Old B&S engine won't start

[judge2b]

If you pull the valve you are going to check and possibly grind it to get the proper valve clearance. If you replace the valve you will have to do this for sure. Do you know how to do this, if not don't remove the valves, just clean them on the engine and replace the head gasket. Make sure that you don't get any of that carbon between the piston and cylinder walls or you will score the cylinder walls. Don't even think about seat work.

You mean grind the face of the valve so it doesn't hit the other side of the chamber when the valve opens? How does the valve/rod change lengths?

I wasn't going to do anything with seat work.

I have a Tecumseh engine that I have to replace the intake valve on. It's crooked and doesn't seal when it closes. It also can be rotated while closed. Can I not just order the right valve for the engine and install it?

 

[Rivets]

No, if you remove the valve and clean it, you will change the valve to tappet clearance. As a valve wears, the valve stem will stretch, due to the heat. When you remove the valve and put it back in or insert a new valve, it is always recommended that you reset the valve clearance to factory specs. If you have never done this I recommend you have a repair shop do it for you. We're talking thousandths of inches. If I were you, I would take a brass wire brush and clean the valves while they are installed in the engine. Have the valve open, put a rag or paper towel in the cylinder to catch the carbon, and brush everything clean. Repeat with the second valve. Watch that you don't leave any carbon in the cylinder as I said before. Clean the top of the piston with the piston at TDC and blow everything off with compressed air to remove all carbon. It's not that hard but you must be careful.

 

[judge2b]

Oh! Yes, I was planning on resetting the clearance with feeler gauges. The tappets are adjustable on the Briggs I believe, so I don't think grinding will be necessary except in the most extreme case. I will try to just clean it the best I can without removing them and see if that works. If not, I may have to remove them, but I can reset the clearance.

I'm not sure about the Tecumseh though. The valve on there definitely needs to be replaced. If I can't set the clearance properly on the new valve myself, it just won't start and I'll have to have a professional shop adjust the valve.

If the valve does not have the proper clearance, it simply won't run, correct?

 

[Mini Motors]

I just checked my B&S Service and Repair Manual, and was surprised to see that they don't publish compression ratings. But they do say to spin the motor backwards to read the compression. That may be why they seem low to some of the advisers here.

 

[Rivets]

No engine manufacturers publish compression rating anymore, due to the fact that everyone has a compression release. Those of us who say it is low, base that on years of testing and experience in doing a compression test. None of the older engines had adjustable tappets. Clearance is set by grinding valve stems, which is why I recommended taking it to a shop. Might want to check your wallet and how much you like the engine before proceeding.

 

[judge2b]

Ok. Thanks for the info. I won't pull the Briggs ones then. Not sure what I'll do with the Tecumseh yet...

 

[therev]

If your down that far and have the vales out. I would get some valve lapping compound (Permatex make some) and lap the valve surfaces. It will show you if there USA valve angle or seat issue plus help the valves seal.

 

[thstearns]

I have a Briggs and Stratton engine that won't start, model 170402, type 1015-01, code 74032510

Basically it won't start. Fuel is not getting into the engine. I pulled the plug and the valve inside opens and closes but no fuel enters the chamber when I pull start.

I have cleaned out the fuel tank, put fresh fuel in, thoroughly cleaned the fuel bowl/valve assembly, replaced the mesh filter in the bowl, replaced the bowl gasket. I also made sure air can get into the fuel tank via the small hole in the tank cap. There is no fuel filter on the line, only the filter in the bowl.
I have replaced the fuel line.
I have completely taken apart the carb and swapped out all the parts in the carb rebuild kit so all the gaskets and springs and such are new. I also thoroughly cleaned out ever single orifice in the carb. The air cleaner isn't spotless, but its decently clean and there's no gunk in any of the airways going to the carb or the engine body.
I changed the oil and replaced the spark plug. When I attempt to pull start the engine I do get consistent sparks from the plug.
I also cleaned out the breather assembly as well.

Any ideas? I've attached the parts manual as well. Some of the parts don't apply since this is one of the older models obviously.

Pull the plug and squirt a small shot of Starting Fluid into the cylinder. Reinstall the plug and try to start. If the engine fires and runs briefly the engine is OK mechanically and there's a problem with fuel flow--plugged float vale or somesuch. If the engine doesn't fire and run you have a problem with it mechanically--valves are not sealing or out of time, ignition timing is off.

 

[mphymel]

Pull the plug and squirt a small shot of Starting Fluid into the cylinder. Reinstall the plug and try to start. If the engine fires and runs briefly the engine is OK mechanically and there's a problem with fuel flow--plugged float vale or somesuch. If the engine doesn't fire and run you have a problem with it mechanically--valves are not sealing or out of time, ignition timing is off.

This is my way of thinking, did it run when it was put up last season? My experience is that it is almost always (actually always!) a fuel problem.

5 for 5 on my small two strokes thanks to ethanol, and the same with my Yamaha Grizzly.

Funny story this year, I replaced the fuel pump on my Toro Z master, only to realize that the fuel tank selector was off. I had piled so much junk on the machine over the winter, something hit the selector, and since I never switch tanks, I never thought to check that!:confused2:

 

[bill1631]

Judge2b,
You said it was a pull start engine. A trick I use on engines that won't start is to carefully remove the pull starter and use an electric drill and socket to turn over the engine - check rotation direction before removing pull starter. Be sure and only slightly engage the socket on the shaft bolt so it doesn't come off the drill when/if the engine starts. I took a 3/8 socket extender and cut/ground off the female end so I could chuck it in my drill. I also read in an earlier post to add a little gas directly into the cylinder. Remove the spark plug, add gas, re-install the plug. This may flood the engine for a few pulls but it should fire. If not i would check the spark. If it is accessible, lightly sand the outside edge of the flywheel to remove rust on the magnet part. This will improve the spark. Good luck with it.
Bill




[