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SOHC.co.uk Forums => SOHC Singles & Twins => Topic started by: Andych on November 02, 2018, 10:07:10 AM

Title: Early 70’s CB250
Post by: Andych on November 02, 2018, 10:07:10 AM
It would appear that laying around in Rehab hospital isn’t good for my wallet....
An ad came up on Facebook Marketplace for this bike and I thought I will go back to that later on and message the seller...
Went down to Physio and after being tortured for an hour or so came back to my room and started looking for the ad again....could not find it.
I eventually gave up and even told my better half it was lucky I couldn’t find it as I would have bought it...
Guess what jumped up into my feed again later on in the afternoon....😊
After talking with the seller on the phone I transferred some $$ and the bike is now mine... I just have to wait till I am able to drive 600km to pick it up.
My wife wasn’t even upset over it...too bad if she had been as I had already paid for it by the time she got here to see me...
While pictures don’t show the full story it is all there...and at A$250 I think I got myself a bargain.[attachimg=1]
Title: Re: Early 70’s CB250
Post by: SteveD CB500K0 on November 02, 2018, 11:07:04 AM
Bryan will chip in with his thoughts on the G5 :)
Title: Re: Early 70’s CB250
Post by: Bryanj on November 02, 2018, 11:40:01 AM
No i wont there are not enough asterisks and exclamation marks to hide the rude words!
Title: Re: Early 70’s CB250
Post by: Andych on November 02, 2018, 11:47:29 AM
Haha...is mine a G5 though? What I looked up showed the G5 as having a disc brake and was apparently de-tuned??
Anyway, I had one when I went for my license originally in 74 and I loved it... nice set of Dunstall mufflers gave it a nice note.
Granted I was a good 30 plus kg lighter and my memory may well be clouded..but they are few and far between here as most have been poorly chopped about as Cafe Racers and rattle can painted flat black... so good condition non butchered items get good $$$
Title: Re: Early 70’s CB250
Post by: Bryanj on November 02, 2018, 02:52:09 PM
G5 tank and cyl head, somebody has fitted an earlier front fork/wheel
Title: Re: Early 70’s CB250
Post by: AshimotoK0 on November 02, 2018, 03:36:03 PM
G5 tank and cyl head, somebody has fitted an earlier front fork/wheel

The early CB250G's (not imported here) had a drum brake like the CB250K4.

We all have our opinions of them but they sure look a pretty bike and I was amazed when I sold some parts how much interest there is in them. Here is a 'before and after pic' of one I sold last year,only 2k miles but unloved and then as restored by the bloke I sold it to.

[attachimg=1][attachimg=2]

Title: Re: Early 70’s CB250
Post by: AshimotoK0 on November 02, 2018, 03:42:11 PM
Manuals you will need Andy ;)

CB250G5, CB360G5, CB250K5 Part Manual (thanks Chris400F)

https://www.dropbox.com/s/mvcm4kgrcyntkp0/Parts%20List%20CB250%20CB360%20G5.pdf?dl=0

SEARCHABLE CB360 G5 SERVICE MANUAL

https://www.dropbox.com/s/mcug2pb5eaj6ydq/CB360_Searchable_Manual.pdf?dl=0
Title: Re: Early 70’s CB250
Post by: AshimotoK0 on November 02, 2018, 03:54:56 PM
Here is a pic of the drum front brake model:

[attachimg=1]
Title: Re: Early 70’s CB250
Post by: Andych on November 02, 2018, 07:50:58 PM
Thanks for the links Ash.. . I will have plenty of work to do..
Once I get it home and can look at the Vin I will have a better idea of what it needs to go back to how it should be...or modify it slightly to appeal more.

And we do all have our own likes and dislikes etc... personally...this one is one of my likes 😆
Title: Re: Early 70’s CB250
Post by: Bryanj on November 02, 2018, 09:54:11 PM
The only reason i didnt like them in the workshop was owner abuse and lack of care/service then expecting me to make them perfect for no money!

