CB750 No Plunger Hellride Freedom Machine

irk miller

You've been mostly-dead all day.
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Thanks to the gracious delivery of this 70's era plunger frame from New Mexico to Alabama by Canyoncarver, 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.



We're in the sketching phase, so things can change wildly. Ultimately, I want to avoid 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 1991 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.







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Hurco550

Keep er' Between the ditches
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Re: 70s Era CB750 Plunger Hellride

I'm in

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SONICJK

Reminds me of...me No, I'm sure of it. I hate him
Re: 70s Era CB750 Plunger Hellride

Work slower. You make everyone else look bad.
Jackass.

Looks cool though ;D
 

trek97

Active Member
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Re: 70s Era CB750 Plunger Hellride

Those forks are AWESOME on that frame.
 

irk miller

You've been mostly-dead all day.
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Re: 70s Era CB750 Plunger Hellride

Grades and comments for midterms are due tomorrow, so what do I do? Make a mount for a headlight...








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trek97

Active Member
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Re: 70s Era CB750 Plunger Hellride

That headlight on there is the shizzle.
 

63SSRagtop

Bikes and more bikes.. yup i like bikes...
Re: 70s Era CB750 Plunger Hellride

Dig the frame, I've never seen one quite like this either.. can't tell if it's a weld on rear half or whole frame.. You are probably aware that the front end may be really spongy for the weight of the bike as the build goes on.. they are designed for much more travel than a street bike front end.. I've read that the fluid movevement can be restricted with a machined piece and/or stiffer springs.. worked on a cafe Suzuki that had 250 forks, they looked cool but damn it moved around way too much.. cool project though! Will keep tabs!

That frame looks to me like a Jammer frame, can’t find any reference to one with a plunger rear, but someone at some point could have grafted in a Santee rear section..
 

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irk miller

You've been mostly-dead all day.
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Re: 70s Era CB750 Plunger Hellride

63SSRagtop said:
Dig the frame, I've never seen one quite like this either.. can't tell if it's a weld on rear half or whole frame.. You are probably aware by that front end may be really spongy for the weight of the bike as the build goes on.. they are designed for much more travel than a street bike front end.. I've read that the fluid movevement can be restricted with a machined Peice and/or stiffer springs.. worked on a cafe Suzuki that had 250 forks, they looked cool but damn it moved around way too much.. cool project though! Will keep tabs!

That frame looks to me like a Jammer frame, can’t find any reference to one with a plunger rear, but someone at some point could have grafted in a Santee rear section..
Yeah, I'm definitely considering the possibility that these forks won't work. I have tried them on a heavier dual sport contraption I built, so I think there's room to make them work here. This is one iteration, with potentially several others. They can be valved and fluid levels adjusted to effect the dampening on these to account for weight. The rake is a big factor, as well.

I've narrowed my opinion of the frame manufacturer to either Jammer or an early Santee. Though, all the Santee plunger frames seem to have a goose neck. You may be right on about the plunger being grafted on a Jammer. The tubes which mount the springs certainly suggest that possibility...






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Maritime

Active Member
Re: 70s Era CB750 Plunger Hellride

Ha, I usually hate rectangle lights but it suits this bike well. Looking forward to more of course.
 

canyoncarver

'hacking is learning'
Re: 70s Era CB750 Plunger Hellride

I barely pull in my driveway from the trip and you've already got a front end on it. ! Sweet.
 

irk miller

You've been mostly-dead all day.
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Re: 70s Era CB750 Plunger Hellride

Had a little convo with Race Tech. I could go as high as .52kg/mm on springs in these forks. Stock is .36kg/mm. We'll see how it acts with weight and go from there. Regardless, I feel pretty good that we'll find a match with rake and trail considerations.
 

jag767

New Member
Re: 70s Era CB750 Plunger Hellride

That front end looks like it has a ton of travel, do you have to limit it with a spacer or something or does it not matter? Btw it also looks fantastic on that frame.
 

irk miller

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Re: 70s Era CB750 Plunger Hellride

jag767 said:
That front end looks like it has a ton of travel, do you have to limit it with a spacer or something or does it not matter? Btw it also looks fantastic on that frame.
I imagine there will be enough travel to hit the frame to floor if I were to jump it, but running on the street will just waste most of what it has available. As long as Race Tech has the right springs, these forks should work well. I have a VZ800 front end to swap in, if this setup doesn't work.
 

irk miller

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Re: 70s Era CB750 Plunger Hellride

I didn't take any glorious actions shots, but man you should've seen me getting all the Bondo off this frame. Fuck that 70s smoothed out look. I learned an old body shop trick with removing paint and bondo, which is to get a fan tip for a torch and go apeshit with a scraper and stiff wire brush. It weakens the Bondo so you can scrape it off, or brush it off. Thick areas require a few passes. Some of it drops in flames. Then clean up the mess on the floor with a broom.
 

adventurco

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Re: 70s Era CB750 Plunger Hellride

irk miller said:
I didn't take any glorious actions shots, but man you should've seen me getting all the Bondo off this frame. Fuck that 70s smoothed out look. I learned an old body shop trick with removing paint and bondo, which is to get a fan tip for a torch and go apeshit with a scraper and stiff wire brush. It weakens the Bondo so you can scrape it off, or brush it off. Thick areas require a few passes. Some of it drops in flames. Then clean up the mess on the floor with a broom.
Sweet, I got a whole Ghia worth of Bondo to strip off. This will be useful.
 

Redbird

Dolor est Magister Optimus
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Re: 70s Era CB750 Plunger Hellride

Subscribed.
I see the bones of the Deviant Hellride in the background. Is she supplying the lump for this girl?
 
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