Briggs and Stratton 7hp Engine Rebuild from Start to Finish

Briggs and Stratton 7hp Engine Rebuild from Start to Finish

(Male narrator) Hi everyone! In this video, I am going to be rebuilding a 7-horsepower Briggs and Stratton engine. Now just so you know I have actually previously released this video series in individual parts, but I thought just to make it easier to watch I have put it all together in one complete video. So hopefully you enjoy the rebuild. I enjoyed doing it. You might even learn something along the way. So I hope you enjoy it. Right, so first of all, we are going to be removing things like the air filter and the muffler. Basically, everything on the outside of the engine, which needs to come off first before we go opening this thing up. Now, my top tip for when taking things apart is to lay them out in the order that you take them off because then if you ever have any doubt about not being sure if you took something off when you put it back together. Then that is your back up because you have got it all laid out so all we have to do is put it back together in the reverse order. Right, so onto the muffler. It’s just these tabs which you need to push back. They should fold back and they are just there to stop the box from coming loose when the engine is running. Then get a spanner[1] or a ratchet same size, right size for the bottom. Then slacken them both off then you will be able to undo them.

So it slips off. Make sure you don’t lose the gasket on the back.

So there is the carburetor. Just removed that. There is the bowl underneath. Very dirty as well. And the gasket is going to need replacing. That is alright, though. I have got a full gasket set. Yeah and that is basically the carburetor assembly. Overall, looking at it though. Although very dirty, first inspection doesn’t look too bad. So fingers crossed that would be okay to reuse.

So now I can remove this throttle plate and this is also where the governor attaches to. That’s what the two linkages are. We have got the throttle and the choke. Then that just comes off here. The spring which attaches onto the governor lever. And there just needs pushing back. And that unhooks off there. And the spring which I am going to keep on the governor lever which is attached here. There’s a nut just on the end of it there. And that can be slackened off. The linkage will come off leaving the governor inside the engine. Just put all of this to one side ready to clean and then everything will be free here. I am then going to move on and remove the valve cover. So the two bolts come out of here. And then there is a gasket on the other side of this which will probably keep it in place. So we need to pry this off very gently and if possible, especially if you are not going to change the gaskets, try not to damage the gasket. Although, if you are changing the gasket obviously it doesn’t matter. So there we go. We can see the gasket is actually still fully intact which is good if you weren’t going to reuse it. In fact, I might be able to reuse this. And then we have got a breather here, valve springs, and then we’ve got the valves in there which run right through. Exhaust which is this one here and then we have got the carburetor which is the intake. And in this engine which I haven’t seen before looks like they have different color valve springs as well which is very handy so you don’t mix them up. Then obviously in here we have got the retainers and the Kaulitz[2] I think is in the exhaust one. Yes, I think it is in there just down there. Here is a closer view of the valve springs and the valves. They just sit in there. So there is the exhaust port and the intake port. You can see obviously the gasket this one here half of it is left and half of it is gone. These will be replaced which is no problem. I have got a whole gasket set as I said. They are going to seat on there. So if you are planning on reusing them it is not a very good idea so you are going to have to replace these unfortunately in most cases unless you are incredibly lucky but in more cases than others you will have to replace them. So if you haven’t done so already this is the time to remove all of your oil out of the engine and if you have kind of done it right in the beginning which is great because otherwise you can forget then you could open it all up and find oil spilling everywhere. So yeah make sure you have done that make sure you have removed all of the oil as much as you can. Run it up if you want to. That will change the viscosity of the oil to make it a lot thinner which means it will come out a lot easier and runnier. So that is one thing you can do. Obviously, if it is not a running engine or you have not got a mount to turn the thing then you won’t be able to run it up, so you just have to try and get as much as you can out just by tilting it on the bench and try to get all of that out into the drain pump.

We are now going to remove the bolts from the shroud which covers the top of the engine. These two at the front and then there is one on the back left and one on the back right.

