Honda CB 125 T2 Worn Camshaft

dougpitcher · L Plate Warrior Joined: 31 Mar 2019 Karma :

Hi - I have recently decided to replace the worn pistons and barrel on my 1980 Honda CB 125 T2, after buying a replacement online; however once the engine was stripped, it is fairly obvious the top end had seized at some point in its life (probably due to oil starvation?)

The camshaft was eating away at the cylinder head and causing it to wear excessively, now I don't fancy the risk of putting the old camshaft back in the bike but I have read about the rarity of the cam. How would I know if my cam is the full power version not the wetdream type - and by some fluke would anyone know where to source one or would it be worth getting it re-machined if it is an original cam.

Thank you for your responses,

Doug

Teflon-Mike · tl;dr Joined: 01 Jun 2010 Karma :

dougpitcher · L Plate Warrior Joined: 31 Mar 2019 Karma :

In the pictures you can see the wear to the end of the camshaft, this has caused it to sit lower in the bushes this in turn causing the sharp edges between the lobes have scored the cut-out in the head.

There is no damage to the head where the banjo's are but we would assume they need be replaced and the camshaft end smoothed?

I'd love to be able to save the original cam... if it is the original cam but before the strip down the engine did rev to ~12,000 rpm but burnt oil and the pistons have shown a lot of blow-by.

If the camshaft cannot be saved it looks like the Chinese replacement may have to do.

dougpitcher · L Plate Warrior Joined: 31 Mar 2019 Karma :

Perhaps this a better picture

Teflon-Mike · tl;dr Joined: 01 Jun 2010 Karma :

Hmmm... dont look good.

TBH, I'd not go for one of the Chinky E-bay specials. I have done... never again! The timing is peculiarly 'soft', based on the later TD-J spec, optimised around the CV carbs that had, and I had a devils own job setting up carbs to run with it, a-n-d, it IS noteably cooler than even the TD-C spec 'Reduced Effect' cam, loath to rev out.

What do the lobes look like? have they actually sustained damage clouting the head, the cam sat cock?

Looks, in the piccie, like there is some scoring on the bearing journal and it 'may' be bad enough to have gone through the surface hardening...

I dont have metal in my mits to actually see more closely, but I would likely be loath to put that back in.... b-u-t... you got two chances, haven't you? If you scrap it, it dead metal. If you chuck it back in, is it gonna get any deader, or worse make something else dead?

Worry there is that 'if' the case hardening has started to break down, in use, accelerated wear could dump more swarf into the oil to wear other bits or clog oil-ways...... b-u-t, its no great shakes do do a few extra oil changes, which you should anyway, early on on a rebuilt engine, and sift and strian what comes out to see; or to lift the rocker cover and have a look-see, which again you'd do at post rebuild early oil-change anyway, to check the tappets.... and worset case? Noy MUCH extra effort to lift the rocker bosses and hoik another cam in after the event....

So, how much you really want or need the 309 cam in there? And how much hassle are you prepared to tolerate..... you are messin with an old Benly twin here, so the answer to that starts from a pretty high threshold, lol but still!
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