CB250N restomod with major tweaks


Hey. I've been on this forum for some time, asked some questions regarding my bike. Took me a long time, since it's my first time ever doing such a project, but it's pretty much completed, one or two things left to do. It started off as a cafe/brat project, but as work had been progressing my pops became more and more interested in what I'm doing with the bike. He went in there to help me once, got hyped, and in the end we completed it together. He was like 'you know shit bout motorcycles and u wanna cut the frame already duhhh' so for the first build we went for the restomod, as we both had no prior experiance with fiddling around a motorcycle. Overall, I'm really content with this project, learned a lot, spent some quality time with pops, got him into motorcycles. Here are a few photos.



In the first picture is the bike as it was. Got it, drove 500km x2, took a picture, went to sleep.
Next, we already stripped it down, wasn't too hard, we found out that the bike has literally ONLY 2 SPOTS of rust on the frame, condition overall was incredible for a 37 year old.
In the next one, you can see some fkd up paint job, as we started with spray cans. We ended up getting an air compressor and painting it the way it should be done, as you can see, the color differs from the last picture.
Swapped the 13HP version cam for a 27hp version. A bit tricky with this engine.
And this is a finished product, went with Chrysler's burgundy, cuz red is the fastest, burgundy is not only the fastest (cuz its red), but also classy ;D

One last thing that remain uncompleted is carbs' calibration. And we can't possibly seem to get it done properly. They were cleaned through, gaskets were exchanged, no leaks. The bike runs roughly. We had 2 test drives. Thing bothering my mind is, that during the first one, the bike was finished. Had some problems with running idle, but other than that, it was running pretty smoothly, just felt like a regular 15 hp, not a horse more. After an hour or hour and a half, it lost majority of it's power, turned out one of the exhaust inlet valves broke. We fixed that, had another run, and sudden surge of power happened. Like, the sharper cam was there before, but we did not feel any increase in power until the valve was fixed. I do believe it has something to do with the timing and we might have had fkd that up, welp, at least we nailed it second time. After that, it did run, sound, feel more powerful than earlier. And here it comes, rpms do not drop after dropping throttle. Well, they do, but slowly. Other than that, it won't really start with the choke, but if I wont pull the choke up after starting, it dies. Even though I've been regulating idle numerous times, It always runs right only during one run. If I leave it to cool off, and try starting it again, I have to regulate idles again, sometimes a little, sometimes it just starts at 6k rpm right off. It lags with throttle a bit when cold. Issue dissapears, when warmed up.

I had asked a year ago about unlocking this engine on this forum, and found out that camshaft and MAYBE carbs need to be replaced. As far as I remember, the differences were carb tops and sliders. But now, when I'm checking the CMSNL, the differences are gone. I do know, that there are 2 versions of CB250N carbs, Keihins VB30A and VB30B. I do not know the exact differences. Other than carbs not fitting the engine, the only thing I can think of is the CDI. I might try both, but a pair of VB30A in a good shape is like 80 quid, and a new replacement for CDI is 75 quid, as I'm located in Poland, it's x5 for me, sooooo... I'm prepared to spend some more money, but I hope some of you might help me out with this issue, and I won't end up buying CDI I don't even need ;D

Cheers, Thomas.

The Jimbonaut

Well-Known Member
Hey Thomas, I won’t be much help with your issue but wanted to say hi and welcome you to DTT, nice looking ride fella

Sent from my iPhone using DO THE TON
Top Bottom