Okay so this is inside of the engine. I do not know how long it has actually been since this was last opened up. By the looks of it, a long time ago. It’s got cobwebs. It’s got some form of foam, probably some packaging or something. One thing I always look for is, well first of all, make sure there is no mice nest in here because mice and other creatures do like to nest inside this area where the fins are where it blows the air down. Obviously, if you start the engine up and it’s all blocks it will start to smoke most likely or overheat the engine and also because mice and other rodents do live in here. You’ve got to check the condition of this HT lead and luckily looking at this one it’s got a bit of perishing but it hasn’t been gnawed at by a mouse or anything. I have done an engine one before this and where it was almost chewed right through this lead. It had almost been eaten in half. It was that bad. There wasn’t actually a nest in there though, which was odd because normally they will come in here in nest then chew this and make the nest out of it. But yeah. Luckily, this engine is absolutely fine. It has been rodent free. While it has not been used for probably over ten years so that is one less cost assuming that the magneto does work. Next, we have got the starter clutch. This is basically four bolts which holds this on. It’s a quarter inch spanner or socket whatever you want to use. Just remove these and take these right off. Then you will be able to remove the flywheel guard which is this mesh here. Then we will be able to inspect everything else below that. Everyone has a different way of removing one of these starter clutches and obviously the main thing you want to do is to make sure you can get it off without chipping one of these notches on the side off. What I use is actually a rubber mallet. Some people will use a block of wood and then hit the block of wood with a hammer on one of these, spin it around. One thing you do not really want to be doing is hitting it with a metal hammer on this. You will miss hitting it directly because you will most likely, if you don’t chip it off or chip it so you don’t really want to be misshaping this at all. The way I do it is either with a piece of wood on there or with a rubber mallet. Okay so I am going to try and remove it now. Sometimes these things are very stubborn, very hard to get off. Sometimes they are very easy. You just have to give them a few light taps with your mallet and it will move. Obviously, it shouldn’t be so light you can just pull it off because otherwise it would have been fairly dangerous if the engine was running because it would not have been screwed in properly but usually they are not too bad to get off. If you are having trouble with it being seized on, then you’ll have to try something a bit more extreme on it. More extreme than a rubber mallet. You would have to move on to the block of wood with a hammer. Really you do want to be avoiding hitting this thing directly with a metal hammer because it is going to chip it. Also, if you are having the problem of it being seized and when you try to turn it it turns the whole crankshaft then you can lubricate it down underneath where the thread is or you can put a piece of rope down in the combustion chamber and that will lock the engine but make sure that you can get the rope out again. So make sure you have some hanging out the side. So yes, I am just going to give this a quick hit and see if it comes off.

This one is fairly easy. There it is. That is the starter clutch taken off. Overall, condition seems fairly good. It is working fine. I probably will let it sit before it goes back on again, but other than that that is absolutely fine. Next, we are going to be removing the coil. So this is removed just with two bolts and a quarter inch spanner or ratchet whatever you want to use, socket. It looks like it is actually not sheared after so that is going to need a looking at. But yeah it is just these two which holds it on. Then this whole coil will just lift off. Then you can check it for wearing, any missing parts, damage. It looks like there is a bit of damage on this one, unfortunately, hopefully not so bad I have to replace the whole thing though. So yeah, just check it over, clean it up a bit. Also, before you put it back on, I’ll show you this later on though, you have to clean the contacts with a piece of emery cloth, with dry paper, some paper whatever you want. Otherwise, it might not create a spark. Make sure the contacts are nice and clean when you put it back together, but like I say I’ll go into more detail when I am actually doing that because I only go through everything full stage of rebuilding so hopefully I do not miss something out. Make sure you keep the bolts safe. Then this should lift off now. If it is against the magnet on the flywheel, then you will probably find it harder, which is you will feel it pulling on there. Yeah, that’s not too bad. Like I say though hopefully you can see I am on it. I just have to focus that. If you can see there, these contacts just here there is rust on them. These ones be shiny when you put this back together. Otherwise, you might get a weak spark almost. These just need to be cleaned up. It’s that easy really. It doesn’t take that long at all, but just clean these up. Also, clean up the magnet on the flywheel if that is rusty too. Just quickly this is where we are so far you can see I have laid everything out here. So we know exactly which order things come off in. It may not look like it’s in any kind of order to you on the screen, but I know which order it is so as long as you know when you are doing your own engine that’s the main thing. Just lay it out. If you have got a nice long bench like I have here, then just lay it all out. You will know exactly which order it all came off in. You just basically can reverse the whole procedure when you’re putting it back together. Obviously, though we are going to clean everything up so just try not to mix anything up when you are doing that. Okay so on to removing the flywheel now. I am going to use one of these hydraulic pullers because from past experience these flywheels get really stuck onto the taper. What you can do if you don’t have one of these is to get a cheap puller. This tooth holds here with threads in and you clamp it onto there, tighten it, and it will pull the flywheel up. Now if you have got a flywheel with the teeth on from the starter motor, then you can’t use one of these pullers on it because you will chip the teeth off. Sometimes they will have a designated pulling area to put one of these, but if it doesn’t then you will have to use one of the ones on here. I am just going to keep tightening this puller until it comes off. If you are going to use one of these, then make sure you wear eye protection because these flywheels can come off with some force because of the way they are sat on the taper. Just be careful when doing that because they can really bounce up. I am going to remove this one now.

