Lawn Boy F100 and F model

viperv10

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Does anyone know the difference between the 78 to 82 F100 engines and the later 80's F engines besides the type of carbs they use?
The F100's do take a different coil than the newer F models.
A friend brought me a model 7229 to work on and said it wouldn't start. It was getting spark and gas. It wouldn't even begin to fire with starting fluid.
So I checked compression and it read 0. I thought maybe the tester was not working so I checked compression on one of my Lawn Boys and it read about 90 psi.
So I took the engine off the deck and cracked it open and found out that the wrist pin needle bearings came apart and went everywhere. The top of the piston looked
like a pin cushion with six bearing sticking out. There was 1 bearing stuck in the spark plug by the electrode. One of the rings were broken and the piston and cylinder
were scored pretty good, so I don't think lawn boy will run again.
This 1979 engine looked just like the newer ones I have worked on and was just wondering if there was really any difference. I think they made F engines into the 90's.
Regards
Jerry
 

viperv10

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Well I think I answered my question myself. The short block or the basic part of the engines look to be the same. I think the differences seem to be the shut off system, or kill switch and the brake stop, and the throttle controls. Things were a lot simpler before before the government rule about the extra safety handles were mandated in the early 80's.
 

viperv10

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I have an extra engine (short block) from a 1987 steel deck that rusted out. I honed it out and put new rings in it and just let it set for 3 or 4 years.
I just put all the other engine parts from the 7229 (1979) together and am hoping it will run ok. The only thing I need is an exhaust gasket between the block
and the mounting plate on the deck. Everything on the 1979 seems to be the same as on the 1987 block. Everything seems to mount perfectly. When I get
the engine back on the deck I will let you know if it runs or not. The 1987 F engine had a Walbro carb and now it has a plastic one. We will see what happens.
Jerry
 
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