I get questions about Virago engine swaps which I have been answering individually, but I have promised an article on this subject so here it is.
When it comes to tasks like this, I am always more comfortable speaking from personal experience-projects/procedures I have actually done in my garage. So lets be clear that my personal swapping experience consists of swapping 920 engines in 920 frames. However, I have talked to a number of people who have swapped engines from different Virago models, across years, and between old-style frames (’81-’83) and new style frames (’84 and up). So I’ll give you my best shot at this, but unless you are swapping the same engine from a similar model, I’ll have to say you need to verify things for yourself before you start laying out money on E-Bay.
My belief is that Yamaha did not alter the external dimensions of the bigger Virago engines and that any 750 (early to late), 920, 1000, and 1100, will bolt up to any of the early (81-’83) and later (’84 on up) frames, and plug into the rear drives O.K. In other words, can be swapped. I cannot verify this personally, but I believe this to be the case.
But that is just the start. Other considerations are:
Carbs can be different, particularly for engines of different sizes, where jets, needles, and even springs, will/maybe different. So, you should try to get the carbs that go with the engine you are going to swap in. Also:
• Early carbs and later ones differ in terms of throttle cables (single versus dual) so be ready to handle this.
• Early carbs and later ones differ in how they route their breather pipes. This canA take some fiddling.
• Early carbs (’81,’82) take different carb holders from later carbs. Try to get the holders that go with the carbs. You’ll need to watch this, and make sure you use the right ones.
NOTE: Mikuni carbs can be mounted on older engines that had Hitachis. The right carbholders have to be used, and differences in engine sizes would probably require some carb tuning.
TCI’s AND ELECTRICS
TCI’s can vary a bit in advance curves and they also can have different pinouts and connectors. Try to get the TCI that came with the engine you are swapping in, if it is different from the one you are pulling out.
In later models Yamaha changed the grounding of their ignition pickups. Earlier ones had two wires coming from them and later ones grounded to the engine and had one wire. You want to check this, and make sure your TCI is compatible.
The smaller engines (750’s and 700’s) were serviced with a gravity feed set up. 1000 and 1100 engines had fuel pumps. While I would guess that the bigger engines could work on a gravity feed set-up, it would be nice get the fuel pump, fuel pump controller, and fuel lines along with any big engine you plan to install. Later frames have tabs for mounting fuel pumps, and you’ll see them (unused) on some later 750 frames. If your wiring harness isn’t set up for fuel pumps, you’ll be into some electrical work. See the article (last half) on Virago fuel systems.
That’s about all I can think of. My main point is that swaps aren’t quite as simple as “out with old, in with the new” unless the engines being swapped are out of similar models. Beyond that expect to need some creativity and do some fiddling (motorcycle mechanics) to make them work. Comments from successful swappers are welcome.