Cam and Governor Briggs 120000 Series

sgkent

sgkent

Lawn Addict
rebuilding a 125K02-0189-E1 06041958 engine on a Toro 20055 mower. Trying to keep costs down on the rebuild or it doesn't make sense. Likewise, it doesn't make sense to put parts back in that only have a short life expectancy left.

Is there any reason not to reuse the cam and governor? The nylon is 2006 vintage, and the engine has somewhere between 300 and 500 hours on it. The cam and governor have been inspected and they appear in good condition, however they are made of nylon, which is not like a metal part. The teeth and lobes appear fine. The governor and compression release lever are smooth in their actions. Both lobes are smooth with no pitting or galling. The exhaust lobe is .0035" shorter than the intake. Not enough to be significant. The cam lobes are tight on the shaft and do not move.

A new Cam is about $66 and Governor $35, so replacing them is a significant cost. I don't see any return mechanism on the compression release other than gravity. The book refers to a spring in the movement, however there is none on this cam, or in any of the photos I have seen of other cams like it. The movement on the governor and its spring are smooth and consistent. Threads posted in various places online seem to think that the nylon cams made today are inferior in quality to new ones. I don't know if that applies to factory parts, or all parts made today. I certainly don't want to replace these to only put in a part that has a higher failure rate than a 20 year old part.

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At the very least, I recommend you replace the cam. When they start turning a dark amber color that means they are getting brittle from years of heat.

I've learned this through many years of dealing with white nylon chain guides in automotive engines that have overhead cams. The white nylon material eventually gets brittle and crumbles apart.
 
Auto Doc's said:
At the very least, I recommend you replace the cam. When they start turning a dark amber color that means they are getting brittle from years of heat.

I've learned this through many years of dealing with white nylon chain guides in automotive engines that have overhead cams. The white nylon material eventually gets brittle and crumbles apart.
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Sounds like wisdom
 
I went ahead and ordered the two parts. Have about $100 less than a new engine of similar displacement. That said, this engine will be fine and last another 10 - 20 years when done. I looked on Ebay and there were probably 25 cams for sale - mostly used, but some new. Nylon does age even sitting in a box on a counter is a shop, so decided better just to go new from Briggs. Found a discount coupon and used it so the price was a little less.

I have a VW bus with a sunroof. Some of the parts are nylon 66 - they get brittle with age, just sitting even though the bus is garaged. Some people say that nylon needs a soaking in water once in awhile to restore the strength, yet too much water will damage them. I don't know, but as to this engine, it has worked seamlessly for 20 years. Would have bought a new mower but gasoline mowers are not allowed to be sold in the state. I looked up the law, and only replacement engines made before 2024 can be sold here too, so even if I ordered a new engine, they might not ship it. I've had that with other things where someone sells something to you then cancels it and says they can't legally ship it to California.
 
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