1973 Fox Thunderbolt

[SamM]

Drove into Pittsburgh today and picked this up for an awesome price. It came with the stock Tecumseh 3.5hp engine, the stock CVT and all the extra parts to complete it. Well, almost all of them. It needs fenders and a seat. Someone has foam and a piece of plywood that’s cut to the wrong size for it. The seller said that it came with the bike when he bought it. The plastic fenders that came with it are going into the trash too. I have already sourced fenders. The fuel tank looks perfect inside but needs a couple dents pulled and some paint. I’ll paint the frame and clean up the wheels.

I honestly do not need another project but this was too good to pass on. My thought is to put the Predator Hemi engine on this instead of my Coleman CT200U. The parts for the 212cc Hemi will arrive tomorrow. I still need to buy a CL-1 cam for it. The new engine would make it sort of like a resto-mod. A little new stuff mixed with some very cool old stuff. Not sure which way to go with it.

The Fox Corporation listed the Thunderbolt has a mini-cycle not a mini bike. These are apparently very rare and worth some money. I’m still researching it before deciding on what to do with it. The stock Tecumseh engine runs. I bolted the stock CT200U engine into the Thunderbolt and it fits. The Hemi will also fit.

The shocks were reversed, so I switched them back but it really needs new bolts. I’ll get those tomorrow.

Does anyone have information on these bikes? Parts sources would be great too. I’m not finding much out there.

SamM

[cheesy]

Never seen one of these before. Cool. Would not expect a leading link fork.

[pete]

i like cool odd ball things like that....



...

[SamM]

The leading link fork is what caught my eye first on this bike. My original plan was to buy the bike and use the leading link suspension on my Coleman CT200U. After looking at it for awhile, I see more potential in this bike than the Coleman. The Thunderbolt is a very different animal and somewhat rare. That’s cool to me. It also has a rear suspension another win, win. This bike would make a great hunting platform and to take to motorcycle/car shows. Last night, I spent some time on eBay looking at motorcycle shocks. A couple pair of hydraulic shocks would do wonders for this thing. The stock shocks are mechanical and not very smooth. I do not have enough original parts for a full on restoration and the original stock 3.5hp engine is not very powerful. That’s why my thoughts have been more towards a resto-mod type rebuild.

The engine plate needs a little work. It’s cracked on the front left corner which is a known issue. Overall, the bike is in very good condition for a 44, almost 45 year old mini-cycle. I have a feeling this was not ridden much. The swingarms on these bike were weak and easily bent. This one is perfect. The shocks were reversed to drop the rear of the bike. It seems that a small child rode this but not very much. The condition seems to be due to time and neglect. Much better than hard use. It’s straight and not bent. Finding a Thunderbolt exhaust, fenders and seat would be difficult if not impossible. A bigger 8hp Tecumseh or a Briggs & Stratton might be a good choice for this.

I’ll ponder this for a short while and then decide what to do with it. I could easily triple my money on it. Many people are looking for parts for these bikes.

SamM

[JerryHawk250]

I remember those bikes. Always wanted one. Sweet looking bike. Sorry for the large picture but some of us old guys can't see that well .
Attachment 10964

[Weldangrind]

I don't recall the Thunderbolt, but I remember that Rupp had a mini with a similar swingarm. I wanted one in the worst way. I'm going to enjoy following this build!

[Adjuster]

Very cool bike. Is the gas tank for real or show?




/

[SamM]

Yes, the gas tank is real. The Thunderbolt is a very cool bike. My dream bike back in the day was the Rupp Black Widow. Honestly, I think the Fox Thunderbolt is a better bike. It has the potential to be a great bike. My Hemi Predator engine is most likely going to go into this bike. It will handle the power better.

SamM

[SamM]

After doing some more research on Fox bikes. I found that Fox made a streetbike version of the Thunderbolt, which I like lot. They called it a Sportcycle. I would like to build a newer version of this bike. This is something that I am now thinking about converting my Thunderbolt into. An aftermarket Honda Z50 extended swingarm will actually bolt right onto the Thunderbolt frame. It shouldn’t be to hard to adapt Yamaha TTR125L forks and brakes to the frame as well. The CT200U needs to be finished before this one gets going.

SamM

[jsumd]

I love oddball stuff like this! looks like a fun project!

[Darkrider]

The Honda swingarm will solve the issue you mentioned before. Some good shocks from an old twin shock dirt bike on both ends if you stay with the leading link. Though might i suggest a Yamaha DT or XS front end. They would be closer to stock length especially the XS650 front end. The TTR front end may be too tall for this bike.

[SamM]

The TTR125L forks that I’m looking at are from a kids 16” wheel dirtbike, not a full size TTR. This thing is rather small as you said. The Yamaha parts are cheap and plentiful. I could add a disc brake to the front as well.

The leading link is definitely coming off this bike. I can probably recover enough money selling parts from this to get me well on my way. We’ll see. I have other priorities right now.

SamM

[Darkrider]

Ahh ok did not realize Yamaha had a youth version of the TTR like Honda does with the CRF. Good points. Kinda wish i had been around this forum when i still had my dads old CZ i would have probably tried to build something like this out of it. However...it now has me considering other ideas.

[SamM]

The TTR125L version was about the same size as the Thunderbolt. My daughter had a 2005 Yamaha TTR125E with electric start. It had the small wheels. The L and LE models had the larger wheels. She started out on a Yamaha PW80. These were all great little bikes. At the same time, I had a 2005 WR250 and 2002 Zuma scooter. We were big Yamaha fans. The Thunderbolt would really benefit from the TTR parts.

Don’t expect any updates to this thread. Next week, I’m picking up a new 2018 KYMCO Spade 150i playbike. I’m looking forward to that. The Fox will have to wait until later. I do plan to keep it and just mess with it a little at a time. Any updates will be posted.

Thanks!

SamM