Just wondering if this can be done relatively easily. wondering about things like: Will the 650 exhaust bolt to the 750 ok? any mods I will have to make? as far as rejetting my carbs to work with the 750, do i just buy some 120's? I think that is what yamaha specs for the 750 carbs.
Input would be great, especially from someone who has done this. (only reason I am wondering is that I can get a 750 YICS motor for pretty much Free.)

nobody knows eh? :wacko:

Not sure if this helps but one of the MAC exhaust systems specifies it fits both the 650 and the 750. That means to me that they'd have to have the same exhaust port spacing and simular mount points.

If the exhaust pipe is the same diameter it should flow the same (unless you're going from the stock 4-2-collector-2 system to a 4-1 pipe). If you have the same exhaust flow then the jetting should be the same.

Never done the swap, just saying that I did see MAC list the same pipe for both bikes.

for those who were wondering too, It can be done. Actually it was very easy. everything on the motor is pretty much exactly the same aside from the shift pedal, which is easily remedied by useing the 650 shift pedal linkage and cover. Another problem I ran into was that the 81 xj650 uses the cam to drive the tach, where as the 750 YICS uses an electronic tach(wanted to swich to the other cluster anyhow). other than those things the engine drops right into place.

Thanks for the report. I did this on a KZ 650 to 750 and it was even easier since all that is different is the jugs.

I take it the 650 was not YICS?

no, the 650 wasn't a YICS.

I have seen a Seca 650 with a Maxim X engine installed in it as well. I'd like to find one and put it in my bike, or a 900. then put the turbo on that!

Best thing to do is to order the XJ CD and then start comparing part codes. To the best of my knowledge, for example, a 1982 Maxim 650 engine is very similair to a 750 engine for components, shaft, etc. If you're doing a swap, ensure you have the carbs from the 750. The shaft, gear box, etc, all should be the same. The only diff from a 650 to a 750 is just the engine block size (I think).

If you get the CD, you can then do a parts # comparison to see what are the same etc.

More than a few people have put 900 blocks, heads and cranks into a 650 Turbo bottom end. A guy on the TMIOA website has had several 900 and 750 motors in his Seca Turbo. The 900 cranks will drop right in, the heads will bolt up, and the 900 barrels will fit with some mild resizing with a die grinder. These are his words, I have no direct knowledge or experience with these mods, although the end results have yielded 136 hp at the rear wheel when turbocharged. Also, non-radial braked R1/R6 brake rotors, and some VMax rotors, will bolt right onto a 650 Turbo front wheel with no modifications, the bolt pattern and spacing is exactly the same. I don't know if other Secas and Maxims would have the same pattern, but it's worth investigating. There are enough "R" bikes getting wadded up and modified, that rotors turn up on Ebay regularly and cheaply. Brakes on the Turbo are woeful, as I think they are just Maxim 400 units, doubled up. R1/R6 calipers can be made to work with an adapter plate (up to you to engineer them though). Anybody have any other swaps they know about? The 750 Maxim tank on the 650 is a useful one, I never heard of that one before.

Hang on here - will the 750 maxim tank bolt directly up to a 650 maxim???

Is it larger? Searching google presently but if there was anyway to put a larger tank on the 650 maxim I'd love to do it... 10 Liters plus 3 reserve is very limiting!!!


(EDIT)

The 750 tank is 4.8 gallons or 17.79 liters... that's an extra 4 liters. Or is it an extra 7 liters?


either way that is a swap to consider!!!!

The 750 Block is exactly the same size as the 650 block. I measured them both top to bottom, side to side, and width. the only difference between the engine that was originally in my bike was that it was not a yics motor, so the tach was mechanincal and some of the wiring is a tad different. Oh, and i had to use the main jets out of some 750 carbs. the 650 uses a 110 main jet, and the 750 uses a 120 main jet. the pilot jets are the same. as far as i could see, from tearing down the 750 carbs, they are identical to the 650 carbs aside from the different main jets. So, If you want to do this swap, just buy 120 main jets rather than buying a whole set of 750 carbs(unless you can find em cheap).
Other things I am gonna swap are the adjustable rear shocks from a 750 seca, as my ol' 81 maxim doesn't have adjustable rear shocks. I was also thinking of swapping over to the 750 seca front forks for adjustabillity, and the dual disc brakes.

You may have to swap out the oil level sending switch. The computer display models of the 750 had a digtal switch & the analog switch was on the 650's. If you are using your 650 gauges use the same switch. It is mounted under the engine on the port side and mounts into the bottom of the engine. May not be able to get to it after the pipes are on. Difference between the two is the digital stays on to send a constant current to the computer for monitoring and the analog stays off since it only needs to light a blub. That's why my oil light stays on until I get low and it tells me by going off. Of course it works for a bassackwards guy like me. ;)

yes, the 750 tank does bolt right on to the 650 frame.

On the Maxim models the 750 tank will go right on the 650 with no modification. Several XJers have done this and really like the extra fuel and range.

Just checked it. All you have to do is swap out just the engine and carbs. The gearbox, etc is all the same.

Now, all you have to do is find one. :blink:

why stop there? there is NO substitute for cubic inches,....or should i say cubic centimeters. why not swap in the xj1100 motor? just for _ hits and giggles :o :D :unsure:

There is a really nice one on ebay right now...
Item number: 4570635935