This just popped up and now I can lift it off. Make sure you do not lose the flywheel key. That is what it looks like underneath the flywheel. It is all in very good condition luckily.
Alright, so this is the cover for the points which are underneath here. It is just three bolts and this will lift off. Then we can gain access to the points. More debris in here. We just need to clean it out but we will clean it later on anyways. Just get off as much as possible.

There is the points. Just in here now will need cleaning up later on. As you can see, I have just removed the points and condenser. The reason for that is because when
I am rebuilding this I don’t want them to get damaged or wet in any way. It is best just to take it off and keep it aside. It is time to flip this thing over. Yeah. Now we are going to remove the head. Alright, so this is the head bolt loosened off. Now if you don’t know the torque setting for putting it back together then before you do this use a torque wrench and just see what they are set at. But for Briggs and Stratton engines normally finding the torque setting is not too hard. You should just do a quick search and it will find it. Obviously, I will tell you for this engine when I am putting this one back together. Now, when removing it you can keep more in the head like this and just lift the head off that means you do not mix any of them up or you can get a piece of cardboard, put a few holes in it of the same layout of the head and then put each bolt in the same layout as it is in the head in the piece of cardboard.

Here is the inside of the cylinder head. This is the piston and these are the two valves. We have got the intake valve and we have the exhaust valve. And obviously the head gasket. Looking at the gasket it does not look too bad which is good for this. Now there is a fair amount of oil in here and this could be just because it has been sat in a certain position for many years and it has leaked in here through the valves or it has been burning it. Now looking at this cylinder here, this piston. It has got a fair amount of carbon deposits on near to where this oil is. So my suspicions are it has been burning oil. Okay so now on to removing the sump. So there is one, two, three, four, five, six some bolts in here. All of these need to be slackened off evenly. Otherwise, it can warp the sump. Then we will see what there is inside.

Here we are inside the crank case. We have got the camshaft. We have got the oil slinger with the governor on. We have also got the crankshaft and the con rod in there with the piston attached and a timing gauge is there. This is the camshaft and you will see if you look carefully there is a timing mark just there. That is what lines up with the timing mark on the timing gear. You can just about see in there that there is a con rod, the connecting rod which connects onto the piston and if I turn it over you will see more of it coming in here. That’s the connecting rod and you can just about see the piston coming through there. This guard is just to protect the engine and also to help the air flow. If I move this bolt out of here, you will see why you have to clean these engines out. This dry grasses and debris on a hot engine is just a fire hazard. These things have to be cleaned out. Also not just a fire hazard but if it gets totally blocked the constriction of air will cause the engine to overheat and potentially seize[3]. This is the oil slinger. This is what lubricates the engine, a very vital part. Then have got the camshaft and it has got lobes on. As it turns, it pushes the cam followers in which then opens and closes the valves in time with the engine. So these can come out. Then, if I stand it up, we will be able to gain access to the two bolts that hold the con rod on. Because this is an older Briggs and Stratton engine, it’s still got these tabs which you fold up and it stops the bolts from coming loose. I don’t think the newer ones have that anymore. But the older ones do. So they just need folding back and then I can remove the two bolts. I am also going to remove this governor from the linkage here just so it is not in the way and get damaged when I am removing the crankshaft. Then you can just slide it out. Make sure you do not lose the washer and that just comes straight out. Most of the bolts that hold the con rod onto the crankshaft vary in size. For this engine, it is half inch, but I have seen lots smaller ones in the past for these types of engines. Okay so those two bolts have now been slackened off and I can now remove them. Now, when you do remove it, the con rod will split in half. You have to make sure you do not mix these two bolts up because sometimes they are slightly different in length. So you have to make sure they go back into the same hole. Now it may be the case that they are exactly the same, but just for good practice it is always best to keep them in the same place. This is the inside of one part of the con rod. You are looking for wearing such as lots of scratches, any heat marks, and, well to be honest, this one is actually very good. I do not think there is any wearing at all. This will definitely be able to be reused. Here is a closer up view of it. You can see it is in very good condition. Now this means I can push the con rod and piston through.

