Topic: Mini Trail 50 1969-70

[MD]

The project bike is a Mini Trail 50, 1969-70 vintage.  It was purchased originally for my aunt.  Several years later it was a Christmas present to my sister and I.  We rode it hard til we physically out grew it.  The upper aluminum triple tree was cracked and welded a couple of times.  Left handle bar has been welded.  My grand father put the luggage rack on the back and some passenger pegs so two could ride.  Had few rear flat tires along the way.  One time this lead to the demise of the seat.  Dad flipped the bike upside down to work on the tire.  While the tube was being replaced oil dripped out of the breather into the seat.  The padding and cover fell apart.   The fix was piece of plywood cut to shape.  It worked but you felt every bump. 

Last fall I dug the bike out from behind some lumber in my parents garage.


Took the spark plug out and squirted some oil in.  Couple of days later, with the plug out, rolled it over with the kick starter.  The oil came shooting out.  Engine not seized.     After a little searching we found the keys.  The ignition switch is frozen.   .   Brought the bike back to my place in January.



This week started ordering new parts.  Seat, battery and float charger have been ordered.  It will need new brake cables as well.  Weather is warming up.  Time to start wrenching. 

-MD

(FYI,  I do not have a heated work space.  We still have 2' of snow in the yard.)

[754]

 Neat bike, I had one.. worth a bit of cash too.. as much as a cb 750 in that condition..

[MD]

When looking at seats, I found some that cost about as much as the bike was new.  I ordered a new seat and pan for around $120 delivered. 

Next order of business is to take the bike to the car wash.

-MD

[MD]

Got the bike washed.  Now I can see the results of all the times the bike kissed the dirt.





Received the new battery, filled it with acid and put it on the float charger.



The battery came with two connectors to attach to the original wiring harness.  Took the one not needed for the bike and used it to attach the charger.  Cut the alligator clips off and replaced with spade connectors. 

I am having trouble getting the key into the ignition.  Have sprayed WD-40 into the lock but so far the tumblers are preventing the key from going in.  Any tricks to try?

Thanks.

-MD

[HondaMan]

You can leave the battery out, jumper the Red to Black, and kick start it. Those run on a magneto. The battery gets charged by a lighting coil in the magneto, to run the lights.

[MD]

You can leave the battery out, jumper the Red to Black, and kick start it. Those run on a magneto. The battery gets charged by a lighting coil in the magneto, to run the lights.

Thanks for the wiring insight.  Any suggestions for the ignition switch?

-MD

[HondaMan]

I'd probably remove it from the bike and drop it into a mix of light oil and kerosene for a couple of days, then wash it out with solvent (like brake cleaner?) and see if it frees it back up.

[754]

 Is Kero ok on the plastic bits ?
 I have run  oil into the key hole and around the tumbler, wait an hour try wiggling, not enough to twistvtge key.. often they loosen up.

[MD]

I'd probably remove it from the bike and drop it into a mix of light oil and kerosene for a couple of days, then wash it out with solvent (like brake cleaner?) and see if it frees it back up.

Another day of playing with the switch produced results.  Squirted it again with WD-40 and played with the tumblers with a small screw driver, followed by wiggling the key into place.  Once in all the way the key turned without a problem.

HondayMan  I believe my picture of my battery charging wires misled you.  My year of the mini-50 battery plug only has two conductors, a red and blue wire.  With the key working, pulled the sparkplug and tested for spark.  Plenty of spark without the battery installed and no jumpers. 

Next order of business is cleaning out the tank.  My dad or myself put oil in the bottom of the tank.  Hopefully that has prevented any rusting.

-MD

[HondaMan]

I still remember (with some pain...) my last ride on a Z50.
I went to a friend's farm for a day of skeet shooting, and he brought out a 1-year-old Z50 they had for buzzing around the farmyard. He asked if I wanted to ride: sure! He pointed out a pasture that was 'pretty smooth' and I took off. It didn't take much to get to full speed (20 MPH?) and I was ripping along happily when...the bike dropped into a large hole covered with weeds (so it wasn't visible) and as it went down, the handlebars neatly caught the tops of both my feet. I then 'supermanned' for about 15 feet before plowing the pasture with my chin.

The Z50 was happily putt-ing away, down inside the big hole!

Hard to forget the Z50 after that.

[MD]

Tightened up the petcock and put enough fuel to cover the tunnel in the tank.  Gave it a good shake.  Petcock did not leak.  Sat the tank down level and will check tomorrow for signs of leaks.

-MD

[richmagee7]

What a great project!  Had one exactly like it, same color, as a kid in Minnesota.  My parents have no idea how far that thing traveled.  Got to call my dad and thank him 45+ years later for buying that thing.  Have fun.

[MD]

Rinsed out the tank today.  Required three partial fills to get the oil out.  Ran fuel through the petcock and had good color and flow.  Went to connect the tank backup and discovered the fuel lines are brittle.  Next step get some good fuel lines.

-MD

[MD]

Yes, it took a year to get back to working on the bike.   

