Newbie Model ID Question

[RoadGlide]

Hey guys, new to the forum. I am afraid I have been hood winked. Heres the back drop. So I purchased a 1979 XS 650 a few weeks ago. Sight unseen cash no title. The bike has been titled and licensced in my state back in 2005 my local office tells me to get a bill of sale and go from there, no big deal.
Anyway... I am now getting the bike torn apart trying to figure out what I have. The frame sticker states built 1/80 frame stamped 3G0-XXXX. So my 1979 is a 1980? I have just got the motor out of frame and seriously degreased. And I am surprised to find the serial # on motor ground down (looks to be done with with a die grinder) Maybe my eyes trick me but I swear it start with a 2. So I take the valve cover off...256-11191-00. Clutch Basket sidecover 256-1 and Stator sidecover 306-15411-04.
The next question will be if the heads I bought off a 1977 will fit this motor? I noticed 2 vacuum valves are not on the head I purchased that I have on mine.
I know there is someone who can help me decipher this. Any help is greatly appreciated!
Nick
p.s. This is the crappy cell phone pic I took when I brought her home.

 

[5twins]

You appear to have an '80 Special II bike with an XS1 or 1B motor swapped in. If it is that motor, there would be no electric start and all 4 valve covers would be held on by 3 bolts (well actually 3 studs w/ acorn nuts). The side cover in your pic is definitely XS1 or 1B. The mounting bolts on the little round oil filter cover being at 5 and 10 o'clock was exclusive to those early engines. All later ones have them near horizontal, like at 3 and 6 o'clock.

 

[RoadGlide]

Thanks for the quick reply. When I was reading through the manual I found it "odd" I couldnt find the starter. That is when I knew something was off. This bike also had the 1979 points ignition and complete wire harness. I was told by local bike nut that between model change years this was common. Maybe not? I have a couple pics I'd like to show you.

If you notice the hose ran from one cylinder to the other, is this a some kind of equalizer or jimmy rig. I noticed on the newer head I acuired there is no such ports. I ordered replacement because the exhaust manifold stud had ben completly broken and someone attempted to either weld or jbweld it back together. New one is off a '77

These were the carbs installed on bike. I am not near my shop now but I swear they were tied together (no splitter inline) does anyone know if these are original to '80?

 

[Splexin]

+1 to 5twins ^^^^^^^^^^^^^^^^

If it weren't for the sidecovers I'd say I've found my long lost twin!!!

Didn't mean to hijack a thread, thought this was uncanny.

I will have to look at my carbs but think you're talking about a mix line?

 

[5twins]

The balance tube between the intake ports was also an XS1 and 1B feature. Later bikes don't have it. The carbs are BS38s but that's all I can tell you without more info or pics. They were used up to '79. In '80, they changed to BS34s. The '77 head will probably work but if it came complete with the cam, you can't use that. The cam chain and the # of teeth on the cam sprocket changed from the early to later engines. You would need to use the cam that came in the XS1 motor.

 

[RoadGlide]

Thanks 5twins. I am now realizing I would need different valve cover and tappet covers. It may be easier to find an earlier Head to replace mine. I got a little carried away on ebay... I should have done my homework.

 

[5twins]

Any head you buy, make sure it comes with it's top cover. The 2 parts are matched and machined as a set. They should have matching numbers stamped on the front .....