Stihl 075 - Cylinder Shim (not the gasket) - Does it belong?

[hacskaroly]

I tore down my coworker's 075 to make sure the piston and cylinder looked good and came across this (see photo below)....a homebuilt shim that has been added. This is not in lieu of the cylinder gasket as that was on there too. Looking at the IPL, I did not see any shims like this listed. There have been several "modifications" I have found on this saw including the decomp hole on the cylinder plugged. Is there a good purpose for this shim? I know people generally delete the base gasket to gain more compression, wouldn't adding this ship effectively lower compression? Maybe this is being used to help the case from coming apart (grabbing at straws here trying to figure it out). Any thoughts about this?

 

[066 redeye]

I recon to lower compression.

 

[Sawking]

I tore down my coworker's 075 to make sure the piston and cylinder looked good and came across this (see photo below)....a homebuilt shim that has been added. This is not in lieu of the cylinder gasket as that was on there too. Looking at the IPL, I did not see any shims like this listed. There have been several "modifications" I have found on this saw including the decomp hole on the cylinder plugged. Is there a good purpose for this shim? I know people generally delete the base gasket to gain more compression, wouldn't adding this ship effectively lower compression? Maybe this is being used to help the case from coming apart (grabbing at straws here trying to figure it out). Any thoughts about this

IMO the cylinder has been decked too much and shim is needed to keep piston from hitting.
WestCoastMuscleSaws
TheChainSawGuy
Rich

 

[beaglebriar]

I’d check the squish and go from there. I see no reason to lower compression but it’s hard to say what they were thinking. If the squish is too tight (say under .020”) without the shim you could always cut a small pop up or cut the band. Assuming your cylinder is in good condition.

 

[av8or3]

Maybe they shimmed it to reduce compression and make it easier to pull.
I blew the decomp out of mine and had to glue it (JBWeld) back in.

 

[qurotro]

To lower the compression for easier starting.. The stock starter handle is terrible for starting a 075. Some of them come out of the factory with decom plugged I think.

 

[Sloughfoot]

IMO the cylinder has been decked too much and shim is needed to keep piston from hitting.
WestCoastMuscleSaws
TheChainSawGuy
Rich

Yeh, way too much. That shim is thiiiick. What is that at the base of the top right bolt in the pic.

 

[hacskaroly]

I recon to lower compression.

Ok, so I am not off track.

IMO the cylinder has been decked too much and shim is needed to keep piston from hitting.

Could be, I will need to check and see what the squish is at. I don't think the cylinder has been modded at all (porting), but it is possible.

If the squish is too tight (say under .020”) without the shim you could always cut a small pop up or cut the band. Assuming your cylinder is in good condition.

I will definitely check and see what it is at. The cylinder is in good shape, it is aftermarket, but not sure what it is made of. It is very smooth inside and does not easily take crosshatching from a Scotchbrite pad.

Maybe they shimmed it to reduce compression and make it easier to pull.

To lower the compression for easier starting.. The stock starter handle is terrible for starting a 075.

When I tried starting it, there was plenty of compression, but not enough I could not overcome it. Most definitely would work better starting with a D-handle or something. I got one for my 2100!

Yeh, way too much. That shim is thiiiick. What is that at the base of the top right bolt in the pic.

Not sure what the top right bolt is mounted into. My guess is that the hole got stripped out and they put in some sort of insert. Here are a couple more pics, best I could do. Whatever it is, it looks like it is holding the shim down, not sure if I want to try to remove that post just to get the shim off, but might have to.





I appreciate all the responses!!

 

[Sloughfoot]

Yeh, hole in the shim may've been too large.
You'll make it a rippah.

 

[av8or3]

It looks like they have installed a nutsert over the shim and into the block. You should begin by unscrewing the cyl hold down bolt. I can’t imagine why they’d do that but ???

 

[hacskaroly]

It looks like they have installed a nutsert over the shim and into the block. You should begin by unscrewing the cyl hold down bolt. I can’t imagine why they’d do that but ???

My curiosity got the best of me and I pried up the shim. Luckily it was not being held down except with the Permatex. There is a nutsert installed. the top thread is broken, but not completely disconnected. It does squish down some, but it is my guess that the shim was put in place because this was sticking up and would not allow for a tight seal with just the cylinder gasket - which I tested in the next image.



There is a very slight gap, hence the need for the shim. I wonder if I can Dremel enough of the nutsert off to allow for a flush fit of the gasket and pitch the shim. I put the piston back in, tightened down the cylinder and gave it a hand crank spin and the piston moved freely and did not hit the top at all, so I don't think there is an issue there without the shim. My coworker was explaining that this saw seemed underpowered after the last repairs, so I am thinking this is part of the issue. Another part I found was the muffler gasket was installed incorrectly and occluded about 1/4 of the exhaust outlet. Seeing stuff like that always reminds me of Eddie Murphy and the banana in the tailpipe from Beverly Hills Cop. That is how I explained blocked spark arrestors to customers and they understood the issue when making that correlation.

