DOHC's blue Z1R Refresh

Back to the bike.  The last big task was getting the carbs on.  As I posted earlier, I had completely rebuilt the carbs but I had not set the float levels.  I made a simple stand and found a metal typing table that I didn’t think would mind getting gas all over it.  In the end it didn’t take as long as I thought and didn’t make as much of a mess as I thought.  I think they are pretty close to where they need to be.



I also added drain hoses and spring clamps that are close to the OEM style.  I never had drain hoses on these before.  I got the hose from amazon, and the clips from JetsRUs.com

www.amazon.com/gp/product/B01LVUEGID
www.jetsrus.com/individual_parts/JRU-9007.html (this should be K&L 33-3923)



Next up was the new OE carb mounting boots and airbox boots from Partzilla.  I also got new clamps for both.  The clamps are made by PMC, and both fit fine.  I also replaced the mounting screws while I was at it.  I mostly stick to OE fasteners, but I have this idea that I’ll replate the original screws and reinstall them later.  Maybe?

www.z1enterprises.com/airbox-boot-clamp-92037-061.html
www.z1enterprises.com/carb-holder-clamps-z1-kz900-1000.html
www.z1enterprises.com/carb-holder-allen-...of-8-6mm-x-18mm.html

I never had an airbox on this bike. It came with pods.  I was not looking forward to installing the carbs with the airbox in the way, but it actually wasn’t that bad.  Easier than a KZ650 or ZRX1100.  Once I folded the airbox boots back over themselves, there was plenty of room to install the carbs.  The one thing that seems less than ideal about this method is that you have to install the airbox clamp rings after the carbs are in place.  They don’t really look like they are intended to be opened and stretched that far.  But they seemed to mostly go back into shape and went on fine.  I’m not sure how many on/off cycles they will survive though.

Really close to Zoom Zoom.

wrote:

Really close to Zoom Zoom.

I've actually been done for a few weeks now.  I'm just trying to catch up with the pictures and story. 

The other part of refitting the airbox was finding a new home for the Dyna III igniter and rev. limiter. When I put those on 10 years ago I made a plate that mounted where the intake silencer lives, using the silencer mount tab and the two screws for the battery retainer. I was pretty happy with this little plate, but it had to go.

My new solution is much lower effort. I zip tied the igniter to the silencer, and plopped the rev. limiter in the tool tray. Simple. Maybe effective? We’ll see.







The last photo shows the new OE silencer mount screw and lock washer and plain washer I paid too much for.
 

I'm enjoying your thread!  Thanks for all the nice photos!

Big fan of Roadrider tires here.  Is there a reason you choose a 80 profile vs. 90?  

Nessism post=853693Big fan of Roadrider tires here.  Is there a reason you choose a 80 profile vs. 90?  

I thought really hard about this. Now that you've asked, you'll see what I meant when I said "I got all balled up in this".

As I mentioned before, I was trying to avoid choosing a tall rear with short front, because I didn't want to reduce the small trail of the Z1R.

All the numbers below comes from here:  
www.avontyres.com/en-us/tyres/roadrider-mkii
www.bridgestone.com/products/motorcycle_...oducts/detail/pr015/

Once I settled on the Roadrider mk2, there was really only one front tire that I thought would work.  The 110/80 and 110/90 seemed too wide, at 111 and 116mm wide respectively.  I didn't want any issue with fender clearance.  I measured my old ME33 front tire width at about 109mm.  The RR 100/90-18 is listed as 108mm, which seemed like it would work fine.  And I got the V rated version just because...

For the rear, there were three sizes I considered.  The 120/80, 120/90, and 4.00-18.  Looking at the actual dimensions:

Name      Actual Width (mm)      OD (mm)         Ref. Rim Width
120/80          120                         652                   2.75"
120/90          129                         675                   2.75"
4.00-18         116                         671                   2.5"

The 120/90 is actually 129mm wide.  This seemed too close to the previous 130 I had on my bike that chewed up my chain guard.  So that left the 4.00-18 and the 120/80.   The 4.00-18 is both narrower and much taller than the 120/80.   Of course, those measurements are taken on different width wheels.  So a 120/80 on a 2.15" wheel might be very close in width to the 4.00-18 on a 2.15" rim.  But if I went with the 4.00-18 I'd have a high rear end, which would reduce trail.  So the 120/80 seemed like the best option.  Of course, the 120/80 isn't actually recommended for use on a 2.15" rim.  The minimum listed is 2.5".  But I didn't like the other option, so I went with it.

The other detail I was thinking about was how these sizes compare to the OE tires.  I have no true dimensions for the OE tires, but the BT45 is available in the old inch sizes, and I used those dimensions as a reference.

Model                     Size                         Actual Width (mm)       OD (mm)           Ref. Rim Width
BT45                      3.50-18 56H W                 104                       651                     2.15"
BT45                      4.00-18 64H W                 119                       673                     2.15"
Roadrider Mk2       100/90 - 18 V                   108                        642                     2.5"
Roadrider Mk2       120/80 - 18 V                   120                        652                     2.75"
Roadrider Mk2        4.00 - 18 V                      116                        671                     2.5"


Again, these are not measured on the same reference rim width, but the RR sizes I selected seem in the same ballpark as the BT45 in terms of width.

