XJR rear wheel swap?

[fb747]

I know the forum members from the united states of A, the majority shareholders in fjowners.com don't have many XJR's around but has any one tried it???

From my limited research their a 17 x 5.5 wheel with a 20mm axle, they run an underslung caliper I'm just not sure on the swingarm to swingarm width though.

Here's some pics for your perusing to help me in my quest for rear wheel fatness.

 






Cheers, Ben.

[FJ111200]

The main problem will be getting the front and rear sprockets to line up.
I fitted an FJ rear to the XJR swingarm and then had to make spacers for the rear wheel.
So the other way round and you will need to get an offset sprocket for the front on the FJ. OK , no big deal they are available, but then you will need to get the XJR sprocket cover because it is deeper than an FJ one.
You know it's the old story, alter one thing and then another 3 or 4 things come along and stand in your way.
If you want me to make a few measurements i've got a spare XJR wheel i can use. I sold all my FJ stuff that wouldn't fit when i made my XJR, so i don't have a swingarm to measure from. HTH.

[RichBaker]

IIRC, the XJR countershaft is longer than an FJs....

[fb747]

Would that be a problem if using an offset sprocket though?
Fj111200, if you could get the hub width measurement it would be greatly appreciated. And if you know the caliper hanger width of the top of your head that also would be handy.

Cheers, Ben.

[andyb]

Rich is correct.  But that's only one piece of the alignment puzzle.  Nevermind that your specific frame may be a pinch twisted or the like, and Randy established that the motor mounts can develop enough slop to get the motor twisted a bit in the frame, which is going to cock and relocate the sprocket anyhow.

Like anything else I suppose, start with a pretty known quantity before you start modding, as fixing something else may eventually impinge on something you've modded.

[fb747]

I'm a little confused,

Are you saying I would have to run an xjr countershaft and an offset sprocket to get the chain straight? and in doing this your saying that it might run wonky or on the wrong angle because my engine might not be in straight anymore due to old engine mounts and frame defects?

Thanks for sharing your brainpowers with me.

[FJ111200]

IIRC, the XJR countershaft is longer than an FJs....

Would that be a problem if using an offset sprocket though?
Fj111200, if you could get the hub width measurement it would be greatly appreciated. And if you know the caliper hanger width of the top of your head that also would be handy.

Cheers, Ben.

Yeah Rich is right, it is longer on the XJR, and so is the gearchange shaft, as i found out when building my XJR from an FJ motor, but can't see it being a problem with an offset front sprocket.
fb, the measurements are as follows, hub width on XJR1200 is 18.50cm +/- 1mm,  the FJ is 17cm +/- 1mm,  and the rear brake caliper hanger is 34/35mm plus or minus the odd gnats cock.
It's all if's, but's and maybe's when you're experimenting, but that's half the joy when it all falls into place ain't it?


Just realised, that shorter FJ gearchange shaft could be a problem when using the XJR sprocket cover.

[axiom-r]

I am nearly done mounting a 6" wide R1 wheel on my 92 FJ.  I am also using the R1 swingarm so I did not want to mill down the sprocket carrier as has been done on many other real wheel conversions...chain clearance on the arm would have been too close for my liking.  So...

I bought a 1/4" offset sprocket for the FJ from PBI Sprockets very reasonably at $40.  My stock FJ sprocket was quite thick at the mounting splines- and the offset sprocket was thinner (both are 530 I am referring to the mounting area).  The 1/4" offset pushed the alignment out close to where it needed to be but not perfect because of the thinner mounting section. So, I had a spacer made to make up the rest of the distance needed for offset. For my particular mod the spacer was 2.32mm set in behind the 1/4" offset sprocket.  I calculated the spacer depth to leave .9mm for the bolt retaining lock tab washer to seat on the countershaft splines.  The lock tab washer does not fit into the offset "well" on the face of the sprocket so I will have to grind the tabs down a bit to work properly.

I never was able to get "a measurement" of what the offset needed to be- that would be rocket science and no method I could think of was one I trusted. Instead, I mounted the wheel and the new sprocket without the lock nut- so the sprocket was "floating" on the countershaft. Then, with chain on, I spun the rear wheel until the countershaft sprocket settled into where it wanted to be.  For my install- this was all the way to the outside edge of the countershaft.  So all I needed was the spacer I made....  And the the counter shaft sprocket effectively rides 1/4" offset to accommodate the 6" rim.  