 

[64poncho]

Looks like a Heli-Coil. If you remove the cylinder stud, it can be carefully trimmed off. Or it can removed by screwing it back out. You’ll need another insert (new) and installation tool. Insert should be flush or below the surface, usually 1/4 turn deeper when it gets even with top edge of the bolt hole. Don’t forget to break the tang off the insert if installing a new one. I have cut coils off of them to shorten the insert before installing so it doesn’t stick out of the bolt hole.

 

[av8or3]

You know, now that the shim is out of the way, it looks like a poorly installed heli-coil to me as well. Trimming it off might be an option for sure, or removal and reinstallation.

 

[hacskaroly]

Looks like a Heli-Coil. If you remove the cylinder stud, it can be carefully trimmed off. Or it can removed by screwing it back out. You’ll need another insert (new) and installation tool. Insert should be flush or below the surface, usually 1/4 turn deeper when it gets even with top edge of the bolt hole. Don’t forget to break the tang off the insert if installing a new one. I have cut coils off of them to shorten the insert before installing so it doesn’t stick out of the bolt hole.

You know, now that the shim is out of the way, it looks like a poorly installed heli-coil to me as well. Trimming it off might be an option for sure, or removal and reinstallation.

I think I will try trimming it first, I don't have the installation tools for these yet, so if I can get away with just trimming it then that will be great. If not, then I need to figure out what size heli-coil I need and get it and the tools to install it.

 

[av8or3]

I think I will try trimming it first, I don't have the installation tools for these yet, so if I can get away with just trimming it then that will be great. If not, then I need to figure out what size heli-coil I need and get it and the tools to install it.

Yep!
You can buy helicoil kits at most auto parts stores.In my area, NAPA has the biggest selection.

 

[Wilhelm]

Ugh!
Been there done that.
Refusing to do it anymore.

"Hey can You change my saws spark plug."
Even if the spark plug needs replaced the list of faults just keeps adding.
Then when notifying the saws owner of all found issues it is "You F-ed up my saw, all it needed was a new spark plug!"

Take a note Y'all!
It is NEVER just the spark plug even if it is the spark plug that causes SOME of the running issues!

Bottom line, I do no longer "look" at anyone's OPE anymore.
If it is a brand product got to a dealership.
If it is a generic knockoff go buy a new one.

Good luck with that overhaul Cary!

 

[drf256]

HR,

Timesert kits are a very good investment once you start working on saws. I bought M4/5/6 and never looked back. Pricey for sure, but boy do they ever come in handy. I used to use helicoils, but the timeserts are so much more reliable. Unfortunately, not cheap.

I would want a timesert there. Hold much more tension than a Helicoil. Do it right one time.

 

[bogieboy]

HR,

Timesert kits are a very good investment once you start working on saws. I bought M4/5/6 and never looked back. Pricey for sure, but boy do they ever come in handy. I used to use helicoils, but the timeserts are so much more reliable. Unfortunately, not cheap.

I would want a timesert there. Hold much more tension than a Helicoil. Do it right one time.

Interesting... i have never had a helicoil fail yet... i never saw the need to go up to a timesert set, since my helicoils have always worked...

 

[av8or3]

Interesting... i have never had a helicoil fail yet... i never saw the need to go up to a timesert set, since my helicoils have always worked...

Different strokes for different folks. I use helicoils myself in thick enough metal parts and time-serts/nutserts in sheet metal.

 

[hacskaroly]

Even if the spark plug needs replaced the list of faults just keeps adding.

So true, I was getting ready to start putting the saw together and found that the new clutch side oil seal was too big. The one that came with the new kit was 25x47x7mm and the one came out was 30x42x7mm. The 075/076 IPL calls for the 25x47x7...I did more digging and searching and had about 100 internet tabs open before I found my answer, the previous mechanic (or whatever you want to call the person who worked on this saw) appears to have modified a 050/051 crank case. I measured the piston at 58mm so it is a 075 piston/cylinder, but the crank case needs the 30x42x7mm oil seal which I found in the 050/051 IPL which this IPL lists both size oil seals (I guess depending on the year the unit was built). It appears that all four cylinder studs are in helicoils, which makes sense if they had to enlarge the 5mm holes to accept the 6mm cylinder studs. Also this case is missing the manual oiler which seems to be found on the 075/076s. If anyone has access to a serial number lookup, the SN on this saw is 8580821. I tried looking for a part number on the crankcase, but I am guessing it is on the inside and I don't feel like splitting the case just to see.

Time to order a 9629 003 3400 30x42x7mm oil seal so I can get this thing back together....