runner.
Click to expand...

So if you paid someone to assemble it for you, why didn't you have that guy finish the job?
 
Jon1270 said:
So if you paid someone to assemble it for you, why didn't you have that guy finish the job?
Click to expand...
I didn't pay him to assemble it...that's as for as he got before he turned into a sloth and I grabbed it from him!
 
ReggieT said:
I didn't pay him to assemble it...that's as for as he got before he turned into a sloth and I grabbed it from him!
Click to expand...

So he mostly assembled it, and you didn't pay him for his time? No wonder they don't want to see you coming.

Looking at your pics up at the top... aside from the missing air filter, the fuel line is disconnected from the carb, and the plug wire is wrapped in electrical tape. It obviously won't run if gas can't get to the carb, and electrical tape is no substitute for intact plug wire insulation so the ignition might be shorting out. Since it wasn't running when you got it, and was disassembled to a degree you haven't described, there could be all sorts of things going on that we don't know about.
 
I agree with Jon there could be lots of stuff that you have not uncovered yet.

Honestly I would first decide how much money and time do you want to invest in this saw ? Once you have made that decision then if there are no good saw shops find a good small engine mechanic. Saws are fairly simple and a small engine mechanic that's been in business for him/her self for a good length of time can probably sort it out for you.

Lots of times these big dealers may hire fresh grads from tech schools or the guy down the road who says he is a good mechanic. However a good small engine mechanic ( probably most known for fixing mowers and snow blowers) has a reputation on the line that's probably more personal to him or her and will make sure the repair is done correctly.

Just have a discussion first about how much ( or little) your willing to spend. Someone you trust that's not just out to squeeze every last penny from you. There are still good honest people out there in small businesses like engine repair you just have to find them.

The other option is sell it as is as a parts saw and put the money towards something newer or something with a known history.

If it were me, and just being honest, I'd sell it as a parts saw. I already have another saw in a box of parts that needs sorted out. I'm not in the business of buying and selling saws for profit I just need saws that get the job done. So for me it would be on CL as a parts saw. But if your intent is to repair it and use it or sell it everyone is different. That's fine too just make sure you don't get so far into it your spending more on it than what it's actually worth. And meanwhile it's not cutting any wood for you .

Good luck with it and let us know what you do with it
 
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I don't think I would buy a box of parts with the hope or plan that I could get someone else to put it together & get it running right for me. I would buy it with the full intention of doing it all myself with the understood chance that it might not be possible to resurrect it - you never know what trouble lurks in a box of parts, or what is missing from it. Or how much time & expense will need to be spent on it.
 
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