So- my two issues were: 1- the replacement sprocket was not as thick as the stock FJ unit at the mounting splines.  2- Guess what offset would be close to accommodate a 6" rim?  My approach was to just get close on the offset and then make a spacer for behind your sprocket for final positioning.  I have a friend with a lathe and was able to have the spacer made to spec out of hard steel.  I was prepared to buy a few offset sprockets of various offsets to find the right one if needed- I just got lucky and the first one- 1/4" was close enough for me to work it out with the spacer.

I have not yet remounted the sprocket cover fully- but I have pushed it into place and peered in from the back.  There is a cad plated metal piece bolted into the inner side of the cover and I may need to remove one or two of its mount bolts or replace them with a shallower head fastener... the clearance is close but not contacting.

If I end up with trouble on the sprocket cover I intend to install one that I saw here made by Coerce from billet aluminum and providing tons of clearance.  I hope to have my bike look OEM at the end of the day so the custom cover is my last resort...

I will be updating my mod thread soon with pictures etc..

You should be able to get that wheel on your bike.- Good luck!

tim

[racerrad8]

I have not yet remounted the sprocket cover fully- but I have pushed it into place and peered in from the back.  There is a cad plated metal piece bolted into the inner side of the cover and I may need to remove one or two of its mount bolts or replace them with a shallower head fastener... the clearance is close but not contacting.

If I end up with trouble on the sprocket cover I intend to install one that I saw here made by Coerce from billet aluminum and providing tons of clearance.  I hope to have my bike look OEM at the end of the day so the custom cover is my last resort...

I will be updating my mod thread soon with pictures etc..

You should be able to get that wheel on your bike.- Good luck!

tim

Tim,
   The XJ sprocket cover is wider and will bolt right on. You will need to change the shift shaft and the clutch push rod to the XJ version as well. The XJ trans is 8mm wider as well as the side cover, shift shaft and pushrod to compensate for the wider wheel of the XJR1300.

IIRC, the XJR countershaft is longer than an FJs....

8mm

Randy - RPM

[FJ111200]

Randy,
the clutch push rod is the same for the FJ and XJR. I've rebuilt an FJ to XJR spec, and the only differences are the main axle shaft, or countershaft as you call it, the gearchange shaft and the sprocket cover.

[axiom-r]

Thanks Randy- great info!  But I am hopeful that I can make minor or no modification to the stock cover and have it work!  If not, I will certainly look at the XJ parts.  Is the shift shaft an easy change out?

tim

[FJ111200]

I tried to make the stock sprocket cover fit, by taking out the damper, but it's just too narrow.
The shift shaft is easy to change, but to gain access to it you need to take the complete clutch and boss out.

[racerrad8]

Thanks Randy- great info!  But I am hopeful that I can make minor or no modification to the stock cover and have it work!  If not, I will certainly look at the XJ parts.  Is the shift shaft an easy change out?

tim

Tim,
        You have to remove the clutch assy at change out the shift shaft, not hard. Let me know if you need parts, I should be able to come up with everything used.

Randy,
the clutch push rod is the same for the FJ and XJR. I've rebuilt an FJ to XJR spec, and the only differences are the main axle shaft, or countershaft as you call it, the gearchange shaft and the sprocket cover.

Believe me when I say they are different; I have rebuilt hundreds of engines and they are definitely different by 8mm. Something has to compensate for the additional width of the cover which also moves the slave cylinder out by the same amount.

Randy - RPM

[FJ111200]

Yeah mate, i must have forgotten. 

[racerman_27410]

the XJR wheel is 5.5" ?

the FZ1 wheel is the same width...... using the honda VF1000R countershaft sprocket you should be able to get the chain to line up with that wheel.

just machine the outside face of the sprocket flush and you will still be able to use the locking ring and nut.


maybe a slight bit of clearancing behind the countershaft cover but everything should work.


only issue i see is fitting the wheel in the FJ swingarm (i just used the entire FZ1 rear end)


KOokaloo!