750 on a 650 Maxim

Would a 1982 XJ750 YICS engine fit on a 1981 XJ650H frame. If not, do you know what the differences are? I was told by the seller of a 750 engine it would be a bolt on fit, but I wouild like it verified by the experts here. Also can I use the 650 carbs on it or does there have to be changes made to the jets?

 

It will physically fit and bolt right in, but you'll run into a couple of accessory issues that you'll have to solve:

1) the '81 XJ650 uses a mechanically driven tachometer, and the 750 engine does not have the provision for the tach drive unit on the block. You'll have to get a tach from an '82-83 XJ650 (same physical size and appearance as your '81 tach) which is an electrically driven tach, and splice it into the wiring harness properly. You'll need to look at the wiring diagram for an '82-3 XJ650 Maxim to see how it's wired and make up a small harness.

2) The shifter mechanism and cover on the XJ750 is completely different than on your 650. You'll have to save the cover and all the hardware "outside" of the cover from your 650 and bolt it onto the 750 engine.

3) The carbs are the same except for the main jet Needle, the main and pilot fuel jets, and the main and pilot air jets, which you'll need to replace or swap. You''ll want the 750 sized pieces in your carbs!

4) The airbox-to-carb rubber Boots are different, you'll have to save the ones from your 650 and use them.

5) Although I don't know whether it'll make a big difference, the ignition advance curve contained within the TCI unit is slightly different between the 650 and 750 engines. So if you can snag a 750 TCI unit that would be a plus...

 

Thanks so much for the reply. I knew this was the right place to ask. I hope the swap will be worth the effort.

 

Here is to hoping for you! Good luck.

 

CHACAL: That was an excellent summary of the differences in the swap.
It brought back memories.