Oil pressure issue / motor rebuild

[royhall]

Been thinking about this for a few hours now and have come to the conclusion that if it was mine (although I did previously say to get them measured) I would just replace the cases. You can waste days playing with what you have and waste money at the engineering shop for no gain. Re line boring them is not really an option unless they are one off historic and valuable. The cost alone will stop that idea dead in its tracks.  I recently rebuilt a CB750K3 for MCTID (Alan) who had damaged cases, and when I put out the call for replacements there was loads available. Thats the way I would go. Cheers.

[AshimotoK0]

I don't believe there are loads of K1 cases out there to be had...I know at least a couple of other people after them but I agree I would replace if at all possible. There would  always be a nagging doubt about it but it's  an engineering challenge for sure. My main fear would be thermal contact between the shell and the blasted surface of the crankcase. The only thing that would sway me is if the those surfaces are smooth enough  and , after measuring you find it's only the centre bearings nipping, then my idea of a shim foil to make those bearing clearing surfaces correct. Freddie has had some  cases for sale on eBay  for well over a year and they are unstamped. Trigger tells me they are not correct for a K0 but not sure which model they would fit. Sometime I am going to get my man in China to replicate some Honda stamps, so you could possibly and legitimatelly stamp with original numbers. You could make Freddie an offer if they are indeed suitable.

[MrDavo]

See Trigger's comments above re the unstamped cases, they appear to be a non starter. A friend of a friend I met at Stafford has a ton of CB750 bits, a text has been sent to see if he has any K1 cases.

As all 10 journals were so FUBAR, I don't think it's just one pair. That said I have plenty of time until more cases turn up, and lots of Plastiguage.

Looking closely last night, the shell carriers are very smooth, I'm pretty sure there's a layer of silver paint, how thick could that be? It's got to be worth trying to strip it off and re measuring, it could be stove enameled/ powder coated, I really don't know, it's that kind of finish. If so, how to get it off?

[AshimotoK0]

Methylene Chroride based paint stripper but be quick to remove once it softens and flush with solvent/soapy water. If powder coat , you will have to burn it off IMHO

[MrDavo]

Unfortunately when I Google that, the word 'free' appears after it in every product, it seems the Eu have banned it for killing people. I'll have to see what strippers I can get down the DIY store.

Burning sounds scary in case I distort the cases, I guess a careful experimental wafting with the blowlamp if necessary.

I do wonder if I'm on to something, though, especially if the journals turned out to be dead round, I won't know until I measure, I'll see if my mate can get an internal mike from work. I'll have a close look at where the paint / whatever got chipped to try and get my head around how thick it is.

[Chris400F]

This stuff was mentioned in a previous thread, says it is based on Methylene Chloride.
http://www.ebay.co.uk/itm/Paint-Stripper-1-litre-Restorations-Car-Bodywork-Metal-Remover-Wood-Furniture-HD-/291808738692?

[royhall]

The shell carriers should not be painted. They should be clean smooth aluminium. The inside of the cases are painted to stop the ally being porous. Maybe after blasting they repainted over the lot? That would for sure lock the crank, but didnt you just Plastigage the shells and they came out good? Weird things happening here?

[AshimotoK0]

Be careful with anything with caustic soda in it as it will attack the alloy. If you need locally go to an automotive paint supplier.

Agree with Roy though .. IIRC you Plastigaged it statically and it was OK > Something not right there.

[MrDavo]

Thanks for the link Chris.

I did plastigauge, Roy, but at an angle of about 45 degrees from the top, as it was before I got the barrels off and I was performing keyhole surgery. I'll have a proper go on Sunday, the next chance I'll get, doing it across the top, also I have ordered a loan of an internal micrometer from Eddie's works.

Maybe I've been barking up the wrong end of the stick, as my dippy missus would say. What I assumed was a vapour blasted finish turns out to be paint, powdercoat, I don't really know yet. They must have used some sort of blasting to get all the chromate finish off the inside of the cases, as its all rough, but the rest maybe they just painted, or blasted then painted, IDK. Maybe they resurfaced the crank joint, as that's smooth, maybe not, we might know when we measure the journal bores. Certainly you can see here the smooth but painted, not bare alloy, journals:



The moment of truth came when I noticed the small patch where it has been rubbed off on the carrier on the left - a lightbulb moment.

The previous photos were all taken with my crappy mobile camera, however I do have decent cameras and lenses, so I dug one out. Here is a closeup of where I have chipped the paint while trying to lever the barrels off (dog rough, I know, but I was getting frustrated by then).



I should have put something there as scale, but the photo is of the leading edge of the upper case, you can make out 2 of the reinforcing ribs.

