1978 KZ650 Bike Build

The rake is changing between models because they are changing the rear wheel to a 16" wheel which lowers the rear of the bike and increases the rake, or also changing to longer forks on the CSR. but the frame more or less stays the same. If your triple tree is from an '81 650 it has less offset because the forks are leading axle forks, essentially moving some of the offset to the axle from the triple tree. trail is going to be very large and handling very slow with 25mm offset compared to stock 45mm

Since Z1 parts command a higher price it might be advantageous to sell your Z1 parts and buy 650 parts since the 650 parts are cheap in comparison. you might even make a couple bucks for the project.

DoctoRot post=845873The rake is changing between models because they are changing the rear wheel to a 16" wheel which lowers the rear of the bike and increases the rake, or also changing to longer forks on the CSR. but the frame more or less stays the same. If your triple tree is from an '81 650 it has less offset because the forks are leading axle forks, essentially moving some of the offset to the axle from the triple tree. trail is going to be very large and handling very slow with 25mm offset compared to stock 45mm

Since Z1 parts command a higher price it might be advantageous to sell your Z1 parts and buy 650 parts since the 650 parts are cheap in comparison. you might even make a couple bucks for the project.

  What he said...!!!      I measured again on my 1981 KZ650 F2, the "normal one", 18 inch rear, 19 inch front wheel combo,  and its definitely 45mm offset, apparently you guys in the US didn't get this model ? As far as I know there aren't any structural changes from 1980 to 1981 in this model, and the triple clamp dimensions right through these 18/19 inch wheel models were the same, please correct me if I'm wrong.   I don't know much about the CSR models, they are rare as hens teeth down under, we didn't really go for the chopper styled bikes here, they didn't sell well.

I have no plans to sell the Z1 parts so it would actually cost more to buy 650 stuff.  My plan is to do this bike with parts at hand.

Despite what the seller said about the 650 triple tree it may not be from a 650.  I've had that happen to me several times with ebay sales...sellers often don't know what they are selling or they mix stuff up.  

750R1, can you run your program to calculate the trail with a 25 mm offset?

OK, so I sat down with a straight edge and a pen, trying to refresh my brain on grade 10 geometry along with manual training graphics to figure out the trail on this project.  First attempt was to verify the trail on a Z1, with 26 degree rake, a 60 mm offset and 90 mm of trail.  The diagram below shows "A" as the top of the headstock, BC as the ground and "D" as the front axle.  "GC" is the trail, which was considered the unknown in the first case.  I had to measure the height off the ground for the top of the headstock and the center of the front axle, which were approximate lengths only because I was holding the bike in the vertical while trying to take the measurements.

It's a bit tricky to get from the knowns to the unknowns, and the calcs are on the left side of the page.  My answer was 89 mm, which compares favourably with the actual 90 mm.  Of course the actual number depends on more precise measurements as well as tire size, inflation, etc.  The tire in this case was a 19" Dunlop F11, which closely resembles the original Dunlop F6 from back in the day.  The rear wheel is stock with a stock K87 tire.  

For a 27 degree rake the trail calculates out to 96 mm.  Again, the assumptions above would apply.  So as long as I use the same size front and rear wheels, and the forks are the same as a Z1 I should be OK.  I'll have to do the calcs again with 1 inch shorter forks to be sure the trail isn't less than 90 mm.


 

There are free calculators out there if you don't want to do it by hand. scroll to the bottom. www.rbracing-rsr.com/rakeandtrail.html
 

That 25mm clamp is designed for leading axle forks, most modern sport bikes have around 30-35mm offset. I wouldn't use the 25mm clamp, you'll end up with huge trail, somewhere around 141mm of trail or 5 and a half inches, that's not useable, {if you want to go around corners !}....For quick reasonable accurate trail conversion use this PDF below, its about .1mm off compared to the complicated one I use as well, so close it doesn't matter...   This is a better one from RB racing, Its originally designed to work out differences in rake and trail for choppers so its more advanced, it needs more information to calculate..          www.rbracing-rsr.com/advchoppercalc.html      
I also use this tire size chart for avon tires as it has all their tire dimensions, they are slightly different for other manufacturers but these measurements will get you in the ball park , scroll down under the tire for all tire sizes.    www.motorcycletyrewarehouse.com.au/avon-roadrider-am26-30
Use this site for wheelbase and other measurements..     www.motorcyclespecs.co.za/model/kawasaki...asaki_z650f%2080.htm
You'll have to either measure or search for fork lengths, the 650 are around 780mm long.... 

Sorry, this bloody site won't accept the PDF file because its an xlsx file...    If someone knows how to fix this please tell me.....   This site is painful at times...
 I've messaged the mods to try and get this fixed, I'll attach the PDF then....  OK  PDF attached  Thanks KZQ
 

It looks like I'll be using the Z1 triple tree.  As for the other one.....I guess I need a boat anchor!

I added the PDF file above, you'll need microsoft Office or I'm currently using "open office" to open these files, its a free download...

Thanks!  It came through as an excel file.  I use Numbers, the Apple version.  It converted OK.

Excellent....

Wheels are back from the Kawi dealer, where I had them dismount the tires.  These are original rims but painted black, so I have some work ahead of me to clean everything up.  Right now I'm pulling the spokes and cleaning them one by one.  The rim chrome looks alright but there is rust inside along the tire bead surfaces.  Only surface stuff, but still rust that must be cleaned up.  I'm thinking of dunking them in metal rescue to fix the rust but interested to know if anyone has tried anything else?

Cases are also back after pressing the bearings in, so I can start to rebuild the engine.  Still looking for someone to weld the tail onto the frame.

 

 

Today I started to rebuild the engine and ran into my first problem.  Unlike a Z1, the shift forks on the small shaft are not the same.  I took photos of the dismantling but they are from the top of the engine and I can't tell which fork is which.  The manual isn't clear either.  Here is what the manual shows to describe the forks....

 

It describes the forks well enough, but then for assembly it says this...

 

Notice in the written instructions it says to insert the shaft through the FIFTH gear fork first, and then through the FOURTH gear fork.  But look at the photo where they show the opposite!  I'm left wondering which way is correct, and it matters because the two forks are different.  Does anyone know the correct way?  I installed according to the written instructions as shown below.  The final photo shows them in position as per the written instructions.