cam box help needed

paulbrice wrote:

At 25k miles bit late in the day to bed the rings I suspect ? .....while I top up the oil to compensate for worn/glazed bores & rings caused by previous owner or cumulative effect of total 8 flat tappets merrily ground into the engine, maybe should look for something else to bed in :-)

Don't top up the oil unless it drops below the 'Add' mark on the stick.

As for the rest of it? Whether ground up tappets will destroy your engine seems to be mainly a matter of chance! There is at least one bloke here who got through something like four sets of flats before he was rollerised and his bike still sings! I've had customers whose top ends were so buggered I couldn't believe the engine would survive but they did! Conversely the two bikes other than mine which have destroyed themselves that I have seen showed damage but nothing terrible to the tappets. Actually I think in the case of Mark's bike it may of gone further? Not sure. Ralf's bike may of died because he does use it pretty hard, as do I mine. The previous history of Mark's is a bit of a grey area.

Pete

Hi Paul, Just use wide open throttle whenever you can, deglaze, bed in ........ or out,

Thanks for all the info, B kit and all extras ordered today from Jim Allan Motorcycles £770 got a sump gasket as well,will keep you all updated with pictures when I get started but will be a few weeks away.

Well Guys the kit is here, will not get it fitted for a few weeks as I need to work every day to pay for it where does the tang go on this one ? and what are the two half ball bearings for ?
Thanks again.
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The tang replaces the old one that went on the head bolt that Pete talked about at the top of this thread, and it goes under the two allen bolts that hold the rocker bridge bearings. It should point inwards & downwards toward the plug hole . The two semi circle bits must be fitted on top of the new tappet 'flat' bits where they meet the 'old' follower arms (if you remember the old 'dumbell' ended rods fitted into the follower arms, and the new tappets come with a flat top end that needs a semi-circle to make it fit & work properly. There are lots of guidance from Pete with pictures on fitting both the tang and the semi-circles (and all the rest of the job), including how to hold the semis on while you reassemble - I used thick assembly grease. Presume you are shimming the inlet valves and replacing the guides; or are you just changing the springs ? See [You must be registered and logged in to see this link.] for Petes pictures and guide

Thanks Paul

That was my first thought with them, I sat them on top but was worried they would fall into the rollers. Any other advice would be appreciated as I know you have carried this out yourself.

I'm not shimming I have the latest springs for inlet valves.

The hemispherical 'Pads' are not just vital because of the shape of the rocker arm ends but they also allow a small amount of *Sliding* movement at the top of the tappet *Tower*. Because the rocker moves in an arc there needs to be some mechanism that allows the purely linear movement up and down of the tappet to be transferred to the rocker without placing a side loading on the tappet. The pads allow this as they will slide on the top of the tappet tower.

We stick them into the ends of the rockers once the rockers are installed in the new camboxes with a gob of assembly lube. Then pick up the cambox while holding the valve ends of the rockers to keep pressure on the pads on the tappets to prevent them falling out as you slip the cambox back on to the studs.

Not. When putting the upper rocker retaining *bridge*, the one the earthing tang sits under the two bolts of, back on make sure you liberally lubricate the bearing surfaces with assembly lube or oil before carefully tightening them down making sure they still rock freely. They can, occasionally, be a bit temperamental and want to jam. Obviously it is vital that they move freely otherwise as soon as you turn the motor over the cams will push the valves open but if the rockers can't rock freely the valve springs may not have the strength to push them back again and allow the valves to close. Valves stay open. Piston rises and 'Bingo'! Bent valves.

We also double check the torque on the bolts the hold the rocker retainer once the cambox is bolted back onto the engine as its a lot easier than trying to do it on the bench.

Don't mislay the oil feed dowels between barrel and head and head and cambox.

Pete

godge wrote:

Well Guys the kit is here, will not get it fitted for a few weeks as I need to work every day to pay for it where does the tang go on this one ? and what are the two half ball bearings for ?
Thanks again.
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And here's a pic of the tang installed

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Pete

Hey Godge, two of the really key personal learnings I got in this were (lots more stuff from hours following Pete et al postings):
1. Make sure you mark up the flywheel for TDC on each side because on my bike at least there are loads of drilling holes around where RHS TDC should be (so needed to white mark the one that best lined up); and no mark at all on LHS TDC. All this because if the top cam sprocket doesn't line up when you rebuild it, you need really clear marks to re-line it up again and decide if it is bottom sprocket slipping a tooth or the engine moved while you were prodding at the piston. Then once head and cam chain is on also turn it over and over many times carefully using pulley bolt and check everything moves right and then recheck TDC markings again & recheck valve settings (I went around several times doing valve gaps & re-did them again after 500 miles).
2. Good torque wrenches and lots of pre-checking all literature followed by 'does that make sense' required to avoid under or over doing the torque settings....MG wording is vaque and torques mixed up it seems....also need to check you didn't unwind the head stud bolts when you undid them (I saw somewhere you are supposed to retorque them down using lock nuts on thread but didn't do that :-(). For exhaust in all cases the studs came out and nut welded on - went back same way.

Overall I only had to chisel off three bolts (the exhaust cover plate on the joint - again); and replaced the two rubbish bolts on the tank front mounting as they were already tired when I started the job).

Great to see this update as I'm starting back to this job after hectic first half of year with no free time and then a holiday break in July. I was wondering what the steel semi-spheres are for.
Thanks

I have left head and cambox on.
*I have a question about the timing sprocket & chain.

