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Discussion Starter · #1 ·
Need some advise to guide dialing in the front suspension on subject bike.

I swapped out the front suspension on the Nighthawk S (39mm stanchions) to go with a 1999 VTR 1000 fork lower/4 pot fixed calipers, VFR 750 cartridge, and custom length 41mm stanchions.
- I had to go with custom length stanchions because they are almost 3" longer than the VTR's so I can keep the NH-S head geometry close to stock.
- I used the stock VFR cartridge because I had it, the control rods were straight, and because the weight of the NH-S and VFR are close.

I am looking for how much fork oil to put in. I have the stock VTR measurement, but believe I have to compensate for the additional air volume due to the longer stanchions. I could look for a solid spacer at the top and keep the oil level the same or increase the oil level a bit more. My previous measurements indicate a 80% oil/20% air is the right ratio and was planning on using that to determine correct height - unless someone else has worked through this before.

Hopefully I don't get flamed for my 1st question...

Thanks
Jerry
 

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Triple nutter
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well if you've got the 80/20 ratio figured out, just use the formula for finding the volume of a cylinder, for the new tube. remember to use the inside dimension of the fork tube when plugging in numbers>

Volume of a Cylinder
A cylinder with radius r units and height h units has a volume of V cubic units given by:

V=(3.14)r^2(h)
 

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Triple nutter
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haha ok, sometimes here on CF people will ask a question like that and when you give them an answer such as mine above they're like :confused:
 

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what you are doing sounds pretty uncharted. man, good luck.

if i went off the books like that, 80/20 would be a good place to start. hell, 80/20 might be the exact ratio you need to be at. see how it rides, if it is too soft, add more oil (or add air thru the valve at the top). another question you need to ask your self (your bike) is what weight of oil.

i'd use the vtr weight oil and fill it up to the vfr recomended height.

btw, those are some fancy pants forks to put onto a retro nighthawk. not to knock what your are doing, i'm a big fan of old&honda&shafts, but i have bought bikes cheaper than you have probly put into that front end. i hope she handles like nothing else on the road
 

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Discussion Starter · #6 ·
Thanks Weazel,

When the springs come in, I'll complete the forks and post back.

Edit: Forgot to mention, I swapped out the wheels (to 17" NT700V) so I could get radials on the bike. There is more $ in there/brake swap than the suspension. It should be a better handling bike...

Jerry
 

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Discussion Starter · #7 ·
I'm waiting for the weekend to get here.

A few pics of some of my other projects:

Dr. Jekyll: A complete PC800 with a ST1100 front end (forks and brakes).
Mr. Hyde: My PC800 parts bike with some interesting mods: CBR600 F4 front end with brakes, 17" NT650V wheels with radial tires, and VT1100 engine... Didn't get finished, so in the process of transferring the suspension and wheels/tires transferred to Dr. Jekyll. Perhaps when I retire, I will have time to complete finish this effort.

Jerry
 

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Discussion Starter · #10 ·
Forks are on tonight, slipped right in the modified triple tree.

I put a set of the new caliper spacers in to check the alignment of the caliper to disc. It is spot on. So, I'll clean up the calipers and install the brake lines. Trying to get first ride in this weekend if it doesn't rain.

While I had a few minutes, I relooked at a couple of mods I'm considering slipping in to get mechanically right before the cosmetic epic that seems to be looming next year.
1. Project 1 is bigger discs up front. I have 296mm mounted now, the set up for consideration are 316mm. To get them to fit, I need adapters. The VTR site has a place that sources adapters that mount to the VTR fork lowers that enable the use of 320mm (I think they are 316mm) discs. They are not too expensive, so I may make this commitment.
2. Second is the addition of a chin spoiler. It was something that was offered back in the day, but they are nearly impossible to find; even aftermarket ones are hard to find as the UJM has faded long ago along with the aftermarket supply. While there are some chin spoilers out there, they don't look like the original. Then a 1983 Kawasaki GPZ750 chin spoiler popped up on ebay for a low price so I snipped it. I think with some adjustments, it will look like the original.

I'll sort these through the weekend to layout the approach to get them on the bike.

Pic 1 = current bike status
Pic 2 = chin spoiler example I'm shooting for.

Jerry
 

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Spacetiger, i have an 86 cb700sc and i wanta know what ki da rear shocks are those?
I'm going kawasaki zrx1200 on those rear shocks....

I guess thanks for that necro bump, never seen this bike on here. I knew a guy with a blue and black 750 night hawk and always loved the way these bikes look...

Especially the tank... Fucker, now I'm off to ebay to see if I cant pick up a cheap night hawk tank to hoard... :mad:
 

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Praying that Jerry is still around here somewhere… popping this thread back up to the top to see if anyone still chats with him. Looking to talk with him about his rear wheel swap on his ‘84 Nighthawk.
 
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