Topic: Basket Case 250 Nighthawk

[Alan F.]

I've had this project on the back burner for a while, picked it up in late 2016 a titled basket case with a chopped frame, rusty wheels, flack blacked engine, a good tank, good seat and good pipes and a few boxes of rusty parts - and a valid Title signed but never dated by the previous...previous owner stating 14,000 original miles. It looks like she let it sit out in the weather until this kid got it and he hacked...no, he ground off the back of the frame with something much fatter than a cutoff wheel. $200 later and I was on my way home with it.

If anyone remembers my 750k3 build thread from over a dozen years ago, I had a front end from a 91-03 750 Nighthawk, rear wheel from same, and a front wheel from a CBR600F (1987) which fit those forks and used the same brakes, left side only. Well life got in the way, marital status changed, kids grew up, and I moved a couple of times so the K3 will happen another day, but those wheels and forks are going on this little bike.

[Alan F.]

I made up some sleeves and spacers on my tiny lathe and milled down the sprocket carrier on my little milling machine and it bolts right on with the 250's axle, chain line is good and it looks ok too.

[Alan F.]

The steering stem from those 750 Nighthawks was much longer than the SOHC 750's, and these little 250's use one even shorter than that. So I turned some old school bearing cups to hold tapered roller bearings, they fit the frame and these forks perfectly. In fact they're only about a half inch longer than the stock forks.

[Alan F.]

Those forks are stock 91-08 CB750 Nighthawk, they're made by Showa and they're 41mm. One day while browsing eBay I spotted some cartridge emulators for 41mm Harley forks for ~$50, and after some more research I bought a set. I made up some little adaptor rings so they'll fit the tops on my fork dampers closely, set their tension locknut as loose as it can get, drilled the 3rd oil hole in the dampers per Racetech and assembled the forks with all new bushings and seals, stock ~6" preload spacer and filled them with ATF. They were rock hard and I was disappointed but a few weeks later all of the air must have bled to the top because they were cushy in comparison.

[Alan F.]

At that point I needed to do something with that chopped frame and the simplest solution was to make some long slugs and bolt it back on solidly. Before final fitment I cut & ground off all of the tabs, and bits. Then I bolted on an old 750k fender Andy750 gave me many years ago. These shocks are from a twin cam 650SC Nighthawk and have 3 or is it 5 damping settings, they came in a Progressive Suspension box with a story that the rear springs are from Progressive for a 230lb rider, true or not they'll be more fun than the rusty stockers. Stock are 1 inch shorter.

[Alan F.]

After that I was stuck for a very long time trying to figure out what to do with the back end of the bike. I trimmed down the stock inner fender to fit reasonably with the 750 fender. Picked up 2 more 250 Nighthawk parts bikes. Experimented with reverse osmosis rust removal, and vinegar rust removal, DIY zinc plating, learned all about spoked wheels and wheel lacing & truing, build a very rudimentary bending brake and bent up some .120" (3mm) aluminum plate to form a tail section that'll probably work with the 750 fender and this stock seat, it'll also support the small Harbor Freight knock-off pelican case for some storage.

Then I set valve clearances, cleaned and checked the clutch, cleaned and checked the oil pump, learned to make gaskets, and did a little polishing.

[Alan F.]

And at some point I got the idea that it'd be pretty cool to have a comfy seat and a big fuel tank on one of these, I'm going to build one of the parts bikes like this with some tubeless Comstars.
It's a Gen 1 Kawasaki Concours 7.5 gallon tank with a Corbin seat from a '90 Ninja 600.

[Alan F.]

Shortly after that with the 2020 Covid lockdowns & furloughs we had here, I picked up my 750K8 basket case and spent some time with that, but that's another thread. Then spring of 2021 brought the sale of the building we were living in and the impending need for a new place mid-pandenic (you're a loser Jose) fast fwd to fall 2021 when I picked this project back up.

First step was a some quick prep and 2 cans of stainless steel appliance epoxy everywhere but the top triple, it got flat black. I added some steering stops after a little encouragement from Shtonecb500 and put it together with a few other unfinished bits. I bought a large pile of stuff for it but then the weather turned and I picked up my Black Friday CB160. I'll pick this up after the 160 is finished.

[RAFster122s]

All that nice fab work and you are going to want to drop a CBR650 motor (recent or current model) in it to add the go to the looks...
But, I wouldn't drop a 650 in that frame as it is too lightweight for the power. The 250 can make a fun curvy road bike if you can accept its low power output.
Wonder if the frame would support and perform well with a cbr300 motor?

