Classic Honda 50's JZ Refurb

[Classic Honda 50's]

I purchased my JZ in the early 90's for $1000.00 registered, it was my first regoed monkey bike, I wasn't looking for a regoed bike as I only wanted it to ride off road and race around the track with the boys from West Wallsend, rode it part of the way home which was pretty exciting with major death wobbles at 80 kmh and having to try and outrun and out manouvre all of the cars trying to get a look at me.

The bike was too good to race offroad so I quickly found a Z50R to replace it, at the time there was no internet, forums or ride days and I didn't know anyone who rode a Z50 on the road, all my mates had big bore 2 & 4 strokes so I rode it around the local bush tracks on my own for a few years until I decided to strip the JZ for a quick cleanup, haha that was almost 20 years ago

This is how the bike has sat for most of that time, I blasted the frame and swingarm with ilmenite and painted them with a gloss black acrylic, replaced the swingarm bushes and fitted Takegawa 280mm shocks:




The fuel tank is is very good original condition but it will be resprayed with the fork legs to match the new plastic Honda OEM fenders:




The engine had an 80's performance upgrade with a cleaned up Honda 70 head and cam, modified 51mm CB400 piston for 85cc, Honda 70 modified inlet manifold and carb that sat straight back, Honda SL70 4 speed gearbox and a stock exhaust, went pretty good at the time, the only strange thing was the J1 air filter, thought they must have needed it for the carb set-up:




When I took the flywheel cover off something looked strange as it had a J1 flywheel, looked at the engine number for the first time that I remember and it was a Z50J1 JE engine not a JZ, well that was surprise number 1:




Extremely clean inside the engine, note the indents in the philips head screw on the gear selector plate to hold it in place, has roller bearings on the non drive end of the main and counter shafts, thought that I would be seeing a brass bush woo woo surprise number 2:




This is the old top end showing the modified CB 400/4 piston, not much meat left above the top ring, re-sleeved cylinder, cleaned up Honda 70 head and stock clutch, had a heap of fun with it:




Surprise number 3 was how worn the countershaft was and also found a case bolt that was seized, drilled off the head and onto the next job, luckily I had parts of an old SL70 box that included a countershaft that was in very good condition :




This is the oil gallery from the oil pump, it had quite a rough finish that I cleaned up with a dremel:




Just needed to be cleaned it up a little:




Honda SL70 4 speed gearbox, thankfully in fantastic condition, I gave this gearbox a real hard time on the track and out the bush for a few years then heard that they had a reputation of breaking easily, this one survived and never missed a beat except for the poor old countershaft:




Rebuilt the gearbox with new clips, washers and bearings all round plus the replacement countershaft:




Happy days with the cases de-burred, cleaned and semi polished and the engine rebuild end in sight:

[Classic Honda 50's]

I use new head studs on any performance build and always feel on the home stretch when I get to this point, then for surprise number 4 when the 52mm cylinder would not fit into the engine cases so close but now so far, been selling TB 52mm cylinders for almost 6 years and this was the first time that I have had a problem with a cylinder fitting, then a customer rings up a week later with the same problem, good mock up now it is time to pull it apart and enlarge the opening into the cases:




Used the base gasket as a template and enlarged the cases with a dremel, come up quite good even if I do say so myself:




Base race prep on the TB Parts roller rocker race head with the ports hand finished, inlet port matched to the intake manifold and valve guides honed:




Polished combustion chamber and a 3 angle valve job with the Neway valve seat cutting kit:




Top end in place with no more surprises, I like to glue the heat spacer in place so that it matches spot on with the intake port, leave it to firm up and then line up the intake manifold, keeps it lined up and the intake port matched every time:

[Classic Honda 50's]

3333333333

[JamoHado574]

Wow what is it.

[Classic Honda 50's]

Putting the pictures up now.

[dex]

tease ,,,!!!

[darkman]

Forum rules = pix!

[Peter]

Looking good.........where do you get your new parts from?

[babu]

Nice 106 stroker. Looks like 6v.

[babu]

Oh just realised you have pics up! .

[Classic Honda 50's]

I support Australia and get all of my parts through Classic Honda 50's Australia

More pix up with more to come, will add comments shortly, it is a 6v stroker motor babu.

Cheers

Jaimie

[MonkeyPower]

Would like to see how the points ignition system works through and beyond 10,00rpm. CDI For the win.

[Twelv10minis]

looks awesome mate. wish that motor was in my white j1..

