XJ and XS engine interchangability.

Looking at a pile of Yamaha parts i have , i have decided i would like to put together a bike over the warmer months.
I have the registration document for a XJ900 and i can collect the matching frame if i want it, I have two xS1100 engines drives and wheels suspension and forks for xs1100s and XJ900 and tanks panel's seats and most other parts.
I am short of an XS1100 frame with any documentation.
I was told the XJ1100 and XS1100 frames are similar and interchangeable.
What i would like to know, is are the XJ900 frame and the XS1100 engines interchangeable please?

 

The 1100 is physically bigger than the 650-900 motors.
I've never seen an 1100 in the smaller XJ's frame, probably a reason for that.

 

Thank you, that is the sort of information i needed thanks.

 

If you are reasonably competent at fabrication and welding, the 1100 engine will fit into a 900 frame. It might not be a good idea though.

 

Why is that? I've wondered about that for some time?
I'm pretty owkay at welding and such. I used to have an XS1100 ('79) that is a truly great motor IMO.
Cheers, 50gary

 

I remember the XJ900s back then, i remember hearing they were not great handling bike at the time.
the XS11 was a bit of a handful too, I am not sure how the 900 frame would behave with the 1100 in. How much heavier is the 1100 compared to the 900s.

 

Weight is'nt the issue, frame stifness is. The 900 handled fine for what it was, it just wasn't the latest-greatest in frame design so the reviewers were pretty harsh.
Honestly I'd hesitate to put the 1100 engine in a 900 frame without having someone who is familliar with chassis engineeering consult on the project. I'd tend to want to overbuild the reinforcment of the frame, and that would likely squash any benefits of the HP gain.

 

Yes the 900 was rated as mediocre, but it's a long bike, with a fair old rake. The frame is from much stiffer tubes than the 650/750, but my guess is the length negates this. Checking and reducing flex isn't hard, and shouldn't add much weight. But, you would also need stiffer front tubes and better rear shocks, otherwise you're wasting your time.
A simple job might be quite involved, but it depends how fast you want to go....

 

Agreed. As an example of my tendancy to overbuild; I did consult with an engineer when I built my trailer, and still decided to add the triangular sections to the tongue. Not a lot of extra weight in terms of numbers, but in terms of percentage of the whole thing it was quite a bit. I think that if I did that engine swap the bike would end up weighing more than the tires could handle
(I exaggerate).

 

Thanks . I am rapidly going off the idea of 1100/ 900 and frame mods. A XJ 1100 frame with a reg document is the way i feel makes most practical sense.
I am going to pick up the 900 frame tomorrow, I will keep it until i find an engine.

 

I suspect the 1100 is too long, too wide and too high.
Modifying it to fit would be a scabbed mess.
An 1100 frame would be a brilliant solution.

 

Wrecker, when you get the 900 frame, contact me via private conversation. I’d like to get the frame number onto the 900 database in case it’s not already on.

dave Fox

 

in Canada the 900 had a little sister with a 750 motor in it.
maybe a 700n motor would bolt in untill you found a 900 motor

 

Will do. i did not go down for the frame It turns out he has an engine but not matching the frame, he sent off the log book in my name its 900 think he said 853cc . Will check when the book comes back.
Looks like i still have a 1100xs frame shortage, but i gained a free XJ900, admitted not very much of a xj900.
Be picking it up once he digs out all the XJ stuff.

 

Talking to another mate he said the XJ1100 emgines should have YICS on the cam box cover. Both my engines are devoid of YCIS on the covers so as thought must be XS1100s but i have a cover in the parts pile with YICS embossed both sides , will this be off an 1100XJ or did some XS11s have YICS too. ? Finally what exactly is YICS.

 

From service manual. Courtesy of Yamaha.

 

Easiest—- show us a pic of the engines. We’ll tell you what they are.

 

there will be a bolt on both sides of the head/cylinder near carbs it is the yics port no bolt not a yics motor

 

Norfolk which side of the Atlantic are you on?

 

YIKES!: ALL ABOUT THE "YICS" SYSTEM.