OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines 4hp Briggs and Stratton Quattro

Thanks Grumpy.
A key point to note was the connecting rod bolt was loose and not snapped. It actually fell out of the rod end which made me immediately think of the engine not being assessbled correctly.
The broken piece in the 6th picture is a piece of the boss and nothing else.
1) The governor was installed properly before I stripped the engine
2) The engine had plenty of oil. Well it could have been filled up after the rod snapped, Who knows some owners don�t care of their machines.
I thought it might not be suitable for repair because of the minimal cost of a replacement block on ebay.
I was hoping you could provide some advice about getting the timing correct if I was in fact going to repair the engine and any other tricks about re-assembling the bottom ends. I�ll no doubt one day be repairing a bigger more worthwhile engine so your advice will come in handy. Ive watched some video�s and they are all slightly different in the way things are explained.

The timing is not much of an issue. The ignition timing will inevitably be correct if the flywheel key is intact and in place correctly. The valve timing requires that you put the camshaft in the correct rotational position when you reinstall it. Briggs engines have timing marks on both timing gears: the one on the crankshaft, and the one on the camshaft. You position the crankshaft so that the dot on its gear is at its nearest point to the camshaft, then you slide the camshaft in so that its dot will end up at its closest possible point to the crankshaft gear's dot. Note that the gears are helical, so the camshaft will rotate a bit as the gear slides into mesh: you have to start with the dot about one tooth below the crankshaft one, because the camshaft will rotate clockwise about one tooth-width as it slides into place. It's a bit like leading a duck slightly when you point a shotgun at it. (Many Hondas don't have a dot on the crankshaft gear, because it is not on a key, it is just pressed on. You use a slightly different method with those - you put the crankshaft on Top Dead Center, then slide the camshaft in so that its dot is as close as possible to the crankshaft gear. I prefer to put a centerpunch dot on the crankshaft gear before I lift out the camshaft, so I don't have the hassle.)

Installing the piston and rod is a bit more complicated, since you have to worry about half a dozen things while you are doing it. This would be a rather long post if I went into all of them.

Grumpy thank�s for your explanation on setting the valve timing. Upon disassembly it was relatively easy to line everything back up as it should be. When find an engine that needs a full re- build and we agree it to be a worthwhile process this post will be good to refer back to as a guide. Your centre punch idea makes the most sense, so I will chalk that up in the memory bank when and if a Honda is on the operating table (my shed bench)
On a separate note I checked the ring gaps of the last 2 dismantled side valve briggs engines and they were both massive. They were not however lined up as Joe thought they might have been.
I have watched a few video�s on correctly installing the piston and rod during a full rebuild and it doesn�t look too complicated however I would appreciate some pointers around the importance of installing the piston and rod correctly before I attempt the process in future.
Thanks
Peter

Hi Peter, there are many old Briggs engines out there with worn-out rings, it is probably the most common wear problem. You'd think the aluminium bore would be a bigger problem, but it has a much bigger surface area than the rings do. I suggest you measure the bore diameter if possible, just 1 cm down from the top, to see if it is worn before spending money on new rings.

There are some especially critical points regarding re-installing the piston and rings. These are not the only things to be careful about, as you will have noted from the video you've seen, but they are extremely easy to mess up. First, do not take the piston off the connecting rod, or you will have problems putting it back on the right way around. Second, put the piston in the right way around: the gudgeon pin is offset, it is not on the centerline of the piston, and if you put it in backwards you will wear one side of the bore excessively. Third, put the connecting rod cap on the right way around. It was bored at the factory with the cap installed, and if you put the cap on backwards the two halves of the big end bearing will not match (there will be an offset in the big end bore), which will cause early failure. Fourth, oil the crankpin before you assemble the big end bearing. Fifth, clean the bottom of the rod and the top of the bearing cap and ensure there is no dirt in the joint between them, then assemble them by hand, don't pull them together by doing up the bolts. Then tighten the big end bolts to the right torque, don't just "do them up". On such a low speed, low stress engine, just doing them up is probably fine after you've used a torque wrench enough times to be accustomed to what the right torque feels like, but with a small bolt in an aluminium rod, until you get the feel of it, it is very easy to get it wrong in one direction or the other. Remember, tighten the two bolts in stages, just snugging both of them first, then bringing them up to torque alternately, a couple of Nm at a time.

There are fifty other things you have to get right, I've just focused on the ones people are prone to getting wrong.