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Messages - MRA464

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1
Anorak's Corner / Re: CB250RS Balancer chain
« on: March 18, 2021, 11:07:28 AM »
Thanks Dave
I have contacted Jason and I will be sending my balancer and CAM chain to him to look at.
A very helpful Guy.
Cheers

2
Anorak's Corner / CB250RS Balancer chain
« on: March 17, 2021, 01:59:44 PM »
Hi Guys
Please can I ask for some advice.
I am in the need to replace the balancer chain on my restoration project.
I have been informed by a fellow member that the chain is actually the same as a 219 Karting drive chain which are substantially cheaper than the hard to get original.

I am happy buying and shortening the Kart chain, but my dilemma is the re joining of the ends.
Can I use a standard split link or should I look at a rivet link?
Does anyone know where I might be able to get one made up, its 72 links.
Thanks for your advice in advance.
Mark

3
Project Board / Re: CB250Rs Rebuild
« on: February 12, 2021, 01:29:02 PM »
Thanks again for all the reply's.

I am now in possession of the blue rs that came free with some parts I had ordered ( that what I told the wife!) again its a runner and has been dry stored. Condition wise its showing its age but oily not rusty.
I have only glanced over it quickly , but it all looks reasonable. The kick start is badly worn, which has caused damage to the peg and brake lever, wheels are painted along with the spokes, which don't look rusty so hopefully I can recover them unlike the ones I have on the black bike.
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So my plans are now to keep this one for another day and continue with the black one. I will use it as a reference to check for originality as I don't know if the black one is right.
My next plan is to get the engine completely stripped down and replace the worn out parts.
Piston & rings, Cam chain, balancer chain and all the o rings. Do you guys have recommendations or have definite don't buys.

Will I need to buy a cam chain tensioner? how do I tell if its worn, the chain is defiantly worn. 9mm upper limit.

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My first task is to remove the pins securing the rockers in place. My plan is to weld a rod or threaded bar to the top of the pin and ease it out with slide hammer or pull it out using the threads in a fixture. Fingers Crossed.
I will continue to clean up and replace where necessary all the other parts and get them stored away ready for the future rebuild.
I will update as I go.

4
Project Board / Re: CB250Rs Rebuild
« on: February 03, 2021, 12:50:05 PM »
Thanks Guys for all your inputs.
I will get a price for the reworks and go from there, as stated I am in no hurry.

I believe these bike will become in a few years the next collectable so best to invest now.
I will upload pics of the new bike once I get it, I will then get the cover off that one and see what its like.

I may have two that need repair !

5
Project Board / Re: CB250Rs Rebuild
« on: February 03, 2021, 08:29:04 AM »
Oh dear guys that was not the news I was expecting, thanks for your replies, this is going to be a big learning curve.
It sounds like this build could get expensive.
This bike as a project was really just to get me out of the house and the bike back and running, rather than rusting in someone's garden.

As the bike is not going to win any shows and is likely to be run very occasionally, do you think I need to get the cams and rockers done straight away? I guess that it will just get noisy over time? I will defiantly get the bottom end split and do the internal work plus piston and rings, but might hold off on the head work and do it at a later stage, thoughts please.

I have also just bought another one in blue which is in much better overall condition and is also a runner, so I will split that one at some point. I hope that if all is well with it, I will get this up to a higher standard and keep it for investment.

I will continue to collect parts and see where we get.
Again thanks for all your comments and advice.

6
Project Board / Re: CB250Rs Rebuild
« on: February 02, 2021, 01:11:18 PM »
The only issue I had removing the head was trying to undo the top sunken 14mm headed bolts, after breaking a 1/4 drive socket, I managed to find an old 3/8 drive socket that I could fit inside the recess and after some force it came loose and all was good, no breakages or damage threads.
The head was eased off and I turned it over to see what I had, HAPPY DAYS all looked good no obvious cracks. Even looked like a good combustion colour
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Now had it had a rebore?
The piston looked ok with no apparent slop although it looked oily. On cleaning I could see no marking so I assume it is original.
The bore was also very good with no steps or scoring, so it looks like I have been lucky and picked up a usable engine. ( hoping your comments don't dash this hope.)

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I will carry out the engine work New piston /Rings, Cam chain, Balancer Chain and a general good clean as part of the rebuild.
It needs the output shaft seal changing as well, not sure if this can be done from the outside or if it needs the cases split.
I will also change all the other external oil seals as I go whilst I am in the mood.

So lets get started on the rebuilding of this little classic. Lots of parts to order and find.
 

7
Project Board / Re: CB250Rs Rebuild
« on: February 02, 2021, 12:48:04 PM »
So now the engine was out I could take a look at its internals.
I had read in various posts that the threads easily stripped, so I had allowed the bolts to soak with oil overnight before attempting the disassembly.
Luck was on my side and they all came out easily with no issues ,moment of truth off came the cam cover.
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All looked good to me, but I am happy for your comments please. The rocker pads were clean with no pitting or damage the close up photos just show the wear lines in the surface and makes them look worst than they do visually.
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The bearing surfaces looked good again with no damage. So next to be removed was the cam chain, never stripped one of these so out with the manual, after some hassle I eventually manged to pull up the cam chain tensioned and pinned it in place. I had measured the tensioner are at approx. 7/8mm so I may change the cam chain on rebuild along with the balancer chain as advised by you kind gentlemen.
Cam sprocket was removed and out with the cam shaft, again it looked ok, bearing surfaces were good and the lobs showed some wear, closer examination with the camera showed some small imperfections, are these acceptable?
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At this point it was time to check the next know issue with these bikes, cracked head.





