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CB250Rs Rebuild

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Skoti:
Yep, the valve gear looks a bit tired.
I notice the tappet adjusters show also signs of pitting, are the valve stem ends OK?

I've seen worse though, but I suppose it would run on a bit longer in that state if you didn't want to throw extra cash at it.

Most of my recent projects have suffered "mission creep" where I've spent much more that I intended to, and more than the bike was probably worth...

Good luck though and please keep the photos coming.



   

Laverda Dave:
You will have to split the cases to renew the output seal. Only buy a genuine seal from Honda, the one I had was part of a kit of seals for the engine, it tore and the oil poured out on start up, oh how I laughed :'(. I am always really careful when I put seals on, plenty of oil on the lip, make sure it doesnt turn in on itself etc and still it tore (a tiny nick but enough to allow the oil to spurt out under pressure). When I compared the genuine item next to the pattern part it was obviously inferior, the rubber was very soft.
Splitting the cases now you have got this far isn't a big deal, you can keep all the gearbox shafts in the case. You will need three hands though when you renew the balance chain as the crank and front balance shaft is in one half on the case but the rear balance shaft is in the other case, you have to feed the balance chain around all three. I did it on my own but do yourself a favour and have a couple of trail runs before going for the real thing to give you the feel of it. To make it more of a challange you need to mark the balance chain links in three places with a bit of paint to ensure the links match the timing marks on the balance shafts. It is difficult but rewarding when you get it right.
Don't forget to use Hondabond on the crankcase joint after your practice runs and when you go to join them for the final time, a very thin smear will do.

MRA464:
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.

Bryanj:
If it ran before it should run again albeit noisey and not at full output, only problem is you might take cam and rocker beyond repair but that shouldnt happen if plenty of good oil present

Laverda Dave:
Take the rocker cover off the one you have just bought and check the condition of the head, cam and rockers. If better than your original engine it could be a case of mix & match to get a good one, very common back in the day when these were throwaway bikes.
I think Newman Cams charged me £27 per rocker and £56 for the cam reprofile about four years ago, so allow for a £100+ spend if you go this route. Try Peter Lovell developments first though to see if he can get the two dowls out. Have a go yourself first with plenty of heat and long nose pliars, you might be lucky and they might come out, you have plenty of time on your hands and its a learning experiance so worth a try, dont give up yet, plenty of help and guidance here so plough through it ;)

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