Big thig was not cleaning the centrifugal oil filter taking out cams and heads then numpties forcing cam chain tensioners and breaking chains, not including reving the nuts off them cold shattering rings and wrecking pistons/bores.
Title: Re: Early 70’s CB250
Post by: Andych on November 02, 2018, 11:05:43 PM
Ahhh, I can see the reason why and fully understand... I don’t get why people buy bikes and expect them to run forever with no maintenance...
I am trying to convince my son NOT to get a bike as he can’t keep up with checking oil and water etc on his car...and I know who will get the call to fix a bike 😤
Title: Re: Early 70’s CB250
Post by: Andych on November 03, 2018, 12:08:12 AM
Thankfully rot isn’t an issue in Australia..well not as much as the UK

I will work my way through the rest and should come out with a fun little bike at the end...
Maybe I should paint it Lemon yellow 😊
Title: Re: Early 70’s CB250
Post by: SteveD CB500K0 on November 03, 2018, 07:16:52 AM
My comment was biased by the fact that my room-mate at uni had a 360.

The rest of us had 400s and 500s

He destroyed the top end twice in one term which used his entire living allowance.

The next October he came back with a brand new (S plate) 750F1 in yellow having worked as a dispatch rider in London over the summer.


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Title: Re: Early 70’s CB250
Post by: Andych on November 03, 2018, 08:33:50 AM
Haha... all comments are welcome. I understand the why’s but they are mainly based on past history.. where these bikes were daily riders and many pushed pretty hard.
This one won’t do too many miles and it will be well looked after and hopefully there may be some modern techniques to minimize the weak areas..
In the end it is something for me to play with after I have finished the CB400F.
Title: Re: Early 70’s CB250
Post by: AshimotoK0 on November 03, 2018, 08:58:03 AM
Member who were around when they first came out  can wax on all day long about them but take it from someone who sold one recently and sold a lot of spare parts ....  in recent years ..... that model is VERY popular. My biggest criticism is that Honda, in their wisdom, omitted  to include a removable plate to gain access to the centrifugal oil filter. This meant removing the exhaust and complete clutch cover to do a routine maintenance job and I guess the average owner, if best,  changed the oil but couldn't be bothered with the hassle of cleaning the filter. I reckon if you rebuild it properly and fit the later modified cam chain tensioner it will a decent project Andy.   
Title: Re: Early 70’s CB250
Post by: Andych on November 03, 2018, 10:54:55 AM
Thanks Ash
Yes, the plan is to maintain it to the highest standards etc...and the beauty of forums like this is the knowledge in here to know what needs fixing / modifying or weak points to ensure I build a reliable bike to have some fun with...
Title: Re: Early 70’s CB250
Post by: Bryanj on November 03, 2018, 12:00:32 PM
You are correct Ash, it todays world a nice one will be looked after well and be a good thing but we all remember the lemons from our working days and as they say hindsite is the only perfect science!!
Title: Re: Early 70’s CB250
Post by: Andych on November 22, 2018, 08:44:17 PM
Still havent been able to get up to where the bike is to collect it.. apparently I am not supposed to be driving long distances at the moment.. something to do with the Pain killers or some such rubbish...

So I have been slowly planning how I will go about this sorting this bike.. which is a bit tough as I dont know the build date / Vin number or condition other than the pics I have posted but... I had in my mind a nice rebuild...certainly not a nut and bolt restoration... and then someone posts a pic on FB of an absolutely gorgeous CL350 in a Candy Red with a wicked high mount exhaust and it gets me thinking.. hmmm how would it look with a CL style high mount exhaust.. retro road / trail tyres and high rise CL style bars?
Hmm maybe it is the drugs...lol But the 70's CL350's are a lovely looking bike.. and I am not sure there is too much difference.. visually anyway.. I wouldnt be worried about lower first gear etc.. just how it looks.
Title: Re: Early 70’s CB250
Post by: Andych on February 01, 2019, 07:29:00 AM
I have finally been able to organise myself into driving 500 odd km to pick the bike up and another 500km back.. apart from breaking a strap early and having to jury rig the broken bits for 20km until I could buy another couple of straps it was fairly uneventful..Having looked over it when I was picking it up I was a bit confused with what I had actually bought..
When I looked for a VIN Tag there was none.. I am not sure what year Australia started to require VIN tags.. but there definitely isnt one on this bike nor any sign of one being there previously.. and.. I know that a couple of other CB250 G5's all have the G5 in the VIN code.. which matches up with the parts book to some extent.. at least for European Direct bikes.. there is nothing about General Export G5 nomenclature other than G5 and K5 Frame and Engine numbers run the same sequence so the G5 in the VIN would make sense..

