Honda CB250RS pic and questions please

[Oggers]

Chaps

Managed to take a photo of my new steed. A 1980 CB250RS in very decent nick - well on the outside anyways. Hopefully an attachment at the end of the post.... Nice round headlamp - which I actually prefer, and I may even replace the square indicators with round to match....such heresy!

It is now all apart, engine out, head and barrel off, and now awaits my tender mercies to replace worn bits with the myriad of spares that came with it. Good news is that rockers, cam lobes and bore all look OK. Nothing too shocking I don't think. I'll just replace things as I go....A  few Qs if I may

I have a camshaft sprocket and a new cam chain. it would seem sensible to replace them along with the crankshaft sprocket. Any clues as to how to pull off and replace the latter woiuld be appreciated. Haynes manual is a bit vague.

I actually have new IN and EX rockers in my pile of bits. Given Dave's troubles with the locating pins I wonder if it is worth replacing them? The existing ones look fine.

I also have both new final drive sprockets, but no new final drive chain. Dave Silver I guess, anywhere else?

Whilst the engine is in bits, is there anything else worth checking or replacing? I'll look at the balancer chain.

I also have a new piston and rings. Is is worth replacing the existing with these?

Many thanks

Mark


 





 

[Bryanj]

Crank sprocket is a big hydraulic press and i dont think you can buy it seperate from crank, chain yes cam sprocket only if visibly worn. Tensioner blade and cushion if worn.
If piston and rings are same size as bore you might as well fit them.balance chain yes everything else is an if damaged/worn scenario

[Laverdaroo]

loving that, its deffo a survivor. Get some dosh thrown at it

[Laverda Dave]

That's a keeper for sure. You don't want to mess about with the crank socket unless you are rebuilding the crank and I would try to avoid that unless you really have to.
How many miles has the engine done (assuming the speedo is original). If the engine is apart I would fit the spares you have but not anything in the rocker box such as the rockers unless they are worn which your are not. Maybe put some photos up to give us a clue?
Did you run the engine before you took it out, any sign of smoke or burning oil? Is there any sign of oil leaking from the ends of the rocker shafts (common problem).
The paint looks really good.
Personally if it were mine I'd take the Motad off keep it as a spare and buy a new pattern exhaust that are available to keep the two silencers and give the bike a balanced look.

[Laverda Dave]

I'd also have a look under those fork gaiters, a good idea to protect the stanchions but may also be hiding some rust as well!
I would also junk the rear rack unless you intend to fit a top box, just a shame imho to hide the duck tail and stripe 😊.

[Oggers]

Gents

As ever many thanks.

Firstly crankshaft camchain sprocket. Off with the RH cover and ATU and gave it a good looking at  - thinking there is no way on Earth I am going to remove it without first removing the shaft. Haynes manual is delightfully optimistic in stating pullers may be used. Aye right as they say up here....So it stays. It doesn't look at all bad, but I will replace the chain - a Morse -  and take a closer look at the camshaft sprocket. Tensioner blade/cushion looks fine.

Spare piston and rings are standard Honda parts. Bore again looks OK, and to the best of my knowledge is also standard. Very slight evidence of honing marks. Haynes suggest refitting cylinder and to check tolerances using feelers. I will do so and revert.

Miles are 32K. Rocker pads look OK but I will put up a pic later.

Engine ran fine. No discernable smoke but I didn't go far. Paint is indeed good and I have a spare tank in even better condition! The rack has been junked, but has revealed a tailpiece which could do with a wee paint touch up in some areas at least. Stonechips mainly. Paint recommendations welcome - maybe I could stretch to a complete repaint as the rest of the bike does seem to deserve it, failing that, touch up paint carefully applied and rubbed down?

Exhaust - in two minds about that. How much is a pattern pair?

Not got to balancer chain just yet......Forks just removed at the moment. I intend to replace the seals and the oil but that's about it. I do have a spare complete fork assembly for R/H side. No idea why! Guess I could use it, but would have to replace the spring in the L/H side perhaps?

I intend to give head/barrel and cover a repaint - thinking about vapour blasting then a good rattle can of satin black. Suggestions welcome. Upper crankcase half could also do with similar. Someone has done a DIY on all of these and it lets the side down.  Don't intend to split the crankcases though! 

Many thanks again...stand by for further questions as I progress - or not as the case may be!

