This is the second part (check out part one here) in our extremely popular video series in which Todd Muller, Head Motorcycle Tech here at Lowbrow Customs, disassembles a unit 650 c.c. Triumph motorcycle engine and rebuilds it. With helpful tips and tricks, Todd takes a step-by-step walk through on the disassembly of a top end from the 1968 Triumph 650 motor. He shows you what to look for and how to know when certain aftermarket motorcycle parts and hardware need replaced or refinished, and what Triumph specialty tools are useful or necessary. You can check out the Triumph 650 Motorcycle Engine Disassembly & Rebuild - Part 3 to continue following along!
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You can read a full transcription of this video below:
These are your pushrods. No need to figure out which one goes where because they're all the same length. As you're going along, if you want to save inspection for later, you can. The main thing to notice on these is they need to be straight. If they're bent, that's an issue. A really easy way to check to see if they're straight is to clean off the ends and roll them on something that's very flat like your kitchen counter. Obviously, this workbench is not the best place to do this but you can get a good indication if they're bent by rolling it. If it's bent, it'll wobble.
There's our pushrods. Now, we have four head bolts left and we can take the cylinder head off. Let's get to it. Once again, always a good idea to say these are coming pretty easy, no problem there. Pretty confident I'm going to find a cylinder that has decent threads in it for the head bolts. You don't want to send a cylinder out to have it board for oversized pistons and then get it back to find out the holes, the threaded holes are bad in it. When you go to start going back together, that's a bad thing.
You may have noticed when I pulled the other head bolts, they were very long because they have to go through the rocker boxes. These are short. Once again, no need to keep track of where they go because they are all the same length. Okay, one other thing that you'll notice when you have the rocker boxes off is these cylinder heads are date coded. Well, the majority of them are unless it's a replacement head that was sent to the factory to reap from the factory to a Triumph dealer to repair someone's motorcycle.
You'll see there's this little oval on the intake side of the head. It does say 68. That means there's a real good chance that this cylinder head came with this motor from the factory. On the other side, you'll see a casting number. Basically, a part number or casting number for the cylinder head. So far everything's looking pretty good. The other thing worth noting, I can tell that these valves have not been replaced recently even though I just found a nice pretty new looking gasket and some grease on there.
You can see where the where the tappets have been running on the tips of these valves. That little bit of wear, there's really nothing to be alarmed with. If you do see a really deep indentation in there, it may be time for some new valves. That doesn't mean that these valves are bad. It just means they've been in service for a while, not unusual to see some wear like that there.
Okay, we're ready to take the head off. There's nothing else holding it on there. Pushrod tubes are probably going to come off with it. Not, and there is our Marvel Mystery Oil that we just dumped liberally dumped in there. The pistons were pretty far up in the bore. It's getting everywhere. Not a big deal. We'll just wipe it off. It's not going hurt anything like I said.
Then we have our head gasket which is made from copper. I know back in the good old days, they used to anneal these, that was where they would heat it cherry-red, dip it in water and that would be annealing, where it would be soft and pliable to reuse it. For the cost of a new head gasket, it's not worth reusing. Then also notice there's some seals on the top of the pushrod tubes.
Very critical on when you're reinstalling the head that you use the correct thicknesses on here to crush that gasket enough to seal it, because I get phone calls all the time from people where they're pushrod tubes are leaking. Also, going to see a seal on the bottom, on the tappet block, so there's our pushrod tubes and our top seals. Then you see there's another seal here on the bottom. Those are much thicker on this particular engine and they are very hard and not very pliable.
Okay, now that I've taken the lower seals off, you'll notice this year motor has a little metal cup looking arrangement that goes on before the seal. Make sure you don't just throw those in the trash can thinking, "I'm replacing these seals. I'll just throw these away now." See, there's that ring that goes on first, supports this. I also like to save my pushrod tube seals because if these were working before, let's say the motor was running and you're just refreshing the top end and you know they weren't leaking because these seals come in three different thicknesses.
I generally just saved them until I'm ready to go back together and then I may use that as a starting point to put the pushrod tube back together again. These cylinder base nuts are 12-point this is a 12-point Whitworth wrench. Oh my god, they're tight. What we can do for that is we can use another wrench to get some leverage. Look at that bada-bing. You can't get a socket in there, there's just not enough room. That one's pretty wobbly.