From what I can gather... I have bought a CB250 K5.. deduced mainly by the Pilot light block as well as the twin leading shoe drum brake.. It appears the tank is also the same for both for General Export..
This is all in a very quick look once I got home.. so I could also be completely wrong.. not that it maters much at this stage.

[attachimg=1][attachimg=2][attachimg=3][attachimg=4][attachimg=5]
Title: Re: Early 70’s CB250
Post by: AshimotoK0 on February 01, 2019, 09:01:08 AM
I think your bike is possibly a CB250G  (the G5 was disc braked). My understanding is that the the old K series bike with disc was the CB250K5 or CB250B in Germany. Could be wrong but as you say ... just enjoy the restoration. That bike was a very early version of the 'G' engine so will have the early problematic  cam chain tensioner issues. I think Common Collective sell a repro of the later modified camchain tensioner.

https://www.common-motor.com/honda-360-engine-transmission
Title: Re: Early 70’s CB250
Post by: billy192 on February 01, 2019, 12:24:39 PM
yes its a G5 but as Bryan said change the oil reguly and clean the funny filter and it will run and run. i have done many K on mine with happy smile.

I think the front wheel is not the correct one and as alway high bars from USA. David silver has loads of new spares for these.

Billy
Title: Re: Early 70’s CB250
Post by: AshimotoK0 on February 01, 2019, 06:27:50 PM
I think the front wheel is correct and its a G model not a G5. I bought a 350G front drum brake plate from the States for one of my CB250K0's and it had the 369 part number printed inside ..the only difference between it and the earlier K series was a little arrow cast into it for the brake wear indicator
Title: Re: Early 70’s CB250
Post by: Andych on February 01, 2019, 11:18:40 PM
Thanks for the info.. with no background on it and no VIN tag stating the age of the bike it is a bit hard to properly identify it.. I will trey through the Motor Registry at some stage and see if they have any info..
For now it will go into hibernation next to the CB400 while I finish the little Yamaha SRX 250 / 350 hybrid.. hopefully not too long though, both the 400 and the 250 are longing for some loving...:)
Title: Re: Early 70’s CB250
Post by: Andych on February 02, 2019, 08:31:49 AM
I had the chance today to have a look at the engine parts that came with the bike.. the bottom end turns over ok with no resistance so it will have some oil tipped in and covered up for now.
I really wanted to have a look at the head and valve cover to see how bad it may be... hmmmm.

While everything is pretty grubby and gritty form being in an open shed in the NSW Country (worst drought on record right now) the camshaft is in a bad way.. the bearing surfaces are not too bad (will need to check dimensions and clearances) but the lobes are in a bad way.. as are the rocker arms.. I am not sure how the back of the lobe gets to be so discoloured.. almost look likee its from heat and the tops of the lobes are quite worn and pitted.. so this camshaft will need to be reworked (welded up and re-ground) as will the rocker arms.

I will pay particular attention to the oil pump when I get to that stage and also the cam tensioner.. I see this engine uses a very similar system to the CB400.. does the cam chain tensioner arm suffer similar issues to the CB400 item?
[attachimg=1]
[attachimg=2][attachimg=3][attachimg=4]

Title: Re: Early 70’s CB250
Post by: Bryanj on February 02, 2019, 10:10:23 AM
Thats the start of an oil starvation problem
Title: Re: Early 70’s CB250
Post by: Andych on February 02, 2019, 08:58:06 PM
Yes...its not looking good is it.. there doesnt seem to be too much around in the way of parts for these either..
There is a good looking camshaft on eBay but it is from the UK and pretty expensive.. or is that the going rate for a good one?
https://www.ebay.com.au/itm/1975-Honda-CB-360-250-CB360-CB250-G5-T-engine-camshaft-cam-shaft/352458634331?hash=item52102bf45b:g:ZYYAAOSwRolbj8UT:rk:1:pf:1&frcectupt=true