Once it is through enough, you better remove the crankshaft. Then you can push the piston out fully. Here is the piston. Also in very good condition. A few marks on it, but nothing which should stop it from running properly. It’s just going to need a good clean up. Get that carbon deposit off and overall very good as well. This is the crank journal where the con rod attaches to it. You can see that it is in perfect condition. That is brilliant and it can be reused. This is the inside of the combustion chamber. There are some scratches in there. That is probably because some carbon deposits have fallen off inside the head and they dropped down and scratched it which would definitely indicate that it’s been burning oil. Now they are at the bottom of here which would mean possibly that is why there is oil getting through. It might not be severe enough to cause that much of a problem, but either way. It is still going to have a good clean out and probably hone it as well just to try and eliminate any problems with oil getting through. I am going to remove these piston rings because there is actually carbon deposits in the grooves. Now it is not that bad in some places but other places like there. I don’t know how clear it is on video. There is a lot of deposits in there. I am going to use one of these piston ring expanders and I am going to remove the top ring, lift it off. Then I am going to get an old piston ring which is broken, put it in the groove, and scrape out all of the carbon deposits. You can see I have removed that ring. Make sure you keep it the same way up so it goes the same way back. So it does not go back on upside down. You can see now hopefully on the camera. I do not know how clear that is. There is a lot of carbon deposits in parts of the groove here. Probably some people would not want to remove this because they would not want to risk breaking the piston ring or expanding it too much and then it not fitting properly. Because I am not planning on taking this engine apart again for a long time it is worth it. Now I have the piston out just to remove that carbon deposit. Now I have got this broken piston ring here. I think this was out of a land rover. I am just going to scrape the carbon deposits out of the groove. You can see looking into what would have been left in the groove if I had not cleaned it out. There is lots more of that in here. There we have it. We have the oil ring off, the second piston ring off, and the first one. Here is the piston. Now with all of its rings off. It is ready to clean now. Now we have one very clean piston. Now I am just going to let that dry off and then I will put the piston rings back on. Then I will move on to the next stage. Alright, moving on quickly. Now we are cleaning the sump which is what attaches to the bottom of the crankcase. I am going to replace this oil seal this crank seal. This stops the oil from leaking past the crank from the sump. I am going to remove this because I am going to replace it. Obviously if you are going to replace it don’t damage it when you take it out. They can be stiff sometimes, but it just pops out like that. You need to clean all in here so it is spotless and then you can put your new one in. Then basically just put a big socket on the top of it. Get a copper hammer and make sure you hit it centrally and it should go down like this. It should be flush with the top[4] and it should not be uneven on any side. Alright, so this is the trickier part. You need to get a valve spring compressor like this one or like this one on here. It is a bigger one as you can see. You need to basically compress the valve spring on the valve. This will allow you to remove the retainer or the collet[5]. Now the exhaust valve on this one has the collet[6]s in place and the intake has a retainer. What you need to do for the exhaust is get the valve springer compressor on it and pull it back. You can see I have already pulled this spring back. I am just trying to zoom in. You can see there is metal collar in there just down there. When you pull it back it should fall out. That is what holds the valve in place. You need to remove them so when it’s pulled back, knock them out with a screwdriver or something. When they have fallen out, the spring will be able to come off. Do it slowly though in case it springs back. Then you will be able to slide the valve out. I have removed the collets now. Then I can let this valve spring compressor off. You can see it is sprung back. You can pull the compressor out. Then because the collets have now been removed you should be able to just slide this valve out. Hopefully you can see this. You can just slide the valve out like this. You need to make sure you don’t mix the valves up. Now the engine is now fully disassembled. Everything now is going to be cleaned completely. I will also be respraying a few things as well. The air filter box, the sump, the crankcase, and also the engine cover. What I am going to do is put some tape over the sticker so it does not get painted. Then I am going to sand down everything and make it all smooth. I just tied this handle back so it does not get painted by accident. The rope doesn’t matter because that is going to be replaced anyway. Then I am going to have to brush paint it because the paint I have got, unfortunately, can’t be sprayed.