[rroodd]

Nice write up Jaimie, looks good so far. Good to see you're putting that new valve seat cutting kit to good use !

[Classic Honda 50's]

Can't wait to get it on the dyno to see what it can do.

I would definately go for CDI if I was after maximum power but this motor will end up in my wife's J1 so hopefully 10000rpm won't be seen very often, it will be interesting to see when the points give up, points were king once upon a time.

The Neway seat cutting kit works a treat, takes a little practice to get the cutting pressure right, still have to get the 75 degree cutter so I can do 4 angle seats.

Have a few versions of the TB 108 stroker to dyno down the track to give people an idea how different set-ups compare:

1) 81 Z50JZ with 6v TB 108cc stroker TB roller rocker race head, Mikuni VM24 carb, stock points stator, stock coil, tuned length exhaust (Next on the dyno).

2) 97 Z50R with 12v TB 108cc stroker TB original race head, Mikuni VM24 carb, Takegawa Super Street Outer Rotor Ignition System, Takegawa Coil, Takegawa CDI, tuned length exhaust.

3) 03 XR50 with 12v TB 108cc stroker TB roller rocker race head, Mikuni VM26 carb, stock stator, stock coil, TB CDI, Fast 50s exhaust, currently an 88cc engine.

4) 76 Z50J1 with 6v TB 108cc stroker TB original race head, Shengwey 24mm carb, stock points stator, stock coil, tuned length exhaust.

Cheers

Jaimie

[Shearer]

looks realy cool Jaimie
Like to build motor like that for my z50r

[rroodd]

how's this motor coming along jaimie..? Been chuckin some hot laps yet..? Bet the poor lil jz doesn't know what's hit it...

[Classic Honda 50's]

Haven't had the motor running as yet, getting there slowly, my biggest hold up is time lately as I am slowly working on a few different monkeybike projects at the same time.

With the JZ have to paint the forks and clean up the old parts as I re-assemble the bike, have the exhaust bent up and almost ready to go, here is the prototype:

JZ Prototype Exhaust.jpg

Have also been waiting on the Heidenau 3.50 x 8 tyres to turn up, they took months to arrive.

Gotta get my finger out, bustin for a ride.

Cheers

Jaimie

[JamoHado574]

Any updates Jaimie ?

[Classic Honda 50's]

Have tyres now am waiting for our supplier to send the tubes so I can assemble the wheels, in the mean time have purchased a 2002 XR50 and a 1980 XR80 that we have been playing with:

2002 XR50 Pic 3 S.jpg


Honda 1980 XR 80 Pic 2 S.jpg


My 12 year old son told me that he needed a bigger bike as he is out growing his Honda 50

[Z50Jay]

My 12 year old son told me that he needed a bigger bike as he is out growing his Honda 50

I hope that you told him to wash his mouth with soap and never speak such filth again!

[Shearer]

^^ haha thats it!
He not as big as me yet jaimie lol.

neat how can bend pipe like that interested to see how see go's

Like the look of couple extra bikes you got too

[dex]

Neat xr jamie. ...
Perfect step up.
Looks in good nick

[JamoHado574]

What's going on with this build ?

[Classic Honda 50's]

The slow road to rego, keep getting side tracked by new bikes, work, family and health issues.

Turned up a custom designed exhaust coupler on the lathe to attach the exhausts primary pipe to the head, can now weld the exhaust system together.

Changed the Takegawa chrome rear shocks to a white spring NHRC 280mm set as my youngest son took the Takegawa shocks for his bike.

Took 5 different cans of white paint to find Alpine White for the forks and tank but it looks to be pretty close to the OEM fenders.

It seems like I have been this close for years.

[TUF50s]

hahaha we might get our bikes on the road at the same time got any new pics? and the old engine mods bring back some memories

[shoggothe]

*whistles*

And THAT is a nice looking motor!

[Classic Honda 50's]

It is coming up to 20 years since I took this bike off the road in July and it is like it punishes me everytime I do something to get it going again.