I will have to check around and see what can be done with mine.. it will probably be cheaper to have it repaired.
Title: Re: Early 70’s CB250
Post by: Bryanj on February 02, 2019, 10:00:15 PM
Problem is they are rare now due to being thrashed to death by inconsiderate UK learners!possibly US for 360 G5 or 360T
Title: Re: Early 70’s CB250
Post by: Andych on February 14, 2019, 12:24:23 PM
Well, I am glad that the CB360 is basically the same engine.. I managed to pick up what looks to be a really nice Came out of the USA which should be here in the next day or so. All up I paid around A$95 to get it here.. and it can with the advance mechanism as well.. the lobe look pretty reasonable as well as the end bearing surfaces.. the centre bearing surface is a little manky but I will check it out properly when it gets here... plus I am not sure on how good the running surface is for the bob-weights.

I also scored an almost complete CB360 engine for spares.. it isnt in real good condition by the photo but for A$10 plus $32 freight to get it here from Victoria I cant dont think I can lose on it..
The engine arrived today and this evening I ripped the rocker cover off to see if I bough a bunch of scrap metal or not...
Before I even pulled it apart I had well and truely covered my cost.. this engine had a Points cover and points backing plate.. those items alone are over A$120 second hand.. and I think the points plate is over $50 new as a pattern part.

With the rocker cover off.. I had more or less struck gold. The cam looked wonderful, other than the centre bearing.. but it may just be dirty and greasy.. the lobes look to be in great shape.. if so I could have a good spare camshaft...lol
The other bonus is that the rocker arms are really good.. so even if I scrap the rest.. I am well ahead.
The USA Camshaft
[attachimg=1]
[attachimg=2]

$10 engine opening up
[attachimg=3]
[attach=4]
[attachimg=5]

Title: Re: Early 70’s CB250
Post by: Andych on February 14, 2019, 12:28:32 PM
A couple more pics..
I also scored a timing cover in really good condition.. just needs a good polish and the black paint refurbed :)

[attachimg=1]

Another view of the $10 engine top end

[attachimg=2]
Title: Re: Early 70’s CB250
Post by: Bryanj on February 14, 2019, 01:00:18 PM
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.
Title: Re: Early 70’s CB250
Post by: K2-K6 on February 14, 2019, 02:36:21 PM
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.
Title: Re: Early 70’s CB250
Post by: Andych on September 07, 2019, 11:47:33 PM
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.

[attachimg=1]
[attachimg=2]
[attachimg=3]
[attachimg=4]
[attachimg=5]
Title: Re: Early 70’s CB250
Post by: Bryanj on September 08, 2019, 08:23:50 AM
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!
Title: Re: Early 70’s CB250
Post by: Andych on September 09, 2019, 01:02:18 AM
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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Title: Re: Early 70’s CB250
Post by: Bryanj on September 09, 2019, 08:53:20 AM
400 or 500 would probably fit ok even 750 if wiring goes through the bars
Title: Re: Early 70’s CB250
Post by: Andych on October 21, 2019, 09:10:27 AM
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
[attachimg=1]
[attachimg=2]

As I said.. the cam and head are toast
[attachimg=3]
[attachimg=4]
Title: Re: Early 70’s CB250
Post by: AshimotoK0 on October 21, 2019, 09:24:44 AM
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.
Title: Re: Early 70’s CB250
Post by: Andych on October 21, 2019, 10:43:05 AM
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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Title: Re: Early 70’s CB250
Post by: K2-K6 on October 21, 2019, 12:03:35 PM
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.
Title: Re: Early 70’s CB250
Post by: AshimotoK0 on October 21, 2019, 12:50:14 PM
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
Title: Early 70’s CB250
Post by: JamesH on October 21, 2019, 02:06:43 PM
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
Title: Re: Early 70’s CB250
Post by: Andych on October 21, 2019, 09:06:18 PM
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 :)
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