8
Project Board / Re: CB250Rs Rebuild
« on: January 29, 2021, 12:49:12 PM »
Thanks all for the 3rd wire info and all your advice.
Do let me know if my posts get too boring.

So my first real issues, I had a stripped out the frame and I was left with a seized centre stand tube and more of a worry the engine with a seized lower rear bolt, all others were free and left loose.
Try as I might I could not remove the stand, so I concentrated on the engine mount bolt.

It was the typical steel corroding in aluminium with added salt and general road dirt.

I tried the usual methods, lubrication, heat, force, time, more lubrication etc not to no avail. Fortunately for me after several attempts I managed to get the unthreaded part of the bolt to move,
So I again tried to get the bolt undone but all I was doing was causing it to twist.
A new plan was undertaken, lucky for me the engine case is two lobs rather than being completely enclosed. This gave me access to the bolt so with a dremel and small cutoff wheel I managed to cut most of my way through the bolt with out touching the case. Now the bolt was weak, so I just sheared it off using a socket on the head, happy days one side off.
I now cut through the protruding threaded side as close to the frame as I dare, ready for it to be drilled out.
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Carefully I centred a drill and drilled enough of the bolt away to allow me to remove the engine with no damage. I then continued to drill the bolt and eventually with a drift it came loose and popped out, Result.
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The center stand was cut out of the frame and will be modified or replaced in a later post.
Now I could strip the engine to see if I had a good one.
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Oil looked like caramel sauce, fingers crossed, as it was running.


9
Project Board / Re: CB250Rs Rebuild
« on: January 25, 2021, 02:49:20 PM »
Thanks for the reply guys, frame alignment was not something I had thought about.
Once the frame is sand blasted I will carry out an inspection for welds and then get the frame checked.
I might even get it to work and build myself an alignment frame to check it against.

The strip down continues.
More rust and debris, but not too many major issues. Front headlight rusty bezel and outside of reflector.
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Full Harness removed along with clocks and all the bracketry. Not sure if this is correct but one wire not connected, may be someone could advice.
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Forks show pitting and chrome damage, we will look at the damage once cleaned.
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As I said before the general idea was to get everything off the bike ready for a top end engine inspection. Parts are set aside ready for inspection and reworks at a later stage.
The only major issue was whilst removing the Carb the inlet boot fell apart -oopps. Apparently these are impossible to get so I will be looking at a repair of some kind.
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The bike had a seized front brake, so after removing the caliper and  brake line it was obvious that the master cylinder was at fault. It looks like it has a seized piston, so another job for the list.
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After several hours work and a pile of parts, I got it down to just the frame and engine.
So this will be the next post, as this did not go as planned, my first real issue.
More to follow

10
Project Board / Re: CB250Rs Rebuild
« on: January 21, 2021, 12:50:36 PM »
So the work started.
I will try and catch up over the next couple of posts, as I have got a long way into the disassembly and the issues I have encountered.

After a more detailed look around the bike it was obvious that certain items were not correct or were damaged past there best, but all nuts and bolts although
rusty were stock Honda issue.

The items that stood out were;

Wheels need a new spokes and rims will need dressing.
Rear shocks were wrong and need replacing
Front brake seized
Forks badly pitted and rusty.
Blowing Motard Exhaust and flaking chrome
Battery was shot
Chain and sprockets worn out
right side panel split
Missing frame info plate.
plus general poor paint and rust everywhere.

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Knowing that these bikes suffered from worn cams and cracked heads, I was keen to take the engine out of the bike to take a look inside the head, before doing too much else.
So out came the spanners.
Seat assembly removed along with tank. This gave me my first real view of the hidden parts and look what I found, some one had made home.

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The tank had issues which I will return to later on. I continued with the strip down, all the fixings came out some with ease and others with a little more work. Taking lots of photos as I went as my memory is not as good as it was.
Battery box was intact with some rusting, air box was good along with good supple rubber boots it even had the original filter still intact.
Rear end was all good apart from odd indicators and more rust.

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The rear end parts piled up and I was soon ready to start the front.
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More to follow.







11
Project Board / CB250Rs Rebuild
« on: January 19, 2021, 01:01:34 PM »
Hi All
Thought I would introduce myself and have a go at posting with photos, fingers crossed, here I go.

I have been riding and maintaining dirt bikes for many years and due to Covid have decided to get myself a project.
Using a well know auction site I have picked up a very tired 1981 CB250Rs in black.
The bike had been used as a spares / donor bike and had been stored under a tarp outside for many years.
The important thing for me was that it ran and sounded ok even with a blown exhaust.

Let the strip down begin.

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