1975 CB250 Engine Swap

[waldo101]

Hello everyone,

I have a 1975 Honda CB250. I have never had this bike running but from looking at the engine I am sure it’s been thrashed out and I do not have the budget to rebuild it. Would it be possible if any other engine would slide straight into the frame? Newer preferably

 

[Hurco550]

I don't have an definite answer, but may be worth looking into a rebel 250 lump. Stateside they are cheap as chips and fairly reliable too.

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[waldo101]

I am located in Australia and I think they are a bit harder to come across here unfortuanlty, do you know if the newer cb250 engines slide into the same frame?

 

[Brodie]

Hey mate. I think you probably would be better off checking your engine before you decide to replace it. A swap might sound easy but keep in mind you will need to replace the carbs, CDI and a host of other things if you go to a newer engine.

Judging by your build thread it is one of the export CB"250" that the UK and Australia got. A small bore CB350 to meet the learners regulations of the time. Not much in common with any other the other CB250s.

You should be able to get a CB350 top end for it and there is a wealth of knowledge here for rebuilding them.
Either that or any engine that fits in a CB350 frame should work.

 

[Hurco550]

With a "bit of work" an xr600 single will fit the 360 frame. Not a bolt in operation, but far from impossible. I've been slowly gathering parts for a similar project. Here's a good write up.

http://www.chopcult.com/forum/showthread.php?t=20728

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[ridesolo]

Hello everyone,

I have a 1975 Honda CB250. I have never had this bike running but from looking at the engine I am sure it’s been thrashed out and I do not have the budget to rebuild it. Would it be possible if any other engine would slide straight into the frame? Newer preferably

I could be wrong, but I believe the CB250 of that vintage were, as stated above not sold in the US. However from what I've seen and based on the year, I believe they were based on the CB360. I don't know if the CB250 and CB360 share the same bottom end and case and just have a different top end or if the entire engine was different. My point is that w/ a little more investigation you MAY find that the engine from a CB/CL360 may just bolt right into your frame. You might try writing CrazyPJ, I'll bet that if anyone on here knows for sure it'll be him.