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Discussion Starter · #1 · (Edited)
Originally got a 1978 CB125s to chop and cafe. I just couldn't do it. Everything was original, and it is a really good looking bike. So i decided to take care of it and fix it up, keep clean. With the urge to mess around I decided to get a second bike. Found a nighthawk 250 and a great deal to pass up. The idea was to find a beater and I'll be honest I think 250 nighthawks are kind of ugly, they are standard that looks chopper-ish, almost trying to be sporty. You get the point. On top of that I love small cc bikes.

Here is a before after of my CB125s
before.jpg after.jpg


Here is the beater Nighthawk 250. I should've taken photos before I wiped it down. trust me, the photos look a lot better than bike in real life.
nh1.JPG nh2.JPG nh3.jpg nh4.JPG nh5.JPG


Want: would love to have 2-into-1 pipe but they are expensive: http://www.hondatwins.net/forums/62-engine-discussion/111217-honda-cl-style-exhaust-nighthawk-250-a.html

Bike is having issues where it dies on throttle: http://www.hondatwins.net/forums/63-fuel-supply-carburation/112673-nighthawk-250-dies-throttle.html

To do:
• clean / rebuild carburetor
• 33 main jet #110 99101-GHB-1100
• 34 slow jet #35 99103-KR3-0350
 

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That looks pretty good actually. If you decide to get rid of any parts shoot me a PM first, I'm interested in tank, seat, rear bodywork and pipes. I've got a set of head pipes with the mufflers rotted off if you're interested in messing around with stock pipes.

On my build I was first interested in 17" wheels (so I could put on some sporty tires) there are lots of ebay sellers that'll put together aluminum rim and stainless spoke sets if you decide to go that route.

Mods that add power are pretty much impossible considering the meager return on investment. But make it comfortable, make it handle, and make it sound better and you could have something interesting.
 

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Discussion Starter · #3 ·
I'd be curious about the 17" wheels. That sounds awesome, I bet it is expensive. Let me know if you know a particular seller.

+

I'm trying to keep this thing simple, nothing crazy, not trying to go 100mph or anything. It needs to look cool and be a easy bike to ride to have fun on.
 

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I can't find the emails I got from the seller, but it was similar to this https://m.ebay.com/itm/-LG3813-HOND...M-SILVER-FRONT-REAR-17-WHEEL-RIM/262671806349

They were in Thailand or Malaysia and the aluminum rim hoops were 'Racing Boy' brand. I did a ton of research and the company that makes them is huge, they have a motor gp team and supply some parts to OEMs. I tracked down a member on another forum who had used them on two bikes, he said quality was as good as any other, and these weren't cheap crap. The only issue was one set he bought had a finish color coat, it faded in the sun in one season. Otherwise mechanically solid, even with the substandard stainless spokes. He said the heads of the spokes weren't bent exactly like stockers and the gauge was a little thinner.

The seller also had stainless spokes, he'd make them to the lengths I needed but wouldn't make them as heavy gauge as stock spokes.

I think I asked for WM2 and WM3 width, 36 spoke drilled for drum brake hubs, with spokes he quoted me $320 shipping included. It was tempting, but I'd need the rim in hand to measure effective rim diameter ERD before I can calculate spoke length.
So no point in ordering them all together.
 

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Discussion Starter · #5 · (Edited)

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Discussion Starter · #6 ·
Looking at tires. The ones on the bike look 18 years old. Found these specs based on a 2004 model owners manual:

90/100 18M/C 54S
DUNLOP K300MA

120/90 16M/C 63S
DUNLOP K327AG

guessing that it still applies to the 2000. It doesn't mention anything about tube sizing. any recommendations?
 

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I did some tire window-shopping the other week, Here's what I found for the 250NH:

I found these all at bikebandit.com
They seemed to have the best prices that day, I don't know if these prices are still good.

IRC* Tube
18, TR-4, Standard, 3.50-18, 4.00-18, 8mm
Part Number: 49261
Price:*$12.85

IRC Motorcycle Tube
16, TR-4, Standard, 4.00-16, 4.60-16 / 4.25-16, 4.60-16, 8mm
Part Number: 1634151
Price:*$11.78

Kenda Rim Strips
16"/17"
Part Number: 1690213
Price:*$1.40

Kenda Rim Strips
18"/19"
Part Number: 1709678
Price:*$1.14

Shinko 712 Motorcycle Tire
Front, 100/90-18, Bias Ply, 18, Tubeless, H, 4-Ply
Part Number: 1633937
Price:*$49.32

Shinko 712 Motorcycle Tire
Rear, 130/90-16, Bias Ply, 16, Tubeless, H, 4-Ply
Part Number: 1633943
Price:*$65.59

Total $142.08 not sure about shipping
Prices April 30 2018
 

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Discussion Starter · #8 ·
Those 17" Supermoto rims/wheels look so firkin awesome. I am going to do more research to see what I can do. It would be cool to be able to get it fit. Found a set for $250 unused on craigslist. Really good deal but the guy is 2 hours away.


