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Author Topic: 1975 CB250 Engine Swap  (Read 290 times)

Offline waldo101

  • Posts: 24
1975 CB250 Engine Swap
« on: Sep 29, 2018, 21:13:25 »
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

Online Hurco550

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Re: 1975 CB250 Engine Swap
« Reply #1 on: Sep 29, 2018, 22:04:48 »
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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"If you just picked up a drug habbit instead of a kawasaki triple at least you could get high while you waste money"
~ bradj
1988 tw200, the swamp donkey: http://www.dotheton.com/forum/index.php?topic=75455.0
2006 Suzuki DR650 Adventure monowheel trailer build: http://www.dotheton.com/forum/index.php?topic=75033.0
1976 BMW R90/6 farkilitious: http://www.dotheton.com/forum/index.php?topic=74349.msg882477#msg882477
1975 RD350 Road Racer: http://www.dotheton.com/forum/index.php?topic=70652.msg833688#msg833688
1976 GT250 Rebuild: http://www.dotheton.com/forum/index.php?topic=64973.new#new
Full Custom Pit Bike: http://www.dotheton.com/forum/index.php?topic=66954.new#new
1971 Yamaha 90cc twin HS1: http://www.dotheton.com/forum/index.php?topic=70498.0
"much ingenuity with a little money is more profitable and amusing than much money without ingenuity" - Arnold Bennet

Offline waldo101

  • Posts: 24
Re: 1975 CB250 Engine Swap
« Reply #2 on: Sep 30, 2018, 01:16:00 »
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?

Offline Brodie

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Re: 1975 CB250 Engine Swap
« Reply #3 on: Sep 30, 2018, 01:30:06 »
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.
« Last Edit: Sep 30, 2018, 01:47:50 by Brodie »
I'm not sure, but don't ask Brodie.

Way to many build and half done projects to list here.
Sr250, Gs750, Z50A, XV1100, A10, Z160A.

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Re: 1975 CB250 Engine Swap
« Reply #4 on: Sep 30, 2018, 20:35:28 »
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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"If you just picked up a drug habbit instead of a kawasaki triple at least you could get high while you waste money"
~ bradj
1988 tw200, the swamp donkey: http://www.dotheton.com/forum/index.php?topic=75455.0
2006 Suzuki DR650 Adventure monowheel trailer build: http://www.dotheton.com/forum/index.php?topic=75033.0
1976 BMW R90/6 farkilitious: http://www.dotheton.com/forum/index.php?topic=74349.msg882477#msg882477
1975 RD350 Road Racer: http://www.dotheton.com/forum/index.php?topic=70652.msg833688#msg833688
1976 GT250 Rebuild: http://www.dotheton.com/forum/index.php?topic=64973.new#new
Full Custom Pit Bike: http://www.dotheton.com/forum/index.php?topic=66954.new#new
1971 Yamaha 90cc twin HS1: http://www.dotheton.com/forum/index.php?topic=70498.0
"much ingenuity with a little money is more profitable and amusing than much money without ingenuity" - Arnold Bennet

Offline ridesolo

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Re: 1975 CB250 Engine Swap
« Reply #5 on: Sep 30, 2018, 21:18:16 »
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.
“Fight on and fly on to the last drop of blood and the last drop of fuel, to the last beat of the heart.”
— Baron Manfred von Richthofen

Please check out:  http://www.VetTix.org

These are on a low simmer out in the shop:
'75 Honda CL360: http://www.dotheton.com/forum/index.php?topic=56547.0
'70 Rupp Roadster: http://www.dotheton.com/forum/index.php?topic=67459.0