Took it outside connected the new batter and gave it a shot of starting fluid.  It barked, it sputtered and it purred for 5 seconds.  There is hope so off came the carburetor.  The oil that had been placed in the tank had found its way into the carb.  Wiped out what I could and then let it soak in cleaner for a day.  After the soak took a wire from a welder brush through all the holes of each jet.  The only tricky part of reassembly was proper assembly of the choke.  Did a google search and found the correct orientation of the slide and lever. 

Wish I could say it fired right up.  Had to play with the air mixture and throttle sets to get it running roughly.  Need to buy more gas and try again tomorrow.

-MD

[HondaMan]

I think I heard it!

[MD]

Could not get it to start today even with premium non-ethanol gas and starter fluid.      Pulled the float cover off and found gas in the bowl.  Set the air mixture at 1 1/2 turns and also tried 1 and 2 turns.  I think that I will be pulling the carb again.  Need to double check the throttle needle and main jet.

Please verify for me that the pointed adjusting screw goes near the intake and rounded adjustment screw goes below the throttle sleeve.

Thanks

-MD

[Don R]

 My Sandcast was purchased with a z50 near Christmas of 69. I wish the minibike was also still around, I'd be compelled to re-unite them. The history with yours is awesome.

[MD]

Played with the carb some more.  Took it off and checked the float height, 19mm.  Reset it to 18mm.  Check the float valve by blowing in the gas line.  It is working correctly.  Blew the air mixture port and the throttle tower as well.  Put it back on the bike and did a lot of kicking.  Pulled the plug, not fouled, sanded the contacts.  Played  with the air mixture some more and finnally got a bark.  Played with the throttle and choke and got it to run.  More adjustments and got it to rev.  More starts and adjusting to get it to not bog when opening the throttle.

It stayed running long enough to do some circles in the driveway.  Under load it will die.  It is leaking around the float bowl.  I am going to order a carb gasket set.  My guess is that some of other gasket/o rings are leaking causing reduced vacuum.

-MD

[MD]

Well the gasket set did not help.     The bowl gasket actually leaked so I put the old one back on.  It has spark and I managed to get it to sputter a bit.  I think my next step will be to check the timing and the valve clearances.

-MD

[HondaMan]

The points may be rusted inside the magneto. This was fairly common on these when I lived in Illinois: they would come into the shop in March/April after sitting since September, with the points happening to be open when it was stopped and parked in a damp shed. I would run a points file (and contact cleaner) across them, fire it up and check timing with a timing light (on a shop battery, as the little bike didn't make 12 volts for my timing light!). It doesn't advance, which is its built-in rev limiter.

I think the air screw was at 1 turn out on the little carb? It also only has 1/2 turn full low-to-high mix adjustment range, like from 3/4 turn to 1-1/4 turn, IIRC.

[MD]

Spent a few more hours on the bike today.  Took the carb off and checked the throttle linkage.  Last week I thought the cable was too short but when I looked in carb body while twisting the throtle the slide full opened.      

Moved on to the points.  Some of the screws on the cover are messed up.  (Don't ever remember working on the points.)  Took the flywheel off and cleaned the points.  Then it was on to setting the gap.  Looking through the flywheel cut outs the points barely moved.  Adjusted the points but then noticed the points closed 5 degrees before F mark.  More playing with screws and got it better.

Since everything was open moved on to checking the valve clearances.  They were loose, more on the intake than exhaust. 

Buttoned everything together and gave it  some kicks.  It popped a few times but did not start.  Pulled the plug to verify it did have spark, yes.  Shot of starting fluid but no start.   

Time to think it through again.

-MD

[MD]

  Went for a ride today 

Pulled the plug and tested for spark again.  Plenty of spark so played with the fuel air mixture some more and it fired.  Opened the choke just a bit and it started.  Adjusted the fuel/air so that I could open up the choke.  At that point I could adjust the idle screw.  Rode for 6 minutes in the driveway.

Now it is time for tires, tubes, and brakes.

-MD

[Medyo Bastos]

Cool! I’ve got a jr50!


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[MD]

Does anyone know the size of the front stays for the fuel tank?  Many wipe outs bent the stays to the point they fell off years ago.  I want to weld replacements on the frame.

Progress today.  Replaced the rear tire and the rear brake cable. 



Thought the split rims would make changing the tire easy.  45 years of rust and hard rubber proved to be a challenge.  It definitely was easier putting the tire back on the rim.  With the rim nuts just to end of the bolts, added air to the tube,  tightened the rim bolts the rest of the way and no pinched tube.   

Ran the new brake line while the inside of the rims were drying from a fresh coat of primer.  After getting the tire back on the bike adjusted the brake, adjusted the chain, adjusted the brake again.  Turned the key on and the brake light worked.  That is one less electrical gremlin the chase down.

-MD

[grcamna2]

I had a blue 69' just like it  bought it used from a dealer in CT. for $40 back in the early 70's 
I fixed it all up,installed parts that were removed(it was a recovered stolen bike and the owners didn't want to pay the dealer to make it complete again)and then rode that little bike all over N. Stamford,CT. with no license or registration..