Honda CB 250N Superdream unblocking the engine?

moubawz

moubawz

New Member
Hey.
I've got myself a 250N for German market, which is blocked to 17bhp. I'm okay with that, but I'd like to know if I can get more power output in case of getting bored of 17bhp too fast. I know, that all of the Superdream engines are basically the same, so how is it blocked? I heard that they got different camshafts and that's all. Anyone of you can confirm/deny?
Thanks in advance!
 
Not sure about that particular model, but a common way of restricting HP is by adding restrictors in the inlet or exhaust ports. Far easier / cheaper to do it this way than to change engine components.

Take off the exhaust and carbs and have a look.
 
I seem to recall that teh restricted version had a softer cam to restrict HP. CHeck teh parts lists at CMSNL and see the differences.


Restricted:
http://www.cmsnl.com/honda-cb250n-1978-germanytype-2-13-ps_model15806/partslist/

Full Power:
http://www.cmsnl.com/honda-cb250n-1980-a-germanyfull-power-type-1_model15818/partslist/
 
It seems like CB250Ns have never been made in such configuration. Stuff with the cams might have something to do, but I doubt it. As hillsy said, there were easier ways to restrict power. I'm gonna check out the exhaust system tommorow and let you guys know, maybe someone will find it useful.
 
CSMNL lists both versions for the German market, restricted and unrestricted. I figured you could open two browser windows side by side and compare essential parts from both parts lists.

I did that and the camshafts are different between the restricted and full power models for 78 model at least. Inlet valves are the same, cylinder heads are the same.

Exhausts down pipes are the same and so are the mufflers.

Carb assemblies have different part numbers and it's not the jets or needles - they are the same. They have different slides and tops though.

CDI ignition units appear to be the same on both versions.

So it looks like you need a full power camshaft and maybe a carb swap.
 
teazer, yeah, it might be just like that, I checked exh system today and it was fine, I want to check throttle body tommorow. If it's not blocked, I'll probably end up buying some used cam from UK. 40$ is a reasonable price for another 10bhp. Just wanted to avoid buying new cam, that's why I'm checking everything before doing that. Thanks for your reply!
 
Yep, changing the camshaft is the way to go. The only thing to do in order to unblock those 10 bhp. Sorry for double post tho.
 
No worries. Takes a while to work this stuff out and lots of research. The advantage we older guys have is that we sometimes have a better idea where to look and what to look for.
 
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