When disassembling these parts (at TDC) first thing I did was cable-tie the cam chain onto the sprocket teeth so no movement could happen. I used 4 ties! (As photo shows)

I wish I had taken a photo before the disassembly began, to check/confirm the position of the L alignment hole at that stage: however I can't see how anything can have changed – the top of chain is locked on and I don't think that the bottom cold have jumped off.
The thing is, putting it back together, with piston at TDC, I saw that the sprocket hole (L) was slightly off. I don't understand how this could have happened. I dropped sprocket from chain and moved it one tooth so that it is in correct timing position.

In the photo you can see the black line where I marked chain and sprocket as they were aligned when tied together. The two parts of line are now separated by one tooth, after correcting the sprocket location in chain.

My question is: how noticeable a difference would one tooth out of sync have made to the timing and the running of the motor? I am wondering if it was like this from the time that a certain 'Official Service Agent' did the first cam replacement? It is entirely in keeping with the quality of work he carried out that he could have mucked up the chain and sprocket alignment, but if so, would I / should I have noticed the effect of that?

A supplementary question is... there couldn't be anything different that I have overlooked, could there? Surely the only option was to move the sprocket so that the L hole was in the correct position? The chain isn't likely to have moved position at the bottom end, is it?

Chain locked on
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Black line on left shows it was one tooth out of sync at TDC
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Given 'The Hammer's modus operandi who can tell what he may of done, or not done.

Yes, it is possible for the chain to jump a tooth at the bottom when the head is off. It can happen but it's rare and will usually only occur if the crank is messed with while the chain is *Un-tensioned*.

Interestingly the 8V is not a collision motor if the chain is off a tooth, at least not one way. It will completely screw the running and performance though if it is!

Pete

After putting the left side together tonight, I opened the right side after turning crank / right piston to TDC. This time I checked and photographed where the cam pin was and it was at 6 o'clock ok.

Dear knows what happened with th left chain, but I'm happy that things are correctly in sync now. If it was a tooth out and that would have a big effect on how the bike runs, then I think I would have noticed, so it's unlikely it was like that for a long time. On the other hand I always kept the chain tensioned when head was off, by tying it up tight to the frame. I did turn the crank a little though, when I was cleaning carbon off the piston top.

A different thing: on opening the right cambox I see that it is the inlet valve tappet cap face that is most worn away. Isn't it usually the exhaust that is more damaged? Maybe it's just chance, which one wears worse. I think it was other way round on left: it was the exhaust valve that was worse.

Photos of right side: inlet valve tappet cap worn more (and concaved) than exhaust tappet cap.
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Normally it tends to be exhausts worn more than inlets but there is no hard and fast rule....

Pete

Have you fitted a new piston as well or have you polished it up already ? - It doesn't look like it has ever seen combustion compared to mine that looks like something drank oil then shat on it.

I cleaned it up. That bit is back in the dark again now. I had planned to get the right side done today – but household plumbing intervened.

well guys got it started today, pulled the left pot off first and here is what I found, Pete is once again correct they all have a problem.
This bike is well cared for and is only used in the summer and not for any short runs, has regular oil changes with Agip recommended oil every 2000 miles or less.

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A little advice needed on a few points
1: Pete talked about the dowels, are they on all the cylinder bolts or just the diagonals , both on the head and cam box (hope this makes sense}
2:The 2 long bolts too the right of the cylinder that need to be loosened before the head bolts are cracked obviously need to come rite out to separate the head, what are these bolts for ? are they to do with the back tensioner.
Thanks for all the help.

1. Dowels are just on the diagonals, there are only two at each level.
2. They are only done up to 10nm so don't appear to do much beyond seal the cam tunnel to prevent oil leakage (presume cos it sits outside the magic square of the head bolts). They don't connect to or affect cam tensioner at all except that they do hold the tunnel together. Worth noting which goes where as on mine there were two washers on one (can't remember which)

Your flat tappets look very early wear so hopefully all good !

Thanks Paul, so far its all went well the cam tensioner locked in quite easily this was the bit I was nervous about.
I have replaced one valve spring, the collets are dam small and fiddly.
Will continue tomorrow and keep you updated.

Yup, Paul has it covered. The studs that have the dowels are the ones that the cam and rocker oil feeds come up. Unlike the pushrod models the hoses that go to the heads on the 8V provide no oil for lubrication, only for cooling. The high pressure lubricating oil comes up those two studs, hence the dowels to discourage leaks.

Pete

Guys a quick question. when I'm putting the head gasket back on should I use any sealing compound, the same with inlet and exhaust,thanks.

Definitely not put any sealant on head gasket - I didn't even coat it with oil or grease and had no problems. For inlets same and I just put the gaskets in as they came from the packet. For exhaust I did use some anti-sieze paste I had around but not sure that was needed and caused smoke for first few miles as well :-(.....the question you didn't ask was which way around the exhaust gaskets go and I can't remember but did use the old ones to get them same as before - there is metal showing on one side, not other.

Thanks Paul , ill start getting the head back on tonight
what's everyone's opinion on polishing up the piston
my plan was for s quick clean , was a little worried about any carbon slipping down the bores.
Also is it ok to leave the bike sitting for a while with the battery disconnected.
thanks.

No need to clean the piston, really. The days of poor fuels and crappy, over-rich fueling are long gone. The 'De-Come' is a thing of the past like magnetos and manual advance and retard levers.

On the head gaskets we usually use a light spray of coppercoat but it isn't vital.

Pete