Magnesium decks?

[Lawnboy77]

Just the aluminum plate is different, the engine should be interchangeable.

Edit: since the carbs might different between the two engines you may need to leave the original carb on the donor engine if you go that route. The reason being is that the throttle cable-to-carb setup may not be the same.

 

[apalmerjr]

No, none of these have a throttle cable, they all use the same type plastic carb. I have a little work to do to the donor engine though, noticed the old fuel was left in the tank so that'll have to be cleaned out. I hate to swap engines before I'm sure the one going in will run. They do have a different shroud around the top of the engine so I'll probably just swap the whole thing rather than just the block.

 

[apalmerjr]

I swapped engines today. While I had everything apart on the bottom of the engine I went ahead and put a main seal in the engine. Just the plate and muffler were different, I had to use the ones that came on the alloy deck. I put some Dirko on the seal to kinda insure it won't come out so I didn't try to start the engine until that dries. I probably won't be around much tomorrow so I'll probably try to fire it up Wednesday, grass is kinda needing cut anyway..

 

[apalmerjr]

I'm wondering now if I shouldn't go ahead and change the upper crank seal in the engine. Since my first post I've acquired a couple more Lawn Boy mowers, all mine have aluminum decks except the one with the mag deck, all run now but two of them run too fast and apparently run too lean, I won't use them until I get them fixed..

 

[jp1961]

I'd replace the seal while you're this far into it.

Regards

Jeff

 

[apalmerjr]

Yep, I'll try to get them all sealed up before next Spring. I have a couple that are running okay. I plan on making a couple of plates for the intake and exhaust so I can do a pressure/vacuum test on them like I do on chainsaws.

 

[jp1961]

Hmmm, I'm interested in your statement on creating plates for the intake and exhaust to do pressure/vacuum tests, can you elaborate a bit more.

Regards

Jeff

 

[apalmerjr]

Hmmm, I'm interested in your statement on creating plates for the intake and exhaust to do pressure/vacuum tests, can you elaborate a bit more.

Regards

Jeff

Sure, I make an aluminum plate to fit over the intake and exhaust flange, the plate is covered with rubber on one side to prevent leakage. I have a nozzle that's threaded to fit in the sparkplug hole which I inject air into like I'm blowing up a balloon only I just use about 7 psi. of air. I have an inline gauge to check for leaks hooked to a blood pressure bulb to blow air into the engine. If the seals and seams of the engine are good it will hold seven pounds of air for a long time, otherwise I look for the leak using soapy water. Some people also use a vacuum test on the engine also by just sucking on the hose attached to the spark plug hole until you get between 5-7 hg. vacuum, I have an inline switch to hold the vacuum. If the engine won't hold pressure and vacuum it won't run right. On a Lawn Boy it requires removal of the bottom plate that holds the muffler.

 

[jp1961]

Nice. That's a good idea. When you perform the test, does the piston have to be at top dead center, bottom dead center, or it doesn't matter?

Regards

Jeff

 

[apalmerjr]

It really doesn't matter, you're checking the crankcase but sometimes when you turn the crankshaft a bit the pressure or vacuum will drop which means you need new main seals. Any leakage at all means you have to get the soapy water out and check where the leak is. I'll be using the intake and exhaust gaskets as a template for the plates. Kinda cold around here today but I'll get to it before next Spring.