84 750 in an 82 650?

Ok so I have searched but I can't find much that specifically answers my question but people here know SO much...

We have an 82 seca 650 (non-turbo) with a toasted motor. not worth it to rebuild. If we are swapping anyway, might as well put in a 750. SO...


Will an 84 seca 750 drop in? shifter issues? carb issues? CDI issues? other issues?


And if not, what model years of 650 can we use?

Thanks

-Tom

 

I'm sure a more proficient member will be along soon, but I believe the short answer is that a 750 engine will not just "drop" right in. I believe there are some wiring differences and pretty sure there are some jetting differences in the carbs as well. I know from maxim 650 to 750 the 750 carbs have bigger jets in them. Hope this helped you. If you do the swap, be sure to put up plenty of pics of all the steps? I've seen people ask about this type of thing many times. Seems most concluded the small increase in power wasn't worth the effort and money it took to do it.

 

You should swap out the TCI and if you use the 650 carbs rejet them.

The 750 transmission is shifted by a linkage from a frame mounted pedal, as opposed to the shifter being mounted directly to the shift shaft like the 650. If you just stick a shifter on it it'll be far forward and be a 1 up 4 down shift pattern.

 

I think the pickup wiring and oil sensor are different also.

 

Thanks for the input! From looking at pictures I understand that the SECA models have the case-mounted shifter & linkage, and the maxims have the frame mounted shifter, so I think I may be OK there since both motors are Seca. If not, I may have to shorten the shifter and ride GP style!

I'm not too worried about sensors and e-tach, we really just need a bike that we can ride.

What size jets should I be putting in the 650 carbs? And how big is the difference in TCI? Will it run on the 650 TCI for the time being?

 

I bet u can switch the jugs!

 

Well, the 84 seca 750 motor has been purchased! Wish us luck, and if anyone who's done this before has any wise suggestions, we are all ears!

 

The ignition should work "for now" and the shifter shouldn't be a problem.
I've heard there's a rear motor mount bolt length difference, but you'll figure that out easy enough.

You'll need 120 Main jets, but if you plan on custom exhaust or Pods, this would be the perfect time to figure out what larger jets you need.

 

Awesome, thanks for the info. We do have pods on it and a jobber OE-style exhaust. So I guess we'll start with 120 jets and experiment.

 

picking up the engine next week! XD

 

Well, we put the engine in, and so far the results are excellent. The oil sensor plug is different, but a splice of the 650 plug onto the 750 harness works as the colors all match up. the extra wire only goes from the 650 ignition box, through the plug and back into another part of the 650 harness, so no issues there. mounting points, shifter are the same. used the 650 starter and engine side covers with no trouble. We had some trouble with getting the 650 carbs into the 750 boots, not sure if they are spaced differently but were eventually able to get them to mate. had 120 jets in the carbs from having pods and exhaust on the 650 and it was a bit rich, so we used the same setup on the 750 and it seems to be just about perfect. Overall, well worth the $400!

now, what to do with all these spare 650 engine parts??