Mark


 





 

[Laverda Dave]

You can check for wear in the cam chain tensioner, the Haynes manual details how to do it.
If you intend to renew the balance chain you need to split the cases as it's inside, you also need three hands as you need to hook the chain over the balance shaft sprocket as you close the cases.
You will struggle to obtain a piston to bore clearance with a feeler gauge, if the barrel is already off use a Vernier and bore gauge. If you don't have these take them to an engineering shop (and one that is used to motorcycle engines if it needs a rebore).
Shame about the tailpiece damage. Unfortunately the blue on the CB250RSA appears to be unique and nobody makes touch up for them. I sent my paint set to Menno and he had the paint specially mixed, I think from memory there was a bit of Porche blue in the mix.
The paint to use on the engine is satin black it is made by PJI and must be cured in the oven for one hour, it stinks so make sure the o/h is out for the day!
Has the Kickstarter been painted black, it should be green olive zinc plated along with a few other bits and pieces including the rear mudguard piece under the seat, the battery tray and the rear brake lever and the bracket on the right hand engine case.
The early model 250RSA was not fitted with a fork oil drain screw to save Honda money so you will need to tip the whole fork leg assembly upside down to let the old oil out.

[Bryanj]

Dont think pattern exhausts exist

[Arch stanton]

Pattern exhausts do exist. A mate bought a full set a few months ago.
Just cant remember where from at the moment. UK supplier too.

[Oggers]

Pic of  the bore- thoughts welcome. Don't want to rebore
Pic of the rocker pads. Clearly I missed the obvious pit on the RH pad! Those locking pins could be an issue Dave!

[Laverda Dave]

Hmmmm....... the rocker is showing signs of pick-up damage. once it breaks through like this it will only get worse. Is the cam lobe marked? You need to decide if it will be worth trying to get the pins out and the mileage you will put on the engine over time. You could try to take the pins out, you may be lucky and they may not put up a fight, just be careful not to snap the pin.

The Classic Bike Shop in Redditch, 3 Dunlop Rd, Redditch B97 5XP, 01527 454158 sell the exhausts and they are British made.
The front downpipes are £107/pair
The silencers are £230/pair
Both are showing as in stock.
I have had two sets of these from this company over the course of 15 years and the chrome is excellent as is the fit and they sound really nice. The joint between the pipe and silencer is also hidden by the footrests (the original Honda pipes are one piece).
I had to wait 18 months for the second set as they guy only makes them when he wants to.

I would get the piston to bore clearance measured properly. You can measure the ring gap first and if its within tolerance I think you'd be ok with the same piston, maybe just fit new rings after a light hone.

[Oggers]

Dave

Lobes look OK - honestly!, but yes that rocker pad is a concern. I won't be doing too many miles on it, but it would be nice to get it - or both - right by replacing it/them with the spares. Reading your pins saga it sounds ominous but I'll give it a go. I have new rings and a new piston. Not sure about new gudgeon pin but for sure replace the circlips.

Just adjusted the balancer chain tension as per the book. It was slighly slack. New cam chain now on....

Cheers for the exhaust supplier. I'll think about it. £337 is probabaly fair enough, but on a bike worth 1500 or so? Motad looks almost new.

Tailpiece attached. Bit of a bodge touch up and decal is somewhat marked.

By the by - is there a parts list anywhere please? I have many spares where the number is there but the description isn't. 

Many thanks again

[Laverda Dave]

Piki who has an advert on the forum as Reddice makes the decals. The quality of his decals are excellent. He also makes the DID decals for the alloy wheel rims and the FVQ decals for the rear shocks. He also makes the black decals for the footrest hangers giving tire pressures etc.
I have a hard copy of the parts list, Andy D who is a forum member kindly scanned the original manual for me and sent it as a pdf but unfortunately I sufferd a laptop crash back in 2018 and I lost the pdf. I should have put it into Ash's Dropbox but stupidly I forgot. I am attemting to trawl all my old drives and memory sticks to see if I still have a copy of the PDF, if I do I will send a copy.
Failing the above and to get you going, visit the CMSNL site where you will find the parts lists in expolded detail (and the prices for spare parts ).

[Laverda Dave]

Here's the details of the balance chain you need. Don't buy a genuine chain, they are expensive (£240+ from CMSNL when I tried to buy one in 2017) and not as good as the kart chain.  I think this chain was about £18 new from ebay. You will need to shorten it, the Haynes manual details the number of links.

[Oggers]

Dave

All good stuff - many thanks. I have found that simply typing the part number into Google comes up with something! I do have a few parts though. I'll see how it goes. I have decided to take the plunge and split the crankcases. More out of curiosity rather than anything. I guess I should replace the balancer chain if I do - might as well!

Is the balancer chain a rivet link or the spring clip type? or neither!