Oh Mother of God. More than one way to skin a cat. At this point, I don't think we're going to take the cylinder off right away. I want to give this Marvel Mystery Oil some time just -- hopefully, it'll go down there. We'll just go ahead and proceed and take some other stuff apart. There's plenty of other things to do here, whatever it takes to get this stuff apart without damaging anything, whether it be an extra wrench on there, rubber mallet. Just use common sense.
if you start doing something and you think it's going to screw it up, it probably will. Now, that we have all these loose, we can go and take them off in preparation for removing the cylinder. Like I said, I don't think we're going to go ahead and take it off at this point. We do have to have these nuts off here for this. I also put some penetrating oil on these before I started.
A lot of times exposed fasteners like this, it'll expose the elements and such they can get some corrosion where it makes it difficult to come apart. Also, another thing I've noticed very frequently when taking these off is sometimes the whole stud will come out of the crankcase. Don't be alarmed if that happens. You can still lift the cylinder off. The stud will come up high enough to get out of here.
You may have to lift it up a little to get it all the way off, but don't be alarmed by that. It's common. If that happens, don't worry about it. You'll be able to get the stud off of the cylinder later and reinstall it back into the crankcase. Right now, it seems like so far these are coming off fairly easily, which is a good thing
Okay, gang, while me and my awesome cameraman, Mikey, were taking a little lunch break. I came back and decided to check and see if maybe the pistons would break free. When you weren't looking, I took a hammer and just kind of the wooden handle and give it a little tap and she broke free, no problem. If you want to get a closer look here, you can see in the bore where the rings were stuck, this side was stuck. It's a little rusty in there.
You can see the rings. That's a good thing. Now, we can go ahead and take the cylinder off. Okay, next thing we want to do is we want to go ahead and put some zip ties on the tappets and what that does is it keeps them from falling out when you're pulling the cylinder off. Basically, if you were doing just the top end, you don't want to tap it falling in the crankcase. There's a couple of grooves on here, what you can do is just start your zip tie before you put it over the tappet. Then there's a couple of grooves on here and you'll see that later after we get this off and we'll show you.
You can also use a couple of pieces of hosing. You can just stuff it over. That'll also keep them in there. I like doing it with a zip tie. It's a little bit faster than looking around for some hose and screwing around pushing it on all four of them. Again, zip tie together. Now, what I found a good way to break the cylinder free from this joint right here. You can see there's some type of sealer someone put on the gasket. A good way to do it is to use your rubber mallet, your dead blow.
When you hit your cylinder, you want to hit it square. See, how easily that broke it free. You can see there's a little gap there now. It's going to go around. You don't want to hit it like this because then you stand the chance -- or like this because then you stand a chance of breaking a fin. See, it's free now. Just give it a little tap to break the seal there. We're ready to go ahead and pull her off. No mystery here.
I'm just going to give it a little rocking motion. She comes right off. Look at that. Next thing, I'm going to show you, very important. If you're doing it just the top end or if you're just assembling everything, you want to protect your rods. We're not so concerned about the pistons because we are going to put new pistons in. I can see now that the bar is very smooth and the pistons aren't in very good condition. We are going to go oversized on the pistons. Have to send the cylinder the machine shop, have it board out for an oversize piston for the new set of rings.
What you want to do is you want to get some 3/16 fuel line. You can just slip it over these studs. What that'll do, you'll see here in a sec as we take the pistons off. Now, you can roll your motor up. Sometimes they're easy to get them to roll up. Sometimes it helps if you put your kicker back on. See, there you go. You'll notice once the Pistons are off, this rod could come in contact with that stud. You don't want these rods banging into those studs. You want to protect your rods.
Next thing, if we are doing just the top end or we don't want the clips, we're going to be removing from here to fall into the crankcase. You want to take some rags and just wrap them around the rod and stuff it in the hall. Go ahead and get our rags wrapped around the rod. Sometimes it takes two or three rags to accomplish this. You just want to put it around the rod and in the holes.
Okay, we can go ahead and cut our zip ties that we put on the tappets. We'll go ahead and I'll demo a tool to remove the tappet blocks in preparation for sending this out to the machine shop. You can see now, the tappets will just slide out the bottom. Generally, the tappets will have a wear mark on them. You can plainly see it on these if you come over here and take a look. That wear mark coincides with the shape of this.
