I have a Briggs 445777 25 hp engine that smokes very bad. I have replaced both head gaskets and the crankcase breather no change at all still smokes badly. So I think the next step would be new rings. If I put new rings on do I have to have the motor bored and replace piston and rings or can I just put new rings on the old pistons? The piston walls look nice and smooth.
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25 hp Briggs&Stratton rebuild question.
- Thread starter hamman72
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Export threadWhat you have to do is have a qualified technician pull the head and do an inspection of the cylinder, piston head, valves, etc. Looks are very discieving and you want him to measure the cylinder to see what will be needed. It's not just a case of slapping a new set of rings in it. Before I will install a set of rings I measure the following. All three crankshaft bearings. Both PTO and mag bushings. Six measurement in the cylinder. (should have done this when you replaced the head gaskets) Inspect the valves. Check the carb and crankcase. I know this sounds like a lot, but you want to make sure that the other parts of the engine are in good condition and worth it before proceeding with this type of repair. Many times it is not worth it and a short block is a better choose. I have had rebuilds cost any where from $100 on a simple Briggs 61000 back in the early 70's, to $2500 on a Wisconsin VG4D about 8 years ago. That is why you must do checks first, by qualified people.
I thought this was a do it yourself type forum not a take it to the shop forum I'm confused. I think I will try a $40 set of rings instead of a $400 trip to the small engine shop.
It is , but good advice is good advice. It is important to check prior to rings. When you replace rings you have to know that they will actually fix your problem.
Although dismissed often as "agricultural" engines, they are nevertheless precision pieces and the forgoing advice is good. You can quickly run up hundreds of $ on hunches or folk wisdom "fixes." That's without valuating your time to tear down and assemble. The pros will chime in but it seems your trade off point to buy a new engine is out around $800?
Finally the bore appearance means little if it is badly tapered. Also there is an oil seal on my Intek valve guides which , if worn. will admit oil into the combustion chamber. You got 'em and do they work?
PS the 6 measurements rivet suggests are difficult for an average homeowner to take. You need a telescoping inside hole gauge. These are not expensive, but tricky to use properly. The best is a 3 point bore gauge available at motorcycle shops. They have a dial and will quickly indicate taper if present.
Finally the bore appearance means little if it is badly tapered. Also there is an oil seal on my Intek valve guides which , if worn. will admit oil into the combustion chamber. You got 'em and do they work?
PS the 6 measurements rivet suggests are difficult for an average homeowner to take. You need a telescoping inside hole gauge. These are not expensive, but tricky to use properly. The best is a 3 point bore gauge available at motorcycle shops. They have a dial and will quickly indicate taper if present.
It is a forum where people come for help and those with answers provide help. Do I know it all, definitely not, but a have rebuilt well over 700 engines and think I can speak from experience. You say that you think you can fix your problem for about $40. Let me know where my thinking is wrong. You have a Briggs V-Twin engine model 445777. This engine has two cylinders. That means two sets of rings at $31.00 each. Two head gaskets at $6.00 each. Two valve cover gaskets at $6.00 each. Breather gasket at $3.00. Sump gasket at $15.00. Two intake manifold gaskets at $2.00 each. Two exhaust manifold gaskets at $2.00 each. $5.00 for oil. If you are going to do it right parts alone cost more than $100.00, at my rough prices and I'm sure I forgot something. You don't know what is wrong, so let's just throw some parts at it and see what happens. Could be one bad set of rings or two, a bad piston which run $65.00, any one four valves which run about $18.00 each, bad valve guides, etc. You don't even think you should have someone take some measurements. As a member of this forum I feel that I should not only help others solve problems, but also warn them when it may be better to leave it to the pros. I could be wrong and you might have a lot of experience in doing large OHV engines, but by your post I doubt it. That's why I try to educate members that sometimes it's better not to try things and maybe save them some money. You probably hate me for my answer, but you are going to have to get in line, your not the only one. Lucky I have thick skin and I'm too stupid to worry about it.
Would the worn valve guide be on the exhaust or intake valve or could it be both? Do I take the head off and disassemble the vavles from the head? How can you tell that one is bad just by a visual check or more?
The only clue I can think of to detect valve seal vs cylinder problems is that I would expect intermittent white smoke , as in start up only , for worn valve seal, whereas constant smoke as in power demand (mowing , climbing ) indicates bore sealing problems. Latter would likely show on plug condition if severe (oil fouled).
Mad Mackie
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Would the worn valve guide be on the exhaust or intake valve or could it be both? Do I take the head off and disassemble the vavles from the head? How can you tell that one is bad just by a visual check or more?
Do you have the latest parts and service manuals for this Briggs engine?? An air compressor, a parts washing tank with clean solvent in it, torque wrenches, a dial bore gauge, micrometers, seal removers and installers, flywheel removal tool, piston ring compressor, a press, a cylinder hone, a clean workbench, I can go on!!! I have all this and more in my shop, but in March I repowered my Scag Tiger Cub with a brand new Briggs 30 Cyclonic engine for $845 delivered to my shop. Old engine was a 44P777 with decreasing compression on just the L/H cylinder. Did a leakdown test on it and it was leaking badly passed the rings.
I strongly recommend that if your machine is worthy of a new engine, then check out some of the small engine suppliers, you may be surprised at how inexpensively you can get into a new engine that may be a drop in.
Mad Mackie in CT
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