1971 xs 1b, xs1f

I have bought an abandoned project, frame only, no forks which has a hard tail tacked on. The serial number is S650-0135xx which makes it an XS 1F. I see lots of examples of the XS 1B, but none of the 1F. Why were there 2 model designations in one year? Did the later numbers in that year have an electric start?
I was not able to refine the search engine tight enough, or I was asking the wrong question.

I'm very curious about this as well.

Our resident model historian here is 650Skull, he might be able to shed some light on this. But, I'll give it a try. From what he's posted in the ID thread, it appears that the B and F models occurred simultaneously, with the B model for U.S. markets and the F model for Europe. The only major differences I could find, in pictures and other posts, were subtle changes in the turn signals.

In the later half of the B production, the camchain adjuster changed from the 4-hole type to the 6-hole type, but retained the 4-hole cylinder mount. Don't take this as gospel, but since the vastly updated XS2 was being developed at this time, I always suspected that Yamaha decided to implement its newer tensioner design early, and possibly would've re-labled it as the 'F'.

The XS1F was sold in Australia and some European countries (but not England).
XS1B was US model only. (In Japan they called it the XS650).
The first approx 3000 were XS1B and after that they were sold simultaneously. So your bike is likely an XS1B.
The differences are cosmetic only. I'll try to list what I remember;
The XS1F has a rectangular style tail light similar to the XS1 whereas the XS1B has a round tail light.
The XS1F has yellow rear turn signals whereas the XS1B has red rear turn signals.
The XS1F has the front turn signals mounted on the sides of the headlight whereas the XS1B has the front turn signals mounted on top of the forks.
A less known difference is that XS1F came with two colour options, either candy green or candy orange whereas I think the XS1B only came in candy orange. The XS1F candy green tank had different stripes to the XS1 candy green tank.

Here are pictures of what I am talking about. I am limited to the VIN on the neck for ID as nothing much else is there. The hard tail is set up for a 200 tire with a jack shaft installed. It is only tacked on.
On a separate thing, last month, I went to buy some parts from a guy and there was half a bike sitting there, so I brought it home. I could probably take the hard tail off the 71 portion and add on the Special rear and have a frankenbike
Looks like a future project to me.

Looks like only the neck / front of the chopped frame may be XS1B.
The half rear etc in the pictures is not early stuff.

You are correct, the freaky half bike is a 78 or 79, sorry to confuse the post.

Update:
Some time before Christmas, a fellow answered my ad and came and bought the XS 1 bare frame. That was just going to be too much project for me, so I am glad it went to someone who had a plan.

As a matter of interest, I have been watching for ads for XS 650's for 2 or 3 years and have bought several for retirement projects. I have not seen a cheap one listed since the summer; most are allegedly rebuilt or cafe'd or bobbed and all are over 2 g's. I wonder if they are getting scarce or if the market demographic has left the building.

Do the internals from a 1978 XS650 fit a 1972 crankcase

peter benders said:

Do the internals from a 1978 XS650 fit a 1972 crankcase

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The earliest bikes did not have an electric starter and I assume you are referring the engine cases.

They do, indeed, all look very similar, but some of the internals changed in <I think> 1974 and the key difference was that the number of teeth on the crank and camshaft timing chain sprockets changed. If you keep in mind that crankshafts make two revolutions for every one camshaft revolution - in ALL ENGINES of any type from lawnmowers to Rolls-Royce Merlin’s - then you will see why that alone is a crucial change.

Anyhow, the key outcome is that you can not mix early and late model crankshafts and camshafts.

Pete

PS: welcome from Canada’s sunny southern coast in Windsor, ON.

Also the 256 (early) rods are a different length than the latter rods (447). Pistons have to match the rods. There were some euro engines with a different rod (556?) that was even different from those 2. As Pete said the cam and crank sprockets have to match. 2 different cam chain pitch and lengths.

peter benders said:

Do the internals from a 1978 XS650 fit a 1972 crankcase

Click to expand...

Yes.......If you are changing over every thing, crank,rods and pistons from the 78, (447 engine), then as mentioned the cam has to be changed as well...........If the XS2 cam was retained the XS2 cam sprocket can be removed and the 78 Cam Sprocket installed on the 72 cam..........

The 72 gears can be left in the 72 cases ..... or the 78 gears can be shifted over as well. Because the 72 has electric start the cases were the same from 72 - 83