1975 CB 250 project

Z

Z-240071

New Member
Hello all

New member and new bike project :)
Got myself a Honda CB 250 that i plan to somthing fun with.
Have not decided what way to go yet. Somthing café/brat-ish i think.
Getting the engine to purr seems to
be a good place to start :)

Since i havent been fideeling around with bikes in years , i would like to ask you experienced guys for some help with choosing some new parts.
I would like to get new carbs and pod filters , and new louder exhaust .

What to buy and where to buy it ?

Any tips is greatly appreciated
 

Attachments

  • image.jpg
    image.jpg
    677.3 KB · Views: 191
you won't gain much of anything with the pods. If you're hoping to pick up a little power through increased air flow in and out (which is what it sounds like) I'd consider replacing the factory filter element with uni foam or similar instead of pods. As far as exhaust... not a lot of options. You could go custom (which is what I did on my 360), but beyond that maybe someone else can help.
 
timberwolffxdl said:
you won't gain much of anything with the pods. If you're hoping to pick up a little power through increased air flow in and out (which is what it sounds like) I'd consider replacing the factory filter element with uni foam or similar instead of pods. As far as exhaust... not a lot of options. You could go custom (which is what I did on my 360), but beyond that maybe someone else can help.
Click to expand...

Uni foam may be a better solution .
Little more power would be nice , but i am not expecting a lot.
It will still be a 250.. But a little more noise would be great :)
Isn`t the 360 the same bike ? apart from cylinder , piston and head ?
 
Z-240071 said:
Uni foam may be a better solution .
Little more power would be nice , but i am not expecting a lot.
It will still be a 250.. But a little more noise would be great :)
Isn`t the 360 the same bike ? apart from cylinder , piston and head ?
Click to expand...

someone else would be able to answer that better than me. but from appearance it sure looks like it. Make you a deal on some pistons, cylinder and top end so you can find out :p
 
360 has a few changes, the rods are 16mm small end, I think the 250 is only 15mm but can't remember for sure as it's about 24 yrs since I did my CJ250 big bore (391cc) If you get motor apart DON'T mess with the intake port, it's way too big for a 123cc cylinder. I think I worked out it's about perfect for a 200cc cylinder. You will not get stock carbs working with 'pods' I used 26mm RD350 carbs and made some adapters to fit manifolds (shrink them onto carb stub)
The exhaust will be similar to the 360, don't go too big on diameter of head pipe, 'correct' diameter is only around 1" but it looks real tiny. MAC are the only people making 250/360 exhaust. Stock baffle is real restrictive but without baffle it's way too loud.
I've heard the 'race' baffle is way less restrictive but personally I don't have any experience with it. Stock baffle can be cut and modified if you have welding equipment (or know someone)
 
Stumbled upon a complete 360 engine today , for a reasonable price .
Could that one with a Mikuni Vm30 or 32 mm kit be a way to go ?
Maybe with some exhaust for MAC ? or custom ?
would like a set of pipes that don´t bends upwards at the rear.
How would a 2 in to 1 exhaust change the sound ?
 
VM28 would give the best drivability...Overcarbureting makes for poor low RPM performance.

I stayed stock. If the bike is going to stay relatively stock, the stock carburetor works best for drivability. CV carbs give very good off idle response.
 
My 391 would struggle up to about 120mph, 90 came up pretty quick and surprised the hell out of a load of people.
Can't remember if the RD carbs were 26mm or 28mm. (may have been off a 250 not 350?)
I have a chart somewhere showing max HP single carb will support. 32mm is about 45~50 bhp so in theory you could use just one on a CB250. If you consider carb size on a 500 Triumph twin from late 60's, even the race versions only used 1-1/8" carbs
30mm is best on 200cc cylinder size, really too big on stock 360
Link to a Triumph 500 racer build
http://www.rocler.qc.ca/ariane/cyctr500.htm#BM012
 
Z-240071 said:
Stumbled upon a complete 360 engine today , for a reasonable price .
Could that one with a Mikuni Vm30 or 32 mm kit be a way to go ?
Maybe with some exhaust for MAC ? or custom ?
would like a set of pipes that don´t bends upwards at the rear.
How would a 2 in to 1 exhaust change the sound ?
Click to expand...

If the geometry is the same, I could build you a set maybe.. built these for my 360:

20141019_162620.jpg

20141019_132348.jpg


I've been thinking about building another set with a different style...only because it's winter here and the bike isn't going anywhere anytime soon... plus I have loads of pipe and love to weld lol
 
Ease said:
Crazy looking exhaust! Super clean looking.

Bet it sounds nice.
Click to expand...
Thanks, no clue on the sound yet. That's just a mockup motor for now. Actual powerplant is a big bore build using the GS850 pistons. What's that make it...a 378 or something? I haven't done the calculations. PJ is working some magic for me currently on the top end.

I might bolt the exhaust on the motor I have on the start up stand this weekend and see how it sounds. My only concern is I have a crack in the chain timing chain tunnel that spits oil, and I don't want to get these pipes oily (yet).
 
timberwolffxdl said:
If the geometry is the same, I could build you a set maybe.. built these for my 360:


I've been thinking about building another set with a different style...only because it's winter here and the bike isn't going anywhere anytime soon... plus I have loads of pipe and love to weld lol
Click to expand...

Thats a piece of art ! I can see that you enjoyed welding them together :)
Guess them will be nice and loud :)
What kind of coating do you use ?
 
It will only be loud at certain rpm, at others it should be remarkably quiet because of the interference wave pattern. (hopefully the round town rpm will be where it's quiet, don't want to get the 'wrong' attention ;) )
250 and 360 are just about identical, same stroke so same cylinder height, same carbs, smaller pistons (56mm vs 67mm)
 
Z-240071 said:
Thats a piece of art ! I can see that you enjoyed welding them together :)
Guess them will be nice and loud :)
What kind of coating do you use ?
Click to expand...
thanks! Right now it's just high temp engine primer. I still need to tack on the mounts. just haven't decided if I want to use a female threaded boss and run a bolt through the bracket (I made that custom as well, see below) or weld on studs and have them slide through with nuts on the other side of the bracket.

3d rendering:
Image.jpg


Actual parts:
20141020_153910.jpg
 
crazypj said:
(hopefully the round town rpm will be where it's quiet, don't want to get the 'wrong' attention ;) )
Click to expand...

would be smart to avoid wrong attention :D most times that kind of attention costs me a bag full of "bike tokens" :p
 
timberwolffxdl said:
If the geometry is the same, I could build you a set maybe.. built these for my 360:

I've been thinking about building another set with a different style...only because it's winter here and the bike isn't going anywhere anytime soon... plus I have loads of pipe and love to weld lol
Click to expand...

Just let me know if you need any assistance to get rid of some piping , and feel the urge to weld ::)
 
Z-240071 said:
Just let me know if you need any assistance to get rid of some piping , and feel the urge to weld ::)
Click to expand...

Always. I've got plenty. 1.5" O.D. DOM tubing. Just let me know what style you're thinking
 
You must log in or register to reply here.

DTT Light or Dark

  • DTT Light
    • www.jadusmotorcycleparts.com
    www.lostapostle.ca/
    www.sparckmoto.com

    Spread the Love

    Back
    Top Bottom