Engine Swap - XJ to F

[XS11UFO]

I need to change the engine (seized), and have found one from an '82FJ.

Question - what do I need to change to make it work in my '79 F? Is the transmission geared differently? Should I do the 2nd gear mod while its out?

Just trying to keep this cluster from getting worse by doing homework first.

[trbig]

To swap an FJ motor into our bikes... Ummm... basically if you get a frame, electronics, chain drive rear wheel.... Just kidding. It'd be like trying to put a Suzuki motor into your bike. Only thing similar between the XJ and FJ is the Yamaha name.

[DGXSER]

Just to clarify, your title says XJ to an F. That would not be to tough, some electronics to swap around, but mechanically bolts right in.

In your post you state an FJ to an F. As Tod indicated, that is a cluster at best.

[IanDMacDonald]

U beat me to it Don. Pretty sure he meant XJ.

[XS1100carbon]

motor change

You couldn't put a fj motor in a xs frame?And yes I know it's a chain drive but was just wondering?

[BA80]

You wouldn't need to change any electronics if you swap out the XJ ignition components under the left cover with the F components. And, put the XS alternator components under the right cover. Fairly simple swaps and you won't have to rewire the bike.

Take a look at the gears, if they look ok you might just do the washer swap and go with that to start. If there's any problems once you get it going the transmission can be fixed with the engine in the bike.

[XS11UFO]

Yep, fat fingers

Definitely XJ into '79 standard. The trans is included so is it geared the same? The electronic stuff sounds like no biggie. Is the engine the same, comp., valves, cams?

[BA80]

Transmission is the same. On second thought though, if you change the timing components you need to change the head and cams also. The are tuned to run together.

Besides, swapping the head will eliminate the YICS ports and you won't have to plug them then.

[DGXSER]

The transmission and its gearing is identical. The engine is very very similar. Not sure of compression numbers, but then almost every year of the XS engine had slightly different numbers for overall performance. Different cams, different pistons in 80-81, timing changes. Etc..

The biggest difference from the XS series engines to the XJ was the YICS system. The XJ has the YICS which basically is a way to equalize engine vacuum across all four cylinders. The biggest hassle is the need to block off the ports to properly synch the carbs. Most folks by the YICS eliminator and leave it installed permanently. Eliminating the YICS system.

The engine will bolt straight up into an XS frame, the same carbs, exhaust, U-joint, etc will all bolt right up. The XJ has an oil level light instead of an oil pressure switch. IT also has the clutch and side stand safety switches.

The XJ uses a vacuum sensor to signal the TCI of engine vacuum and the vac advance is built into the TCI. So you will want to pull the timing assembly off your F engine and put it in the XJ, so it continues to place nice with your TCI. The XJ being a one year model those TCI are harder to come by.

From a performance reference, the F was a stronger engine than the XJ. more powerful timing setup, stronger cams, head, piston combo. The 80's models got detuned a little for EPA purposes. However, I still believe that most of us will never use the full capabilities of these machines enough to notice.

[BA80]

If he swaps the head it should actually have higher compression than the F engine Don. The piston domes are slightly higher on the 82 engine.

[natemoen]

Would there be any interference with the valves due to the higher dome on the XJ pistons?

[WMarshy]

Would there be any interference with the valves due to the higher dome on the XJ pistons?

I have not read anything that confirms interference exists. Only some posts saying compression gains and more smiles per mile.

[natemoen]

I have not read anything that confirms interference exists. Only some posts saying compression gains and more smiles per mile.

No one has ever confirmed or denied that there is interference, that's why I ask. Everyone just say to check for interference when people ask but no one has ever come back and stated results.

[crazy steve]

Transmission is the same. On second thought though, if you change the timing components you need to change the head and cams also. The are tuned to run together..

If you swap the F cams to the XJ motor, that will help with performance when using the early ignition. The alternator is a easier swap; you can leave the XJ unit in place as all the harness wiring is the same, but you do need the matching XJ regulator.

[trbig]

If you swap the F cams to the XJ motor, that will help with performance when using the early ignition. The alternator is a easier swap; you can leave the XJ unit in place as all the harness wiring is the same, but you do need the matching XJ regulator.

If I remember right, the reg/rectifier unit can be used, but the plug ends are different. Same wires, just a different plug shape. I used the early cams on my XJ and it absolutely killed low end torque. Don't know if just a bit of timing difference would overcome that.

And as Nate said.. Using the early head on the the later motors should bump compression up considerably, but as yet, I've never heard anybody posting if there was any piston-to-valve clearance issues.