Couple racers several years back took an old EX500 motor and stuffed it into a cb550 frame properly braced and reinforced to make a fun track bike.
Lots of custom one-off solutions for that bike.

What's your vision of what this bike will be like, or will be used for?

BTW, some cool work!

David

[Alan F.]

Thanks David! I'm thinking it'll be good around town and even better out on twisty back roads. I'm about a mile from the New Hampshire border and it's pretty easy to find a full day of riding up there.

The rear sprocket I'll be using is 5 teeth larger than stock, it won't have a 75mph top speed but I think 3rd through 5th gear will be much more useful. I'm also planning a tachometer to better manage available rpms. I've got a second set of pipes with rotted mufflers, I'm going to try adding VW Beetle exhaust tips right onto the headpipes, it'll either be great or it'll be terrible but I can add a baffle if needed. Front brake will be all stock Honda with adjustable levers, I'm working on a few ideas to move the footpegs and controls back about 4 or 5 inches, hopefully it'll work out. The bike is tall without that 90lb engine, I'm almost on my toes in sneakers.

I'm hoping I calculated everything correctly, hopefully there won't be any surprises. Stock wet weight is about 330lbs, I'm hoping to drop that by at least a few, I think these wheels, tires and front brake are going to help performance more than save weight though, they're just a few pounds lighter than stock.

[Alan F.]

Last time I put a bathroom scale under each wheel I came up with 265lbs
*EDIT: It was 235 lbs.

That was without a headlight and fork ears, any handlebars or electrical system & battery, sidestand, pegs or shift & brake levers, or front master cylinder, brake line or caliper. I don't expect less than 285lbs dry weight, but I'll cut weight where I can.

The CB160 weighed in at 265lbs with 16.5hp
Stock this 250 was 290 dry with 19.5hp

I wonder if the 160 being a 180 degree engine vs the 250 being a 360 degree engine will make them feel very different?

[Alan F.]

I ordered these on Nov 21 and they just arrived today.
Slow boat shipping to go with the $1.60/ea +free shipping price.

I'm going to mount these on the top triple and mount my cheapest of the Chineseium cheap mini-speedo & tach on top of them. Some bracket design will be needed.


https://www.ebay.com/itm/324771717494?_trkparms=amclksrc%3DITM%26aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20180105095858%26meid%3Df4137b78e2484f4ba6a53827c20e64d0%26pid%3D100904%26rk%3D3%26rkt%3D20%26sd%3D333710970655%26itm%3D324771717494%26pmt%3D1%26noa%3D1%26pg%3D2332490%26brand%3DUnbranded&_trksid=p2332490.c100904.m5276

They're about 1.5" square and .5" thick, designed for mounting cameras and logic boards to aerial drones.

They're cushy and should do the job quite well.

[RAFster122s]

Ebay link is broken

[Alan F.]

Edited, how's that one?

[RAFster122s]

$8.07 each... Ouch!
They went up a bit.

[Alan F.]

With taxes I paid $4.46 Canadian = $3.50 US for the pair, I figured if they didn't seem appropriate I could use them for something else. EBay Canada sometimes has better deals than eBay us.

[Just John]

I have a Nighthawk 250 sitting in the garage.  It is titled, but someone lopped off the rear frame rails just like your bike. 

[Alan F.]

Do you have the sawn off section? You'd think they'd come up on eBay now & then. Maybe call around to some junkyards?

Another thing I've seen done is to pick up an appropriately sized threaded rod that fits inside the frame tubing, heat it and bend a radius and weld that in for your rear loop. Cover it up with a street-tracker tail because cafe racers....

[Just John]

The rear frame section was long gone when we got the bike.  A local Atlanta guy is a very talented fabricator and I'll probably have him weld on a hoop if or when I decide to do something with it. 
The appliance stainless looks great on your frame.  I used the same paint for my CL360 wheel hubs when I laced up new aluminum rims.  I had an idle thought a few years ago about having the 250 Nighthawk frame powder coated in "chrome illusion". 

[spotty]

looking good, some nice work to get it all to this stage

[Alan F.]

Thanks man, I've got a few other surprises for it too as soon as warmer weather and a little free time arrive. I'm hoping it'll be good ~slow~ fun at high revs on twisty roads.

[RAFster122s]

When is the engine going into the frame...

[Alan F.]

Probably closer to spring.

[RAFster122s]

Looking forward to future installments of your progress. Interesting build.

[Alan F.]

Thanks! Work has been picking up lately so I'll be a little sparse on the updates for a few weeks. The CB160 will be a priority though. I'll need to clear what bench space I have for both the 160 and 250 engines so I can work on cleaning and buttoning them both up at the same time. 

I really hate being without a shop.