Early 70’s CB250

[Bryanj]

I rebuilt worse back in the day when neither 16 yr old nor parents had cash, usually not quiet but did run. Mix n match best bits and clean that filter.

[K2-K6]

Looks like you've got a good couple of cam choices there on those ones.

As well as the lobe tip,  I usually judge it on the base circle to see if original machining is there as it indicates if it's been run with too little valve clearance. Normally a good sign for general cam health if ok.

Good for you to pick up those other parts at low cost Andy.

[Andych]

I havent been able to get to this one for a while but have been gathering a few items... then I managed to get this bike... while it has been butchered to be a Cafe Racer I was really after the Tank and the header pipes (they are so hard to find).
I like the way they retained the 'Patina" on the tank by just clear coating it...Oh well, I was changing colour anyway. At leeast it appears rust free and pretty much dent free.
I may have been lucky with the motor as well...it appears to have new gaskets and the points and coils are new. I will need to lift the lid to see what the cam etc is like but at least it is a complete motor... even if it has hideous cap screws and "joker" tappet covers.
The wiring has been attacked but hopefully it will be OK. I do have enough bits now to basically build 2 bikes.. so maybe I use the best parts for the restoration and then build a Cafe Racer to sell off... hmm decisions.

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[Bryanj]

Most common service problem with those, apart from nobody cleaning the oil filter, was it would run perfectly till you fitted the points cover, many points covers had insulating tape on the inside to stop the poits shorting out!

[Andych]

I will check that out. Before I pull the engine out of the frame I want to see if it runs so I will need to check the wiring first.

My biggest problem is finding a good low rise Euro handlebar for it.
The other bike has the high rise USA bars and I am not a fan of them.
Silvers don’t show them for the G5. Maybe I should look for CB360 parts as they seem more plentiful lol


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[Bryanj]

400 or 500 would probably fit ok even 750 if wiring goes through the bars

[Andych]

I was told to tidy up all my crap in the main garage so I decided to have a quick look at the CB360 engine to see if it was worth salvaging as the head was absolute toast.. as was the camshaft.
Well the barrels are pretty good and when I separated the cases all inside looks to be really good.. Crank is nice and free and conrods look and feel nice as well..
I also whipped the rocker cover off the latest bike to see what the can etc was like and it is like brand new.. at least as far as I can see.. I will need to take it out of the frame and strip it down.. if only to replace the gaskets (currently silicon sealant) and make sure all oil galleries etc are OK.
I would like to build up the 360 engine as a possible donor for the bike but I am short 1 Cylinder hear and they seem to be in short supply. I did find one in the USA but it will need valves, seats etc and even before that it will cost me close to A$500 landed.
I asked this question in Honda Twins and have not had an answer so I was hoping somebody here might know.. can the 250 head be machined out to suit the 360 piston crown?
I have a spare 250 head with really good cam journals and looking at it the combustion chamber seems to be the same apart from a large chamfer to account for the larger diameter Piston crown.
I guess I could always take it to my machinist and have him look at it..
Valves are identical between the 2, as is stud spacing etc. It may end up a better option for me than trying to source a 360 head.

It is actually better in the flesh than the pic looks
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As I said.. the cam and head are toast
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[AshimotoK0]

Sorry I can't be 100% certain but I know on the CB250/350K head, the chamfer on the 325cc head is the only difference.

I never seem to get much response from question on Hondatwins forum either... dare I say it on here....  you are likely to get a quick answer on the relevant Facebook group.

If you don't use FB I can ask for you.

[Andych]

Thanks Ash
I will get a chance to mostly measure it up this weekend.
I figure if the chamber shape is the same and the dome height is the same it should only be the chamfer that’s is the difference.
I have had 25 odd views on the post but no comments at all.
Certainly not as helpful or friendly as in here


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[K2-K6]

We had a thread on here a few years back discussing the chamber shape on these (I can't currently find it) that covered it in detail that may be worth finding.

[AshimotoK0]

We had a thread on here a few years back discussing the chamber shape on these (I can't currently find it) that covered it in detail that may be worth finding.

Think that was for K series though Nigel not G5 ... although I know 250 G5 pistons fit the K series, so I guess the same difference ... i.e chamfer on the 360 version.

http://www.sohc.co.uk/index.php/topic,13849.msg110761.html#msg110761

[JamesH]

Andy - have sent you a Pm. I’ve got a NOS 250/360 G5 seat that I’m about to sell. Let me k ow if you’re interested and we can discuss over Pm. James

[Andych]

Thanks guys... I think it is pretty much answered but I will still measure up over the weekend to get a better idea before taking it all down to my machinist.
I think I will just use Honda Twins as an info resource for vague stuff now rather than ask questions