Engine Swap - XJ to F

[BA80]

Ivan and I talked about that a while back I think. I was going to try that on an SG I had but I ended up selling that bike.

I think, in theory, the valve clearance would be OK since the early heads have slightly smaller valves.

[XS11UFO]

Engine is on the way

Well, I will have the engine in a week or so.

If the valves are smaller in the '79 head, wouldn't that hurt the performance? Blocking the YICS ports sounds like a pain so I wouldn't mind swapping the heads (especially for more compression) but I'd sure hate to kiss a valve. Back in the day, I remember reading that you'd use a little clay on top of the piston, assemble, hand crank one cycle, then disassemble and check clay depth. Is it worth it? I would also to loose low end torque like trbig said, should I use the XJ cams? Or, would you just block the ports? The engine is on the bench so now is the time.

The ignition sounds straightforward enough. Sounds like its easiest to swap the alternators, nothing to gain from the XJ stuff and no re-wire. Wouldn't mind sourcing a regulator but rewiring connectors I avoid when there isn't really any benefit. The oil pressure switch/light, I guess I swap the F unit into the XJ engine? The safety switches for the clutch and stands, guess there is nothing I have to do, just leave disconnected?

Thanks for the help!

[BA80]

FYI........the 78 engine was the fastest and it had the smaller valves. The larger intake valve was put in the later engines in an attempt to compensate for the milder cam grind.

The only difference the slight valve difference will make is if you run the engine @ 8 - 10K all the time.

It would be a good idea to clay the pistons and check the valve clearances though. I really don't think it will be an issue but it's better to be safe than sorry. It really isn't much work and the cost is minimal using the old head gasket. I was going to do this about 2 years ago but circumstances changed and it never got done. Scott (3Phase) was going to do it too. I don't know if he ever did.

[DGXSER]

Dan Hodges has tried every possible combo of parts on these bikes, read through his post and you will see what did or did not work for him. He makes me feel stupid about this stuff, so I take his word on his results, that and he uses dyno results for his conclusions of performance.

In short though, there is no magic combo that gives true performance improvements across the board. Some will gain top end, at the loss of low end torque, some vice versa.

[trbig]

Dan Hodges has tried every possible combo of parts on these bikes, read through his post and you will see what did or did not work for him. He makes me feel stupid about this stuff, so I take his word on his results, that and he uses dyno results for his conclusions of performance.

In short though, there is no magic combo that gives true performance improvements across the board. Some will gain top end, at the loss of low end torque, some vice versa.

We've spoken in great length and that's one combination he hasn't tried and also suggested making sure of the piston to valve clearance.

The bigger valves in the later heads required a larger space, or pocket in the heads, (Valve relief) thus reducing the compression ratio. Yamaha tried to compensate by doming the pistons considerably higher in 80' and up than the 78/79 models. Here's a 78/79 piston on the right next to one of the later models on the left.









If you're taking the head off to swap with an early head just for the sake of convenience thinking the YICS ports needing blocked is too much a pain, if you add the early head, you'll still have to block the YICS ports on the cylinder. On the XJ, there's a tube attached to the back of the cylinders with 4 ports that match up to 4 ports in the head. Here's a set of cylinders off an XJ.









And here's a picture of an XJ head, with arrows pointing to the ports in the head, with an early model head at the bottom for comparison.









If you use the XJ head on the XJ cylinders, just plugging either the cylinder ports or the head's ports will fix it. If you want to install an earlier head on the XJ cylinders, you'll still need to block of the ports in the cylinders since they'll be exposed to air and your carbs will be lean and your motor will be sucking unfiltered air.

As others have said, you can permanently install a YICS tool in there, but you're dependent on rubber O-rings staying sealed and I don't know how well that would do in the long run with all that heat. I just tap them and install these allen plugs with some teflon tape around them. It's permanent, but I guess I could always pull them out if I ever changed my mind for some reason.

[BA80]

I don't see why the YICS ports in the jugs would need to be blocked if an XS head is used, they are hooked into nothing but themselves. The only thing blocking them would do is keep dirt out of that tube.

[trbig]

I don't see why the YICS ports in the jugs would need to be blocked if an XS head is used, they are hooked into nothing but themselves. The only thing blocking them would do is keep dirt out of that tube.

