motor swap

[bp.leep]

I know this is a complex project but I have a 99 m750 carb bike and need to know what issues i would have swapping the motor for a 93 900ss carb (i have complete bike) and can i use my m750 swing arm or do i have to use/easier to use the 900 swingarm
basically i want the dryclutch 6sp 900 motor in my monster
i searched all threads and havent come up with an answer
or if someone can point me in the right direction

[ducpainter]

I'm pretty sure that is a bolt in swap...swingarm included. The only thing that may be different is the engine mounting bolt size, but I think they're the same. I'm not sure of the year they changed. If they're different the monster  bolts would be larger and the 900 cases would need drilling. The only other difference might be the alternator, but that would just mean swapping the regulator also.

You'd have to use the monster swing arm or do a bunch of fabrication on the monster frame to use the SS swinger.

[junior varsity]

I think the engine bolts are the same. My 99 M900 came with the threaded frame ends on one side you have to drill out to use Nichols bolts. I think those are/were the smaller bolts.

[bp.leep]

The swingarm sounds good i dont really like the way the 900ss swingarm looks anyway.
So just drill the cases for the swing arm and the motor is a direct swap sounds good.
why is the alternator a issue?

[Ddan]

I don't think the alternator will be an issue, IIRC, the monster didn't switch to 3 phase until '00

[junior varsity]

99.


EDIT:  98. My source of info would be the listing for Nichols Flywheels:
1p Carb'd Flywheel = Pre 1998 Monster 600/750/900, SS, Paso
3p Carb'd Flywheel = 1998 up Monster 600/750/900, SS.

All -ie Monsters and Supersports get a 3p system.

(I only knew this because I had to sort it out when I went to get a flywheel for my '99 M900).

OP, Does your donor Monster frame have an aluminum or steel hooped swingarm?

[bp.leep]

from your specs above it looks like the 93 900ss is 1p and the 99 m750 is 3p
(i have a complete donor bike 900ss)
so there should be no issue as long as i keep everything on the bike 1p right

[bp.leep]

the swingarm is steel i would assume the hoop is the same

[junior varsity]

It definitely is a 1p --> it has a small side alt case, you'll notice it looks different.

I have the aluminum version on my M900 (99) that would bolt right up. This winter I'm planning on tearing the bike down, and putting on a fancy schmancy aftermarket swingarm. Let me know if you'd be interested in upgrading yours to the lightweight version.

[bp.leep]

how would the 1p affect the swap into the m750 frame

[junior varsity]

Not going to affect the frame. You'll just need to make sure to bring the rectifier regulator along with it. the electrical system needs to come from the 1p donor bike.

[bp.leep]

so the motor is a direct swap (meaning the holes will line up) and the swing arm is also a direct swap?
sounds like the only possible issues about fitment are worst case machining cases for swingarm and frame

[junior varsity]

I don't think it will be an issue. The bolt holes for hanging the motor seem to be identical across the board, only difference is the newer/newest Duc's use a larger diameter bolt (and thus the hole is a wee bit larger).

Similarly, the swingarms mount up at the same location of the motor, use the hardware from the monster to bolt up the monster's swingarm to the supersport's motor.

[brad black]

the engine bolts changed in 2001, yours will be the same.

you'll need 900m headers, the ss ones are different thru the swingarm and the 750 ones don't really fit due to the 900's longer cylinders.

use the 750m swingarm, goes straight on.

the 900m seem to use larger jets than the 900ss if you run open airbox, otherwise they're much the same.  i'd probably fit the 900 carbs, as they are slightly different internally between models and capacities aside from the jets which you can swap.

the 3 phase regulator (3 yellow wires) in the 750 will be fine with the single phase alt (2 yellow wires) in the 900.  just leave one of the yellow wires from the reg unattached.  don't use the flat blade connectors though - they burn out if used with single phase alts.  use round "bullet" style and heat shrink them individually.

that's all i can think of.  you may need to move the front sprocket in a little - not sure if it will line up with the sprocket on the narrow rear wheel.

[junior varsity]

You might be able to swap the wheel over. The SS used a 17mm rear swingarm that year I think, dunno about the 99 750, but my 99 900 has the same dia axle. Not sure if there would be any other issues, but since the speedo is off the front wheel, there's not much else.