91' CB250 Nighthawk cafe

[cbdork190]

Though it is reliable and economical, Hear I have one of the ugliest and slowest bikes of the nineties. I picked it up on Cl for 500 bucks back in October. The engine ran good but the bike needed a lot of attention. To get it steetable again i replace both sprockets, chain, rear tire, oil, spark plugs, front brake shoes, removed a few unnessicary accessories, and bent a few things (pegs, forks, ect ) back in to place.

Then the fun begins.(I should mention this is my first motorcycle so i am feeling a lot out).

I swapped the front 14t sprocket with a new 13t.
I drilled the exhaust baffles and eventually chopped off the heavy ass mufflers off completely.
I port matched the intake manifold.
I removed the air box for a pod filter, and eventually replaced that with a velocity stack that i machined my self.
I rejetted the Carb and drilled the slide vacuum control hole.
I purchased an 85 rebel parts bike (for 100 bucks).
I chopped up the rebel bars to make clubman bars.

It's still not pretty but It's getting there.
The future holds much for this bike.
I plan on things like a new seat pan arangement, rearsets, custom/tunable exhaust, flat slide carburetor, and swapping out the front end from my rebel for the disk brake and larger forks.

 

[cbdork190]

After a tune up

 

[cbdork190]

Looks goofy, but this is the shape i want.

 

[cbdork190]

Some of the custom stuff im trying my hand at.
Top left is an aluminum velocity stack.
Top right are stainless exhaust flange spigots
Botom left is the rebel tank after hammering and sand blasting.
Bottom right are custom clubman bars.

 

[cbdork190]

With the new bars, and plastics removed

 

[clem]

Looks better already. Clean up the back end and it will be fine.

 

[john83]

Interesting. I have a Rebel, those little engines are bullet proof.

 

[cbdork190]

I think this bike has more potential than people tend to think. After a few inexpensive modifications, its much more fun than stock. Since no one does much with these I'm kind of mapping uncharted territory. I hope I can make it look good.
I just got my hands on some 1.25" ss tubing that shall become my new exhaust. The Id of the old pipes is .900" and id of the new tubing is 1.100". That is about 50% larger so hopefully this will help revving and top end.

I'm wondering about exhaust tuning with baffling and an h-pipe. Im thinking about making an h-pipe with a butterfly valve for balancing stuff out.

 

[cbdork190]

Cleaned up OK. Waiting on the new tail lamp to come in.
I weighed it on the shipping scale at work. 294 with a full tank of gas.

Also. About the exhaust chopping. I found out when I was cleaning up cable routing and de-accessorising that the throttle cable was pulling the choke cable out of its seat. So i was riding around withe choke on for a while and I had tuned it to run that way. So it was running great with the exhaust chopped off. After I fixed the choke it did have problems picking up from a stop. But I just shimmed up the needle and turned out the a/f screw. Now it runns great.

Using steel mesh, a hose clamp, and a du-rag I made an air filter. Hehehe. the du-rag looked a bit more resilient than stockings

 

[Tim]

Spend $15 and buy a clamp on UNI foam filter. Oil it up and it's going to protect your engine and let it breathe a lot more freely than that will. You're blocking off at least 50% of the airflow with that cloth.

 

[cbdork190]

It doesn't seem to effect top-end performance much at all, but that is a good idea and I will probably do that. I looked around town and couldn't find a good solution and somebody suggested panyhose , so I tried this out and iit works good. Its just not the most effective filtering solution.

 

[cbdork190]

So! i replaced the carburetor with a 28mm mikuni round slide that i got on ebay for $26. it still needs rejetting- but DEAR LORD, it helps! i haven't benchmarked anything but top speed, but the butt dyno says its better.

 

[AbbyRider]

Looks so much nicer without all the plastic. Too bad the tank has that lip and flare out along the bottom. If it's just cosmetic and you're going to repaint anyway you might be able to cut it off to clean up the lines.

 

[cbdork190]

I have it cleaned up since, and replaced the tail light and it looks a little better. hopefully the in the future i will be able to pick up an older cb500 tank and redo the whole tail section with a tracker loop style flat seat with a removable speed hump. I am also collecting parts for a good rebel front end so I can have a disk brake and beefier forks. In the near future is a port job and stainless exhaust. my goal is to do the ton.

more pics and info coming soon...

 

[killer poncho]

Bump! Looks great! How's the project coming along? How much did port matching the intake / re-jetting help for performance? How does the bike handle the 13T front sprocket?

Edit: 13T front sprocket boosts acceleration, so it'd be easier on the bike. D'oh! Did you do the intake before the sprocket?

 

[Fresherome]

Im driving the same model and I removed the side cover to see what effect it had on the look. The bike looks much better now.
Just some questions :

- How did you shorten the tail (document compartiment)? Did you use other parts for it?
- How did you cover the battery?

Greetings

Jerôme