I run a lawnmower sales and service store. A customer has brought a Craftsman tractor type mower to me for repair. The engine is a Briggs and Stratton, 26 HP, vertical crankshaft V-twin. The intake valves are stuck and the intake push rods are bent, the exhaust valves are OK. The engine has about 130 hours on it and seems to be in good condition, other than the valves. The story is that they started the engine and ran it for about an hour, it did not run well but it ran. They tried to start it again the next day and it would not start, they pulled the rocker arm covers and gasoline ran out of the left cover. The fuel pump pulls it's vacuum to operate from the left valve/rocker arm cover. Briggs technicians tell me that this was caused by ethanol in the gasoline but I tested the gasoline and there was no ethanol. Any ideas what is going on here??? I was also told that if the engine backfired that could cause bent push rods, but the stuck valves seem to be the problem. Help!!!!!!!!!!!

Old Okie

 

Usually on those engines, I have found that stuck intake valves usually coincide with old gas in the tank. I don't know what does it, if it's varnish in the gas, or what, but I think every time I had stuck valves in a V-twin briggs, they were always the intake valves and always old gas in them.

 

That sounds reasonable, I think this mower sat for a while. The gas in the tank seems fresh but.......... What is the solution for the stuck valves????
Pull the heads and free them up???? Briggs techs said replace the heads, that seems extreme. This is a good mower and the cost of the repair is justified, in my opinion.

 

I spray the valves with carburetor cleaner and get them unstuck/wash out the gum and put it back together. I've had a time or two when the owner didn't want to spend the time/money pulling the heads and removing the valves for cleaning, so I unstuck them with the heads on the engine and never once had a problem afterwards.

 

Briggs tech guys say put on new heads and throw away the old ones, but they are in the business of selling parts. I will try the heads on the engine method first and then go to a more drastic method if I need to. I guess it is my country raising, but we always fixed or repaired things rather than discard them. I will let you know in a day or so how this turned out.

 

My 2 cents, don't suppose it is still under warranty???
I had a Briggs on my power washer where the intake valve froze up. Mine was from leaving it sit with gas in it. I thought I was going to use it again but never did, forgot all about it. I pulled the head and soaked the whole thing in a pail of gas over night. The valve came right out. As for the bent push rods, my guess is it fired when it shouldn't have.

 

The bent push rods is because the valves stuck. When the valves stick, the rods can't push them, so they bend instead.

 

I used Deep Creep penetrant and freed up the valves today, was really pretty easy, the guys at the shop said it would never work but it was worth a try. I removed the carburetor and put the penetrant directly on the valves through the intake ports in the head. Waiting for the new push rods and some gaskets. No warranty, this is an eight year old engine. The push rods bent because they could not open the valves due to them being stuck to the seats by sludge and varnish caused by using very old gasoline. The Briggs techs said the push rods may have bent because of a backfire, not likely.

 

I have heard many people talk about bent pushrods being from a backfire. I don't see that as being possible.

 

Started her up today, purrin' like a kitten. The engine smoked for a few minutes until it burned the penetrant and carb cleaner out of the cylinders. I want to thank the board for the help and advice on this matter. Another lesson learned.

 

Glad to hear it worked! Thanks for the update!