# Rebuilding a stihl 034 av



## Dstang97 (Dec 21, 2014)

Need to rebuild my 034. Who makes a good quality kit? Hyway? Is it the same kit as a 036. My saw over heated and the cylinder was scored on the exhaust side. Is the exhaust a problem on these saws?


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## salecker (Dec 22, 2014)

Hi
 You can probably clean up the jug and get a new meteor piston and be good to go.
 The scoring is probably caused by an air leak if you didn't use bad gas.I'v been going through my pile of dead saws to see what is rebuildable.
 I have vacuum and pressure tested over a dozen saws in the last couple of weeks.Every one with a piston scored had an air leak of some sort.Seals were the most common,the one 034 i did had an intake boot leak,scored heavily on the exhaust side.A couple of Husky 61's with intake leaks,and a few clam-shell motors leaking between the cylinder and pan.
 Find the leak before you take it apart.Don't just replace the part and run again because you will just have to by more parts.
If you decide not to clean up the cylinder i would be interested in it.
 Thomas


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## Jon1270 (Dec 22, 2014)

Salecker is on the money; unless you straight-gassed it or messed with the carburetor settings, you almost certainly have an air leak that will wreck the new top end in short order if you don't find it and fix it.

The Hyway kit is a good one, but as far as I know they only make an 036 version.  It will fit on an 034 and give you more displacement and more power, but there are some complications.  The exhaust flange on the 036 cylinder sticks out a few millimeters further than the flange on the 034 cylinder, and this affects the fit of the muffler.  You'll likely end up needing to either pick up an 036 muffler, or use the original and improvise some spacers behind the lower corners where it bolts to the crankcase.  The 036 cylinder is also taller, so you'll need to trim back a rib in the inside of the plastic engine shroud.  

Another option is to refurbish the original cylinder (often possible) and just get a new piston, rings, clips and base gasket.


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## Mad Trapper (Dec 22, 2014)

If you buy an AM P/C kit I would get a tecomec.  Most kits are 48mm that is the same size as the 034 super or 036, the 034 was 46mm.  You may have to shim to fit the muffler.

Your cylinder may clean up if it just aluminum transfer.  Hit it with some wet/dry 320 paper and dish detergent to get the oil off, then use some muriatic acid which is 6M hydrochloric acid, (gloves/goggles) on a q-tip to dissolve the aluminum transfer.  Avoid getting the acid in the ports or anything besides the plated part of the cylinder.  You may have to go back and forth with the wet/dry and acid to get all the transfer off.  If the plating is still good under the transfer a new piston and rings is in order.  Buy a new stihl gasket set and replace the crank seals and carefully check the intake boot and impulse line.  May also want to do a carb kit and fuel line as these can also cause lean conditions.  A vac/pressure test before and after is recommended.


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## Dstang97 (Dec 25, 2014)

No doubt my cylinder is messed up. I need a new muffler anyway so that's not a problem. Should I just buy a new intake boot? Is that the only leak there could be? What's the best way to pressurize and test?


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## Jon1270 (Dec 26, 2014)

No, there are a number of places where leaks can develop. The impulse hose can crack, crankshaft seals can fail. More catastrophically, a failed clutch-side crankshaft bearing can spin and ruin the crankcase.  There are other possibilities besides. 

On an 034, I seal the exhaust port by slipping a strip of rubber sheeting (as from an inner tube) between the muffler and cylinder flange, and tightening the muffler bolts. On the intake side the carb is removed and replaced with a rigid aluminum plate backed with spacers so the carb nuts can be used to press the plate against the intake boot. Then I connect the vac and pressure testers to the impulse hose. 

I got my vac and pressure testers secondhand so I don't have a source to recommend, but I don't think they'd be easy to improvise from common household tools.


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## salecker (Dec 26, 2014)

Hi Dstang97
 I made a adapter from a spark plug to hook my vacuum and pressure testers to.I have a box of plates and rubber that i have made to block off intake and exhaust.Most of the time i use the muffler or carb with a piece of inner tube sandwiched between the jug and muffler,and between the carb and mount.
 For a Vacuum tester you can use a blood pressure cuff bulb.I have a vac tester that also builds pressure,the gauge is nice.For pressure testing i use my air pressure regulator/filter set up.I set the pressure to 7PSI .
 Test the saw before you take it apart.
 When i get a saw to either fix or part out the first thing i do is pull the muff and have a look at the piston,then sandwich in the rubber.Pull the carb and do the same.Then i hook up the vac tester and see if it will hold vacuum for a while.If not i hook up the air pressure and start soaping down the saw.I soap the spark plug adapter and the rubbers sandwiches first.If it still leaks i pull the flywheel and clutch and soap the seals.If i haven't found it by then you have to look further,intake rubber,impulse hose,jug to block gasket,pan to cylinder seal,and in some cases the duckbill that pressurizes some oiling systems.
 It takes me about 1/2 hour to have a saw tested completely,and reassemble.That includes removing flywheel and clutch and all shrouds and covers.I usually just take the saw down to where i can soap everything that needs to be checked.If you have a difficult leak to find remove the coil and submerse the pressurized saw in water and follow the bubbles.If you do have to submerse the saw take the carb off and use a plate to block off the intake.Saves getting water in carb for more hassles.
 Hope that helps.
 Thomas


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