It's always a good idea to notice wear patterns and replace parts the same way they came out. These are just going to slide out. Then you also want to inspect the face of these. You can see on these they have just a tiny bit of wear. As you can see, there's a line on there. That line across there is from when these are going up and down inside here. These are going up and down, the cam lobes are coming by and opening and closing the valves. That wear mark is from the cam lobe.
Now, if you see where that line is very pronounced and very wide, I believe the speck in the book is 3/16. Generally, if I see anywhere like perceptible wear that I can feel with a fingernail, I'm going to have these resurfaced or I'm going to replace them. At any rate, once again, pay attention to your wear marks. Now, one other thing here that I want to show you is these were assembled incorrectly by the previous motor engine guy.
You'll see there's a hole in there. This is on the exhaust side. You can tell that by this hole for the cylinder head is facing forward. These are on the exhaust. This is a [sic] early motor you're not going to see any holes. They don't oil. Later motor or cylinder, you're going to see this plug in there. That's a cross drill. Pressurized oil comes through there and feeds these tappets.
Well, whoever put this together, put the holes facing in see. There's a little hole on there that the oil comes to. Those aren't going to get any oil if they're facing in. They needed to be this way. That just blows our wear patterns all the heck, so something else to pay attention to on this motor. Earlier motor is not going to oil the exhaust tappets. Go ahead and I took the gasket off. We're going to throw that away.
We'll go ahead and take a look at the intake tappets. Once again, there is no oil hole on the intake. You don't have to worry about which way those face. Once again, we're concerned with looking at the wear on the tappet itself and does it need to be resurfaced or replaced. On this one, you can plainly see the wear pattern. I'm suspecting that this motor may have been run with those backwards.
Okay, next thing we're going to do, we're going to use this tool, available on the website. This will remove the tappet blocks. Now, before you do that, you have to remove these two small screws. They also have a ceiling washer on them. That one is really stuck. There she goes, sealing washer. Now, notice on this, it gets smaller. That actually locates in a hole on this. Very important when reassembling that that hole lines up was you're inserting this. If it acts like it doesn't want to go the rest of the way, this is not lined up correctly. We have that one out.
Okay, now that we have all four tappets and the screws out of there, the little stud that has the funny end on it. We can go ahead and grab a larger hammer here. One thing, I've seen these ears break off. These two holes index in there and that fits like so. There is your tappet block. There's the hole that this locates in. Now, what can happen is if when this is inserted in there and you'll use the tool to send it back home, if this is turned ever so slightly, that will hit it. It won't want to thread in.
If you're having an issue with this, it might be a good idea to remove this, reinsert it. When you're installing these, you have to make sure that that hole lines up with that perfectly. We can cover that on reassembly. Okay, so there's one. No harm, no foul, nothing broken. Go ahead and take the other one out of here. Pretty simple. One other thing to notice on here, there's an O-ring there. It's so old, greasy, and dirty that you can hardly see it.
I'll go ahead and remove one so you can see what it looks like and that is one of the main reasons I'm removing these. Well, number one for the machine shop. Here's the O-ring. You want to replace that when reinstalling the tappet blocks. See, that one just broke. I don't think that's going to do its job. There is also a guide to tappet block fit. In other words, the fit, the clearance between this and that hole has a specification. You can get a general idea of how well it fits by putting it in there and see is it loose or is it -- this one feels nice and tight like it'll be pulleys, no problem putting this back into service again.
Now, if you felt a ton of slop back and forth, you can measure the OD of this, the ID of this and subtract and that will give you the clearance. There's a specification in the book for that. Now, one other thing I'm noticing here looking at the tops of these pistons. There's no carbon buildup. It seems to me that someone had this motor apart judging by the fresh gaskets on the rocker box and the grease. They did clean something up here.
Normally 99.9% of Pistons I find in these engines will have some type of marking on the top of them, whether it be a series of numbers which generally mean it's a stock bore. It's never been taken apart, original Pistons from the factory. Then what you'll see is oversizes. Pistons are available on the website in twenty-thousandths, forty-thousandths, sixty-thousandths, and eighty thousandths over.
Basically, what that means is let's say we were at stock bore and we want to clean up our cylinder bore to put new pistons in, we're going to send this to the machine shop and we're going to have them machine the bore twenty-thousandths over for the new Pistons plus the running clearance for the piston, the cylinder clearance. I don't see any markings on these, a mystery. We have a mystery here.