These are Wrap9. I don't particularly like the tires.
 

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If you're keeping the drum brake hubs, you need rims with spoke holes drilled at the correct angles. Larger diameter drum brake hubs require rims that have the spoke holes drilled at sharper angles than do the smaller hubs on disc brake wheels.

There are threads on supermoto forums where guys were trying to make rims with wrong spoke hole angles work with their hubs, not all rims will work because the spokes will bend trying to make the angle fit. You can file the holes a little to help, but it doesn't always make a difference.

That's why so many of those supermoto wheel kits include new hubs, that way they have engineered the whole thing to fit and work correctly, but they cost a lot, plus tires... Ouch.

My approach was to find bikes that had drum brakes of similar diameters, find ebay sellers that would sell me rims for that specific bike in the diameter and widths I wanted for the tire sizes I wanted to use, and make him swear up and down that the spoke holes are drilled at the correct angles for drum brakes. Maybe shoot an email to these guys: http://stores.ebay.com/linly7878
 

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Here are some links to have a look at, scroll down to see other bikes that used the same part, maybe you'll find a match for a rim on one of those bikes.
https://www.partzilla.com/product/honda/06430-KBG-700?ref=cb972a73549bd3acdd67b8fa051ae1165845b3ff

*https://www.partzilla.com/product/honda/44601-402-000?ref=377395545ffa1918c0ad3b3482f97275c431eb74

Same brake shoes means same diameter brake drum, that doesn't mean stock length spokes will fit, but with the right diameter and width rims with spoke holes drilled for drum brakes in hand, its not too hard to measure effective rim diameter ERD, which is used along with some measurements from the hub you wanna use to calculate correct spoke lengths, then its back to ebay to find someone to make some spokes to your spec. Easy.
 

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OK, I've done a little checking around and these two seem to be the simplest swaps as the front or rear rim will remain stock with either choice.

Option 1
Obtain another 1.85 x 18 front rim and calculate spoke length for lacing it to the rear hub.
Spoke length calculator found at: Spoke length calculator
These are the same tire sizes our friends with CB350's enjoy.
-Avon AV83 Streetrunner 3.00-18 Universal Front/Rear Tire Part #974-395 $57.99
https://www.jpcycles.com/search/search?Ntt=Avon+AV83+Streetrunner+3.00-18+rear&N=28012733&Ntk=All

-Avon AV83 Streetrunner 2.75-18 Front Tire Part #974-397 $47.99
https://www.jpcycles.com/product/974-397/avon-av83-streetrunner-2-75-18-front-tire






Option 2
Converting to 16 inch rims, lace a second rear to the front if it even fits between the forks, more measuring and calculating will be needed for this one.
Spoke length calculator found at: Spoke length calculator
Tires that may fit include: (in order by price low to high)
-Kenda K671 Cruiser ST
Front, 100/90-16, Bias Ply, 16, Tubeless Rear, 130/90-16, Bias Ply, 16, Tubeless
-Pirelli MT 75 Motorcycle Tire
Front, 100/80-16, Radial, 16, T Rear, 120/80-16, Radial, 16, T
-Dunlop K630 Motorcycle Tire
Front, 100/80-16, Bias Ply, 16, Tubeless, 50, S Rear, 130/80-16, Bias Ply, 16, Tubeless, 64, S
-Dunlop K330 Motorcycle Tire
Front, 100/80-16, Bias Ply, 16, Tubeless Rear, 120/80-16, Bias Ply, 16, Tubeless
-IRC Durotour RS-310 Motorcycle Tire
Front,100/90-16,Bias Ply,16,Tubeless,H,4-Ply Rear,120/90-16,Bias Ply,16,Tubeless,H,4-Ply
-Pirelli Sport Demon Motorcycle Tire
Front, 100/90-16, Bias Ply, 16, Tubeless, 54, H Rear, 130/90-16, Bias Ply, 16, Tubeless, 67, V


Tire to rim reference: https://www.blogotive.com/wp-content/uploads/2017/07/Motorcycle-Wheel-Rim-Width-for-Tires-Size.pdf
 

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Here's a little bike-porn with 18" spoked wheels at both ends.
I know...it's a CM400.

 

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Solved, cheap and easy wheel upgrade for 250 Nighthawk

I've measured the 250 Nighthawk hubs and measured the effective rim diameters and calculated the spoke length to lace a 250NH front rim to the rear hub to be 165mm, here's a set on ebay https://www.ebay.com/itm/36pcs-4mm-...gth-/352249638121?vxp=mtr&hash=item5203b6ece9

I haven't mocked up a set of 250NH forks to determine if the 16" rear rim will even fit between them, but the spoke length would be 135mm, here's a set: https://www.ebay.com/itm/Motorcycle...331294?hash=item4b349e375e:g:42kAAMXQDjhQ9BUI


So for $116 in tires (not counting new tubes and rim strips) and under $26 for new spokes and you're in business with 18" wheels front and rear.

