70s era CB750 Plunger Hellride

[deviant]

Thanks to the gracious delivery of this 70's era plunger frame from New Mexico to Barber Vintage Festival by a buddy, I'm jumping into this chopper build with two feet. I've reached out to several forums, sorted through various catalogs and ads from the 70s, but have yet to identify the manufacturer with complete confidence. I think it's definitely a production style frame, considering the neck. It has two pressed in cups for a common neck tube. The CB750 triple tree that came with the frame has a modified stem to account for the longer neck. So far, my best guess is it's a Jammer frame with a plunger kit welded on.



I'm in the sketching phase, so things can change wildly. Ultimately, I want to avoid some more common cues like peanut tanks....


It took some machine work on the steering neck cups and the RM stem to make this RM front end work...



Here is sits with a 1994 RM250 front end and RM wheels front and rear. I like the dimension of the dirt bike wheels, plus they're aluminum. If I decide to go drum on the rear wheel, I may go 70s era XL350.

[deviant]

Fabricated a mount for the headlight...

[Sky]

Nice, I dig on dirt choppers.
What are you doing to address the extra weight on that front end?
Preload spacers? Heavy oil?

I always thought those plunger frames were cool.
But they really could benefit from a stabilizer bar and maybe some dampening...

[deviant]

Nice, I dig on dirt choppers.
What are you doing to address the extra weight on that front end?
Preload spacers? Heavy oil?

I always thought those plunger frames were cool.
But they really could benefit from a stabilizer bar and maybe some dampening...

Thanks, Sky. I had a conversation with Race Tech. The max spring they offer is .52 kg/mm vs the .36 kg/mm that comes stock with these forks. I'll see about working that angle with their gold valves, possible preload and oil to boot. Considering the rake, there's no telling what the true math is on these.

[CarloFreeze]

This appears to be an Amen Savior or AEE frame.

[deviant]

This appears to be an Amen Savior or AEE frame.

Consensus so far is that it is a Jammer frame with a plunger kit welded on. Everything on my frame- tabs, peg mounts, neck gussets, etc- are identical to the Jammer frame in this pic. The VIN stamping, however, is not a manufacturers stamping or number plate. It was done by a private owner or customizer. This frame was smoothed out with Bondo at some point in it's life as I have a shitload to remove to bring it back...

[xriccix]

Consensus so far is that it is a Jammer frame with a plunger kit welded on. Everything on my frame- tabs, peg mounts, neck gussets, etc- are identical to the Jammer frame in this pic. The VIN stamping, however, is not a manufacturers stamping or number plate. It was done by a private owner or customizer. This frame was smoothed out with Bondo at some point in it's life as I have a shitload to remove to bring it back...

I'd agree about the jammer with weld on.

If you haven't already head over to hondachopper.com, pretty much everything you will ever need is there.

[Duane]

It's a Jammer Velvet Ride. The rear ends came like that at one point. I'm building one now.

[deviant]

It's a Jammer Velvet Ride. The rear ends came like that at one point. I'm building one now.

Oh wow. Thanks for the info!

[Duane]

No problem. That's what I'm building for the next Born Free. Something different for me.

[deviant]

I wish I had heard from you earlier, because by that point I had already converted to hardtail ...



I know plungers have their own special issues. Part of me wonders if I'll face regret, but as long as it comes out well I'll forget. Needless to say, it's caused much debate amongst friends.

Here's a detail that shows off the boxed out axle plates recycled from the plungers. It also shows the RM250 rear brake and rim...



With the RM rims come a 520 sprocket conversion opportunity. I went with a 38T rear and a 14T counter sprocket from an 70s XL250. To accommodate the XL cs, I machined a spacer (VW Bug alternator shims which can be bought cheaply in packs of 10 can also be used to shim sprockets on 750s since they have a 25mm ID).

[deviant]

Something common on dirt is a frame tab brake stay, instead of a rod. It's a nice, clean and inconspicuous setup. I machined and welded one to mount the brake...




To finish out the rear brake, I machined an oil bronze bushing to press into the pivot tube. I have a 77 motor, and I believe the earlier 750s had a larger pivot shaft. This gave me room for the bushing...

[deviant]

One thing of note: I'm a member at another site where this build is also happening. I'm trying to catch this up, so I apologize if I'm jumping around.

I guess I didn't take any detail shots of process, but here's a first look at the seat pan I'm forming. You'll see a few changes in later pics...



That pic also shows an XL175 tank. I have since gone to an XL350 tank. One thing unique about the pre-78 XL350s is the cutout in the tank for the offset carb. I like the shape and size of that tank and I had an idea I wanted to try on the cutout, so I fabbed switch box for the cutout...



Made an under tank M/C so I can get the M/C and reservoir off the bars, but still have front disc brakes. I'll run a late 70s/early 80s Z50 front brake cable...

[deviant]

I'm running a hinged mount for the seat that shares a mounting point with the tank...

[deviant]

Progress shot. Still waiting on the good condition tank that's shipping to me and I’m crossing my fingers on a couple of eBay auctions for a rear fender...

[OleDirtyDoc]

looking sweet

[deviant]

Bobbed, shaved and stretched a Softail rear fender to run on here...





I also machined an enclosure to house a micro-switch for turn signals and mounted it with an old bar end mirror mount...

[deviant]

I'm running one side of a HD tail light, wet sanded and polish to look new.



I also decided not to run a sissy bar above the fender...



I machined a sprocket carrier for the rear RM hub with the idea of making my own cush drive. Then a DR350SE hub fell into my lap for the cost of shipping ($13). These can go for $150 on eBay, so I was pretty psyched to get it...

[deviant]

Front brake work is complete...

It utilizes a Z50 front brake cable to an under tank m/c...







Stainless lines and 3an fittings. A straight fitting on the m/c and a banjo to an fitting on the caliper...



Since these are dirt bike forks, they offer a fork guard. I took the top mounts for the fork guards, trimmed off the guard mounting tabs and made a cable guide for the brake line. The line runs through a machined acetal sleeve...





Then a little Rub n' Buff helps the plastic blend...