Valley Vintage Minibikes

As the tires on the pit bike were worn out, a choice had to be made as to what would replace them.    The little 2.50x 10 size is available in many styles and brands. I ordered a pair of Michelin Starcross tires as they had an aggressive knobby pattern.     It was also a chance to remove the wheel bearings from the hubs and put new ones in.     One of them was a bit loose in the bore, so a prick punch was gently hit in several places to raise the surface the bearing sat in.     I couldn’t find new wheels at reasonable prices, so a good rubbing with Autosol made them shine as much as possible.     The new small tires were tough to install, as the bead is stiff.     Dish soap and patience prevailed! Well, after three months of working on the bike project, the day came to fire it up and take it for a spin.     I changed the oil and put a new drain plug gasket on, not knowing when or if ever the oil had ...

Being unable to find a proper Fox chrome gas tank,  😔 meant finding an alternative. They look so good, nothing comes close. There was no way I was going to use the pit bike tank.  It looked like something from Star Wars!   A friend, George’s dad collected old engines, mowers, tillers, etc. and I grabbed about five different ones.    There were some neat looking types, but n one fit well enough.  I had a black Briggs & Stratton tank left over from other projects, so I used it.   I grabbed an old governor mounting plate and trimmed the original gas tank mounts from it.     These two ends were shaped to fit the main tube of the bike and welded on.  This finished up the tank install.  Being plastic, rust won’t be a problem in the fuel system.  Should I come across a nice Fox tank, I could cut the tabs off easily  and having kept the original tank tabs, it could be installed.  Next, tabs...

I saw a pitbike exhaust online for sale for about $60!  Free delivery, too.  Anyways, once the suspension was figured out, lining up the exhaust system was next. The new larger diameter pipe fit like a charm at the front, but angled upward to much to suit the vintage nature of the bike. It would appear I needed a way to bend the muffler down, but without heating or damaging the chrome on the pipe.  If I cut the pipe ahead of the factory upward bend and fit a sleeve inside the pipe, I could rotate it to the angle I needed.  So, out came the cut off tool and I began.  This would also hide the clamp and cut behind the heat shield. Once clamped and the heat shield was put back on, you’d never know it was bent upwards.  Thanks again to my friend John V for the chrome handle bar pipe and clamp! The rear brake pedal from the pit bike wouldn’t work at all on the Fox bike, so into the parts bin I dug.  I came up with a 1...

I wasn’t happy with how high the bike sat in the rear, as this negatively affected caster in the front.  Positive caster is the rearward tilt of the steering axis as views from the side.  It is a stability angle.  Too little and the bike would be hard to keep in a straight line.  Also the spring in the rear was too weak and provided no means of adjustment.   I ordered a new adjustable heavy duty spring and shock from Keith at PhatMX. He also sold me a set of handlebar mounts for the new 13” bars I ordered online.  They were the closest thing to the original look, I could find. As the new larger spring would only raise the rear even more, I cut the lower shock mount off the swing arm and rotated it back.  This lowered the rear, which increased the caster at the front and allowed me to stiffen up the spring without raising the rear of the bike. Here is the relocated mount below.  It was rotated about 30 degrees rearward, a...

When moving the bare engine into place, it became apparent that the frame was too narrow to allow the engine to sit correctly.  Out came the torch and the four tubes were moved outward about one inch each.  A hydraulic body jack was used at the front tubes so this could be done both carefully and evenly. Having the engine plate out of the frame is the only way stretching the frame this way would be doable.  I know I will have to add reinforcement to both where the lower tubes meet up front and at the bottom, below the engine.  This will put the strength back in that was lost.  Now, the engine was placed in and was able to slide forward enough that the kickstart lever sits ahead of the right rear frame tube. The rear suspension was pulled into place and clearances were very tight around the rear swing arm pivots and the rear foot brake lever mount. Blocking everything into position and careful tweaking showed it would work. ...

Thinking of a way to mount the front suspension and keeping the correct caster angle was on my mind, when staring at the bare frame, it came to me.  If I could cut the Fox steering tube and use it for a guide to both provide a good welding joint and the correct caster, that problem would be solved.  Sometimes the best solution comes from just looking at the parts you have to work with! Here’s the pit bike steering tube being cut from the frame.  Below is the steering tube ground down and ready to fit onto the Fox bike. Now, the Fox steering tube is cut, leaving about 1/3rd of the original tube to position the new part. An added bonus to using the Fox tube is that I can fit Honda style tapered roller bearings into the steering head, giving a nicer feel to the bike!  As well, the new front end has increased travel, compared to the original.  As a sidebar, I really considered the Piranha disc brake front end, but I was trying to keep costs down!  H...

To see if the engine would fit in, the original chassis was stripped.  Here you see the front and rear suspension being removed from the Fox. Next, all the plastic parts were removed from the pit bike and more measuring was done. The Fox engine plate was definitely in the way, so it was removed from the frame courtesy of Mr. Dewalt. A cut was made ahead of the rear upper spring mount on the pit bike, basically severing the bike in half. I removed the engine from the pit bike frame to ease trial fitting into the Fox bike.  Here, the first positioning helps me figure where it needs to sit in the frame while also maintaining the suspension mounting angle.   Stay tuned for the next instalment!