The D.I.D. 18 X 1.85 rear rim I have left over from a 78 CB400T1 (sold the hub to a member here)
is identical to the D.I.D. front 18 x 1.85 rim from the front of my 93 250NH, same spoke hole angles, same markings except the date code is 10 92 instead of 3 98, I wish there was a cross reference available.
 

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Discussion Starter · #16 ·
This is amazing information. Oh my word, you must've spent a ton of time on this.

18" looks good, from the photo and sounds good. Question is what about the rear suspension? would that accommodate the new diameter? or do we need longer shocks?
I've seen several folks simply raising the rear with 14" shocks and sliding the triple tree down a bit on the front. I don't know what this would mean in terms of handling or safety of the whole contraption.

So far I've taken few things apart. Ill upload some of those and I have some mock-ups too. This weekend was a bit busy with mothers day stuff. photos coming tomorrow. And Thank you again for this info. I really need to lock down on a design direction / budget, too easy to go all nuts. :)
 

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I'll have to compare physical dimensions of the stock tire vs the tire i recommended, but with a 2 inch jump in rim size the tire is bound to be 1 inch taller, I'll post back later on.
 

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Discussion Starter · #18 ·
Here are some my thoughts

As I've mentioned before in the thread, "I'm trying to keep this thing simple, nothing crazy, not trying to go 100mph or anything. It needs to look cool and be a easy bike to ride to have fun on." I have some inspirations but of couse budget and skill will be a major factor. On top of this I am not locked into a particular look, but trying to keep an open mind. I made some Photoshop comps for possible looks, far from reality.

Inspiration 1: I love the 60's racers. Particularly the Honda RC's
nh250 inspiration 1.jpg
Looks fantastic but in reality, I don't think I plan to hug the tank all day for casual rides. My favorite feature is the slim tank and the bubble hump seat.

Inspiration 2: I do like some Cafe racers. I comped this image up to see what this bike could look like but man this is going to be impossible in so many ways.
nh250 inspiration 2.jpg
the front is significantly lowered. Trying to work the the curved nighthawk frame.

Inspiration 3: This is a mix of both 60s racer / cafe-ish thing. This comp came out of a cheap tank and seat found on ebay.
nh250 inspiration 3.jpg
Working with the frame may be quite difficult here. and the proportion of the tank might not be realistic.

Inspiration 4: this is taking measurements into consideration, trying to get a feel for what that tank might look like with a hump seat that is somwhat comfortable (plan to not hug the tank) It is weird, I've seen that tank on this bike here and I don't love it.
nh250 inspiration 4.jpg

Here are couple that looked interesting:
nh250 idea 1.jpg
this has a 14" rear suspension by emgo, front is lowered 1.5" CB360t tank. Looks good

nh250 idea 2.jpg
few cheap attachments, front lowered significantly.

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Long story short, I am keeping my options open and see where this thing ends up. Trying to stay on budget where i can sell some old stuff and pay for this.
1. Parts are in mail to get the carb issue worked out.
2. I don't mind the curve on the frame, feel like it will look good depending on how the thing is executed.
3. really want to experiment with 2 18" wheels and 13"-14" rear shock.
4. I like the stock exhaust, may take the baffles out to make it sound a bit heavier.
5. So far I took the plastics off and it already looks better, the factory tank is kind of growing on me. It could totally go in another direction as far as looks. Would like to upload photos but it is raining quite a bit here.
6. Seat / handlebars keeping a comfortable tucked position, nothing extreme.
7. Just noticed this headlight fairing of a Ducati monster and man I want it!


Long post but this is what's in my head, let me know if you like/hate anything here in particular. I am here so that I am pointed the right direction. I don't mind critical feedback. Thanks in advance.
 

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I'm liking this one:



It looks like a 750 Nighthawk tank and side covers with a stock 250 seat with a simple seat cowl.

You could certainly do this but the 750 tank would be a lot wider than the one you have. I'm not sure if 750nh side covers will blend with a 250 tank, they might.

I've got another style to throw at you, not sure what its called but its definitely Pacific rim in origin.





I'm not crazy about the brat seat, but with the right seat it could really be something. Its a little bit scrambler and tracker, but very hooligan.

My 250 will keep the stock tank and seat so it's recognizeable as a 250NH, but I'm thinking about modifying the rear of the seat, its just too tall and points upward at a 45 degree angle, not a good look with a real rear fender.

 

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Discussion Starter · #20 · (Edited)
That is actually 250 tank and side cover cut to look like a normal side cover. I used a silver bike
for the base because I looked at a silver one at the time. Maybe I should try to cut the side covers and see what it looks like.

That rear end is looking good.What did you do to trim that excess stuff?
 
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