You are correct and it was late last night. The only thing you'd want to plug them for is because they would be exposed and water and crud would get in there.

[XS11UFO]

What would you do?

The engine / trans is supposed to be here next Wednesday! My question - I'd like to get parts ordered so other than ignition cover, head, and valve cover gaskets, what else do I need. Since the engine / trans will be on the bench - what would you do? Dremmel fix, 2nd gear fix, clutch springs? The engine supposedly has only 10k mi. total and I'd like to take care of anything I need to do while it's easy to get at.

After some searching and reading it seems that the lay the bike on its side method is preferred choice for solo engine changes. Any other suggestions? I know I gotta pull the swing arm but what about the front end?

BTW - got a couple of quotes for shipping from uship.com and ended up at $175 w/lift gate pickup for engine/trans from Mi. to Fl.

[IanDMacDonald]

Wait, what? Why do you have to remove the swingarm for engine installation? I've removed every engine on all of the bikes I own, and requires nothing more than mount bolts, trans-shaft bolts, and electrical connectors. I can't see how the XS11 would differ . . .

[trbig]

The engine / trans is supposed to be here next Wednesday! My question - I'd like to get parts ordered so other than ignition cover, head, and valve cover gaskets, what else do I need. Since the engine / trans will be on the bench - what would you do? Dremmel fix, 2nd gear fix, clutch springs? The engine supposedly has only 10k mi. total and I'd like to take care of anything I need to do while it's easy to get at.

After some searching and reading it seems that the lay the bike on its side method is preferred choice for solo engine changes. Any other suggestions? I know I gotta pull the swing arm but what about the front end?

BTW - got a couple of quotes for shipping from uship.com and ended up at $175 w/lift gate pickup for engine/trans from Mi. to Fl.

Valve cover and ignition cover gaskets aren't needed. Use silicone. Head gasket... Ehh. I've re-used them many times. If it isn't all delaminated, you might consider it.

I also wouldn't automatically Dremmel the gears. Take a really close look at them. If they aren't rounded bad, and no way they should be with only 10k miles, just move the washer from one side to the other on 2nd gear and run with it.

You DO NOT have to pull the swingarm. Laying on it's side is supposed to be good, but they can also just be lifted in. They're @ 225 pounds, and the rest of the bike you're laying down will be slightly more than that. THEN you've got to pick everything up. I just stick the motor in tail first from the right side, then turn the motor after it's in the frame. A floor jack lifting slightly at this point helps you maneuver it in place. Take care and watch out for the rubber boot around the u-joint and don't tear it. I like to install the motor with the middle drive in place as that's about the only good hand hold on the back of the motor, but it also adds a few pounds.

When installing, it's easier if your valve cover is off, but it's much easier to get your valve cover on and sealed while out of the bike. That's your own call, but make sure you have the oil pan on to protect the oil pump and leave your oil filter and cup off until after installation to free up quite a bit of room.

[IanDMacDonald]

To piggy-back off Todd, this method will for sure scratch the pee out of your frame, so either protect your frame or get a partner to help you out. Also, place a piece of osb or whatever under the engine, or on-top of the jack. Then, have the engine right next to the frame and slide it in just as Todd said. That engine is going to be one heavy mo-fo. Be careful.

[BA80]

this method will for sure scratch the pee out of your frame, so either protect your frame or get a partner to help you out.

We Duct Taped some cardboard around the frame rails when we installed Docs engine in his freshly powder coated frame. Didn't scratch a thing.

Get a friend to help with lifting the engine out and back in. If you don't have a friend, now would be the time to make one.

It'll be a bear however you do it if you can't get someone to help. And wear gloves. I say that from experience.

[IanDMacDonald]

It makes me respect those dudes from old Orange County Choppers episodes, watching them throw those engines around like they were a sack of flour.

[natemoen]

Tipping the engine and bike on its side really only works better if you have a near bare frame. If you have a bunch of stuff on the frame then it won't be easier.

[BA80]

So nate, you think it's easier stripping the frame to make it easier to tip the frame to remove/install the engine or just bribing a neighbor with a 6 pack to help lift the engine in or out?