inquisition for XJ acquisition

[dingleberry]

Hi guys (and girls?). Have just bought another project bike, an XJ650 shaftie (about 1980). I know a few of you have these bikes and want to know about compatability of parts, namely front calipers, tank, rear shocks, master cylinder. There are some 900 and 750 bikes dismantling around my parts, just not sure what will fit/work. I have a kawa440 caliper that bolts up and fits fine but only the one unfortunately. Funny what will fit eh?   

[The Prophet of Doom]

Is that one with the swirly wheels? I quite like them over the XZ's swastika wheels.  I've heard the wheels just swap over, but then I've heard lots of things - most of them bullshit.

Didn't some of those come with anti-dive? That would be cool.

I had a couple of GS's in the day and I never really warmed to inline engines.  They just sound weird.

[jefferson]

I'm not sure which model you have, but I had the 82 Seca 650. One of my major mistakes was selling it. I liked the Vision wheels better than the swirly ones and put a Vision one on the rear, it was lighter too due to a smaller brake diameter, and on the front I replaced the whole front end with one off a 650 turbo. that got me the wheel style I liked and later model brakes. I didn't want to use a Vision front wheel on the front as it was 18" and the stock size was 19" which the turbo Seca was. If you have what we called a maxim I have no idea.

Jeff

[dingleberry]

I have no idea which model it is yet except for the swirly wheels. I'm pretty sure front wheel is 18". POD, I think my RG250 forks are anti dive but probably way too short for a swap over, unless perhaps motor was mounted higher in frame for ground clearance...
As for sounding weird I kind of like inlines. It probably stems from aspiring to own one when I was a teenager in the '80s. But the sound that makes me weak at the knees is a highly tuned vintage single revving hard.

[The Prophet of Doom]

But the sound that makes me weak at the knees is a highly tuned vintage single revving hard.

I've been thinking about this.  What if one was to re-phase the engine by turning the cams 180 degrees on one cylinder.  It would still detonate relative to TDC but only 70 degrees apart instead of 290 degrees.   Perhaps re-phase is not quite the word for it, as I think this usually refers to making the pistons go up and down out of sequence rather than all together.

The bike is wasted spark, and carbureted so no other changes would be needed. Then the power strokes would be nearly together.  It might not sound quite like a single but certainly different.

[fret not]

PoD, that sounds interesting.  I wonder how much changing the firing order would change any balance issues.  Curiosity and questions begin to form.

[Rick G]

Triumph's 900 cc twin in the  Bonniville America, is fired at 270  rather than 180 deg. giving it the sound of a V twin. Your idea sounds like  a reverse of that .

[fret not]

I don't think it would sound like a single but certainly different from stock.  Might be rather alluring.

[Rikugun]

I don't think it would sound like a single but certainly different from stock.  Might be rather alluring.

Maybe it would sound like a Puch Twingle!  ;D   :P

Sound differences aside I wonder about power delivery. The two cylinders fire relatively close followed by a very long lapse before the next power stroke sequence. I wonder if it would shudder when lugged up hills like a single?

[dingleberry]

It all sounds very interesting. I would also wonder about the balance factor but I would't know, its all too scientific for me.
Found out today the XJ I have is the same as XJ650RJ Seca in N.America. Mine has a 750 (YICS) engine fitted to the 650 frame. Apparently this is how they came from factory. Was going to be for the wife but maybe theres some horsepower lurking in there for me

[Rikugun]

Agreed changing cam phasing and engine characteristics on the V is a very interesting proposal but back to the topic I'm equally intrigued by this XJ.

I'd found a Honda 650 Nighthawk for my brother's first bike which he loved. Hydraulic cam followers and shaft drive meant minimal maintenance plus it was a capable fun bike. I also remembered Suzuki had a shaft 650 but I completely forgot Yamaha's 650 shaft drive. I think there was both a 650 and 750 (Seca or Maxim) offered in North America. Is that what yours is, a 750?

[dingleberry]

Yes a 750 in a 650 frame. There were other oddities  according to this website. http://xjbikes.com/Forums/viewtopic/t=14577.html
Sounds like they are good for about 76hp...nice!

[Rick G]

Before you buy an XJ check the price on the rubber valve cover gasket.  its over $100.00  and no amount of goop will seal those things when there as hard a  brick.

[dingleberry]

Paid next to nothing for it as its not quite complete. Is there a way to soften hard old rubber gaskets like this. Soaking in WD40 or oil or suchlike? I read that some people soak old inlet manifolds in oil to make them supple again. Would it be similar?

[Rikugun]

Unfortunately this comes with the territory for most out of production/vintage bikes.  :( There are several XJ gaskets on E-bay running $32 to $54 US. Theses prices are typical of what you might pay for a Vision (also rubber) valve cover gasket too. The only difference - 2 are required for a Vision making the XJ a much better value at twice the cylinders covered for half the price.  :)