Author Topic: CB250RS Rebuild Progress  (Read 6359 times)

Offline Laverda120

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CB250RS Rebuild Progress
« on: January 23, 2017, 11:18:55 PM »
Hi All.
Thought I'd share the progress of the CB250RS rebuild with you all.
The idea is to restore the bike without spending an absolute fortune as lets face it, they are not worth a lot which is a shame as they are lovely little bikes. I thought I'd restore this one as it has served me well for 12 years and its about time the more obscure SOHC CB's were restored otherwise there wont be any left in a few years.
I began the strip down over Christmas with the intention to strip, label and photograph everything as it came apart.  I have decided that unless the cylinder head is in good condition (or I can get decent replacements if it isn't) it won't be worth restoring.
I've attached a couple of photos of progress so far, the bike is now all but striped into chassis component parts and the engine as a complete unit. 
Today I began stripping the engine, the moment of truth!
Initially all looked good, the cam head journals are in near perfect condition.......unfortunately the cam lobes are marked and pitted with the corresponding pad of the rocker arms also being scored.
Does anyone know if these can be reclaimed, years ago I had a can and followers metal sprayed and re-profiled but I don't know anywhere that does this service now, any recommendations would be helpful :)  DK have one on e-bay but it appears to be worse then mine! Unless I can find somewhere to reclaim these the engine is toast :(
1976 Honda 400/4
1977 Honda 400/4
1981 Honda CB250RSA
1977 Rickman Honda CR750
1999 Honda VFR 800FX
1955 750 Dresda Triton
1978 Moto Morini 350 Sport
1982 Laverda 120 Jota
1924 Triumph 550SD
2012 Stanley Battery Drill

Offline Bryanj

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Re: CB250RS Rebuild Progress
« Reply #1 on: January 24, 2017, 06:50:22 AM »
Have you tried dave silver for parts, some obscure stuff can be stupidly cheap

Offline Laverda120

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Re: CB250RS Rebuild Progress
« Reply #2 on: January 24, 2017, 02:22:51 PM »
DS advise cams are no longer available. CSML advise the same.
I'm going to send it to Newman Cams, £45 for a regrind that they say is possible as these cams apparently are child iron and the hardening is quite deep. They will resurface the pads on the rocker arms @£37 each. This is not going to be an 'inexpensive' restoration!
1976 Honda 400/4
1977 Honda 400/4
1981 Honda CB250RSA
1977 Rickman Honda CR750
1999 Honda VFR 800FX
1955 750 Dresda Triton
1978 Moto Morini 350 Sport
1982 Laverda 120 Jota
1924 Triumph 550SD
2012 Stanley Battery Drill

Offline kettle738

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Re: CB250RS Rebuild Progress
« Reply #3 on: January 26, 2017, 05:21:23 PM »

I would have suggested Newman Cams if I'd seen this earlier, having used them several times......their work is very specialised and in my experience has always been top notch.....so it bodes well for your cylinder head.

Mick.

Offline Laverda120

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Re: CB250RS Rebuild Progress
« Reply #4 on: January 26, 2017, 09:22:53 PM »
I had a spot off luck with the cam, someone on ebay was selling a brand new one still in its packet. I offered £50 and it was accepted.  I'll send the rockers to Newman Cams though as they need some help. They have a good reputation and do a lot of work for F1 teams. Mike Newman actually dealt with my call and was very helpful with advice.
1976 Honda 400/4
1977 Honda 400/4
1981 Honda CB250RSA
1977 Rickman Honda CR750
1999 Honda VFR 800FX
1955 750 Dresda Triton
1978 Moto Morini 350 Sport
1982 Laverda 120 Jota
1924 Triumph 550SD
2012 Stanley Battery Drill

Offline Laverda120

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Re: CB250RS Rebuild Progress
« Reply #5 on: January 29, 2017, 05:14:11 PM »
Some post-weekend progress photos following a good Saturday :) but a frustrating Sunday  :( in the garage.
The engine is now apart in large lumps with some bits going into the parts washer for an initial clean.  The crankcase is still together, I need to ask Mr Honda dealer up the road if I can borrow his 22mm x 1.6mm pitch puller, if not I'm going to have to buy one to use it once!
A photo of the camshaft is attached, I've tried to show the pits, the photo doesn't do it justice, the pits are quite deep. I've managed to obtain a NOS part on e-bay :D. The rocker pads are both pitted, although difficult to see in the photo. I'll be sending these to Newman Cams for some specialist refacing treatment.
The most frustrating problem is the pins holding the rocker spindles into the cover, the Haynes manual says apply some heat to get them out, I did that, they still didn't budge, alternatively the Haynes manual advises to use a dremel to grind a slot into the pins and lever them out, I did that and they still won't budge  >:( I've now soaked them in duck oil.  Any ideas anyone, they are too small and close to the casting to get mole grips on, I might have to get them spark erroded out, swearing at them hasn't worked either??????
Dave
1976 Honda 400/4
1977 Honda 400/4
1981 Honda CB250RSA
1977 Rickman Honda CR750
1999 Honda VFR 800FX
1955 750 Dresda Triton
1978 Moto Morini 350 Sport
1982 Laverda 120 Jota
1924 Triumph 550SD
2012 Stanley Battery Drill

Offline Bryanj

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Re: CB250RS Rebuild Progress
« Reply #6 on: January 30, 2017, 07:25:29 AM »
Needle nose mole grips(yes they exist) along with heat mate