That is the engine cover painted. I do not think it will need another layer. It should just do with one. I am going to let that dry. Then I am going to move on to other things that need painting as well.

For removing all of the old gaskets, in the dirt and in some cases the rust like the flywheel I have been using a wire wheel on a drill. I have also been using a handheld wire brush, but if you do not have one of those this is something that will come in handy. It’s a gasket scraper. Basically, all you do is just scrape the old gaskets off. It is a fairly cheap tool. It is fairly lightweight. You just basically scratch the gaskets off. There you have it. Here is all the parts of the engine except for the crankcase itself. These are all clean. Some are painted. They are pretty much ready now to go back in the engine. One thing I will be doing though is spraying the sump and the crankcase with some heat proof paint. Just to make it look a bit smarter. That is the crankcase and the sump all clean now. You can see I have removed the majority of the paint from the outside. So what I am going to do is reassemble the whole engine. When it is all assembled, I will respray it. The next stage is to grind the valves in. I have already done the exhaust valve which took over twenty five minutes alone just to get the seat there. Just to get the valve to sit in that seat. The exhaust valve was very bad. This is the intake valve, which isn’t so bad. I am going to do this for now which goes into this one into this seat. Basically, what you do is get your valve grinding paste which looks like this. This is the fine paste and the other end is the coarse. Obviously, if it is very bad you would start with the coarse and then move on to the fine. This one is not so bad so I am going to use the fine. Then what you do is you get some and try not to get it on the valve stem but you put it around the seat. You do not have to use too much just enough to cover the whole of this rim like that. Then lower it into the slot in the valve seat like that. Then you need to get your valve grinding tool which looks like this. You press down on it on the valve. Then you rub it like this. Lift up now and then twist it around. Again it can come off quite easily. Anyway this can take quite a long time but what you are doing is you are making the seat. You are grinding the valve into the valve seat on the crankcase. This took about twenty-five minutes just to do the exhaust valve. The intake won’t take as long. You have to make sure that all of the pitting is out of the seat. Obviously, I have only started doing this one, but a good seat, I will wipe it, a good seat should have no black pits in it. It should be smooth all the way around. I will just try to focus on it. I hope you can see that is in focus. Yeah it should be like this, but obviously more nice and shiny, no black pitting in it and definitely no carbon on it. So you need to clean up the valve before you do this. So really you just need to keep doing this until you’ve made a really good valve seat. The valves are now all lapped in and reseated. I have honed the engine out. I am just going to clean the inside of there out to get any metal shavings off any dirt as well. I am just going to use this cleaner. It is actually carb cleaner, but you can see what a good job it does. It gets all of that out. I am just going to clean the cylinder wall.

Because we don’t want any deposits of dirt or metal shavings or anything in here. We want it nice and clean just to get any dirt off. Time to put the valves back in. Now if you have got trouble putting valves back in I always recommend to put the ones with collars back in first then you have got more space in the compartment where you put them in. If you put the retainer one in first then you are really going to limit the space you have got to slide these in. So that’s just something I always do. Make sure I put the exhaust one in first.

Alright, it is time to put it back together again then. This is the gasket set. 299577 is the part number. This pretty much contains everything so this is everything we get in the gasket set. Head gasket, crankcase seals, gaskets. Let’s see oil seal for dipstick. Some parts for the carburetor. The intake that’s for the carburetor. All kinds of different seals.

Next, I am putting the piston in. Make sure the gaps are not lined up. It has to be evenly spaced apart. Otherwise, it could leak or burn oil. I am happy with that. I am going to put the piston ring compressor on top. Tighten up. Next I am going to slot this into the combustion chamber. Then with the end of a mallet like this just hit it through. There it is. It is in. Now I can connect that onto the crankshaft. Now make sure when you are putting it back together you use plenty of oil. Because before the oil slinger is come into effect when you are using the engine for the first time, there won’t be enough oil around the engine to lubricate it. So you just need to give it enough to use before the oil slinger has slung it around the engine. That’s to say all engines vary for torque settings, but for this engine it is 165 inch pounds or 13.75 foot pounds. That’s the piston in place as well. You can see I put some lubrication on it as well so that when it starts to turn over then it will lubricate that cylinder wall. That’s the big end attached to the crankshaft.