The overall diameter of the RR front is about 1cm shorter than the BT45, where the OD of the RR 4.00-18 is pretty much the same as the BT45 4.00-18. 
If I went with the RR 4.00-18 rear I would very likely have lowered the front end and have less trail than with the OE tires.  This was a second reason why I went with the RR 120/80-18 rear.  In the end I probably ended up with a lower rear end than the OE configuration, but this seemed like a safer direction to go.

Of course all of these diameter differences are small and could likely be adjusted away with the rear spring preload adjusters. But as I said before, this is how I spend my time. 
 

Wow!  You are even more anal then I am, and that's saying something!  It's all good my friend, I'm sure your choice is fine!

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Wow!  You are even more anal then I am, and that's saying something!  It's all good my friend, I'm sure your choice is fine!

 

I definitely know how to overthink things.  Pretty much whatever you've got, I can overthink it.

In the end the tires feel great. No complaints.

Finally all that was left was reinstalling the exhaust and the bodywork.

I’m not really a big fan of how chrome looks, I certainly wouldn't be inclined to add chrome to a motorcycle, but it turns out it is a good way to keep steel from rusting. I wasn’t expecting my megaphone to clean up much, but just a few minutes with some soap and Mothers polish and it looks shockingly presentable. I didn’t have the energy to do the header. That’s a lot more effort. Just don’t look too close. 

wrote:

wrote:

Wow!  You are even more anal then I am, and that's saying something!  It's all good my friend, I'm sure your choice is fine!


 

I definitely know how to overthink things.  Pretty much whatever you've got, I can overthink it.

In the end the tires feel great. No complaints.

 Haha, I went through the exact same process when selecting my tires as well, we may have to host an overthinking competition...!!!!

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we may have to host an overthinking competition...!!!!

Isn't that what we do here most days?

And finally that all leads to this.  Just a bit shy of 2 years after it rolled onto the lift, it’s now finally off.



Here it is in the wild.



Going back to the stock jets and airbox was totally worth is.  The carburetion is better than it’s ever been.  It starts easily and I can take the choke off almost immediately.  When it warms up it idles well and eagerly pulls away from a stop, whereas it used to stumble off idle.  It still goes like stink, and I have confirmed that the rev. limiter is still working.  The only issue I’ve seen is down low if I whack the throttle open all the way the bike will stumble.  But I think that’s probably just the way it is with slide valve carbs and no accelerator pump.  I still need to do a vacuum sync and twiddle the idle air screws, but it’s great as is.

On the other hand, all that work to the front brakes has made very little difference.  The front brakes are still just as wooden and uninspiring as they were before.  The lever is very solid, but it takes a lot of force on the lever to reach a moderate level of braking, and it seems like the brake force plateaus at what’s is maybe 60%.  The brakes work ok, well enough that it’s not an issue on a casual outing, but my concern is that in a panic situation I just wouldn’t really ever get any more out of them no matter how hard I pull on the lever.  Either that or lock up suddenly without any warning.  They don’t feel good.

The Z1R has an oddball remote master cylinder connected to the lever with a cable.  I filled the cable up with spray lube, but maybe the cable is binding as the force increases and that’s part of why brake force plateaus?  I have not tried fitting a new cable, but I think I did when I rebuilt everything last time (I can’t remember).  I’d like to find a new production cable, but I don’t know of any.  There are vintage cables but they would be the same design as the one I have.

Another thing I’ve been thinking about is the 1978 vs 1980 Z1R calipers.  Both the ‘78 and ‘80 Z1Rs used the same master cylinder part number (5/8” piston), but the ‘78 used 38mm pistons and the ‘80 used 42.8mm pistons.  That would provide more leverage and lower the force required at the lever.  

There is also this article I found:   web.archive.org/web/20180122004818/http:...m/mastercylinder.htm

This guy says that the ideal master/caliper ratio is in the 14:1 to 12:1 range for single piston calipers, and anything below 12:1 will feel very wooden.

Doing the math, the ‘78 has a ratio of 11.46:1, while the ‘80 is 14.54:1.  Those numbers line up very well with the recommendation in that article.

I’m tempted to switch to a set of ‘80 calipers.  So far I haven’t been able to find a set on Ebay that look decent and are reasonably priced.  I think most of the KZ1000 calipers from ‘79 and ‘80 would have the 42.8mm pistons, and maybe kz650 calipers as well.  I’ll have to do some research.

Alternately, I wonder if I could find a 14mm piston assembly that would fit the Z1R master, and have the master resleeved and reduced.  The Z1R master is compatible with the standard KZ1000 dual-disk master cylinder rebuild kit.  Maybe the single-disk KZ1000A2 master parts would fit in a resleeved Z1R master?  That would allow me to keep the stock calipers that I just rebuilt.  The ratio would be only a bit larger, at 14.73:1.

Anyone else with a ‘78 Z1R who thinks the front brakes feel really wooden?  Is this just how they came from the factory, or is there still some issue that I haven't found?  Anyone out there who has ridden both a ‘78 and ‘80 Z1R?