Offline Laverda120

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Re: CB250RS Rebuild Progress
« Reply #7 on: February 26, 2017, 10:50:37 AM »
I've admitted defeat.....I cannot remove the two hardened pins holding the rockers into the head. I've tried everything,  penetrating oil, heat (lots of it) and swearing  >:(. The result is one pin snapping flush with the surrounding rocker box casting. I attempted to drill it out but the material is smoothed hard it blunted the centre punch!
Last resort now will be to spark erode the remaining stud out.
Does anyone know of an engineering company in West London or Middlesex that has this equipment?  I've tried a few places without success.
1976 Honda 400/4
1977 Honda 400/4
1981 Honda CB250RSA
1977 Rickman Honda CR750
1999 Honda VFR 800FX
1955 750 Dresda Triton
1978 Moto Morini 350 Sport
1982 Laverda 120 Jota
1924 Triumph 550SD
2012 Stanley Battery Drill

Offline Tomb

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Re: CB250RS Rebuild Progress
« Reply #8 on: February 26, 2017, 02:30:21 PM »
Try a masonry drill sharpened for steel drilling, keep the tip cool/wet as the heat generated will melt the braze and the tungsten carbide tip will come out (DAMHIK :o)

Sometimes a good quality high chrome steel will work harden when drilling the surface, even just a resharpened HSS drill bit will cut through this with slow speed and cutting compound, compound for tapping holes works well.
Tom
'73 CB550 with CB500 engine café racer
'62 CB77 Sprinter
'70 CD175
'78 CB550 with sidecar
'80 Z50R
And a load of old Yamaha 1100's

Offline Laverda120

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Re: CB250RS Rebuild Progress
« Reply #9 on: February 26, 2017, 11:25:03 PM »
Thanks for the advice Tomb, I'll give it a go if what a mate told me turns out to be correct, he was charged £80 a few years ago to have a 6mm exhaust stud spark eroded out of a cylinder head. If true I'll be looking at the thick end of £200 to remove these studs  :'(.
1976 Honda 400/4
1977 Honda 400/4
1981 Honda CB250RSA
1977 Rickman Honda CR750
1999 Honda VFR 800FX
1955 750 Dresda Triton
1978 Moto Morini 350 Sport
1982 Laverda 120 Jota
1924 Triumph 550SD
2012 Stanley Battery Drill

Offline Laverda120

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Re: CB250RS Rebuild Progress
« Reply #10 on: April 22, 2017, 02:46:30 PM »
The bike is now in 100's of bits  :o.  Just about to load it all up and take it to the aqua blaster at I Cleenz Machineez in Penge a quote.  I'm going with stove enameling this time for the frame and other painted parts.  All the nuts and bolts have been cleaned up and the burrs taken off before dropping off at the chrome/zinc platter. I have filled the rough passivated casting posing as a kick start lever, I have polished it and will have this chromed along with the rear brake pedal, I know its not stock but a grey rough casting really ruins the look of the black engine. ;)
Piki, do you have the DID decals for the wheel rims in stock and the tank, mudguard and seat decals?  I'm already thinking about the finishing touches  ::)
1976 Honda 400/4
1977 Honda 400/4
1981 Honda CB250RSA
1977 Rickman Honda CR750
1999 Honda VFR 800FX
1955 750 Dresda Triton
1978 Moto Morini 350 Sport
1982 Laverda 120 Jota
1924 Triumph 550SD
2012 Stanley Battery Drill

Offline Laverda120

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Re: CB250RS Rebuild Progress
« Reply #11 on: June 12, 2017, 07:56:53 PM »
Chrome Porn  :) I collected this little lot from the chromer today, fantastic job he made of everything.  £98 all in. Before anyone says anything.... I choose to plate the kick-start and rear brake lever, I couldn't stand the rough finish of the originals. I took me a full day to file the kick-start shaft and knuckle smooth and blend the contours.
1976 Honda 400/4
1977 Honda 400/4
1981 Honda CB250RSA
1977 Rickman Honda CR750
1999 Honda VFR 800FX
1955 750 Dresda Triton
1978 Moto Morini 350 Sport
1982 Laverda 120 Jota
1924 Triumph 550SD
2012 Stanley Battery Drill

Offline Green1

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Re: CB250RS Rebuild Progress
« Reply #12 on: June 12, 2017, 08:02:24 PM »
Nothing wrong with a bit of bling
Chrome looks good on almost everything 
Current bikes
Honda CB750k1 Valley Green Metallic
Honda CB750k1 Candy Gold
Honda CB550k Candy Jade Green
Honda CB400 Parakeet Yellow
Honda CG125
Aprilia Pegaso 650
Moto guzzi 1200 sport
Kawasaki EX650R (Mine until dave pays for it)

Offline Laverda120

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Re: CB250RS Rebuild Progress
« Reply #13 on: September 23, 2017, 11:29:57 AM »
A bit of progress to report.
The rocker arms have been refaced and ground by Newman Cams and arrived back today, lovely job  :).
Piki has manufacture of the new decals in progress and I'm cleaning up the panels to send to Menno for paint.
I'll post some more photos later of progress so far. The other half passed her module 1 bike test 10 days ago on the same day we went on holiday, module 2 is about to be booked so the pressure is now on to rebuild the bike for her to use!
1976 Honda 400/4
1977 Honda 400/4
1981 Honda CB250RSA
1977 Rickman Honda CR750
1999 Honda VFR 800FX
1955 750 Dresda Triton
1978 Moto Morini 350 Sport
1982 Laverda 120 Jota
1924 Triumph 550SD
2012 Stanley Battery Drill

Offline Jamesh_sussex

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Re: CB250RS Rebuild Progress
« Reply #14 on: September 23, 2017, 12:18:16 PM »
Chrome Porn  :) I collected this little lot from the chromer today, fantastic job he made of everything.  £98 all in. Before anyone says anything.... I choose to plate the kick-start and rear brake lever, I couldn't stand the rough finish of the originals. I took me a full day to file the kick-start shaft and knuckle smooth and blend the contours.
Who did the chrome? Looks very nice...