After taking the forks back to bare metal it took me 4 goes to paint them, the first rattle can of Alpine White left Aero Bar bubbles in spots in the paint, rubbed back the forks bought a new rattle can of paint and the same Aero Bar bubbles again. Had our local automotive paint supplier make up 4 litres of acrylic Alpine White and it looked a little off white but I sprayed it to see what it dried like and it had a hint of light tan so I started to rub off the paint and then checked the OEM fenders that I purchased in 1996 and they looked the same white/tan colour banghead.gif

I had a 4 litre can of generic acrylic white paint that has been sitting unopened for more than 20 years in the bottom of a cupboard in my shed, opened it and it stirred up and sprayed ok, the forks came up well with no sign of the Aero Bar bubbles. The paint was a high opacity white and was a close match to the Honda OEM white fenders from the 1987 Z50R that I has stashed away.

Have new bolts for the alloy rims and will be assembling them over the weekend to get the bike rolling again, paint the tail-light bracket and footpeg stay and complete assembly, so close:

Dsc05895 S.jpg


Dsc05912 S.jpg


I have the original fuel tank set aside and a China tank for offroad

Cheers

Jaimie

[dex]

Good to see you into it jamie ,,,
Keep it up

[shoggothe]

DANG if this doesn't look like the most pimped, lowest low-rider EVAH.... then I blinked and realised you had the wheels BEHIND the frame...

Dsc05895 S.jpg

Jaimie

[Classic Honda 50's]

- Heidenau 4.00x8 tyres fitted to a 2.75x8 rim for the front and a 3.50x8 rim for the rear:

DSC09971.jpg


- The 3.50x8 rim pulls the sidewall of the tyre out much flatter than the 2.75x8 rim:

DSC09999.jpg


- Just have to sand and paint the hubs to get the wheels back on:

DSC09978.jpg

[dex]

Not long now ,,!!

[Knut on a Gorilla]

Hey there,
Out of curiosity, what is the procedure for making the cases pretty....is it bead blasting, then sanding with? wet and dry??
cheers Peter

[Classic Honda 50's]

With my own cases I lightly media blast them with fine glass then I use a steel wool soap pad to bring them to the finish I like, if you want them show finish smooth you can use a fine grade of wet and dry paper to remove any scratches or blemishes.

Hard to go past vapourblasting these days for a finish better than a factory finish: https://www.newcastlevapourblasting.com/

[z nut]

you slow ******* your as bad as me!

[Classic Honda 50's]

My JZ is finally back on it's wheels, woo bloody woo, just waiting on Kitaco rear sprockets and TB brake pads to bolt up the rear end

Dsc01943 S.jpg

Dsc01944 S.jpg

Dsc01946 S.jpg

[dex]

Good to see ,,,

Raiding the kitaco bin are we ,
Ill tell nichole ,,,

[Diggs]

Good to see it moving along there Jaimie! I do like the slammed look though!

[Classic Honda 50's]

Have been in a back spasm since the Tuesday before Easter and finally got back on my feet over the weekend and straight down to the shed to work on my JZ.

Have been waiting on our Kitaco order with sprockets included, Woo Woo:
DSC01976.jpg


Hubs painted with Duplicolor Silver Ceramic Caliper Paint, Hi-tensile rim bolts installed, replaced the original Honda OEM 8 x 16 hub bolts with OEM 8 x 20 bolts so that the threads go all the way to the ends of the holes in the hubs with the thicker alloy wheels:
DSC01990.jpg


Kitaco 28 tooth rear sprocket:
DSC01997.jpg


The Heidenau 4.00 x 8 tyre fits perfect on a 3.50 x 8 rim:
DSC02000.jpg


Takegawa brake arms, the back arm is the same length as stock but the front is longer than stock:
DSC02004.jpg


The duplicolor caliper paint is not exactly the same as cloud silver but will do the job:
DSC02005.jpg


I like to use a yellow marking pen to paint the end of bolts when they have been loctited and tensioned:
DSC02008.jpg


The 28 tooth sprocket is a tad smaller than the stock 37 tooth sprocket:
DSC02010.jpg


Tried an NHRC down pipe to see how it looked as the down pipes make the most power on the dyno but I plan on doing a lot of riding on the dirt and it would of got damaged quite quickly if I fall off the bike, have fitted an NHRC up pipe which also sticks out a bit but not as much so I will go with this pipe till I finish the exhausts that we are making that tuck in like a stock pipe:
DSC02017.jpg


So close and getting a little excited to be getting back on the road, just have to keep my spine together to be able to enjoy a decent ride
DSC02013.jpg


Not far to go now just need to be able to stay on my feet long enough to get it finished, have to prepare the document to give to the engineer to get the engine capacity increase to the TB Parts 108cc stroker approved for rego.

Cheers

Jaimie