Well, there's a couple different ways you can figure this out. There's a tool called the dial bore gauge. Basically, you slide it in the bore and it has a gauge and you rock it back and forth and you read it. Then you put your micrometer and it tells you what the bore size is. For you guys in your garage, probably everyone doesn't have a dial bore gauge. I don't have one because I'm not doing cylinder fitting.
You probably use a vernier on there. That's going to give you a pretty good general idea of what our bore size is, 71 millimeter being a stock bore. We'll switch our meter to millimeters. That doesn't look like a very good measurement or that or I bumped it when I took it out of the hall. We're at 69 millimeters. I'm guessing that this may be a stock bore. There's another way you can check it with a different piston, go or no go.
I actually have a whole bunch of Pistons hanging around the garage because I've done so many of these jobs that I could easily check it like that to determine what size you need. If you're not sure, you could always ask the machine shop you're taking it to, to measure the bore for you and let you know what size of pistons you need. They do need the Pistons when they're doing the work in order to fit because they measure the piston skirt. Then they bore the cylinder and then add the running clearance.
One of the things I get on the telephone occasionally is people ask me what the running clearance needs to be. They've seen some specification in the book right around three-thousandths and that would be the piston to cylinder clearance. I probably wouldn't recommend doing that with the modern Pistons. That might have been fine back in the day. I'd rather see it right around four to five-thousandths.
On our race engines, we go as high as six to seven-thousandths clearance. The reason for that is because as the engine warms up and heats up, the pistons actually grow. As a matter of fact I just had a call the other day from a fella and said just bought a bike. The motor was supposedly rebuilt. Now, the second or third time he rode it, the pistons stuck in the bore.
Basically, what happened was they didn't give enough clearance for when the pistons heated up and got larger and then they got stuck. Hence, tear it back down, redo the whole job, so something to keep in mind when you're thinking about having machine shop work done on your cylinder. Okay, we can go ahead and remove the pistons next. Now, you might find that there's three different types of clips used on these piston pins.
This one has one that a snap-ring plier works for. There's another one that's just a C-clip and you're just going to put a pick on this little groove right here. You can see there's a groove. You're just going to put a pick and pop it out. This one takes this and then there's also one called a spiral lock. Those are a little more difficult to remove. Most of the pistons you're going to be getting for these are not going to have a spiral lock. Simply remove that using your snap-ring pliers.
You only need to remove two of them and you can push your pins out. Go ahead and do the same thing on this one. I can't see. There it is. Boom, piece of cake. Now, there is a tool available for removing those. I don't really feel that it's necessary. Generally, you can get in from the other side and force that pin out. If it acts like it doesn't want to come out, I do have a punch I use for this. Very carefully do it that way or you can also get your torch and heat the piston a little bit. The piston will grow, pin will slide right out.
Since we took both outside clips out, we go from this side. Once again, a little common sense goes a long way. Obviously, you don't want to use something that's going to get stuck down in there. You don't want to have to beat the hell out of it to get it out of there. If that's the case, if it's very tight in there, you want to heat it up a little bit. There we go, top end removed. Pretty simple.
One other thing to take a look at -- once again, if you're doing only a top end and you're not taking the cases apart, there's some bushings inside here. You can take one of these old pins and once you get your new pistons, you can always try it with your new pin. This is a similar fit when I was just talking about tappet to block fit. This is a very similar type of thing. There's a specification to fit on this pin to this bushing. It needs to be a nice sliding fit with no rocking motion in any direction. In other words, you want to slide it in there and you want to rock it this way and you want to rock it this way. See that? That one is borderline.
Once again, we'll try both of them. That one's pretty good. I probably wouldn't have a problem reusing these. See, we have a little bit of rocking up and down, no rocking back and forth. When these are changed, I actually have a set of rods over here that I've changed those in. This is a new bushing in the old rod for another engine I'm working on. If I had the pins -- see that? See how tight that is? This pin doesn't you want to go in there.
Well, I have sized this bushing to the pins for the new pistons I'm using and it needs to be a nice sliding tight fit with no rocking motion. If you slide your PIN in there and that thing's wobbling all around, that means it's time to replace the upper rod bushings, which we also have these on the website. Now, they do require to be reamed to size so you're not just going to install it and slide your pin in, because anytime you install a bushing like this, it diminishes some of their clearance. Another thing you need to check.