You can see I have timed the engine by lining up this timing mark here with this dot on the camshaft. So I will turn the engine over now and show you the valves moving. See that is the exhaust. Pushing the exhaust out. Intake and then spark and the ignition, that’s the power stroke and then the exhaust again. Then there is the oil slinger which is very important. You can’t forget this. That is the governor on there. Now it will push against it when the engine speeds up and slows down. Next, we are going to put the gasket on all around the edge here. Then we can put the sump pump. So in a gasket set you are given quite a few gaskets for this sump and the crankcase because you need to have a certain amount of crank end play. This means you have to be able to move it a certain amount when the sump is on. So for a start I am going to put these two gaskets on and then check if that is enough.

Then just make sure that is not in the way and make sure that will still touch that. Then you can put the sump pump. If you do this carefully, otherwise you can damage the seal on the bottom of it. Make sure it is fully on all the way around. That seal looks to be fine so I can now put the bolts in. So I have done those bolts up tight now. They just need torquing and they need to be 140 inch pounds for those with the split washers on. You need to make sure you have got a split washer on your bolts. When you are happy everything is ready, you can put the head gasket and the head on. So you just need to get a new head gasket or the old one if it wasn’t too bad. And you just need to line it up. You can then get the head and place that on top of the head gasket. Make sure you go through all the holes and then you can tighten those bolts up. Just snug those bolts up. They need torquing now. For this engine, it is a 165 inch pounds so you need to make sure you do that. Do not go around in a circle just a word of warning. It is better to go diagonally if you can so you do not warp the head. So you might do that one, then that one, then over here and over there. Something like that. Just don’t go around in a circle.

So if you are having trouble setting the points up then essentially all that happens here is this spring goes onto that pin in there. It also goes onto this plate. That plate slots into this it is like a brush which goes on here with a bolt through it. Then basically the breaker point is clamped in here with this clamp and there is another bolt through there. To set it up all you do is you turn the flywheel so that it is fully open. You put a feeler gauge in here and put it to 20 thou. When you got it to the right setting, all you do then is clamp it down with that bolt. I will show you it working now. See it is opening and closing. Open and closing again. That is how it is set up. It is a certain way around this cover goes on. You will see there is an indentation there for the points underneath. So it will only go on one way around and it is just like that. So that is the flywheel on. Now we have got the starter clutch those threads on. You need to make sure that is tight. Then when you have got the starter clutch on, you can remove the bolts which holds the flywheel guard on. You can put the flywheel guard onto here. Line up the holes like that. Then you can put the other bolts in. When you have tightened that up make sure you can still turn the starter clutch. Now remember it’s one way so it should go backwards, but not forwards because that is obviously locking for when you use a pull start. Next, we are doing the armature. So we need to do is slot the coil onto here. Then you just slightly tighten up the bolts just so it holds it in place. Then when you have cleaned the contacts on the magnet, which is on the flywheel, you slide it against the magneto, you can see now, they have attached with the magnet. Then you need to get a feeler gauge. Now this one is point zero ten. You need to slot it in there on one side. Then it will pull back and then you can tighten it up on that side. Then you can take it out and do the same to the other side. So you can see now that it is on the left-hand side and then slide that feeler gauge into there and it should just rub. It should not be too tight. It should not be too loose. You should just be able to put it in there smoothly and you should be able to feel a bit of resistance. On to cleaning the carburetor. Alright, you can see it is very dirty. First of all . . .

Gives the outside a good clean. I have cleaned all the way round the outside of the carburetor and on the inside the float in there is absolutely fine. It has got no petrol in it from previous users. It is not leaking and the float valve in there is also working as well.

So this carburetor is mounted. I just need to attach it down here and also this breather elbow which goes onto here. It just needs fastening on. This clips in there. You push it in as far as it will go.

That brings an end to the engine rebuild. Hopefully you have enjoyed it. Also, if you want to see it running, then please search my channel for seven horsepower engine running and you should be able to find it. So thanks for watching and I’ll see you in my next video.
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