Anyhow, you can see the thickness where it has chipped, and for a circular bearing housing we are looking at twice that. It only needs to be a thou thick to steal my 2 thou clearance, though the positive plastiguage result is still a mystery, as it would be uniform around the bearing.

Maybe its a combination of two cockups, we may know more after Sunday when I will be mostly measuring. If it were a paint problem though, that could be good news, as it can be removed from the gearbox bearing housings as well as the crank journals. We'll see.

ETA: Bought the paint stripper, got a mask and safety specs (not before time!) while I was at it.

[MrDavo]

Right, news from the front, which means theres at least a good chance we can save the cases by getting this &%#*@ silver paint out of the journals.

Ed the engineer turned up with his works' digital bore guage, accurate to 0.001mm, a lovely bit of kit, about £1,400 a pop. We could only get at the two outermost journals though. I had taken the crank and shells back out, cleaned everything, and torqued the cases together back up to 18 ft lbs.

Basically, the holes are circular  but measure only 38.955, they should be 39.000 minimum, all the Honda shell options are for this (A, as originally stamped on the cases, is 39.000 to 39.008mm) and above.

The difference, near enough .05mm, is 2 thousanth of an inch, he thinks its quite feasible that this is the 2 layers of 1 thou thick paint either side of the journal. I showed him the patch where it had chipped, in the above photo, and he could catch his nail on it.

When I get the paint stripper I'll get the silver out of all the bearing housings, and he will return next week with the same guage. I showed him the photo I took of my plastiguage attempt, he pointed out that it was squashed almost to the max for that colour (red), the proof of the pudding will be when we try again without the paint. Most people say green is the one to use, though I'm a bit confused as to why, I have both.

[MrDavo]

A brief update, I decided I needed to know if I needed another bottom end before I went to Stafford tomorrow morning.

I donned my mask, safety specs ( soon gave up with these as they kept misting up, and I was hardly sloshing the paint stripper around), and on the advice of Ed I wore double gloves. Once I'd scraped the bulk of the paint off I could almost wipe it off with the Loctite gasket remover, I noticed when I was scraping away the base gasket that it was shifting the silver paint, I don't know what's in it.

I got the paint out of all the main journals, and all the gearbox bearing housings while I was at it.

Ed has flown off to Korea, his job's like that, so I couldn't borrow the bore gauge again. However when I spoke to him last night, he suggested I just put the crank & shells back in, lube everything & torque it up, if our theory was correct it would work, if not the cases are scrap.

I was nervous as I tightened the bolts, having been here before, but I kept checking as I tightened each bolt. I finally got the last one up to 18ft lbs, and guess what? It still turns!!!

Jobs a good 'un, as we say up here, and I know the rods shells are right, so hopefully no more dramas, though I'm not in a tearing hurry.

Who would have thought that an uneccesary layer of paint could wreck a fresh engine? I reckon they realized there was a problem too late, and made it turn over.

[AshimotoK0]

Nice result in the end Dave .. are you Plastigaging again or just 'going with it' ?

Don't think you would have found any K1 cases at Stafford. I did see the same bottom end I saw a week or so back at Newark but it's a very late engine with weird numbering

[MrDavo]

I decided today not to bother with Stafford show, seen most of it before and nothing I need to buy right now, and spent the day in the garage instead

I did a plastiguage check, 1.5 thou imperial, within spec.

I built the bottom end upside down, into the top case, it was much easier to align the gearbox bearings with the half rings etc, got the crank in the chains, rods on and the cases together, checked I had 5 gears too. Then after I torqued the crank bolts up for the hundredth time I checked Hondaman's book for the torque setting for the small bolts. Only then did I notice his warning that it's easy to put the large final drive gear on the layshaft the wrong way round, which wears it and the gear next door out. Earlier it had been rolling across the garage floor, and I realized the was a 50/50 chance of this

I decided to split the cases again before the sealant went off. I'm still not sure which way round the gear is, but I'd rather redo it than get it wrong. Hopefully the drawing in the parts book may help, but I'm done for today.

[MrDavo]

Another update, this is where I'd got to on Monday evening.



There will now be a delay while I scrape off the remains of the base gasket from the barrels, as it was very well stuck on, which is why I couldn't get the barrels off. I'm about to nip to B&Q to buy a couple of large hose clamps to use as ring compressors - you polish the burrs off the inside, as per Hondaman's book. Edit - got ones that were smooth inside, no serrations, £2.54 the pair!

I'm minded to fit the plug to the end of the oil gallery, and fill it through the oil pressure light switch hole, so the mains have some oil. Whether it will slowly drip out, I'm not sure. I'll pick up the oil pump body later, they've got the central seal out and pressed the new one in.

[Trigger]

The centre seal will come out easy with a bit of heat