Stihl 076 rebuild......

[Lakeside53]

That's a 51... Had the exact same thing happen to me.. Bought an 075..but it was an 051..


You can get an aftermarket 051/510 piston and cylinder quite cheaply though... Stihl one heck of a saw.

 

[martrix]

That's a 51... Had the exact same thing happen to me.. Bought an 075..but it was an 051..


You can get an aftermarket 051/510 piston and cylinder quite cheaply though... Stihl one heck of a saw.

I take it the 076 (58mm) piston and cylinder will bolt straight on if I can find one? They both have the same stroke.

So would a feasible explanation be, that the saw was originally an 076, but when it needed a new P&C they just changed it to an 051(52mm piston)because it was cheaper and easily available?

I guess I should just get a new 051 P&C kit?

Did you see my Video of the crankshaft needle cage? What should I look for to see if that needs replacing? Could the broken skirt be a result of the extra play in the crankshaft, or just from excessive piston to cylinder clearance from wear and tear?

 

[Lakeside53]

It will work, but the 076 takes studs not bolts, and the decomp valve is in the other positon so you MIGHT require a mod to the rear cover.

I bet they lost the top cover and just replaced it with that from an 076..
sorry.. can't view videos at the moment... computer the in middle of a rebuild.

 

[martrix]

It will work, but the 076 takes studs not bolts, and the decomp valve is in the other positon so you MIGHT require a mod to the rear cover.

I bet they lost the top cover and just replaced it with that from an 076..
sorry.. can't view videos at the moment... computer the in middle of a rebuild.

Cool, I'm gonna just go for the 051 P&C change over. I'm convinced now that it is an 051 and not an 076.
Can someone change the bloody thread title!:hmm3grin2orange:

Does US$155 sound cool for a new 051 P&C kit?

Cheers for all the help.

 

[cbfarmall]

In addition to the broken piston, looks like there's a crack running up the skirt. I picked up an 075 at a local auction for $20. Totally locked up, found the piston grenaded worse than yours, but the cylinder very intact. One $90 piston later and she is still running 4 years later on a chainsaw mill.

Like Andy said, the wore piston probably slapped hard enough to break the skirt. My 090 did the same thing, and was possibly helped along by using an impact wrench on the clutch nut.

All things considered, between the broken piston, missing gasket, hammered and wore cylinder, it's amazing you got it to run decent at all.

One caveat when you put it back together and use it: pay attention to the screws and maybe use blue loctite. These saws like to shake themselves apart. Mine likes to looses the recoil/gastank. Rebuilt my friend's, and his intake block gave me fits--took me 3 or 4 tries to get it to say together.

Chris B.

 

[martrix]

One caveat when you put it back together and use it: pay attention to the screws and maybe use blue loctite. These saws like to shake themselves apart. Mine likes to looses the recoil/gastank. Rebuilt my friend's, and his intake block gave me fits--took me 3 or 4 tries to get it to say together.

Chris B.

Yeah, will do. At one point while playing with it, changing a few gaskets and other bits and pieces and running it again, the muffler managed to remove itself. So I know what you mean, they sure got some serious vibes.

Will use a little Loctite on most of the major screws.

 

[martrix]

In addition to the broken piston, looks like there's a crack running up the skirt.
Like Andy said, the wore piston probably slapped hard enough to break the skirt. My 090 did the same thing, and was possibly helped along by using an impact wrench on the clutch nut.

All things considered, between the broken piston, missing gasket, hammered and wore cylinder, it's amazing you got it to run decent at all.



Chris B.

Just had another closer look at the piston to see if they were cracks. Looks like they are just scratches. About a 1/4 way round on the piston I noticed another small chunk out of the skirt. Probably happened at the same time.

I also assume the missing gasket piece was torn away when the skirt broke off and grabbed the gasket with it. The missing gasket would also explain why that area would keep getting messed up and dirty after each time that I cleaned it and ran it. Fuel mix escaping the crank case.
Happy now that I am pretty crystal on how this saw operates and what I need to get it running like new. Glad in some ways that it is actually an 051 parts wise.
I think its worth spending the time on one of these because here in Australia they are worth AU$600 minimum for a non-abused one in excellent condition, if and when they come up for sale. A new 660 Magnum (91cc) out here is not far off AU$2000.

