Stihl 028 wb to Super - Huztl build

[JonCraig]

I believe I recall a picture showing the differences between materials somewhere. The tan looking ones are the best, if I recall, except in certain older equipment where they may be too strong. Or something like that. Lemme see if I can find the pic...

I don't know what's technically correct, but I call that one (the "flappy" one) the pump diaphragm, and I call the other side (where the needle is) the metering diaphragm. I don't know 100% what the correct wordage is.

 

[tmessenger]

I rebuilt an 032 that had the same surging at WOT it was a crank seal. It would idle fine but at WOT there was enough crankcase vacuum to pull air trough the seal. When it went lean it would drop RPM's until it resealed then as RPM's increased it would again go lean and etc...

New seals and the problem was gone.

 

[JonCraig]

There it is!

 

[sven556]

Thanks for the picture JonCraig, looks like I shouldn't worry about the pump diaphragm.

tmessenger - That does seem like a possibility here. With all the trouble I had installing the clutch side seal, I wouldn't be surprised it something still wasn't quite right. Is there anyway to test for that? I did use a mityvac and did a pressure/vac test to 15 mmhg or about 7 psi.

 

[sven556]

Well, I messed with this saw a bit more yesterday and found that the air filter did have an effect on the saws performance. Without an air filter it ran pretty good, but did spit quite a bit of air/fuel mixture out. I ran it with and without an air filter several times trying to isolate the problem. Then I heard a noise and the saw shut off. After that the piston no longer followed when the starter rope was pulled. I figured I had lean seized the engine and something broke.

Today, I tore apart the saw and found the piston/cylinder in good shape. I pulled off the starter and found the nut on the flywheel loose and the flywheel key was sheered. I never have torqued a flywheel nut, just give it a slight rap with a cordless impact. Maybe I should use locktight from now on?

 

[BuckthornBonnie]

Well, I messed with this saw a bit more yesterday and found that the air filter did have an effect on the saws performance. Without an air filter it ran pretty good, but did spit quite a bit of air/fuel mixture out. I ran it with and without an air filter several times trying to isolate the problem. Then I heard a noise and the saw shut off. After that the piston no longer followed when the starter rope was pulled. I figured I had lean seized the engine and something broke.

Today, I tore apart the saw and found the piston/cylinder in good shape. I pulled off the starter and found the nut on the flywheel loose and the flywheel key was sheered. I never have torqued a flywheel nut, just give it a slight rap with a cordless impact. Maybe I should use locktight from now on?

Probably no need for Loctite. Degrease the shaft and flywheel. Install new keyway and put rope in cylinder. Put on nut and crank to spec or use a small cheater bar til tight. Don't over crank, though.