Is the worn piston & cylinder the only cause of piston slap? What else can cause it?

A quick measure with my calipers suggests a difference of about 0.07mm from the cylinder to piston.

 

[Lakeside53]

In your case, the bore wore too... probably from the lack of a decent air filter.

 

[martrix]

Hi Lake, as I am getting a new piston and cylinder, it would make sense to split open the crankcase for a good clean and check up while I've got it stripped. The oil tank could also do with a thorough clean, as it is black and looks like the lazy previous owner used old car engine sump oil.:taped: Guess it could also be black from a leak in the crank chamber gasket?

I have the service manual, but can I split open the case without remove any bearings from their seats?

 

[Lakeside53]

Unless it needs it, it dosen't make sense... You can clean it out without splittiing. On the other hand, if it's now a "restoration", go for it


Whether the bearings stay on the crank or pull out of the case is often up to the gods... If you do split it, I'd replace the bearings. You can get generics cheaply (use a good brand though).

 

[martrix]

On the other hand, if it's now a "restoration", go for it

...well, I didnt want it to be, but now it is.:bang:


Managed to get the case split, but it was a fair job.

Bearings dont feel good, so I will replace them.

Pretty ugly hey?

 

[Ax-man]

Ya, it is pretty bad, what a mess poor saw

 

[Lakeside53]

bad mix oil and blowby... nasty. Take a real good look at that crank also...


One thing to consider - buy another say and build one out of two.. or three.

 

[martrix]

bad mix oil and blowby... nasty. Take a real good look at that crank also...


One thing to consider - buy another say and build one out of two.. or three.

I will post some pics when I get the bearings off and all cleaned up, but what issues should I look for in the crank?

I checked with a little test I read on AS with the crank pin at BDC, and the crank doesn't touch either of the counter weights, so I assume it is still in good nick? Will also inspect the needle cage up close for any cracks. Anything else?

Lake, if I could find another for spares I would definitely do that. Problem is, not many come up for sale here, and if they do they are $500+!

 

[Lakeside53]

051 parts are relatively cheap here... I just sold a real nice 051 with a 41 inch bar/chain for $250... I figure the bar/chain is worth nearly half of that!

 

[martrix]

051 parts are relatively cheap here... I just sold a real nice 051 with a 41 inch bar/chain for $250... I figure the bar/chain is worth nearly half of that!

Know of any more going cheap?:help:

I have found all the bits I need from CheapStihlparts .

There are no second hand parts in Aus, and the dealers are un-reliable and very expensive. For example, I just paid AU$100 for a clutch drum and 3/8 rim sprocket . I think I saw somewhere on a website where you can get the same thing for about US$35 in America?

 

[Lakeside53]

I probably sold/swapped most of those parts to Cheapstihlsawparts! He's a buddy of mine, and about 20 miles from me.

 

[martrix]

I probably sold/swapped most of those parts to Cheapstihlsawparts! He's a buddy of mine, and about 20 miles from me.

Cool, I know who to blame then if the parts are crappy!

 

[martrix]

Here is a pic of the flywheel puller I made to get it off. Geez it was stuck good! It was an old brass tap (faucet?) that I tapped the outside thread on and also tapped a thread on the inside. I think the pitch on the thread was a little off, but being brass, it was going to damage anything.

Can anyone tell why someone put silicone over this terminal? Stop it vibrating off?

 

[martrix]

Here are pics of the case cleaned up. You can see a raised ridge in the crank shaft case which was caused by the broken piston skirt as it was driven into the case by the crank counter weight. I filed off the edge(carefully) and gave the contact surfaces a light rub with 800grit on a flat block.

The bearings were stuffed, don't know how they still turned.

These bearings (***) were not sealed. Can I put sealed bearings in when I get new ones? Or is it better to stick to the same style as what was there?:newbie:

cheers.